The viruses used in this article are in the table below

The ability of animals to respond to life-threatening stimuli is essential for survival. Although vision provides one of the major sensory inputs for detecting threats across animal species, the circuitry underlying defensive responses to visual stimuli remains poorly defined. Here, we investigate the circuitry underlying innate defensive behaviours elicited by predator-like visual stimuli in mice. Our results demonstrate that neurons in the superior colliculus (SC) are essential for a variety of acute and persistent defensive responses to overhead looming stimuli. Optogenetic mapping revealed that SC projections to the lateral posterior nucleus (LP) of the thalamus, a non-canonical polymodal sensory relay, are sufficient to mimic visually evoked fear responses. In vivo electrophysiology experiments identified a di-synaptic circuit from SC through LP to the lateral amygdale (Amg), and lesions of the Amg blocked the full range of visually evoked defensive responses. Our results reveal a novel collicular–thalamic–Amg circuit important for innate defensive responses to visual threats.

Figure 1. The lateral posterior nucleus of the thalamus is the critical monosynaptic relay underlying the ILSCm–LA circuit.

In the present study, the authors aimed to examine the cell-type-specific circuit connectivity of the subcortical route for visual processing and determine the role of this pathway in mediating innate fear-related defensive behaviours. The authors show that the sustained network activation of the LA mediates the expression of the ILSCm-induced innate fear-related defensive behaviours.
 
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