Figure 2.

Illustration of a typical stimulation experiment and the effect of stimulation on psychophysical performance. (a) Individual saccade vectors obtained with suprathreshold stimulation at an FEF site in monkey A, illustrating how the MF was mapped. Vector traces show eight saccades evoked in eight trials at a current of 38 μA. (b) The proportion of evoked saccades was measured at different current levels, both before (●) and after (○) the attention task, to determine the current threshold. The open arrowhead indicates the subthreshold current (13 μA) used during the spatial attention task. (c) Staircase data and luminance change threshold estimates (% contrast) obtained with (●) and without (○) microstimulation (stimulation onset asynchrony = 175 ms). Each staircase plot shows the relative progress made by the monkey and the asymptotic level reached after 11 blocks of testing.