AsianScientist (Apr. 24, 2015) – Researchers have identified the neural circuits that link visual stimuli to defensive behaviors in mice. Their results have been published in Nature Communications.
How the brain makes sense of emotion-laden external stimuli is a fundamental question for researchers studying cognition. Being able to detect the biological significance of affective stimuli and decide whether to approach or avoid the source confers a selective advantage. More specifically, reaction to unexpected but salient stimuli, especially of potential danger or emergency in the natural environment, is crucial for survival. However, the brain mechanisms underlying these general behavioral phenomena remain largely unclear.
In the present study, Dr. Wei Pengfei and his colleagues, led by Professor Wang Liping at Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, report a non-canonical, subcortical circuitry underlying defensive behaviors elicited by predator-like visual stimuli in mice.
They identified a sub-population of neurons in the medial region of the intermediate layers of the superior colliculus (ILSCm) that mediates the innate defensive response of mice to overhead looming stimuli. Using optogenetics, they dissected a subcortical pathway from the glutamatergic projecting neurons in the ILSCm to the lateral posterior nucleus of the thalamus (LP), showing that it could be activated to innately initiate stereotyped long-lasting freezing behaviors.
Retrograde trans-synaptic viral tracer labeling revealed that the LP serves as a key intermediate relay between the ILSCm and the lateral amygdala (LA). Their study showed that the sustained network activation of the LA mediates the expression of the ILSCm-induced innate fear-related defensive behaviors.
This pathway encodes specifically a stereotyped unlearned fear-like freezing behavior. Current studies on the subcortical innate fear circuit in rodents may lead to new implications regarding the circuit mechanisms that underlie mental disorders in humans.
The article can be found at: Wei et al. (2015) Processing of Visually Evoked Innate Fear by a Non-Canonical Thalamic Pathway.
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Source: Chinese Academy of Sciences.
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