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Conditioned fear response induced by electrical brain stimulation of the auditory cortex as a conditioned stimulus

The Korean Journal of Cognitive and Biological Psychology / The Korean Journal of Cognitive and Biological Psychology, (P)1226-9654; (E)2733-466X
2013, v.25 no.4, pp.581-594
https://doi.org/10.22172/cogbio.2013.25.4.010



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Abstract

Auditory fear memory is represented as long-lasting changes in the two input pathways into the lateral nucleus of the amygdala (LA): thalamo-amygdala and thalamo-cortico-amygdala pathways. Previously in our laboratory, we have shown that plasticity in the thalamo-amygdala pathway is critical for fear memory formation when electrical stimulation of the medial division of the medial geniculate nucleus of the thalamus (MGm) was used as the conditioned stimulus (CS). This short-circuit approach with the electrical brain stimulation as the CS (eCS) allowed us to test the efficacy of a particular pathway of interest without involving other sensory pathways. In the current study, we tested whether synaptic plasticity in the cortical pathway could support fear memory formation in rats by pairing the electrical stimulation of the secondary auditory cortex (Te3) with the footshock unconditioned stimulus (US). Following six paired presentations of the eCS and US, rats in the Te3-paired group showed significant level of freezing in the eCS-only test session, compared to a group that received unpaired presentations of the eCS and US. In addition, we also included MGm-paired group that received paired presentation of the MGm stimulation and US. The level of freezing to the eCS in the test session was comparable between Te3- and MGm-paired group. To examine the long-term maintenance of conditioned fear memory, freezing was measured 3 weeks after the acquisition session with the eCS. Both MGm-paired and Te3-paired groups showed considerable level of freezing and there was no significant difference between the two groups. In conclusion, both thalamic and cortical input pathways into the amygdala effectivly support fear conditioning when brain stimulation was used as the CS, suggesting that learning-induced changes in either the thalamo-amygdala or the cortico-amygdala synapse might be sufficient for storing fear memory.

keywords
fear conditioning, plasticity, cortico-amygdala pathway, thalamo-amygdala pathway, 공포 조건화, 가소성, 피질-편도체 경로, 시상-편도체 경로

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The Korean Journal of Cognitive and Biological Psychology