A parvalbumin-positive excitatory visual pathway to trigger fear responses in mice

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Science  26 Jun 2015:
Vol. 348, Issue 6242, pp. 1472-1477
DOI: 10.1126/science.aaa8694

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Looming in on the threat-response circuit

What are the neural elements that transmit threat-relevant inputs in the brain? Shang et al. systematically identified the key neuronal subtypes in the mouse superior colliculus underlying active avoidance and defensive-like behaviors. They found a pathway that responded to looming objects, linking input from the retina to the fear center in the brain.

Science, this issue p. 1472


The fear responses to environmental threats play a fundamental role in survival. Little is known about the neural circuits specifically processing threat-relevant sensory information in the mammalian brain. We identified parvalbumin-positive (PV+) excitatory projection neurons in mouse superior colliculus (SC) as a key neuronal subtype for detecting looming objects and triggering fear responses. These neurons, distributed predominantly in the superficial SC, divergently projected to different brain areas, including the parabigeminal nucleus (PBGN), an intermediate station leading to the amygdala. Activation of the PV+ SC-PBGN pathway triggered fear responses, induced conditioned aversion, and caused depression-related behaviors. Approximately 20% of mice subjected to the fear-conditioning paradigm developed a generalized fear memory.

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