Region-dependent Millisecond Time-scale Sensitivity in Spectrotemporal Integrations in Guinea Pig Primary Auditory Cortex

Spectrotemporal integration is a key function of our auditory system for discriminating spectrotemporally complex sounds, such as words. Response latency in the auditory cortex is known to change with the millisecond time-scale depending on acoustic parameters, such as sound frequency and intensity. The functional significance of the millisecond-range latency difference in the integration remains unclear. Actually, whether the auditory cortex has a sensitivity to the millisecond-range difference has not been systematically examined. Herein, we examined the sensitivity in the primary auditory cortex (A1) using voltage-sensitive dye imaging techniques in guinea pigs. Bandpass noise bursts in two different bands (band-noises), centered at 1 and 16 kHz, respectively, were used for the examination. Onset times of individual band-noises (spectral onset-times) were varied to virtually cancel or magnify the latency difference observed with the band-noises. Conventionally defined nonlinear effects in integration were analyzed at A1 with varying sound intensities (or response latencies) and/or spectral onset-times of the two band-noises. The nonlinear effect measured in the high-frequency region of the A1 linearly changed depending on the millisecond difference of the response onset-times, which were estimated from the spatially-local response latencies and spectral onset-times. In contrast, the low-frequency region of the A1 had no significant sensitivity to the millisecond difference. The millisecond-range latency difference may have functional significance in the spectrotemporal integration with the millisecond time-scale sensitivity at the high-frequency region of A1 but not at the low-frequency region. (c) 2021 IBRO. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study examined the sensitivity to millisecond latency differences in the primary auditory cortex (A1) using guinea pigs as subjects. The results showed that the high-frequency region of A1 had a linear relationship between millisecond latency differences and nonlinear integration effects, while the low-frequency region did not show significant sensitivity to millisecond differences.