Figure 2.

Hand representation in area 1. Distribution of neural activity on 2 different arrays (array of monkey A and the first array of monkey B in the left and right columns, respectively) evoked by stimulation at 3 skin locations (rows). The neural activity is integrated over 1200 ms following the onset of a 2-mm, 10-mm/s indentation (lasting a total of 1 s) delivered to the location indicated by an arrow on the hand diagram to the left of the heat map. The colored dot on the array represents the location of the hotzone (highest responding) electrode for that skin location. As the site of stimulation shifts in the ulnar direction (red to blue to green), the hotzone of cortical activity shifts in the medial direction, consistent with the previously established somatotopy of the hand in area 1. In the hand diagram to the left of each heat map, each colored dot represents a different site of stimulation, with the dot radius proportional to the response of the electrode marked on the array when that skin location was stimulated. The response at the electrode tends to decrease as the stimulation site moves farther from the arrow, as expected. Responses are averaged over 75+ trials in each condition.