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

Figure 9

Compensatory plasticity in the auditory zone of the V2L cortex preserves audiovisual temporal processing following moderate hearing loss. Using the AVREC amplitude as a measure of the overall strength of postsynaptic currents in a given cortical region, the magnitude of the multisensory response interactions was then calculated at each SOA to determine how noise-induced 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. Ultimately, the temporal profile observed in V2L-Mz of control rats (a), in which there was a significant increase in the magnitude of the multisensory response interaction at SOAs of 30 and 40 ms, was consistent with the temporal profile that emerged within V2L-Az of noise-exposed rats (d). 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 . (e, f) As schematized, it appears that noise exposure did not result in a loss of temporally precise audiovisual processing but instead caused a functional transition in the cortical region displaying this temporal sensitivity—findings which are suggestive of compensatory plasticity having occurred following moderate hearing loss.

(a) Multisensory zone of V2L in controls

(b) Multisensory zone of V2L in noise exposed

(c) Auditory zone of V2L in controls

(d) Auditory zone of V2L in noise exposed

(e) Sensory profile in controls

(f) Sensory profile in noise exposed