Abstract
It has been hypothesized that gamma-band oscillations (e.g, 25–80 Hz) of the electroencephalogram (EEG) support the active maintenance of representations in working memory. Consistent with this hypothesis, gamma-band activity has been reported during the retention interval of visual working memory tasks in humans. In the present study, we tested this hypothesis by recording EEG from surface electrodes on macaque monkeys during the memory retention of locations in the memory-guided saccade task. We found a decrease in gamma power evoked by the onset of the memory stimulus. However, the inconsistent increases in the gamma-band range relative to baseline were not associated with more accurate task performance when examined on a session-by-session basis. This is inconsistent with gamma activity being an effective mechanism of working memory maintenance. In addition, on a number of days we found a decrease in gamma-band power relative to the baseline during both the stimulus-evoked response and during the memory retention interval of this often-utilized working memory task. These findings show that gamma band activity unlikely to be related to spatial working memory retention macaque monkeys.
Supported by Robin and Richard Patton through the E. Bronson Chair of Neuroscience and grants T32-EY007135, F32-EY015043, RO1-EY08890, P30-EY08126, P30-HD015052, and a Vanderbilt University Discovery Grant.