Selective Corticofugal Modulation on Sound Processing in Auditory Thalamus of Awake Marmosets

Abstract

Cortical feedback has long been considered crucial for modulation of sensory processing. In the mammalian auditory system, studies have suggested that corticofugal feedback can have excitatory, inhibitory, or both effects on the response of subcortical neurons, leading to controversies regarding the role of corticothalamic influence. This has been further complicated by studies conducted under different brain states. In the current study, we used cryo-inactivation in the primary auditory cortex (A1) to examine the role of corticothalamic feedback on medial geniculate body (MGB) neurons in awake marmosets. The primary effects of A1 inactivation were a frequency-specific decrease in the auditory response of MGB neurons coupled with an increased spontaneous firing rate, which together resulted in a decrease in the signal-to-noise ratio. In addition, we report for the first-time that A1 robustly modulated the long-lasting sustained response of MGB neurons which changed the frequency tuning after A1 inactivation, e.g., neurons with sharp tuning increased tuning bandwidth whereas those with broad tuning decreased tuning bandwidth. Taken together, our results demonstrate that corticothalamic modulation in awake marmosets serves to enhance sensory processing in a way similar to center-surround models proposed in visual and somatosensory systems, a finding which supports common principles of corticothalamic processing across sensory systems.

Lemniscal Corticothalamic Feedback in Auditory Scene Analysis

“…In addition to the modulation of tuning properties, it was observed that lemniscal corticothalamic feedback generally facilitates excitability of MGBv neurons (cats: Ryugo and Weinberger, 1976 ; Villa et al, 1991 ; He, 1997 ; guinea pigs: He et al, 2002 ; Yu et al, 2004 ; mice: Guo et al, 2017 ; Lohse et al, 2020 ; marmosets: Zhang et al, 2021 ). Deactivation of the auditory cortex decreases the spontaneous firing rate in MGBv neurons ( Ryugo and Weinberger, 1976 ; Villa et al, 1991 ; but see Zhang et al, 2021 ) while cortical activation enhances their responses to sounds ( He, 1997 ; He et al, 2002 ; Guo et al, 2017 ). The effect is, however, heterogeneous, and a minority of MGBv neurons can show suppression.…”