Neural circuits for somatosensory control of auditory thalamocortical processing

To form a coherent representation of the environment, the brain must integrate information across different senses. Such multisensory convergence is widespread at the level of the cortex, where it is thought to arise primarily from corticocortical connections. Much less is known about the role of subcortical circuits in shaping the multisensory properties of cortical neurons. We show that sound-evoked activity in the mouse auditory cortex is widely suppressed by whisker stimulation. This suppression depends on the primary somatosensory cortex (S1), but surprisingly is implemented through a circuit linking S1 and the auditory thalamocortical system via the auditory midbrain. We also show that an additional, direct pathway exists from S1 to the medial sector of auditory thalamus, which facilitates auditory responses in neurons that do not project to the auditory cortex. The thalamus thus occupies a pivotal role in integrating multisensory signals by somatosensory top-down control of auditory subcortical processing.