Fig. 3.

Data features of interest. The middle subpanel shows the gamma peak frequency as a function of the different contrast levels which were presented. Note that a gamma peak was not detected in the 0% contrast condition (no visual stimulation to the receptive field) nor reliably in the 0.05% contrast condition, and these are therefore omitted. The upper panel shows a U relationship between gamma peak frequency and power in the gamma band (30–80 Hz). The middle subpanel shows the relationship between contrast and gamma band power, for all nine experimental conditions.