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Abstract:
The human EEG shows short bursts of 40 Hz (gamma) activity
after auditory and visual stimulation. Human gamma activity has
been functionally correlated with perceptual binding, attending to
stimuli, and keeping stimuli in working memory. However, some
authors have failed to replicate these reports of human gamma
activity. We performed a visual detection task with stimuli that
varied in shape, size, contrast, and duration. Stimuli could be
either Kaniza squares or Kaniza triangles, large (subtending 5.4
degrees of visual angle) or small (subtending 1.8 degrees of visual
angle), high contrast (100%) or low contrast (50%), and long
duration (700 ms) or short duration (150 ms). This gave a total of
sixteen stimulus types. Varying sensory parameters led to different
levels of gamma activity. These results suggest that stimulus
parameters as well as task conditions influence the degree of gamma
activity recordable in the human EEG. Supported by NINDS grant
21135.
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