Figure 2.

Estimation of FFR duration (83 and 62 Hz). A, Auditory stimulus of 8 tones with high-frequency carriers at 83 Hz followed by 8 tones at 62 Hz presented at a 2.5 Hz rate (envelope). B, C, Waveform of the 83 and 62 Hz tones, made up of 14 and 11 oscillatory cycles, respectively. D, E, Evoked unfiltered response of 8 example sEEG channels, from different participants and different brain regions (Heschl's gyrus, motor cortex, and superior temporal sulcus). After a small delay, the neural response contains more cycles than the stimuli (highlighted in red arrows, 14 + 8 = 22 cycles in this example). F, G, Survival distribution of sEEG channels with consecutive significant activity after onset; 118 and 232 channels outlast the 0.170 s duration of the 83 and 62 Hz stimuli, respectively. H, I, Localization of sEEG channels showing an FFR during the stimulus. Channels with activity outlasting stimulus duration are circled. Color intensity indicates the number of cycles outlasting stimulus duration. J, K, Survival distribution of MEG vertices activity showing consecutive significant activity after onset. L, M, Localization of MEG vertices showing an FFR. Color intensity indicates the number of cycles outlasting stimulus duration.