Association between high-frequency hearing sensitivity and visual cross-modal plasticity during active visual stimulus processing

Visual cross-modal plasticity after deafness describes when the sensory cortex compensates for auditory deprivation by increasing sensitivity to visual information. Cross-modal plasticity is evident in humans and animal models with deafness and is linked to improved visual perception, but it is unclear whether this occurs for mild, partial hearing loss. Here, we investigated cross-modal plasticity in adults with mixed levels of high-frequency hearing loss, but normal mid- and low-frequency hearing sensitivity, and whether this plasticity was associated with visual short-term memory recall. A total of 25 participants (aged 18-78) completed a modified Sternberg task with text-based words. Participants viewed a five-word sentence presented word-by-word during an encoding period and held these words in short-term memory during a retention period. After, they reported whether a target word probe was present in the encoding period. Multichannel electroencephalogram recorded visual cortical activity throughout. Results showed separate effects of high-frequency hearing and age on visual cortical responses. Visual N1 amplitudes were larger with worse sensitivity, and P2 latencies were longer. In contrast, age was associated with shorter P2 latencies. Source analysis found that the N1 amplitude increased with worse high-frequency hearing sensitivity in the right auditory cortex, but no effects were found in the visual cortex. Hearing sensitivity and visual encoding activity did not correlate with behavioral performance or neural oscillations during the retention period. Results suggest that even a mild decline of high-frequency hearing sensitivity is associated with increased visual activation of the right auditory cortex during an active visual processing task, consistent with cross-modal plasticity.<b>NEW & NOTEWORTHY</b> By recording the electroencephalogram and analyzing visual cortical potentials, we provide evidence for enhanced visual cortical sensitivity and recruitment of the auditory cortex during visual text perception in individuals with worse high-frequency hearing sensitivity. These individuals otherwise had normal middle- and lower-frequency hearing sensitivity, suggesting that visual cross-modal plasticity is initiated in early stages of hearing loss.