This Article Full Text (PDF) All Versions of this Article: 1545968307311103v1 22/4/374    most recent References Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Hermsdörfer, J. Articles by Nowak, D. A. Search for Related Content PubMed PubMed Citation Articles by Hermsdörfer, J. Articles by Nowak, D. A. Social Bookmarking                   What's this?

Preserved and Impaired Aspects of Feed-Forward Grip Force Control After Chronic Somatosensory Deafferentation

Clinical Neuropsychology Research Group, Academic Hospital München-Bogenhausen, Munich, Germany, Joachim.Hermsdoerfer{at}extern.lrz-muenchen.de

Z. Elias, MD

Clinical Neuropsychology Research Group, Academic Hospital München-Bogenhausen, Munich, Germany

J. D. Cole, DM

University of Southhampton, Great Britain

B. M. Quaney, PT, PhD

University of Kansas Medical Center, Kansas City, KS, USA

D. A. Nowak, MD, PhD

Department of Neurology, University Hospital Cologne, Cologne, Germany

Background. Although feed-forward mechanisms of grip force control are a prerequisite for skilled object manipulation, somatosensory feedback is essential to acquire, maintain, and adapt these mechanisms. Objective. Individuals with complete peripheral deafferentation provide the unique opportunity to study the function of the motor system deprived of somatosensory feedback. Methods. Two individuals (GL and IW) with complete chronic deafferentation of the trunk and limbs were tested during cyclic vertical movements of a hand-held object. Such movements induce oscillating loads that are typically anticipated by parallel modulations of the grip force. Load magnitude was altered by varying either the movement frequency or object weight. Results. GL and IW employed excessive grip forces probably reflecting a compensatory mechanism. Despite this overall force increase, both deafferented participants adjusted their grip force level according to the load magnitude, indicating preserved scaling of the background grip force to physical demands. The dynamic modulation of the grip force with the load force was largely absent in GL, whereas in IW only slower movements were clearly affected. Conclusions. The authors hypothesize that the deafferented patients may have utilized visual and vestibular cues and/or an efferent copy of the motor command of the arm movement to scale the grip force level. Severely impaired grip force-load coupling in GL suggests that sensory information is important for maintaining a precise internal model of dynamic grip force control. However, comparably better performance in IW argues for the possibility that alternative cues can be used to trigger a residual internal model.

Key Words: Feed-forward and feed-back motor control • Grip force • Sensory afferents • Deafferentation • Internal model.

This version was published on July 1, 2008

Neurorehabilitation and Neural Repair, Vol. 22, No. 4, 374-384 (2008)
DOI: 10.1177/1545968307311103


CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?