Cerebral organization of motor imagery: Contralateral control of grip selection in mentally represented prehension

The principle of contralateral organization of the visual and motor systems was exploited to investigate contributions of the cerebral hemispheres to the mental representation of prehension in healthy, right-handed human subj ects. Graphically rendered dowels were presented to either the left or righ t visual field in a variety of different orientations, and times to determi ne whether an underhand or overhand grip would be preferred for engaging th ese stimuli were measured. Although no actual reaching movements were perfo rmed, a significant advantage in grip-selection time was found when informa tion was presented to the cerebral hemisphere contralateral to the designat ed response hand. Results are consistent with the position that motor image ry recruits neurocognitive mechanisms involved in movement planning. More p recisely, these findings indicate that processes within each cerebral hemis phere participate in mentally representing object-oriented actions of the c ontralateral hand.