Improved Speech Hearing in Noise with Invasive Electrical Brain Stimulation

Abstract

Speech perception in noise is a challenging everyday task with which many listeners have difficulty. Here, we report a case in which electrical brain stimulation of implanted intracranial electrodes in the left planum temporale (PT) of a neurosurgical patient significantly and reliably improved subjective quality (up to 50%) and objective intelligibility (up to 97%) of speech in noise perception. Stimulation resulted in a selective enhancement of speech sounds compared with the background noises. The receptive fields of the PT sites whose stimulation improved speech perception were tuned to spectrally broad and rapidly changing sounds. Corticocortical evoked potential analysis revealed that the PT sites were located between the sites in Heschl's gyrus and the superior temporal gyrus. Moreover, the discriminability of speech from nonspeech sounds increased in population neural responses from Heschl's gyrus to the PT to the superior temporal gyrus sites. These findings causally implicate the PT in background noise suppression and may point to a novel potential neuroprosthetic solution to assist in the challenging task of speech perception in noise. SIGNIFICANCE STATEMENT Speech perception in noise remains a challenging task for many individuals. Here, we present a case in which the electrical brain stimulation of intracranially implanted electrodes in the planum temporale of a neurosurgical patient significantly improved both the subjective quality (up to 50%) and objective intelligibility (up to 97%) of speech perception in noise. Stimulation resulted in a selective enhancement of speech sounds compared with the background noises. Our local and network-level functional analyses placed the planum temporale sites in between the sites in the primary auditory areas in Heschl's gyrus and nonprimary auditory areas in the superior temporal gyrus. These findings causally implicate planum temporale in acoustic scene analysis and suggest potential neuroprosthetic applications to assist hearing in noise.

Multivariate fMRI responses in superior temporal cortex predict visual contributions to, and individual differences in, the intelligibility of noisy speech

“…Invasive recordings in patients with epilepsy have found that larger responses to noisy speech in STC in patients with better task performance ( Nourski et al, 2019 ); that STC restores missing acoustic content from the incoming speech signal ( Leonard et al, 2016 ); and that STC responses to visual speech correspond to its perceptual benefit for noisy auditory speech ( Karas et al, 2019 ). Magnetoencephalographic recordings track the maintenance of online speech representations in STC for the resolution of ambiguous speech tokens ( Gwilliams et al, 2018 ) and electrical stimulation of STC results in improved speech-in-noise perception ( Patel et al, 2022 ).…”

“…More invasively, there is great interest in implanted brain-computer interfaces as remedies for communication deficits and to compensate for lost peripheral sensory function ( Beauchamp et al, 2020 ; Moses et al, 2021 ; Vansteensel and Jarosiewicz, 2020 ). Electrical stimulation of intracranial electrodes implanted in superior temporal cortex of a single patient resulted in improved speech-in-noise perception ( Patel et al, 2022 ). A neural prosthetic implanted in superior temporal cortex could help normalize the pattern of activity to make it easier for patients to understand speech.…”