Imitation and matching of hand and finger postures

Converging evidence from patients with unilateral brain lesions, from a pat ient with callosal disconnection, and from functional imaging in healthy su bjects suggests different competencies of both hemispheres for imitation an d matching of hand and finger postures. Whereas the left hemisphere is full y competent for processing hand postures, an additional right hemisphere co ntribution is needed for finger postures. I propose that the left hemispher e is responsible for coding gestures with reference to knowledge about the structure of the human body, whereas a right hemisphere contribution is nee ded for visuospatial exploration and analysis of gestures. Single case stud ies of patients with visuoimitative apraxia and results of functional imagi ng suggest a prominent role for left area 40 for body-part coding. Addition al activation of left MT/V5 in the functional neuroimaging study may be rel ated to processing of the motion implied by the gesture which is presented as a static image. (C) 2001 Academic Press.