Fig. 5.

Current source density (CSD) activity. A: scalp topographies of CSD activity time-locked to target onset in the cued and uncued conditions for right arm reaching. In the cued condition, a negativity over left precentral regions and a positivity over left parietal regions are evident at ∼375 ms. In the uncued condition, CSD activity at these scalp sites is delayed, with peaks at ∼475–525 ms. B: CSD traces of contralateral parietal and precentral electrodes in the cued and uncued conditions. Note that data for the 2 arms are collapsed into a single estimate (see materials and methods). RT, reaction time.