title: The role of cutaneous sensation in the motor function of the hand.
abstract: We studied the effect of abolishing cutaneous sensation (by infiltrating local anaesthetic around the median nerve at the wrist) on the ability of 10 healthy volunteers (a) to maintain a submaximal isometric pinch-grip force for 30 s without visual feedback, and (b) to perform a fine finger-manipulation 'handwriting' task. Blocking cutaneous sensation had no effect on ability to maintain pinch force, suggesting that muscle afferents have the major role in force-control feedback. However, a near-linear fall in force, present with or without block (mean slope=-1.3+/-0.2% s(-1)), which cannot be attributed to motor fatigue, reveals a shortcoming of the afferent feedback system. Blocking cutaneous sensation did impair ability to perform the more demanding writing task, as judged by an 18+/-6% increase in the length of the path between target points, a 22+/-9% increase in the duration of the movement and a 63+/-24% in 'normalised averaged rectified jerk', an averaged time-derivative of acceleration (all significantly nonzero, P < 0.04). These experiments demonstrate the relative importance of muscular and cutaneous afferent feedback on two aspects of hand performance, and provide a way to quantify the deficit resulting from the lack of cutaneous sensation.
authors.affiliation: Department of Musculoskeletal Science, University of Liverpool, 4Z Link, Prescot Street, Liverpool L69 3GA, UK. ayman_ebied@hotmail.com
authors.forename: Ayman M
authors.initials: AM
authors.lastname: Ebied
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Kemp
authors.forename: Simon P
authors.initials: SP
authors.lastname: Frostick
mesh_terms: D004576:Electromyography; D005260:Female; D006225:Hand / Q000294:innervation*; D018737:Hand Strength / Q000502:physiology*; D006236:Handwriting; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007699:Kinesthesis / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D012683:Sensory Deprivation / Q000502:physiology; D012867:Skin / Q000294:innervation*; D014110:Touch / Q000502:physiology*