A study by Park and Choi published in the latest journal of Learning & Memory provides evidence that dual plasticity in the lateral nucleus, the gateway to the brain’s fear center (amygdala), is necessary to establish fear extinction in anesthesized rats. Here is parts of their abstract:
Employing a novel training procedure, in which stimulation of the medial geniculate nucleus (MGm) of the thalamus served as the CS, we tested necessary and sufficient conditions for extinction in anesthetized rats. Repeatedly applying the brain-stimulation CS was neither sufficient to produce activation of the mPFC nor behavioral extinction when the animal was under anesthesia. Only when the CS was combined with contingent stimulation of the infralimbic cortex (IL) of the mPFC was the CR markedly reduced, emulating extinction…The results showed that paired stimulations of the IL and MGm significantly enhanced the neural response at the IL-LA synapses and reversed conditioning-induced synaptic potentiation at the MGm-LA synapses. Taken together, our results provide strong evidence that dual plasticity within the LA underlies suppression of conditioned fear response following extinction.
Park, J., & Choi, J. (2009). Long-term synaptic changes in two input pathways into the lateral nucleus of the amygdala underlie fear extinction Learning & Memory, 17 (1), 812-823 DOI: 10.1101/lm.1482910