Cerebral processes during visuo-motor imagery of hands.

We investigated the role of cerebral motor structures during mental hand rotation. Neural activity was measured with event-related potentials (ERPs) in 16 healthy participants while they performed handedness judgments of visually presented hands. Mental rotation was associated with ERP amplitude modulations as early as 170 ms but most strongly during a time window of about 600-800 ms. Source analysis of ERPs during these time windows indicated generators in bilateral extrastriate and parietal cortices. The results do not support a direct involvement of anterior motor cortices in the neural computations underlying mental rotation. However, motor regions may play a role in providing ongoing kinaesthetic feedback during mental rotation or in checking the results of the imagined transformation.