MOTOR CORTEX AND HAND MOTOR-SKILLS - STRUCTURAL COMPLIANCE IN THE HUMAN BRAIN

Recent studies in humans and nonhuman primates have shown that the fun ctional organization of the human sensorimotor cortex changes followin g sensory stimulation or following the acquisition of motor skills. It is unknown whether functional plasticity in response to the acquisiti on of new motor skills and the continued performance of complicated bi manual movements for years is associated with structural changes in th e organization of the motor cortex. Professional musicians, especially keyboard and string players, are a prototypical group for investigati ng these changes in the human brain. Using magnetic resonance images, we measured the length of the posterior wall of the precentral gyrus b ordering She central sulcus (intrasulcal length of the precentral gyru s, ILPG) in horizontal sections through both hemispheres of right-hand ed keyboard players and of an age- and handedness-matched control grou p. Lacking a direct in vivo measurement of the primary motor cortex in humans, we assumed that the ILPG is a measure of the size of the prim ary motor cortex. Left-right asymmetry in the ILPG tvas analyzed and c ompared between both groups. Whereas controls exhibited a pronounced l eft-larger-than-right asymmetry, keyboard players had more symmetrical ILPG, The most pronounced differences in ILPG between keyboard player s and controls were seen in the most dorsal part of the presumed corti cal hand representation of both hemispheres. This was especially true in the nondominant right hemispheres. The size of the ILPG was negativ ely correlated with age of commencement of musical training in keyboar d players, supporting our hypothesis that the human motor cortex can e xhibit functionally induced and long-lasting structural adaptations. ( C) 1997 Wiley-Liss, Inc.