Corticothalamic gating of auditory information

Abstract

Corticofugal projection of the auditory system is believed to play a crucial role in tuning our auditory attention while filtering unwanted noise. Our in vivo data from medial geniculate body (MGB) neurons of anesthetized guinea pigs showed that both their temporal firing pattern and onset responses to sound were modified by electrical stimulation of the auditory cortex (AC). The majority of neurons in the lemniscal MGB showed acoustic-evoked depolarization and facilitatory response to electrical stimulation of AC. However, the majority of non-lemniscal MGB neurons showed acoustic-evoked hyperpolarization and received inhibitory corticofugal input via the thalamic reticular nucleus (TRN). These suggest that corticofugal projections amplified the matched ascending auditory information via the lemniscal MGB but switched off the non-lemniscal MGB so as to prepare the AC for sole processing of auditory information via the lemniscal route. Using c-fos expression, we further demonstrated that activation of rat MGB neurons was triggered by synchronized corticothalamic oscillation that did not involve TRN. Our results thus suggest that the transmission of ascending auditory information, especially for attentive purpose, is critically governed by corticothalamic modulation.