ASYMMETRY IN THE HUMAN MOTOR CORTEX AND HANDEDNESS

Handedness is one of the most obvious functional asymmetries, but its relation to an anatomical asymmetry of the hand representation area in the motor cortex has not been demonstrated. This would be a crucial t est for the hypothesis of structure-function correlation in cortical m otor organization. Using magnetic resonance morphometry, we show for t he first time that the depth of the central sulcus is related to hande dness. In right-handers, the left central sulcus is deeper than the ri ght, and vice versa in left-handers. Macro-structural asymmetry is com plemented by a microstructural left-larger-than-right asymmetry in neu ropil volume (i.e., tissue compartment containing dendrites, axons, an d synapses) in Brodmann's area 4. These asymmetries suggest that hand preference is associated with increased connectivity (demonstrated by an increased neuropil compartment in left area 4) and an increased int rasulcal surface of the precentral gyrus in the dominant hemisphere. ( C) 1996 Academic Press, Inc.