A non-lemniscal thalamic interface connecting alerting sensory cues to internal states in mice

Alterations in internal states, such as elevated arousal level and increased anxiety or fear, triggered by alerting environmental cues are required for behavioral state transitions promoting survival. However, the specific brain region that plays an interfacing role between alerting stimuli and internal states remains to be identified. Here, we report that the medial sector of the auditory thalamus (ATm), which consists of a group of non-lemniscal thalamic nuclei, can fulfill this function. VGluT2-expressing ATm (ATmVGluT2+) neurons receive direct and strong inputs from both visual and auditory midbrain regions, and project to multiple downstream structures critically involved in brain state regulation. Their activity was correlated with, and indispensable for, both blue light- and sound-induced NREM sleep-to-Wake transition, and their arousing effects were mainly mediated by, but not limited to, the temporal association cortices. ATmVGluT2+ neuron activation in awake behaving mice induced pupil dilation and behavioral responses suggestive of anxiety. Blocking the neurotransmitter release of ATmVGluT2+ neurons receiving auditory inputs selectively abolished loud noise-triggered escape behavior but not locomotion. Thus, the ATm is an interface in mouse brain that can transform alerting environmental cues into internal arousal and emotional state alterations that promote survival.