Figure 2.

Oscillatory Power and Phase Coherence Changes with Tinnitus Suppression

Electrode locations are displayed with respect to a left lateral view of the convexity (A); coronal sections illustrating the location of depth electrode contacts with respect to the gray matter of Heschl’s gyrus (Ai; shown in dark gray); a superior view of the superior temporal plane centered on Heschl’s gyrus (Aii); the inferior surface of the temporal lobes (B); an axial slice through the anterior temporal lobes (Bi); an axial slice through the mid to posterior temporal lobe (Bii), with electrodes 173 and 174 in posterior parahippocampal cortex (PHC); and an axial slice through posterior temporo-occipital cortex, including the epileptogenic lesion (Biii). Axial slices in (Bi), (Bii), and (Biii) are viewed from their inferior aspects (in keeping with the view in B). In (Bi), the solid blue area indicates the lateral nucleus of the amygdala, and the solid yellow area the hippocampus proper, based on an automated segmentation algorithm implemented in FreeSurfer (https://surfer.nmr.mgh.harvard.edu/). In (Biii), the red area represents the lesion, and the gray area (also in A) represents the extent of tissue subsequently resected. Subdural electrodes are represented by solid black circles and depth electrodes by gray filled circles. Significant oscillatory power changes are denoted by colored hollow circles, with circle radius representing the peak correlation, within any of the specified frequency bands, between power and tinnitus suppression. Note that neural activity changes are displayed on all sections except (Ai), which is for illustrative purposes only. Blue, magenta, and orange circles indicate delta/theta/alpha (1–12 Hz) decreases, theta/alpha (4–12 Hz) increases, and beta2/gamma (28–148 Hz) increases, respectively. Phase coherence (PLV) changes were found only in the delta (1–4 Hz) band and are represented by solid blue lines. Each PLV connection was calculated between two bipolar electrode pairs (each consisting of two adjacent electrodes), and each end of each line is placed in between the two electrodes comprising that bipolar pair. Green boxes indicate sites where local cross-frequency coupling correlated significantly with tinnitus suppression (see Figure 4). Yellow and black boxes denote electrodes showing induced oscillatory and steady state responses to tinnitus-matched tones (see Figure S1B). See also Figure S2 for a full summary of power changes for both repetitions of the experiment.