Cortical spread as a function of frequency. A, Median LFP cortical spread for Monkey 3. The RF sizes (in degrees) were first estimated at each frequency and then the model was applied to obtain the cortical spread (in millimeters). B, Median LFP cortical spread across three monkeys (Monkeys 1–3; for Monkey 4,the model could not be applied; data from Monkey 5 were excluded because of the presence of noise at high frequencies). C, D, Median ECoG cortical spread for Monkey 3 and population data across four monkeys (Monkeys 1–4). The SEs (after bootstrapping) are shown in lighter shades.