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A Case Study of Tinnitus-related Residual Inhibition Induced by Electrical Stimulation of Heschl’s Gyrus
Abstract   Open access   Peer reviewed

A Case Study of Tinnitus-related Residual Inhibition Induced by Electrical Stimulation of Heschl’s Gyrus

Nour Alsabbagh, Inyong Choi and Phillip Gander
Brain stimulation, Vol.18(1), pp.586-586
01/2025
DOI: 10.1016/j.brs.2024.12.1077
url
https://doi.org/10.1016/j.brs.2024.12.1077View
Published (Version of record) Open Access

Abstract

Tinnitus is an auditory disorder whereby an internal sound is perceived without external stimulation. Tinnitus loudness can be temporarily suppressed after exposure to an acoustic stimulus, a phenomenon known as residual inhibition (RI). However, the brain mechanisms underlying RI are still poorly understood. Here, we aimed to explore the brain regions responsible for inducing RI by directly electrically stimulating primary auditory cortex located in Heschl’s Gyrus (HG) in an epileptic patient case study. The participant was a 49-year-old, right-handed female patient who underwent intracortical electrode implantation for epilepsy. The participant had normal hearing to 8kHz and a moderately severe hearing loss from 10-16kHz, and exhibited bilateral tonal high-frequency tinnitus. Intracortical electrodes were implanted over the left frontal and temporal cortices. Bipolar deep brain stimulation was delivered on the 8-contact electrode implanted along the long axis of HG, moving across electrode pairs medial to lateral. A standard electrode functional mapping protocol was implemented, i.e., a 50Hz stimulus was delivered at 7.5V for 1-2s duration. On separate sessions the patient was stimulated acoustically (30s white noise at a sound level that masked the tinnitus) to determine whether RI differs between electric and acoustic stimulation. Description of the effects of RI were given verbally to the experimenter. During electrical stimulation, at all sites except the most medial pair, the patient experienced RI that lasted for 1-2min at a depth at which the tinnitus was just audible. Notably, the strength of induced RI was similar across stimulation pairs. Acoustically generated RI was at a shallower depth and lasted for less than 30s. The overall character of RI was similar between the two stimulation modalities. These results indicate that electrical stimulation can be used to induce RI, and that RI is largely driven by stimulation at the level of early auditory cortex.

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