Fig. 5.

Gamma power spectra and envelopes. Frequency spectra and power envelopes associated with the onset of noise and the transition to RIN. Power change is expressed relative to the baseline period before stimulus onset (i.e. normalised to spontaneous neural activity). a, b) Group level results from MEG virtual electrodes. a) Power envelope for whole stimulus. The solid line indicates the pitch condition and the dashed line the control condition. Noise onset occurs at 0 ms in both stimuli, and RIN onset at 800 ms in the pitch condition only. Dots below the time axis indicate significant power increases (p < 0.05 uncorrected) in the pitch condition over the control condition after the onset of RIN. Stimulus offset occurs at 2000 ms. b) Power spectrum of RIN transition response, with power spectrum during the equivalent part of the control stimulus, and spontaneous (prestimulus) power spectrum shown for comparison. The RIN power spectrum was significantly greater (P < 0.05 uncorrected) at every frequency shown except 50 Hz where electrical noise was present. c, d) Power envelopes and RIN onset power spectra, respectively, from depth electrode recordings. Power changes are calculated as in plots a and b. Solid and dashed lines in c indicate subjects 154 and 156 respectively, and responses to control stimuli are not shown. Fig. 5d is equivalent to b, with one plot for each subject.