Speech-Like Vibrotactile Stimulation Is Associated With Enhanced Cortical Activations in Single-Sided Deafness: An fMRI Study

Abstract

Audiotactile cues can enhance speech perception in noise, yet the neural mechanisms underlying vibrotactile speech processing remain poorly understood, particularly in individuals with single-sided deafness (SSD). The present study investigated how adults with acquired SSD process a complex amplitude-modulated speech-derived vibrotactile stimulus compared to simple periodic vibration, and how these responses differ from normal-hearing (NH) controls. Twenty adults with acquired SSD and 20 age- and sex-matched NH controls underwent functional magnetic resonance imaging (fMRI) during vibrotactile stimulation using a simple periodic vibration (125 Hz) and speech-derived vibrotactile stimulus. Behavioral performance (hit rate, reaction time) was measured. Region-of-interest analyses quantified activation in primary auditory cortex (PAC) and primary somatosensory cortex (S1). Additional analyses assessed differences in left versus right SSD and correlations between neural measures and clinical variables. Both groups responded faster to 125 Hz than vibrotactile speech stimuli (p = 0.03). Compared with NH controls, adults with SSD showed widespread activation of bilateral middle cingulate gyrus and the frontal operculum when processing the speech-derived vibrotactile stimulus. Region-of-interest analyses revealed reduced stimulus selectivity in primary somatosensory cortex in SSD compared to NH, together with increased recruitment of the inferior frontal gyrus during speech-derived vibrotactile stimulation. Furthermore, left-hemisphere dominance was found in primary auditory cortex for both left and right SSD during both stimuli conditions. Exploratory correlation analysis revealed associations between right inferior frontal gyrus activation and sound localization scores at 3 months after treatment with cochlear implant (r = -0.59, p = 0.026). Speech-derived vibrotactile stimulation was associated with activation of auditory and cognitive control networks in individuals with SSD, including the bilateral middle cingulate cortex. This pattern may indicate increased attentional demands when processing temporally complex vibrotactile signals. While the present findings are correlational and exploratory, they provide a basis for future studies investigating neuronal plasticity following hearing loss.

Keywords: cochlear implant; cross‐modal plasticity; fMRI; neuroplasticity; single‐sided deafness; vibrotactile stimulation.