Reversible inactivation of ferret auditory cortex impairs spatial and non-spatial hearing

Abstract

AbstractA key question in auditory neuroscience is how far brain regions are functionally specialized for processing specific sound features such as sound location and identity. In auditory cortex, correlations between neural activity and sounds support both the specialization of distinct cortical subfields, and encoding of multiple sound features within individual cortical areas. However, few studies have tested the causal contribution of auditory cortex to hearing in multiple contexts. Here we tested the role of auditory cortex in both spatial and non-spatial hearing. We reversibly inactivated the border between middle and posterior ectosylvian gyrus using cooling (n=2) or optogenetics (n=1) as ferrets discriminated vowel sounds in discriminated vowel sounds in noise. Animals with cooling loops were also presented with vowels in clean conditions, and then retrained to localize noise-bursts from multiple locations and tested with cooling. Cortical inactivation impaired sound localization and vowel discrimination in noise, but not discrimination in clean conditions. We also tested the effects of cooling on vowel discrimination in noise when vowel and noise were colocated or spatially separated. Here, cooling impaired discriminating vowels with colocalized but not spatially separated noise, such that we could observe spatial release from masking during cortical inactivation. Together our results show that auditory cortex contributes to both spatial and non-spatial hearing, consistent with single unit recordings in the same brain region. The deficits we observed did not reflect general impairments in hearing, but rather are consistent with a role for auditory cortex in auditory scene analysis.