4 Roberts L.E. Residual inhibition.

8 Sedley W.

Teki S.

Kumar S.

Barnes G.R.

Bamiou D.-E.

Griffiths T.D. Single-subject oscillatory γ responses in tinnitus.

13 Roberts L.E.

Moffat G.

Baumann M.

Ward L.M.

Bosnyak D.J. Residual inhibition functions overlap tinnitus spectra and the region of auditory threshold shift.

Figure 1 Summary of Experiment Show full caption The experiment was performed on 2 days (upper and lower rows). On each day, the experiment was divided into two sessions (left and right columns), separated by a short break (gap between columns). Time is denoted by the horizontal axis. In each trial of the experiment, a masker was presented lasting 30 s (gray blocks), followed by four periods in which the subject rated the intensity of his tinnitus (green blocks) that were separated by three silent taskless recording periods of 10 s each (pale green/white blocks) whose data formed the basis of further analysis. Note that the duration of each session was not fixed, but rather depended on the sum of response times (green blocks) across a fixed number of repetitions. The rating scale used consisted of integers from −2 to +2 (though the range of responses given by the subject was −1 to 1, as shown here). A rating of 0 corresponded to the subject’s usual baseline tinnitus intensity, which he confirmed was the same as it had been immediately before the start of each experiment. Each recording period had a tinnitus rating value assigned to it that was the average of the ratings immediately preceding and following that period; these ratings were mainly −0.5 (average of −1, preceding, and 0, following) or 0. Data corresponding to the single rating of +1 (0 pre and +2 post) on day 2 were removed prior to analysis. As tinnitus ratings showed some correlation with overall time elapsed since the start of the experiment and with time elapsed since the end of the preceding masker, the tinnitus ratings were orthogonalized with respect to these variables, yielding partial tinnitus ratings. Tinnitus ratings corresponding to each recording period are shown in blue, and the corresponding partial ratings are shown in red. Note that partial tinnitus ratings have been centered to a mean of zero as part of the partialization process. See also Figure S1 for the subject’s audiological assessment.

The subject was a 50-year-old left-handed male with a typical tinnitus pattern of bilateral tonal tinnitus in association with bilateral hearing loss ( Figure S1 A). See the Supplemental Experimental Procedures for further subject details and the Supplemental Discussion with regard to the typicality of his case. He underwent chronic intracranial monitoring of the left hemisphere (contralateral to his better hearing ear) for intractable focal seizures. During the invasive monitoring period, his tinnitus was repeatedly transiently suppressed using residual inhibition (RI; transient reduction in tinnitus loudness after presentation of a sound) [] and assessed by periodic ratings of tinnitus loudness, in between which were 10 s blocks (from which data were used for analysis) in which he was presented no stimuli and had no task to perform. RI can be achieved in the vast majority of tinnitus patients and is thought to suppress tinnitus by temporarily reducing the underlying hyperactivity in the ascending auditory pathway []. The subject reported that all masker presentations produced some RI, but there was variation in the duration of the effect across trials. Data collection used for the main analyses commenced after the subject provided his first post-masker rating of tinnitus loudness, and we classified trials as “RI trials” when his tinnitus remained suppressed at this time. The experiment was performed on two separate days, with 15/30 trials on day 1 and 14/30 on day 2 constituting “RI trials.” Efficacy was greater in the first half of each experiment ( Figure 1 ) . Given that the task and acoustic stimuli were identical in all trials, the observed results could be considered to represent changes in tinnitus itself, with minimal influence of confounding factors. The presented results were derived from regression of neural activity, recorded electrocorticographically, against the degree of subjective tinnitus suppression. Neurophysiological results were nearly identical across the two experimental days ( Figure S2 ), and the data were therefore pooled for further analysis. Though we recorded mainly from the left hemisphere, we assume that similar results might have been obtained from the right hemisphere as the subject’s tinnitus, the maskers used, and the RI achieved, were all symmetrical.