Compensatory Plasticity in the Lateral Extrastriate Visual Cortex Preserves Audiovisual Temporal Processing following Adult-Onset Hearing Loss

Figure 8

The magnitude of multisensory response interactions varied across the regions of the V2L cortex before and after noise exposure. To assess how hearing loss affected the sensitivity of neurons in the multisensory and auditory zones of the V2L cortex to the relative timing of the auditory and visual stimuli, the magnitude of the multisensory response interaction was calculated by comparing the amplitude of the granular sink in response to the combined audiovisual stimulus to that of the separately presented unimodal stimulus that evoked the largest response. Overall, a differential effect was observed between the noise-exposed rats () and control rats () within (a) V2L-Mz and (d) V2L-Az, with a significant difference between groups at 30 ms SOA (). (b, c, e, and f) Bar graphs show the change in the multisensory response interaction at each SOA within each group. In controls rats, only the neurons in V2L-Mz showed multisensory interactions that were sensitive to the relative timing of the auditory and visual stimuli (compare (b) and (e)). In contrast, only the neurons in V2L-Az showed a newfound temporal sensitivity after the noise-induced hearing loss (compare (c) and (f)). Following two-way repeated-measures ANOVAs, paired sample -tests were completed between each SOA and 0 ms (synchrony) to investigate the temporal profile within each cortical region ( and ). Values are displayed as .