A sex difference in reliance on vision during manual sequencing tasks

The manual praxis system is a left-hemisphere based motor programming system that is involved in the selection of hand and arm movements and is particularly important for the control of movements made with minimal external sensory guidance. Few studies have explored the parameters surrounding normal praxic function, but preliminary data suggest that men may rely less heavily on praxic control than women. To further investigate this possibility, we tested healthy individuals on two tasks designed to recruit the praxis system and on a visually-guided control measure. Participants performed each task with vision and without. We hypothesized that, if men are less fully reliant on the praxis system than women, then their performance should be more adversely affected by the removal of vision on tasks that are ostensibly praxic. Consistent with this prediction, we found a significantly larger drop in men's scores than in women's when vision was occluded. Importantly, this pattern was selective to the praxic measures. In contrast, men were no more impaired by the loss of vision than were women on an externally-guided pegboard task. These findings may reflect an anatomical sex difference in the organization of the praxis system within the left cerebral hemisphere.