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bioRxiv · 10.1101/2022.02.05.479215

A longitudinal CA2/3 to CA1 circuit for initiating context-dependent associative learning

Chen, H.-S.·Qiu, S.·Wang, G.-L.·Yang, R.-R.·Zhang, N.·Wu, J.-N.·Yang, Q.-X.·Xu, C.
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Abstract

Associating environmental context with emotional experience is a vital brain function that requires the activity in both dorsal and ventral hippocampus. While only ventral hippocampus connects with the amygdala, a hub for fear learning, it remains unclear how the two hippocampal areas interact during contextual fear conditioning (CFC). We found that projections from dorsal CA2/CA3 (dCA2/3) to the dorsal part of ventral CA1 (vCA1d) contributed significantly to CFC. Deep-brain Ca2+ imaging revealed a CFC-enhanced difference in neuronal activities evoked by conditioned vs. neutral environmental context in both dCA2/3 and vCA1d areas. Notably, contextual fear retrieval correlated with changes in conditioned context-evoked activity in vCA1d, but not in dCA2/3. Furthermore, slice recordings showed that CFC potentiated dCA2/3-to-vCA1d projection strength, in line with coordinated elevation of monosynaptic excitation and reduction of disynaptic inhibition mediated by somatostatin-expressing interneurons. Thus, vCA1d represents a critical site for initiating emotional association with contextual information from dCA2/3.

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Chen, H.-S., Qiu, S., Wang, G.-L., Yang, R.-R., Zhang, N., Wu, J.-N., Yang, Q.-X., Xu, C.. 2022-02-08. A longitudinal CA2/3 to CA1 circuit for initiating context-dependent associative learning. https://doi.org/10.1101/2022.02.05.479215

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