Auditory and visual cortices differentially modulate auditory responses in the midbrain

Abstract

The cortex is commonly thought of as the site at which ascending projections from all sensory modalities are integrated, yet cortical feedback to subcortical nuclei modulates early information processing. Here, we demonstrate that descending inputs from both auditory and visual cortex are integrated in the auditory midbrain. Using BOLD fMRI to measure sound-evoked responses throughout the auditory midbrain, we show that auditory cortical input normally suppresses the gain of midbrain response, while visual cortical input increases the gain. Our results demonstrate the large-scale influence of cortical projections from more than one sensory modality, demonstrating that while ascending integration occurs in cortex, descending integration occurs in the brainstem.