Publications
2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 1993 1992 1991 1981
2005
Kalveram,K.T.; Schinauer,Th.; Beirle, St.; Richter, St.; Jansen-Osmann, P.
Threading neural feedforward into a mechanical spring: How biology exploits physics in limb control. Biological Cybernetics , Biol. Cybern. 92, 229-240 (2005). DOI 10.1007/s00422-005-0542-6, Springer-Verlag 2005
Abstract Full-Version (PDF, 0.42mb)
2004
Kalveram, K.T. (2004).The Inverse Problem in Cognitive, Perceptual and Proprioceptive Control of Sensorimotor Behaviour (Towards a Biologically Plausible Model of the Control of Aiming Movements). IJSEP (lnternational Journal of Sport and Exercise Psychology) 2004, 2, 255-273
Abstract Full-Version (PDF, 0.3mb)
Richter, S.; Konczak, J.;Maschke, M.; Kalenscher, T.; Timmann, D.; Illenberger, A.R.; Kalveram, K.T. . Adaptive Motor Behavior of Cerebellar Patients During Exposure to Unfamiliar External Forces . Journal of Motor Behavior, 2004, Vol.36, No. 1, 28-38
Abstract Full-Version (PDF, 1.32 mb)
Schinauer T, Prentki D, Pledger N, Kalveram KT (2004) Skill acquisition and motor memory in the control of pointing movements. In: Z Waskiewicz, G Juras, J Raczek (eds) Current research in motor control II. Katowice: University School of Physical Education, pp 185-191.
Full-Version (PDF, 0.6 mb)
2003
Richter, S., Jansen-Osmann, P., Konczak, J., Kalveram, K.T.
(2003). Motor adaptation to different dynamic environments is facilitated by indicative context stimuli.
Psychological Research, 2004 , Vol. 68, 254-251
Abstract Full-Version (PDF, 0.5 mb)
Kalenscher, T., Kalveram, K. Th., & Konczak, J.
(2003). Effects of two different dynamic environments on force adaptation: Exposure to a new force but not the preceding force experience accounts for transition- and after-effects.
Motor Control , 2003, Vol.7, 242-263.
Abstract
Full-Version (PDF, 1.48 mb)
Konczak, J, Jansen-Osmann, P., & Kalveram, K.T.
(2003). Development of force adaptation during childhood.
Journal of Motor Behavior,
35(1), 41-52. Abstract
Full-Version (PDF, 1.1 mb)
Top
2002
Jansen-Osmann, P., Beirle, S., Richter, S., Konczak, J. & Kalveram K.-Th.
(2002). Inverse Motorische Modelle bei Kindern und Erwachsenen: Die Rolle des visuellen Feedbacks.
Zeitschrift für Entwicklungspsychologie und Pädagogische Psychologie, 34
, 167-173.Abstract Full-Version (PDF, 781 kb)
Jansen-Osmann, P., Richter, St., Konczak, J. & Kalveram, K.-Th.
(2002).
Force adaptation
transfers to untrained workspace regions in children: Evidence for developing inverse dynamic
motor models.
Experimental Brain Research, 143
, 212-220. Abstract
Full-Version (PDF, 232 kb)
Kalveram, K.-Th. & Schinauer, Th.
(2002). The problem of adaptive control in a living system or
how to acquire an inverse model without external help. In M. Verleysen (ed.),
ESANN'2002
proceedings – European symposium on artificial neural networks – Bruges, Belgium
(pp. 89-94). Evere: DeFacto.
Abstract Full-Version (PDF, 191 kb)
Top
2001
Hanisch, C., Konczak, J., & Dohle, C.
(2001). The effect of the Ebbinghaus illusion on grasping
behaviour in children.
Experimental Brain Research, 137, 237-245.
Abstract Full-Version (PDF, 112 kb)
Kalveram, K.-Th. & Natke, U.
(2001). Motor control and movement optimization learned by
combining auto-imitative and genetic algorithms. In M. Verleysen (ed.),
ESANN'2001
proceedings – European symposium on artificial neural networks – Bruges, Belgium
(pp. 165-170). Evere: DeFacto.
Abstract Full-Version (PDF, 63 kb)
Top
2000
Kalveram, K.Th. (2000). Sensorimotor sequential
learning by a neural network based on redefined Hebbian Learning. In: H. Malmgren,
M. Borga & L. Niklasson (eds.), Artificial Neural Networks
in Medicine and Biology (pp. 271-276). London: Springer Abstract Full-Version
(PDF, 155 kb)
Timmann, D., Richter, S., Bestmann, S., Kalveram, K.T.,
Konczak, J. (2000). Predictive control of muscle responses to arm perturbations
in cerebellar patients. Journal of Neurology, Neurosurgery
and Psychiatry, 69 , 345-352. Abstract Full-Version
(PDF, 211 kb)
Top
1999
Kalveram, K.Th. (1999). A modifed model of the
Hebbian synapse and its role in motor learning. Human Movement
Science, 18, 185-199, Abstract Full-Version (PDF,
214 kb)
Kalveram, K.Th. (1999). Psychobiologie der Zeit.
Über Zielgerichtetheit, Werkzeuggebrauch, Handeln und Gegenwartsbewußtsein.
In J. Bilstein & G. Miller-Kipp (Hrsg.), Transformationen
der Zeit. Erziehungswissenschaftliche Studien zur Chronotopologie (S.
339-347).Weinheim: Beltz.Abstract Full-Version (PDF,
162 kb)
Konczak, J., Brommann, K., & Kalveram, K. Th.
(1999). Identification of time-varying stiffness, damping, and equilibrium position
in human forearm movements. Motor Control, 3, 394-413.
Abstract Full-Version (PDF, 824 kb)
Konczak, J., Himmelbach, M., Perenin, M.T., & Karnath,
H.-O. (1999). Do patients with neglect show abnormal hand velocity profiles
during tactile exploration of peripersonal space? Experimental
Brain Research, 128, 219–223. Abstract Full-Version
(PDF, 62 kb)
Metta, G., Sandini, G., & Konczak, J. (1999).
A developmental approach to visually-guided reaching in artificial systems.
Neural Networks, 12, 1413-1427. Abstract Full-Version
(PDF, 1220 kb)
Top
1998
Biermann, K., Schmitz, F., Witte, O.W., Konczak, J.,
Freund, H.-J., & Schnitzler, A. (1998). Interaction of finger representation
in the human first somatosensory cortex: a neuromagnetic study. Neuroscience
Letters, 251, 13-16. Full-Version (PDF,
361 kb)
Kalveram, K.-Th. (1998). A neural oscillator model
learning given trajectories, or how an "allo- imitation algorithm" can be implemented
into a motor controller. In J. Piek (ed.), Motor control and human skill: A
multi-disciplinary perspective (pp.127-140). Champaign: Human Kinetics.
Abstract Full-Version (PDF, 254 kb)
Kalveram, K.-TH. (1998). Wie das Individuum mit
seiner Umwelt interagiert. Der motorische Apparat (Kap. 4, S. 165-249). Lengerich:
Pabst. Full-Version
(PDF, 542 kb)
Konczak, J.,& Karnath, H.-O. (1998). Kinematics
of goal-directed arm movements in neglect: control of hand velocity. Brain and
Cognition, 37, 387-403. Abstract Full-Version (PDF,
245 kb)
Topka, H., Konczak, J.,& Dichgans, J. (1998).
Coordination of multi-joint arm movements in cerebellar ataxia: Analysis of
hand and angular kinematics. Experimental Brain Research, 119, 483-492.
Abstract Full-Version
(PDF, 516 kb)
Topka, H., Konczak, J., Schneider, K.,
Boose, A. & Dichgans, J. (1998). Multi-joint arm movements in cerebellar
ataxia: Abnormal control of movement dynamics. Experimental Brain Research,
119, 493-503. Abstract Full-Version (PDF,
503kb)
Top
1997
Ackermann, H., Konczak, J., & Hertrich, I. (1997).
The temporal control of repetitive articulatory movements in Parkinson's disease.
Brain and Language, 56, 312-319. Abstract
Kalveram, K.Th. (1997) Zur Theorie und Therapie
des Stotterns. Sprache-Stimme-Gehör, 21, 130-139.
Abstract Full-Version (PDF, 805kb)
Karnath, H.-O., Dick, H. & Konczak, J. (1997).
Kinematics of goal-directed arm movements in neglect: control of hand in space.
Neurophysiologica, 35, 435-444. Abstract,
Full-Version (PDF, 738 kb)
Konczak, J. (1997). Zum Problem der Lokalisation
motorischer Funktion [On the problem of localization of motor function]. In
P. Hirtz, & F. Nüske. (eds.). Bewegungskoordination und
sportliche Leistung integrativ betrachtet (pp.42-50). Cwalina: Hamburg.
Konczak, J. & Dichgans, J. (1997). The development
toward stereotypic arm kinematics during reaching in the first three years of
life. Experimental Brain Research, 117, 346-354.
Abstract, Full-Version
(PDF, 614 kb)
Konczak, J., Borutta, M., & Dichgans, J. (1997).
Development of goal-directed reaching in infants: II. Learning to produce task-adequate
patterns of joint torque. Experimental Brain Research, 113,
465-474. Abstract,
Full-Version (PDF, 621 kb)
Konczak, J., Ackermann, H., Hertrich, I., Spieker, S.
& Dichgans, J. (1997). Control of repetitive lip and finger movements
in Parkinson's disease: influence of external timing signals and simultaneous
execution on motor performance. Movement Disorders, 12,
665-676. Abstract, Full-Version
(PDF, 1011 kb)
Konczak, J., & Dichgans, J. (1997). The development
of hand trajectory formation and joint kinematics during reaching in infancy.
In M. Fetter, T. Haslwanter, H. Misslich, & D. Tweed (eds.), Three-dimensional
kinematics of eye- head, and limb movements (pp. 313-318). Amsterdam:
Harwood Academic Publishers. Full-Version
(PDF, 169 kb)
Konczak, J., & Dichgans, J. (1997). Das Erlernen
stereotyper kinematischer Bewegungsmuster bei Greifbewegungen in der Ontogenese.
In E. Loosch & K. Tamme (Hrsg.), Motorik-Struktur und Funktion
(Vol. 79, pp. 87-91). Hamburg: Czwalina.
Topka, H., Konczak, J., Schneider, K. & Dichgans, J.
(1997). Three-dimensional upper-limb movements in cerebellar ataxia.
In M. Fetter, T. Haslwanter, H. Misslich, & D. Tweed (eds.),
Three-dimensional kinematics of eye- head, and limb movements (pp. 319-327).
Amsterdam: Harwood Academic Publishers.
Top
1996
Cress, M.E., Conley, K.E., Balding, S.L., Hansen-Smith,
F. & Konczak, J. (1996). Functional training: muscle structure, function,
and performance in older women. Journal of Orthopaedic and
Sports Physical Therapy, 24, 4-10. Abstract
Konczak, J., & Dichgans, J. (1996). The concept
of "normal" movement and its consequences for therapy. Behavioral
and Brain Sciences, 19, 79.
Top
1995
Jäncke, L., & Steinmetz, H. (1995). Hand motor
performance in monozygotic twins. Cortex, 31,779-785.
Abstract
Jäncke, L., Hefter, H., & Kalveram, K.Th. (1995).
Fast finger extensions are slower in stutterers than in nonstutterers. Perceptual
and Motor Skills, 80, 1103-1113. Abstract
Konczak, J. (1995). Benutzt das Gehirn "Motorische
Programme" zur Steuerung von Bewegung? In R. Daugs, K. Blischke, F. Marschall
und H. Müller (Hrsg.), Kognition und Motorik (pp.
41-58). Sankt Augustin: Academia.
Konczak, J., Ackermann, H., & Hertrich, J. (1995).
Die zeitliche Kontrolle repetitiver Lippenbewegungen beim Parkinson Syndrom.
Arbeitsblätter des Instituts für maschinelle Sprachverarbeitung, 2, 17-28.
Konczak, J., Borutta, M., Topka, H., & Dichgans, J. (1995). Development of
goal-directed reaching in infants: Hand trajectory formation and joint force
control. Experimental Brain Research, 106, 156-168.
Abstract
Müller, F., & Konczak, J. (1995). Neuromotorische
Kontrolle bei Funktionsstörungen der Basalganglien und des Cerebellums. Psychologische
Beiträge, 37, 664-686. Abstract
Top
1994
Konczak, J. (1994). Effects of optic flow on the
dynamic balance of human gait in young and older adults. Journal
of Motor Behavior, 26, 225-236. Abstract
Konczak, J., & Thelen, E. (1994). The dynamics
of goal-directed reaching: a comparison of adult and infant movement patterns.
In J. H. A. Van Rossum & J. L. Laszlo (eds.), Motor development:
aspects of normal and delayed development (pp. 25-40). Amsterdam: VU
University Press.
Top
1993
Kalveram, K.-Th. (1993). Power series and neural-net
computing. Neurocomputing, 5, 165-174. Abstract Full-Version
(PDF, 565 kb)
Kalveram, K.-Th.. (1993). A neural-network model enabling sensorimotor learning:
application to the control of arm movements and some implications for speech-motor
control and stuttering. Psychological Research, 55, 299-314. Abstract,
Full-Version (PDF, 1888 kb)
Top
1992
Kalveram, K.-Th. (1992). A neural network model
rapidly learning gains of reflexes necessary to adapt to an arm's dynamics.
Biological Cybernetics, 68, 183-191. Abstract,
Full-Version (PDF, 982 kb)
Top
1991
Kalveram, K.-Th. (1991). Controlling the dynamics
of a two-joined arm by central patterning and reflex-like processing. A two-stage
hybrid model. Biolocical Cybernetics, 65, 65-71.
Abstract, Full-Version
(PDF, 757 kb)
Kalveram, K.-Th.(1991). Pattern generating and
reflex-like processes controlling aiming movements in the presence of inertia,
damping and gravity. A theoretical note. Biological Cybernetics,
64, 413-419. Abstract, Full-Version
(PDF, 688kb)
Top
1981
Merz, F., Kalveram, K.-Th., Huber, K. (1981).
Der Einfluß kognitiver Faktoren auf Steuerleistungen. In L. Tent (Hrsg.), Erkennen,
Wollen, Handeln. Festschrift für Heinrich Düker zum 80. Geburtstag (S.
327-335). Göttingen: Hogrefe. Abstract Full-Version
(PDF, 496 kb)
Kalveram, K.-Th. (1981). Erwerb sensumotorischer
Koordinationen unter störenden Umwelteinflüssen: Ein Beitrag zum Problem des
Erlernens von Werkzeuggebrauch. In L. Tent (Hrsg.), Erkennen,
Wollen, Handeln. Festschrift für Heinrich Düker zum 80. Geburtstag (S.
336- 348). Göttingen: Hogrefe. Abstract Full-Version
(PDF, 632kb)
Top
Abstracts
Kalveram,K.T.; Schinauer,Th.; Beirle, St.; Richter, St.; Jansen-Osmann, P.
Threading neural feedforward into a mechanical spring: How biology exploits physics in limb control. Biological Cybernetics 92, 229-240 (2005). DOI 10.1007/s00422-005-0542-6, Springer-Verlag 2005
Abstract:
Abstract. A solution of the hitherto unsolved problem is proposed, how neural feedforward through inverse modelling, and negative feedback realised by a mechanical spring, can be combined to achieve a highly effective control of limb movement. The revised spring approach that we suggest relinquishes of forward modelling, and produced simulated data which were as close as possible to experimental human data. Control models based on peripheral sensing with forward modelling, which are favoured in the current literature, fail to create such data. Our approach suggests that current views on motor control and learning should be rethought.
Keywords:
Top
Kalveram, K.T. (2004).The Inverse Problem in Cognitive, Perceptual and Proprioceptive Control of Sensorimotor Behaviour (Towards a Biologically Plausible Model of the Control of Aiming Movements). IJSEP (lnternational Journal of Sport and Exercise Psychology) 2004, Vol. 2, 255-273
Abstract: Aiming movements with an arm (one to three joints) confined in a vertical plane are described in terms of control theory. The framework includes two levels of motor control, namely the discrete and the continuos level, both with respect to time. On the continuos level, movement control is configured for physical execution. On the discrete level, planning takes place, which covers the selection of a perceptual goal, its serialisation into a desired trajectory by pattern generation, the perceptual paralleling of the resulting actual movement trajectory by pattern recognition, and the final check whether the goal is hit. The fundamental term is the ‘tool transformation’, which quantitatively relates muscularly generated joint torques to the effects on the environment– here to the changing Cartesian positions of the arm’s tip. Feedforward control then is exerted by an inverse model of the tool transformation. The acquisition of the inverse model is guarantied by the proposed ‘learneroperator model’ of sensorimotor control, which is based on auto-imitation combined with Hebbian learning, masters redundant degrees of freedom, and allows to quickly update the model parameters while the arm is moving. The approach relinquishes of a forward model of the tool transformation, and explains anticipation as predisposed by the perceptive goal, not as predicted by efferences flowing through a forward model.
Keywords: inverse adaptive control, sensorimotor control, inverse modelling, levels of control.
Top
Richter, S.; Konczak, J.;Maschke, M.; Kalenscher, T.; Timmann, D.; Illenberger, A.R.; Kalveram, K.T. . Adaptive Motor Behavior of Cerebellar Patients During Exposure to Unfamiliar External Forces . Journal of Motor Behavior, 2004, Vol.36, No. 1, 28-38
Abstract: The authors investigated adaptation of goal-directed forearm movements to an unknown external viscous force assisting forearm flexion in 6 patients with cerebellar dysfunction and in 6 control participants. Motor performance was generally degraded in cerebellar patients and was markedly reduced under the force condition in both groups. However, patients and controls were able to adapt to the novel force within 8 trials. Only the healthy controls were able to improve motor performance when readapting to a null-force condition. The results indicate that cerebellar patients' motor control system has imprecise estimations of actual limb dynamics at its disposal. Force adaptation may have been preserved because single-joint movements were performed, whereas the negative viscous force alone and no interaction forces had to be compensated.
Key words: cerebellum, human, inverse dynamic models, motor
control, motor learning
Top
Richter, S., Jansen-Osmann, P., Konczak, J., Kalveram, K.T.
(2003). Motor adaptation to different dynamic environments is facilitated by indicative context stimuli.
Psychological Research (in press).
Abstract: When humans are exposed to external forces while performing arm movements, they adapt by compensating these novel forces. The basis of this learning process is thought to be a neural representation that models the relation between all forces acting upon the system and the kinematic effects they produce, a so called inverse dynamic model (IDM). Recent evidence indicates that subjects are able to learn to move in different dynamic environments. The present study investigated whether and how the predictability of a given external force affects the selection of an appropriate motor response to compensate such force. Adult human subjects (N=32) held a handle that could rotate around the elbow joint and learned to perform goal-directed forearm flexion movements, while an external velocity-dependent damping force was applied. Subjects were randomly assigned to two groups. In the associative group, the applied damping force was always associated with a specific portion of the workspace. Thus, after initial learning, the force application became predictable. In the non-associative group, the applied force was independent of workspace, so that no association between force and location could be formed. We found that only the associative group significantly reduced target error when damping was present. That is, the location cue aided these subjects in generating appropriate limb dynamic responses. Our results indicate that motor adaptation to different dynamic environments is facilitated by indicative stimuli.
Top
Kalenscher, T., Kalveram, K. Th., & Konczak, J.
(2003). Effects of two different dynamic environments on force adaptation: Exposure to a new force but not the preceding force experience accounts for transition- and after-effects.
Motor Control (in press).
Abstract: This study investigated force adaptation in humans during goal-directed flexion forearm motion. The ability of the motor system to adapt to changes in internal or external forces is essential for the successful control of voluntary movement. In a first experiment, we examined how under- or overdamping differentially affected the length of the adaptation and the arm kinematics between force transitions. We found that transitions diverging from a null-force produced larger transition effects than transitions converging to a null force condition, indicating that re-adaptation was less error prone. Whether the subjects had previously experienced underdamping or the null-force had no significant impact on the spatial trajectory after switching to overdamping. That is, prior force experience had no differential effect on the spatial transition kinematics. However, the transitions underdamping-to-overdamping and underdamping-to-null-force did produce differently strong transition effects. These results indicate that exposure to the new force rather than previous force-field experience is responsible for transition- and after-effects. In a second experiment, we investigated whether a learning was law-like, that is, whether it generalized to unvisited workspace. Subjects were tested in new, unvisited workspaces in the null-force condition after sufficient training in either force condition. The occurrence of transferred after-effects indicated that adaptation to both positive and negative damping was mediated by rule-based rather than exclusive associative processes.
Top
Konczak, J, Jansen-Osmann, P., & Kalveram, K.T.
(2003). Development of force adaptation during childhood.
Journal of Motor Behavior,
35(1), 41-52.
Abstract. Humans learn to make reaching movements in novel dynamic environments by acquiring an internal motor model of their limb dynamics. Here, the authors investigated how 4- to 11-year-old children (N = 39) and adults (N = 7) adapted to changes in arm dynamics, and they examined whether those data support the view that the human brain acquires inverse dynamics models (IDM) during development. While external damping forces were applied, the children leamed to perform goal-directed forearm flexion movements. After changes in damping, all chil-dren showed kinematic aftereffects indicative of a neural controller that still attempted to compensate the no longer existing damping force. With increasing age, the number of trials toward co-plei" adaptation decreased. When damping was present fore-arm paths were most perturbed and most variable in the youngest children but were improved in the older children. The findings indicate that the neural representations of limb dynamics are less precise in children and less stable in time than those of adults. Such controller instability might be a primary cause of the high kinematic variability observed in many motor tasks during childhood. Finally, the young children were not able to update those models at the same rate as the older children, who, in turn, adapted more slowly than adults. In conclusion, the ability to adapt to unknown forces is a developmental achievement. The present results are consistent with the view that the acquisition and modification of internal models of the limb dynamics form the basis of that adaptive process.
Key words: development, human, inverse dynamics models, motor adaptation, motor control, motor learning, reaching
Top
Jansen-Osmann, P., Beirle, S., Richter, S., Konczak, J. & Kalveram K.-Th.
(2002). Inverse Motorische Modelle bei Kindern und Erwachsenen: Die Rolle des visuellen Feedbacks. (Inverse Motor Models in children and adults: The role of visual feedback.)
Zeitschrift für Entwicklungspsychologie und Pädagogische Psychologie, 34 , 167-173.
Abstract:
Neurobiological evidence reveals that neurally coded inverse models of limb dynamics form the basis of feed-forward motor control in humans. This study investigates the role of visual feedback for the acquisition of inverse motor models in children and adults. Eight 9-year-old and eight 5-year-old children and eight adults performed goal-directed horizontal forearm movements using a single-joint arm manipulandum. When visual feedback was not available before and after movement execution (partial feedback), spatial error increased in adults and children. However, the lack of visual information during movement execution did not affect adult motor performance. In contrast, spatial error increased in both children groups when visual feedback was removed. Spatial accuracy was improved during the partial feedback condition, if children had prior practice under full visual feedback. The increased dependence on visual feedback, especially in the younger children, is a sign that children relied predominantly on central feedback mechanisms for motor control, because their feed-forward control was not yet functional. The reasons for the lack of feed-forward control are twofold: First, there are problems in motor planning, specifically with the inverse kinematic transformation (from hand position to joint angles). Second, there are deficits in the neural controller, specifically due to imprecise neural estimations of the true limb dynamics.
Keywords: childhood, humans, motor control, motor learning, visuomotor
Top
Jansen-Osmann, P., Richter, St., Konczak, J. & Kalveram, K.-Th.
(2002). Force adaptation transfers to untrained workspace regions in children: Evidence for developing inverse dynamic motor models.
Experimental Brain Research,
143 , 212-220.
Abstract When humans perform goal-directed arm movements under the influence of an external damping force, they learn to adapt to these external dynamics. After removal of the external force field, they reveal kinematic aftereffects that are indicative of a neural controller that still compensates the no longer existing force. Such behavior suggests that the adult human nervous system uses a neural representation of inverse arm dynamics to control upperextremity motion. Central to the notion of an inverse dynamic model (IDM) is that learning generalizes. Consequently, aftereffects should be observable even in untrained workspace regions. Adults have shown such behavior, but the ontogenetic development of this process remains unclear. This study examines the adaptive behavior of children and investigates whether learning a force field in one hemifield of the right arm work-space has an effect on force adaptation in the other hemi-field. Thirty children (aged 6–10 years) and ten adults performed 30° elbow flexion movements under two con-ditions of external damping (negative and null). We found that learning to compensate an external damping force transferred to the opposite hemifield, which indicates that a model of the limb dynamics rather than an association of visited space and experienced force was acquired. Aftereffects were more pronounced in the younger children and readaptation to a nullforce condition was prolonged. This finding is consistent with the view that IDMs in children are imprecise neural representations of the actual arm dynamics. It indicates that the acquisition of IDMs is a developmental achievement and that the human motor system is inherently flexible enough to adapt to any novel force within the limits of the organism’s biomechanics.
Keywords Development · Motor control · Motor learning · Sensorimotor adaptation
Top
Kalveram, K.-Th. & Schinauer, Th.
(2002). The problem of adaptive control in a living system or how to acquire an inverse model without external help. In M. Verleysen (ed.),
ESANN'2002 proceedings – European symposium on artificial neural networks – Bruges, Belgium
(pp. 89-94). Evere: DeFacto.
Abstract Recent research uncovers that goal directed sensorimotor behaviour is governed by negative feedback of positional error, and by feedforward through inverse modelling of the limb’s dynamics. Thereby, forward models seem to provide the kinematic state of the limb. The question addressed in the paper is, how the neural network representing the inverse model can be trained. Because in this case an error based learning algorithm seems to be unavailable, an alternative non error based method called auto-imitation is proposed. It is demonstrated, that, if combining a special type of neural network (the power net) with a modified type of a Hebbian synapse, the inverse dynamics of an onejointed arm can be precisely identified using auto-imitation. This holds for a simulated arm and a real robot arm as well.
Keywords inverse modelling, Hebbian learning, auto-imitation, motor control
Top
Hanisch, C., Konczak, J., & Dohle, C.
(2001). The effect of the Ebbinghaus illusion on grasping behaviour in children.
Experimental Brain Research
, 137, 237-245.
Abstract: Within the context of the Ebbinghaus illusion, adults regularly misjudge the physical size of a centre disc, yet scale their hand aperture according to its actual size. Separate visual pathways for perception and action are assumed to account for this finding. The dorsal visu-al stream is said to elaborate on egocentric (visuomotor), while the ventral stream is involved in allocentric trans-formations (object recognition). This study examines the ontogenetic development of this dissociation between perception and action in 35 children between the ages of 5 and 12 years. We report four major results. First, when children judged object size without grasping the disc, their judgements were deceived by the illusion to the same extent as adults. However, when asked to estimate size and then to grasp the disc, young children’s (5–7 years) perceptual judgements became unreliable, while adults were still reliably deceived by the illusion in 80% of their trials. Second, the younger the children, the more their aperture was affected by the illusional surround. Discs of the same size were grasped with a smaller aperture when surrounded by a small annulus, although they were perceived as being larger. Third, young children used the largest safety margin during grasping. Fourth, the reliance on visual feedback decreased with increas-ing age, which was documented by shorter movement times and earlier maximum hand opening during grasping in the older children (feedforward control). Our results indicate that grasping behaviour in children is subject to an interaction between ventral and dorsal process-es. Both pathways seem not to be functionally segregat- ed in early and middle childhood. The data are inconclusive about whether young children predominantly use a specific visual stream for either a perceptual or motor task. However, our data demonstrate that children were relying on both visual processing streams during percep-tual as well as visuomotor tasks. We found that children used egocentric cues to make perceptual judgements, while their grasping gestures were not exclusively shaped by viewer-centred but also by object-centred information.
Keywords: Human · Development · Dorsal visual stream · Motor control · Visual perception
Top
Kalveram, K.-Th. & Natke, U.
(2001). Motor control and movement optimization learned by combining auto-imitative and genetic algorithms. In M. Verleysen (ed.),
ESANN'2001 proceedings - European symposium on artificial neural networks
- Bruges, Belgium
(pp. 165-170). Evere: DeFacto.
Abstract. In sensorimotor behaviour often a great movement execution variability is combined with a relatively low error in reaching the intended goal. This phenomenon can especially be observed if the limb chain under regard has redundant degrees of freedom. Such a redundancy, however, is a pre-requisit of movement optimization, because without variability changes in movement execution are impossible. It is, therefore, suggested, that, given a fitness criterion, a related optimal movement trajectory can be learned by an genetic algorithm. However, precise reaching must also be learned. This requires to establish at least an internal inverse model of the (forward) "tool transformation" governing the physical behaviour of the limb chain. Learning of an inverse model can be performed best applying the so called auto-imitation algorithm, a non-supervised learning mechanism equivalent to (modified) Hebbian learning. The paper shows theoretically, how these two learning algorithms can be combined in motor learning, and exemplifies by simulation of a three-jointed arm confined in a plane, how the problem of combining goal invariance under motor variability with movement optimization can be solved practically in a biologically plausible manner.
Top
Kalveram, K.Th.
(2000). Sensorimotor sequential learning by a neural network based on redefined Hebbian Learning. In: H. Malmgren, M. Borga & L. Niklasson (eds.),
Artificial Neural Networks in Medicine and Biology
(pp. 271-276). London: Springer
Abstract: A two-jointed arm is used to discuss the conditions under which a neural controller can acquire a precise internal model of a plant to be controlled without the help of an external superviser. The problem can be solved by a 'modified Hebbian rule' ensuring convergence of the synaptic strengths, a feedforward network called 'power network', and a learning algorithm called 'auto-imitation'. The modified Hebbian rule describes a neuron, that - in addition to a number of inputs with plastic weights - has also a teaching input established with a fixed synaptic weight. The power network can adopt accurate models even of non-linear plants like the two-jointed arm when established with modified Hebbian synapses. The auto-imitation algorithm provides the power network with the values to be achieved by the network after learning. The training must be able to generate arbitrary movements, first of low velocity, then of higher velocity.
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Timmann, D., Richter, S., Bestmann, S., Kalveram, K.T., Konczak, J.
(2000). Predictive control of muscle responses to arm perturbations in cerebellar patients.
Journal of Neurology, Neurosurgery and Psychiatry,
69 , 345-352
Abstract:
Objectives—To examine changes in predictive control of early antagonist responses to limb perturbations in patients with defined lesions of the cerebellum.
Methods—Eight cerebellar patients and eight sex and age matched control subjects participated. Subjects held a handle that was rotated around the elbow joint. They were instructed to hold the forearm at 90° flexion against a mechanical perturbation. Extensor torque (5 Nm) was applied for 140 ms (pulse), or for 1400 ms (step) through an external motor. Motor responses were tested under two different conditions of anticipatory information. In the expected condition, subjects anticipated and received a pulse. Under the unexpected condition, subjects expected steps, but received unexpected pulses. Biceps and triceps EMG as well as angular kinematics were compared between expected and unexpected pulse perturbations to quantify possible effects of prediction. gree of overshoot in the return flexion
Results—In all healthy subjects, the degree of overshoot in the return flexion movement was significantly less in expected pulse perturbations compared with unexpected trials. The degree of amplitude reduction was significantly smaller in the patient group than in the control group (22.8% v 40.0%). During the expected trials, latency of peak triceps activity was on average 20% shorter in the control group, but 4% larger in the cerebellar patients.
Conclusions—In the expected condition, controls achieved a significant reduction in angular amplitude by generating triceps activity earlier, whereas the ability to use prediction for adjusting early antagonist responses after limb perturbation was impaired in cerebellar patients.
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Kalveram, K.Th. (1999). A modifed model of the Hebbian synapse and its role in motor learning.
Human Movement Science, 18, 185-199
18, 185-199
Abstract:. The `Hebbian synapse', an old neuro-psychological concept which describes the process of associative learning at the synaptic level, is being increasingly confrmed by neuro-biological explanations. The purpose of the present paper is to show that sensorimotor learning, which is essentially non-associative, can also be explained by Hebbian learning. This requires a re- defnition of the Hebbian synapse ensuring convergence of the synaptic weight. Re-defned Hebbian learning then appears as a linear adaptive filter known in the field of adaptive signal processing, which in turn is equivalent to the delta rule used to train artificial neural networks. For motor learning, the modified Hebbian synapse must be embedded into a special learning algorithm called `auto-imitation'. This is a non goal-oriented inductive learning algorithm, enabling a controller to adopt a general rule from being shown only a few examples of that rule. When applied to motor learning, the neural controller can acquire the capability to online invert the behavior of the plant to be controlled. The complete learning process then can be described as a relaxation process between the controller and the controlled system, which is governed by long-term potentiation (LTP), the neuro-physiological process underlying Hebbian synaptic shaping.
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Kalveram, K.Th.
(1999). Psychobiologie der Zeit. Über Zielgerichtetheit, Werkzeuggebrauch, Handeln und Gegenwartsbewußtsein. In J. Bilstein & G. Miller-Kipp (Hrsg.), Transformationen der Zeit.
Erziehungswissenschaftliche Studien zur Chronotopologie (S. 339-347).Weinheim: Beltz.
Abstract: Im Gegenwartsbewußtsein wird das Hier und Jetzt nicht als Schnitt erlebt, welcher Vergangenheit und Zukunft trennt, sondern als Bereich, in welchem Teile von Vergangenheit und Zukunft simultan präsent sind und der Zeitfluß scheinbar aufgehoben ist. Dieses wird als mentale Repräsentation der Art und Weise angesehen, in der das Individuum mit seiner Umwelt interagiert, wenn es selbstgestellte Ziele über die Manipulation der Umwelt herbeiführt. Zielgerichtetes Handeln bedeutet biologisch/ physikalisch, zu einer intern vorgebenen gewünschten Perzeption letzten Endes die sie verwirklichenden Muskelkräfte zu finden. Das perzeptive Ziel liegt dabei parallel vor, d.h. zu seiner Beschreibung wird die Dimension Zeit nicht benötigt, während Handeln seriell ist, d.h. aus einer Folge von selbst gesetzten Ereignissen (hier: Folge von Muskelkräften) besteht, zu deren Beschreibung die Dimension Zeit erforderlich ist. Die Wahrnehmung muß dann die Serie der muskulär herbeigeführten sensorischen Einzelereignisse wieder zu einem Wahrnehmungs-Gebilde zusammenzufassen, dessen Beschreibung die Dimension der Zeit nicht erfordert. Dieser Vorgang kann als Serien-Parallel-Wandlung bezeichnet werden. Die Verwirklichung eines perzeptiven Ziels durch (zeitlich erstrecktes) Handeln und das Erkennen der Konsequenz einer durchgeführten Handlung können, so gesehen, als Zeiterzeugung und Zeitelimination beschrieben werden, Vorgänge, welche sich als Gegenwartsbewußtsein mental widerspiegeln.
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Konczak, J., Brommann, K., & Kalveram, K. Th.
(1999). Identification of time-varying stiffness, damping, and equilibrium position in human forearm movements.
Motor Control,
3, 394-413.
Abstract: Knowledge of how stiffness, damping, and the equilibrium position of specific limbs change during voluntary motion is important for understanding basic strategies of neuromotor control. Presented here is an algorithm for identifying time-dependent changes in joint stiffness, damping, and equilibrium position of the human forearm. The procedure requires data from only a single trial. The method relies neither on an analysis of the resonant frequency of the arm nor on the presence of an extermnal bias force. Ist validity was tested with a simulated forward model of the human forearm. Using the parameter estimations as forward model input, the angular kinematics (model output) were reconstructed and compared to the empirical measured data. Identification of mechanical impedance is based on a least-squares solution of the model equation. As a regularization technique and to improve the temporal resolution of the identification, a moving temporal window with a variable width was imposed. The method's performance was tested by (a) identifying a priori known hypothetical time-series of stiffness, damping, and equilibrium position, and (b) determining impedance parameters from recorded single-joint forearm movements during a hold and a goal-directed movement task. The method reliably reconstructed the angular kinematics of the artificial and human data with an average positional error of less than 0.05 rad for movement amplitudes of up to 0.9 rad, and did not yield hypermetric trajectories like previous procedures not accounting for damping.
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Konczak, J., Himmelbach, M., Perenin, M.T., & Karnath, H.-O.
(1999). Do patients with neglect show abnormal hand velocity profiles during tactile exploration of peripersonal space?
Experimental Brain Research
Abstract:
It has been suggested that the movement im-pairments experienced by patients with neglect are not restricted to spatial disorders, but also affect higher-order kinematics (velocity and acceleration) to the extent that movements towards the neglected side are slower than movements away from it. In a recent study, we could not confirm this hypothesis, but found that patients with uni-lateral neglect exhibited no distinct direction-specific deficits in hand velocity when performing goal-directed reaching movements. Here we investigated whether neglect patients might reveal direction-specific deficits during exploratory hand movements. Six patients with left-sided neglect and six age-matched healthy control subjects scanned with their right hands the surface of a large table searching for a (non-existent) tactile target. Movements were performed in darkness. Time-position data of the hand were recorded with an optoelectronic camera system. Median activity of the patients' exploratory hand movements was shifted to the right (Karnath and Perenin 1998). Hand trajectories were partitioned in-to sections of leftward/rightward or, along the sagittal plane, into sections of near/far movements. For each movement section average and peak velocities were computed. The patients' hand movements were bradykinetic when compared with the control group. However, we found no evidence that average or peak velocities of leftward intervals were systematically lower than during rightward motion. Direction-specific deficits in velocity were also not observed for movements to and away from the body (sagittal plane). In conclusion, we found evidence for general bradykinesia in neglect patients but not for a direction-specific deficit in the control of hand velocity during exploratory hand movements.
Keywords: Arm movements · Directional bradykinesia · Motor control · Movement planning · Parietal cortex
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Metta, G., Sandini, G., & Konczak, J.
(1999). A developmental approach to visually-guided reaching in artificial systems.
Neural Networks, 12
Abstract
The aim of the present paper is to propose that the adoption of a framework of biological development is suitable for the construction of artificial systems. We will argue that a developmental approach does provide unique insights on how to build highly complex and adaptable artificial systems. To illustrate our point, we will use as an example the acquisition of goal-directed reaching. In the initial part of the paper we will outline (a) how mechanisms of biological development can be adapted to the artificial world, and (b) how this artificial development differs from traditional engineering approaches to robotics. An experiment performed on an artificial system initially controlled by motor reflexes is presented, showing the acquisition of visuo-motor maps for ballistic control of reaching without explicit knowledge of the system's kinematic parameters.
Keywords: Development; Learning; Motor control; Human infants; Robotics; Artificial systems
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Kalveram, K.-Th.
(1998). A neural oscillator model learning given trajectories, or how an "allo- imitation algorithm" can be implemented into a motor controller. In J. Piek (ed.),
Motor control and human skill: A multi-disciplinary perspective
(pp.127-140). Champaign: Human Kinetics
Abstract:
The 'central target pattern generator' (CTPG) is defined as an interface into which mentally represented targets, not containing time as a variable, can be put, and which responds by putting out a set of time courses of efferences, representing the target sequentially in terms of exteroceptively defined co-ordinates. The CTPG model proposed consists of several coupled oscillators generating sinusoidal output waves with period lengths of T, T/2, T/3, .... , where T is the movement duration. The model operates like a Fourier analyzer and synthesizer: In the learning phase, the analyzer is active, while the learning system 'observes' an experienced system performing the movement under concern. Thereby, a Hebbian like learning mechanism correlates the 'visually perceived' velocity traces with the oscillator outputs, thus establishing synaptic weights used later on. This is termed by "allo-imitation". After learning is completed, the synthesizer again gets active and starts the oscillators. Their outputs, modulated by the synaptic weights previously determined, are summed yielding time courses, which, being fed through the inverse kinematics network related to velocity and then through the inverse dynamics network, reach the motor neurons and force, for instance, the tip of an arm to draw the intended target figure at the selected position, principially in a complete feedforward manner. Obviously, the synaptic weights related to that movement can be regarded representing the "internal image" or the "plan" of that movement. In simulation experiments, a two-segmented arm furnished with inertia is induced by the model proposed to reproduce characters written by hand, using 6 oscillators. The movements produced are close to the intended ones. However, perturbations at various levels of control can cause errors. Analyzing these errors may lead to the identification of the underlying neural control system..
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Konczak, J.,& Karnath, H.-O. (1998). Kinematics of goal-directed arm movements in neglect: control of hand velocity.
Brain and Cognition, 37
Abstract: Do patients with unilateral neglect exhibit direction-specific deficits in the control of movement velocity when performing goal-directed arm movements? Five patients with left-sided neglect performed unrestrained three-dimensional pointing movements to visual targets presented at body midline, the left and right hemispace. A group of healthy adults and a group of patients with right-hemispheric brain damage but no neglect served as controls. Pointing was performed under normal room light or in darkness. Time-position data of the hand were recorded with an opto-electronic camera system. We found that compared to healthy controls, move-ment times were longer in both patient groups due to prolonged acceleration and deceleration phases. Tangential peak hand velocity was lower in both patient groups, but not significantly different from controls. Single peak, bell-shaped velocity profiles of the hand were preserved in all right hemispheric patients and in three out of five neglect patients. Most important, the velocity profiles of neglect patients to leftward targets did not differ significantly from those to targets in the right hemispace. In summary, we found evidence for general bradykinesia in neglect patients, but not for a direction-specific deficit in the control of hand velocity. We conclude that visual neglect induces characteristic changes in exploratory behavior, but not in the kinematics of goal-directed movements to objects in peripersonal space.
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Topka, H., Konczak, J.,& Dichgans, J.
(1998). Coordination of multi-joint arm movements in cerebellar ataxia: Analysis of hand and angular kinematics.
Experimental Brain Research, 119
Abstract: Kinematic abnormalities of fast multijoint movements in cerebellar ataxia include abnormally increased curvature of hand trajectories and an increased hand path and are thought to originate from an impairment in generating appropriate levels of muscle torques to support normal coordination between shoulder and elbow joints. Such a mechanism predicts that kinematic abnormalities are pronounced when fast movements are performed and large muscular torques are required. Experimental evidence that systematically explores the effects of increasing movement velocities on movement kinematics in cerebellar multijoint movements is limited and to some extent contradictory. We, therefore, investigated angular and hand kinematics of natural multijoint pointing movements in patients with cerebellar degenerative disorders and healthy controls. Subjects performed self-paced vertical pointing movements with their right arms at three different target velocities. Limb movements were recorded in three-dimensional space using a two-camera infrared tracking system. Differences between patients and healthy subjects were most prominent when the subjects performed fast movements. Peak hand acceleration and deceleration were similar to normals during slow and moderate velocity movements but were smaller for fast movements. While altering movement velocities had little or no effect on the length of the hand path and angular motion of elbow and shoulder joints in normal subjects, the patients exhibited overshooting motions (hypermetria) of the hand and at both joints as movement velocity increased. Hypermetria at one joint always accompanied hypermetria at the neighboring joint. Peak elbow angular deceleration was markedly delayed in patients compared with normals. Other temporal movement variables such as the relative timing of shoulder and elbow joint motion onsets were normal in patients. Kinematic abnormalities of multijoint arm movements in cerebellar ataxia include hypermetria at both the elbow and the shoulder joint and, as a consequence, irregular and enlarged paths of the hand, and they are marked with fast but not with slow movements. Our findings suggest that kinematic movement abnormalities that characterize cerebellar limb ataxia are related to an impairment in scaling movement variables such as joint acceleration and deceleration normally with movement speed. Most likely, increased hand paths and decomposition of movement during slow movements, as described earlier, result from compensatory mechanisms the patients may employ if maximum movement accuracy is required.
Keywords: Cerebellar ataxia ´ Limb movement ´ Multijoint movement ´ Kinematics ´ Human
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Topka, H., Konczak, J., Schneider, K., Boose, A. & Dichgans, J.
(1998). Multi-joint arm movements in cerebellar ataxia: Abnormal control of movement dynamics.
Experimental Brain Research, 119
Abstract: In cerebellar ataxia, kinematic aberrations of multijoint movements are thought to originate from deficiencies in generating muscular torques that are adequate to control the mechanical consequences of dynamic interaction forces. At this point the exact mechanisms that lead to an abnormal control of interaction torques are not known. In principle, the generation of inadequate muscular torques may result from an impairment in generating sufficient levels of torques or from an inaccurate assess- ment and prediction of the mechanical consequences of movements of one limb segment on adjacent joints. We sought to differentiate the relative contribution of these two mechanisms and, therefore, analyzed intersegmental dynamics of multijoint pointing movements in healthy subjects and in patients with cerebellar degeneration. Unrestrained vertical arm movements were performed at three different target movement velocities and recorded using an optoelectronic tracking system. An inverse dynamics approach was employed to compute net joint tor- ques, muscular torques, dynamic interaction torques and gravitational torques acting at the elbow and shoulder joint. In both groups, peak dynamic interaction forces and peak muscular forces were largest during fast movements. In contrast to normal subjects, patients produced hypermetric movements when executing fast movements. Hypermetric movements were associated with smaller peak muscular torques and smaller rates of torque change at elbow and shoulder joints. The patients² deficit in generating appropriate levels of muscular force were prominent during two different phases of the pointing movement. Peak muscular forces at the elbow were reduced during the initial phase of the movement when simulta- neous shoulder joint flexion generated an extensor influence upon the elbow joint. When attempting to terminate the movement, gravitational and dynamic interaction forces caused overshooting extension at the elbow joint. In normal subjects, muscular torque patterns at shoulder and elbow joint were synchronized in that peak flexor and extensor muscular torques occurred simultaneously at both joints. This temporal pattern of muscular torque generation at shoulder and elbow joint was preserved in patients. Our data suggest that an impairment in generating sufficient levels of phasic muscular torques significantly contributes to the patients² difficulties in controlling the mechanical consequences of dynamic interaction forces during multijoint movements.
Keywords: Cerebellar ataxia ´ Limb movements ´ Dynamics ´ Human
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Ackermann,H., Konczak, J.,
& Hertrich, I. (1997). The temporal control of repetitive articulatory
movements in Parkinson's disease. Brain and Language, 56(2),
312-319
Abstract: Recent clinical data indicate that internal cueing mechanisms
required for the triggering of movement sequences are impaired in Parkinson's
disease (PD). Nevertheless, most PD subjects produce maximal syllable repetition
rates similar to those observed in healthy control individuals during oral diadochokinesis
tasks. There is some evidence that tremor oscillations may pace repetitive movements
in Parkinsonians giving rise to hastening phenomena. Conceivably, the performance
of PD patients in syllable repetition tasks thus reflects a specific timing deficit,
i.e., articulatory hastening. It is the aim of the present study to investigate
the contribution of speech hastening to oral diadochokinesis in the presence of
internal and external cues. By means of an optoelectric movement analysis system,
the displacements of the lips during repetitions of the syllable /pa/ were recorded
in two akinetic rigid PD individuals. Subjects were asked to synchronize labial
diadochokinesis to sequences of periodic acoustic stimuli (2.5 6 Hz). One of the
PD patients showed speech hastening, i.e., he produced repetitions of 8 to 9 Hz
whenever stimulus frequencies exceeded 4 Hz. The other Parkinsonian adequately
matched the stimulus frequencies required. However, she achieved a higher diadochokinesis
rate in the matching task than under the instruction to repeat ''as fast as possible.''
Thus, the presence of an external cue improved performance. In conclusion, our
data indicate two deficits of the temporal control of repetitive articulatory
gestures in PD: speech hastening and impaired self paced sequencing. These two
pathomechanisms may allow to reconcile the controversial findings on oral diadochokinesis
in PD reported SO far.
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Kalveram, K.Th.
(1997) Zur Theorie und Therapie des Stotterns.
Sprache - Stimme - Gehör , 21, 130-139.
Abstract:
Speaking is considered a sensorimotor and stuttering a neuropsychological disturbation of speaking. This suggests an explanation of stuttering consequently based on control theoryand related issues. The main components of the presented theory can be traced back to information thory (regards speaking as parallel to serial transformation, with the vocal nucleus used as the synchronization signal), control theory (regards speaking as tool use, demanding the inversion of the tool transformation), theory of motor learning (assumes auto-imitationas a means to aquire the inverse tool transformation, which however leads to an 'ill-posed problem' causing misguided learning), linguistics (draws attention to the double function of the vocal nucleus as synchronization signal and prosodic carrier), developmental psychology (points to the rearrangement of the prosodic flow, and therefore also fo the neural speech controller at an age of about four years), and the rpoperties of audio-phonatoric coupling (indicating that stressed and unstressed syllables require different types of control). Simulations using scenarios reflecting distinct kinds of stuttering show, that the derived model tends to iterate syllables respectively parts of syllables, which follows the first auto-immitation process establishing speaking basically, which however has been misguided. Consequences concerning basic therapeutical interventions in stuttering are shortly discussed.
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Karnath, H.-O., Dick, H. & Konczak, J. (1997).
Kinematics of goal-directed arm movements in neglect: control of hand in space.
Neurophysiologica, 35(4), 435-444.
Abstract: The present study investigated unrestrained, three-dimensional
arm movements during goal-directed pointing in five patients with clinically
manifest neglect to targets positioned either in the center of the left and
right hemispace. Five patients with unilateral right hemisperic lesions without
neglect and six healthy subjects served as controls. All subjects were able
to point to these targets. Terminal accuracy of pointing did not differ between
the three groups along the horizontal, vertical and anterior-posterior axis.
Subjects' hand trajectories did not reveal direction-specific deviations from
a straightline hand path. Our data show that deviations in the trajectories
toward the ipsilesional side are not characteristic for patients with spatial
neglect. We argue that exploratory and goal-directed motor behavior might not
share the same egocentric, body-centered reference frame. A spatial reference
frame for exploratory behavior is disturbed in patients with neglect resulting
in a failure to explore the contralesional part of space by eye or limb movements.
Its failure does not induce a spatial bias in hand trajectory formation during
goal-directed arm movements in peripersonal space. Such deviations of reaching
or pointing rather seem to be characteristic for patients with optic ataxia.
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Konczak,J., Ackermann, H., Hertrich, I., Spieker, S.,
& Dichgans, J. (1997).
Abstract:Control of repetitive lip and finger movements in Parkinson's
disease: influence of external timing signals and simultaneous executuion on
otor performance. Movement Disorders, 12(5), 665-676. This study addresses the
question whether external timing signals and/or simultaneous rhythmic movements
of other limbs can alleviate sequencing motor deficits associated with Parkinson's
disease (PD). Subjects performed rhythmic lip and finger movements simultaneously
or in isolation. In addition, they had to self-pace their movements or match
them to an external signal. Our results are summarized as follows: First, 7
out of 12 patients showed adequate mean repetition rates, that is, they fulfilled
the task requirements on a global scale. The remaining 5 patients showed various
degrees of hastened responses and were not fully able to synchronize their movements
to an external pacing signal. Second, PD patients exhibited hypometria in the
finger, but not in the lip movements. Their movements were not abnormally slowed,
but peak velocity was appropriately scaled even to reduced movement amplitudes.
Third, mean repetition rates, stability of frequency response, and kinematics
did not differ between conditions of external or internal stimulation within
the PD group, but were different from the control group performance. Fourth,
kinematic measures were not improved during dual-task execution. PD patients
were not able to maintain a 1:1 rhythm between effectors but drifted to various
modes of relative co-ordination. The incidence of hastening increased during
simultaneous motor execution. We conclude that the use of external pacing signals
might aid movement initiation of PD patients, but does not improve their temporal
or spatial coordination when generating repetitive movements. Simultaneous execution
did not improve motor performance but was actually detrimental in patients prone
to hastening.
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Konczak,J., Borutta, M., & Dichgans, J. (1997).
Development of goal-directed reaching in infants: II. Learning to produce task-adequate
patterns of joint torque. Experimental Brain Research, 113,
465-474.
Abstract: Nine young infants were followed longitudinally from 4 to
15 months of age. They performed multijoint reaching movements to a stationary
target presented at shoulder height. Time position data of the hand, shoulder,
and elbow were collected using an optoelectronic measurement system. In addition,
we recorded electromyographic activity (EMG) from arm extensors and flexors.
This paper documents how control problems of proximal torque generation may
account for the segmented hand paths seen during early reaching. Our analysis
revealed the following results: first, muscular impulse (integral of torque)
increased significantly between the ages of 20 (reaching onset) and 64 weeks.
That is, as infants got older they produced higher levels of mean muscular flexor
torque during reaching. Data were normalized by body weight and movement time,
so differences are not explained by anthropometric changes or systematic variations
in movement time. Second, while adults produced solely flexor muscle torque
to accomplish the task, infants generated flexor and extensor muscle torque
at shoulder and elbow throughout a reach. At reaching onset more than half of
the trials revealed this latter kinetic profile. Its frequency declined systematically
as infants got older. Third, we examined the pattern of muscle coordination
in those trials that exhibited elbow extensor muscle torque. We found that during
elbow extension coactivation of flexor and extensor muscles was the predominant
pattern in 67% of the trials. This pattern was notably absent in comparable
adult reaching movements. Fourth, fluctuations in force generation, as measured
by the rate of change of total torque (NET) and muscular torque (MUS), were
more frequent in early reaching (20 28 weeks) than in the older cohort (52 64
weeks), indicating that muscular torque production became increasingly smoother
and task efficient. Our data demonstrate that young infants have problems in
generating smooth profiles of proximal joint torques. One possible reason for
this imprecision in infant force control is their inexperience in predicting
the magnitude and direction of external forces. That infants learned to consider
external forces is documented by their increasing reliance on these forces when
performing voluntary elbow extensions. The patterns of muscle coordination underlying
active elbow extensions were basically the same as during the prereaching phase,
indicating that the formation of functional synergies is based on a basal repertoire
of innervation patterns already observable in very early, spontaneous movements.
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Konczak, J., & Dichgans, J. (1997). The development toward stereotypic arm
kinematics during reaching in the first three years of life. Experimental
Brain Research, 117, 346-354.
Abstract: We recorded reaching movements from nine infants longitudinally
from the onset of reaching (5th postnatal month) up to the age of 3 years. Here
we analyze hand and proximal joint trajectories and examine the emerging temporal
coordination between arm segments. The present investigation seeks a) to determine
when infants acquire consistent, adult-like patterns of multi-joint coordination
within that three-year period, and b) to relate their hand trajectory formation
to underlying patterns of proximal joint motion (shoulder, elbow). Our results
show: First, most kinematic parameters do not assume adult-like levels before
the age of 2 years. At this time, 75% of the trials reveal a single peaked velocity
profile of the hand. Between the second and third year of life "improvements"
of hand- or joint-related movement units are only marginal. Second, infant motor
systems strive to obtain velocity patterns with as few force reversals as possible
(uni- or bimodal) at all three limb segments. Third, the formation of a consistent
interjoint synergy between shoulder and elbow motion is not achieved within
the first year of life. Stable patterns of temporal coordination across arm
segments begin to emerge at 12 to 15 months of age and continue to develop up
to the third year. In summary, the development toward adult forms of multi-joint
coordination in goal-directed reaching requires more time than previously assumed.
Although infants reliably grasp for objects within their workspace three to
four months after the onset of reaching, stereotypic kinematic motor patterns
are not expressed before the second year of life.
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Cress, M.E., Conley, K.E., Balding, S.L., Hansen-Smith,
F. & Konczak, J. (1996). Functional training: muscle structure, function,
and performance in older women. Journal of Orthopaedic and
Sports Physical Therapy, 24(1), 4-10.
Abstract: Response to physical training at the cellular and whole muscle
level has been established in older adults. However, the underlying molecular
mechanism responsible for change has not been described nor have the relationships
between change in muscle structure and functional performance been established.
The purpose of this research study is to evaluate the changes of muscle ultrastructure,
muscle strength, and whole body functional performance as a result of a functionally
directed exercise program (stair climbing).Woman (65-83 years old) selected
either the control (no exercise; N = 6) or exercise (N = 7) group. The 1-year
functionally based exercise program was both aerobic ( 75% heart rate reserve)
and resistive (weight stair climbing). Muscle ultrastrucutre, determined by
quantitative morphometry of the vastus lateralis tissue, and maximal step-height
achieved by each subject were related to isokinetic strength and muscle morphology.
Change in muscle contractile protein was the underlying basis for change in
thigh strength which, in turn, was the basis for functional performance. These
data provide evidence that, in older women, a mild functionally based training
program results in improved muscle structure and performance of the lower body.
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Jäncke, L., & Steinmetz, H. (1995). Hand motor
performance in monozygotic twins. Cortex, 31, 779-785
Abstract: To determine whether the absolute degree of asymmetry of
hand motor performance (irrespective of direction of this asymmetry) may have
a heritable component we examined 20 pairs of monozygotic (MZ) twins of whom
10 pairs were concordantly right-handed (MZ-RR) and 10 pairs discordant for
handedness (MZ-RL). The tests comprised measurements of the maximum left and
right hand tapping rate as well as a paper-and-pencil test of left and right
hand motor proficiency. Intraclass correlations within MZ-RR and MZ-RL for absolute
degree of hand motor asymmetry were not significant. In contrast, significant
intrapair correlations emerged for overall hand motor performance, a measure
unrelated to laterality. These results demonstrate that at least in MZ twins
the degree of hand motor asymmetry is mainly determined by non-genetic factors,
whereas overall hand motor skill is more likely to be influenced by the genome.
In addition, the lack of a difference in overall hand motor performance between
MZ twins and 40 singletons studied as controls would not support hypotheses
explaining behavioural asymmetry in twins, or their discordance for asymmetry,
by developmental dysfunction.
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Jäncke, L., Hefter, H., & Kalveram, K.Th. (1995).
Fast finger extensions are slower in stutterers than in nonstutterers. Perceptual
and Motor Skills, 80, 1103-1113.
Abstract: 10 adult stutterers and 10 nonstutterers were required to
extend as fast as possible their right and left index fingers under isometric
conditions in response to an auditory signal. Force developed during finger
extension was measured continuously during each trial. From these force records
reaction time, contraction time, and peak force were measured. For stutterers,
contraction times were longer (about 36 msec.) than for nonstutterers. Possible
reasons for this result are discussed.
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Konczak, J., Borutta, M., Topka, H., & Dichgans, J.
(1995). Development of goal-directed reaching in infants: Hand trajectory formation
and joint force control. Experimental Brain Research, 106,
156-168.
Abstract: Nine young infants were followed longitudinally from 4 to
15 months of age. We recorded early spontaneous movements and reaching movements
to a stationary target. Time-position data of the hand (endpoint), shoulder,
and elbow were collected using an optoelectronic measurement system (ELITE).
We analyzed the endpoint kinematics and the intersegmental dynamics of the shoulder
and elbow joint to investigate how changes in proximal torque control determined
the development of hand trajectory formation. Two developmental phases of hand
trajectory formation were identified: a first phase of rapid improvements between
16 and 24 weeks of age, the time of reaching onset for all infants. During that
time period the number of movement units per reach and movement time decreased
dramatically. In a second phase (28-64 weeks), a period of "fine-tuning" of
the sensorimotor system, we saw slower, more gradual changes in the endpoint
kinematics. The analysis of the underlying intersegmental joint torques revealed
the following results: first, the range of muscular and motion-dependent torques
(relative to body weight) did not change significantly with age. That is, early
reaching was not confined by limitations in producing task-adequate levels of
muscular torque. Second, improvements in the endpoint kinematics were not accomplished
by minimizing amplitude of muscle and reactive torques. Third, the relative
timing of muscular and motion-dependent torque peaks showed a systematic development
toward an adult timing profile with increasing age. In conclusion, the development
toward invariant characteristics of the hand trajectory is mirrored by concurrent
changes in the control of joint forces. The acquisition of stable patterns of
intersegmental coordination is not achieved by simply regulating force amplitude,
but more so by modulating the correct timing of joint force production and by
the system's use of reactive forces. Our findings support the view that development
of reaching is a process of unsupervised learning with no external or innate
teacher prescribing the desired kinematics or kinetics of the movement.
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Müller, F., & Konczak, J. (1995). Neuromotorische
Kontrolle bei Funktionsstörungen der Basalganglien und des Cerebellums. Psychologische
Beiträge, 37, 664-686.
Abstract: Die Rolle der Basalganglien und des Cerebellums bei der Planung
und Ausfuehrung von willkuerlichen Extremitaetenbewegungen werden beschrieben.
Aus der Dysfunktion dieser motorischen Subsysteme resultieren charakteristische
neurologische Syndrome. Stoerungen der Basalganglien werden exemplarisch am
Parkinson-Syndrom diskutiert, das durch die Kardinalsymptome Akinese, Rigor
und Tremor gekennzeichnet ist. Bei den Kleinhirnstoerungen steht die Dyskoordination
der Bewegung (Ataxie) im Vordergrund. Diese aeussert sich klinisch in einem
ungeordneten Zusammenspiel einzelner Bewegungsablaeufe und kann sich betont
in der Augen-, Sprech- und Extremitaetenmotorik zeigen. Ausgehend davon, dass
die Beteiligung neuronaler Strukturen an der Generierung spezifischer Innervierungsmuster
fuer Extremitaetsbewegungen kompliziert ist, wird die einfache Zuordnung von
Lokalisation und Funktion, die klassische Modellvorstellungen suggerieren, diskutiert.
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Konczak, J. (1994). Effects of optic flow on the
dynmaic balance of human gait in young and older adults. Journal
of Motor Behavior, 26(3), 225-236.
Abstract: Investigated the effects of imposed optic flow on gait in
six young (mean age 22.1 years) and six healthy older (mean age 74.0 years)
adults. Subjects were exposed to various patterns of optic flow while walking
in a moving hallway: eyes open, eyes closed, global (movement of whole room)
backward flow, global forward flow, peripheral forward flow (side wall movement
only), and central forward flow (front wall movement only). Results showed few
cases of impaired postural control (staggers, parachute reactions) and no falls
were recorded. Kinetic patterns of gait were altered when vision was absent
or when inconsistent optic flow was presented: 92 percent of the subjects' mean
step velocity differed from that under normal vision. Compared with imposed
central flow, imposed peripheral optic flow had a greater impact on kinematic
changes than central flow. Global backward flow tended to slow down step velocity;
step velocity was increased under forward flow. No significant differences were
found between the two age groups with regard to sensitivity to manipulations
of optic flow, although within-group variability was larger in the kinematic
measures for the older group. It is concluded that in an uncluttered environment,
imposed optic flow has a modulating rather than a destabilizing effect on human
locomotion. (Journal/Martha Keating - ZPID)
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Kalveram, K.-Th.
(1993). Power series and neural-net computing.
Neurocomputing,
5, 165-174.
Abstract: A power series expansion is represented by a three-layer feedforward network, the number of nodes in the hidden layer corresponding to the number of terms retained in the series, and the synaptic weights in the hidden layer representing the exponents used. The activation functions addressed to input, hidden and output nodes are log, anti-log and linear. The training rules applied to determine the weights of the output layer, that means the optimal power series coefficients, are the ordinary delta rule and a least squares based simultaneous leaming rule called LSQ-ruIe. The performance of this network is compared to a three-layer network with the same number of nodes but sigmoidal activation functions, trained by backpropagation. With respect to the selected four functions to be approximated, the delta rule yields an output error considerably less than the error of the sigmoid network. Best results, however, are obtained combining the power network with the LSQ-ruIe. In this case, 'performance related to number of training trials' is - on average - about 30,000 times better, compared to backpropagation.
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Kalveram, K.-T. (1993). A neural-network model
enabling sensorimotor learning: application to the control of arm movements
and some implications for speech-motor control and stuttering. Psychological
Research, 55(4), 299-314.
Abstract: Low-level motor control is defined as adapting an organism
to the unique physical properties of its own limbs. The two-jointed arm serves
to exemplify that effective low-level motor control demands a neurally medicated
inversion of the dynamics, as well as of the kinematics, of a limb system. Reflex-like
processing--that is, feedforword of either actual or predicted proprioceptive
signals--is thereby assumed to be the principle of the dynamics control. As
regards speech-motor control, the overall tool transformation is assumed to
transform the force pattern of the articulatory muscles into speech sounds.
Like the arm model, the vocal-tract transformation thus defined is also divided
into two parts, namely the transformation relating the muscle forces to the
mechanospatial states of the vocal tract (which is analogous to the forward
dynamics including natural interarticulatory couplings), and the transformation
relating the mechanospatial states to the speech sounds. Low-level speech-motor
control, then, needs to invert both transformations, each of which can be learned
by means of the self-imitation algorithm. Erroneous learning can fail to decouple
interarticulatory coupling and therefore lead to abnormal feedback loops through
the reflex-like operating neural network, which in turn can cause stuttering
if audiophonatoric coupling is involved in learning.
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Kalveram, K.-T. (1992). A neural network model
rapidly learning gains of reflexes necessary to adapt to an arm's dynamics.
Biological Cybernetics, 68(2), 183-91.
Abstract: Effects of dynamic coupling, gravity, inertia and the mechanical
impedances of the segments of a multi-jointed arm are shown to be neutralizable
through a reflex-like operating three layer static feedforward network. The
network requires the proprioceptively mediated actual state variables (here
angular velocity and position) of each arm segment. Added neural integrators
(and/or differentiators) can make the network exhibit dynamic properties. Then,
actual feedback is not necessary and the network can operate in a pure feedforward
fashion. Feedforward of an additional load can easily be implemented into the
network using "descendent gating", and a negative feedback control loop added
to the feedforward control reduces errors due to external noise. A training,
which combines a least squared error based simultaneous learning rule (LSQ-rule)
with a "self-imitation algorithm" based on direct inverse modeling, enables
the network to acquire the whole inverse dynamics, limb parameters included,
during one short training movement. The considerations presented also hold for
multi-jointed manipulators.
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Kalveram, K.-T. (1991). Controlling the dynamics
of a two-joined arm by central patterning and reflex-like processing. A two-stage
hybrid model.Biolocical Cybernetics, 65(1), 65-71.
Abstract: It is demonstrated, that a two-joined arm performing goal
directed movements is controllable (a) by two central pattern generators (CPG)
representing sampled data control, each referring to one joint, initiated for
exactly one period, and producing the angular movement width about this joint,
and (b) by reflex-like processes operating continuously with respect to time.
The latter eliminate the effects of dynamic coupling, gravity, inertia, and
mechanical impedance on the movement by 'proprioceptive feedforward' of position,
velocity and acceleration signals, thus enabling the CPGs to handle the arm
segments as if they were independent and free from forces. Higher ordered centers
(with respect to the CPGs) therefore only need to control the kinematics, not
dynamics, of the arm.
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Kalveram, K.-T.(1991). Pattern generating and
reflex-like processes controlling aiming movements in the presence of inertia,
damping and gravity. A theoretical note. Biological Cybernetics,
64(5), 413-9.
Abstract: A model is proposed, in which goal-directed movements of the
forearm are controlled by a central pattern generator (CPG) initiated for exactly
one period, and by reflex-analogous processes. Movement width is proportional
to the amplitude factor of the CPG's output, and to the square of the CPG's
period length. The period duration can be freely selected, thus enabling the
CPG to accommodate its time scale to the period of others CPG's. Parameters
which influence movement accuracy can be adjusted by means of closed control
loop, which are discrete with respect to time: The time unit corresponds to
the period of the CPG. For instance, momentum adjustment balances the CPG in
such a manner that the velocity of the arm becomes zero on termination of the
period, while gain adjustment serves to attain a correct movement length in
the presence of an inertial load. Friction, stiffness and gravitational force
are neutralized by additional reflex-type processes, interpretable as positive
feedback loops with adjustable gain factors, using position and velocity signals.
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Kalveram, K.Th.
(1981). Erwerb sensumotorischer Koordinationen unter störenden Umwelteinflüssen: Ein Beitrag zum Problem des Erlernens von Werkzeuggebrauch. In L. Tent (Hrsg.),
Erkennen, Wollen, Handeln. Festschrift für Heinrich Düker zum 80. Geburtstag
(S. 336- 348). Göttingen: Hogrefe
Abstract: In einem Tracking-Experiment führte die Experimentalgruppe (6 Vpn) die erste Hälfte des Versuchs mit ungestörter Rückmeldung und die zweite Hälfte mit gestörter Rückmeldung (Störgrößenaufschaitung) durch. Die Kontrollgruppe (6 Vpn) führte den gesamten Versuch mit gestörter Rückmeldung durch. Regelstrecke (,,Werkzeug") war ein Totzeitelement mit 0,5s Verzögerungszeit. Obwohl die Kontrollgruppe mehr Übung im Tracking bei Störgrößenaufschaltung hatte, war die Steuerleistung in der zweiten Versuchshälfte bei der Experimentalgruppe signifikant besser als bei der Kontrollgruppe. Dieses Ergebnis kann durch die Annahme erklärt werden, daß durch eine gestörte Rückmeldung die Ausbildung motorischer Programme erschwert wird. Dieser Gesichtspunkt wird mit Bezug auf eine allgemeine Modellvorstellung über motorisches Lernen eingehend diskutiert.
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Merz, F., Kalveram, K.-Th., Huber, K.
(1981). Der Einfluß kognitiver Faktoren auf Steuerleistungen. In L. Tent (Hrsg.), Erkennen, Wollen, Handeln.
Festschrift für Heinrich Düker zum 80. Geburtstag
(S. 327-335). Göttingen: Hogrefe.
Abstract: Um den Einfluß kognitiver Faktoren auf Steuerleistungen zu überprüfen, wurde bei einer Folgetrackingaufgabe mit Kraftsteuerung dafür gesorgt, daß die Vpn entweder wußten, daß sie über ein Steuerrad bedienten oder aber, daß sie das nicht wußten. Es zeigte sich, daß dieses Wissen die Leistung beeinflußt. Zur Erklärung wird angenommen, daß die Kenntnis der Situation dazu führen kann, daß geeignete, früher erlernte Bewegungsprogramme zur Bewältigung der gestellten Aufgabe herangezogen werden. Der Versuch und seine Interpretation wurden in eine allgemeine Theorie eingeordnet.
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