Role of descending control in the auditory pathway

The profuse descending connections of the auditory cortex to the thalamus, midbrain, and brainstem demand a reevaluation of the simple hierarchical model of ascending auditory processing. This article summarizes the mechanisms of corticofugal modulation on the auditory pathways. It reviews the anatomy and physiology of the medial geniculate body (MGB; the auditory division of the thalamus), which is the main target of the corticofugal system. The corticofugal modulation of subcortical the nuclei, including the MGB, thalamic reticular nucleus (TRN), inferior colliculus (IC), and brainstem nuclei, including non-auditory brainstem sites is discussed. The article demonstrates that the corticothalamic system selectively facilitates or inhibits frequency-specific responses of neurons in the MGBv, amplifies or attenuates signals with weak or strong intensity, and minimizes the interference of other sensory inputs. This article shows how TRN neurons inhibit the MGB neurons mainly in non-lemniscal regions and draws comparison between corticocollicular and corticothalamic modulation.