Figure 10.

Source-imaged EEG measurements of the attentional modulation index. A, The modulation index was calculated as the increase in response of the attended over the unattended condition, relative to the sum of the attended and unattended condition. Modulation in V1 and area hV4 show a similar trend to the pattern obtained from psychophysics for orientation discrimination: populations tilted 20° away from the target orientation are selectively modulated in the orientation task, while area V3a does not show such a trend (*p < 0.05, **p < 0.01). For contrast discrimination, there is no discernable pattern across orientation in any of the ROIs. B, The data are replotted to isolate the effect of feature attention in each cortical area. Feature attention is the difference between the attend-orientation and attend-contrast conditions. Only area V1 shows clear peak at 20° in the orientation tuning function.