聴覚感度と能動的視覚刺激処理中の視覚的クロスモーダル可塑性との関連

Visual cross-modal plasticity after deafness describes when 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. Twenty-five participants (aged 18 to 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 if a target word probe was present in the encoding period. Multichannel EEG 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 right auditory cortex, but no effects were found in visual cortex. Hearing sensitivity and visual encoding activity did not correlate with behavioural performance or neural oscillations during the retention period. Results suggest that even a mild hearing decline of high-frequency hearing sensitivity is associated with increased visual activation of right auditory cortex during an active visual processing task, consistent with cross-modal plasticity.