The precuneus in motor imagery: a magnetoencephalographic study.

Magnetoencephalography was applied to subjects who imagined themselves hurdling in self-centered space. In three of six subjects all 300 trials in the motor imagery condition revealed the precuneus dipole. When we divided the 300 trials into four overlapping blocks (one block = 150 trials), all six subjects showed precuneus activity. The latency of the precuneus dipole was about 220 ms. We suggest that the precuneus activity during motor imagery involves retrieval of spatial information and/or setting up spatial attributes. Only in one subject but twice, the current dipole located in the supplementary motor area was observed 60 ms after activation of the precuneus, which suggests that the signal from the precuneus for motor imagery is transferred to the supplementary motor area.