Dissociated Role of Thalamic and Cortical Input to the Lateral Amygdala for Consolidation of Long-Term Fear Memory

Abstract

Post-encoding coordinated reactivation of memory traces distributed throughout interconnected brain regions is thought to be critical for consolidation of memories. However, little is known about the role of neural circuit pathways during post -learning periods for consolidation of memories. To investigate this question, we optogenetically silenced the inputs from both auditory cortex and thalamus in the lateral amygdala (LA) for 15 min immediately following auditory fear conditioning (FC) and examined its effect on fear memory formation in mice of both sexes. Optogenetic inhibition of both inputs dis-rupted long-term fear memory formation tested 24 h after FC. This effect was specific such that the same inhibition did not affect short-term memory and context-dependent memory. Moreover, long-term memory was intact if the inputs were inhib-ited at much later time points after FC (3 h or 1 d after FC), indicating that optical inhibition for 15 min itself does not pro-duce any nonspecific deleterious effect on fear memory retrieval. Selective inhibition of thalamic input was sufficient to impair consolidation of auditory fear memory. In contrast, selective inhibition of cortical input disrupted remote fear mem-ory without affecting recent memory. These results reveal a dissociated role of thalamic and cortical input to the LA during early post-learning periods for consolidation of long-term fear memory.