Fig. 4.

Time-frequency analysis of the visual gamma response in V1/V2 and V4. The virtual sensor data were reconstructed at the left and right peak voxel locations in V1/V2 (A, B, C and G) and in left and right V4 (D, E, F and H). The data were analysed separately for attended (A, D, red line in G and H) and ignored gratings (B, E, blue line in G and H) and compared statistically with a cluster-based permutation test (C, F). The clusters (p < 0.05, corrected) were highlighted by changing the transparency value of the colours in the plots. Note that one of the two positive clusters in C (500–800 ms, ∼48–60 Hz, p = 0.018) and one of the two clusters in F (∼300–500 ms, ∼50–60 Hz, p = 0.092) are reported for illustrative purposes only. The thick lines in G and H represent the percentage change in gamma power (averaged between 30 and 70 Hz) and the shaded areas represent ±1 SEM, across participants.