2026-07-10 東京大学,科学技術振興機構
図１：特定の他者に対する感情を形成する脳の仕組み
＜関連情報＞
- https://www.iqb.u-tokyo.ac.jp/pressrelease/260710/
- https://www.science.org/doi/10.1126/science.adx8231
社会的記憶における価値更新のための神経回路 Neural circuits for valence updating in social memory
Narutoshi Suto, Mu-Yun Wang, Shota Morikawa, Myung Chung, […] , and Teruhiro Okuyama
Science Published:9 Jul 2026
DOI:https://doi.org/10.1126/science.adx8231
Structured Abstract
INTRODUCTION
Social animals recognize familiar conspecifics and assign valence based on prior social interactions. This ability allows individuals to promote adaptive social interactions while minimizing the cost of antagonistic encounters. Because social relationships are dynamic, the capacity to continuously update the valence attributed to specific individuals is essential. Although hippocampal ventral CA1 (vCA1) neurons encode social memory, the neural circuit mechanisms that selectively update social valence remain largely undefined.
RATIONALE
We hypothesized that valence updating for familiar individuals is mediated by circuit-specific interactions between social memory representations in vCA1 and downstream valence-processing pathways. To test this, we developed a behavioral paradigm in which a previously neutral familiar conspecific was transformed into an aggressive individual, enabling controlled manipulation of social valence. We combined neural circuit–specific manipulation, memory engram-based approaches, in vivo calcium imaging, and synaptic physiology to examine how valence updating is implemented across the vCA1–basolateral amygdala (BLA)–nucleus accumbens (NAc) circuit.
RESULTS
We found that valence updating is associated with enhanced synaptic connectivity and physiological changes within the vCA1–BLA–NAc circuit. Circuit-specific inhibition demonstrated that both the vCA1–BLA and the BLA–NAc pathways are required for specific social avoidance, whereas the direct vCA1–NAc pathway associated with social familiarity is not. Engram-specific manipulations revealed that projections from vCA1 social memory engram neurons to the BLA are both necessary and sufficient to drive valence updating, and optogenetic induction of synaptic depression abolished the updated avoidance. Consistently, synaptic strengthening in the vCA1–BLA pathway was confirmed by increased AMPA/NMDA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid / N-methyl-D-aspartate) ratios in BLA fear neurons.
At the population level, BLA fear neurons exhibited elevated responses to the aggressor without changes in the proportion of responsive cells, whereas downstream dopamine receptor D2–expressing neurons in the NAc showed both amplified responses and recruitment of additional responsive cells, accompanied by synchronous activity within neural ensembles. These results reveal a stepwise transformation of neural coding schemes along the vCA1–BLA–NAc pathway, from stable identity representation in vCA1 to dynamic population-level reorganization in downstream regions. Despite representational drift across sessions, valence assignment increased the stability of neural representations.
CONCLUSION
Our findings reveal a circuit mechanism that links stable social memory representations in vCA1 to flexible valence updating in downstream regions through the vCA1–BLA–NAc pathway. This organization enables animals to selectively update valence assigned to specific individuals without disrupting identity representations. This study provides a framework for investigating biologically relevant mechanisms underlying the formation of emotions toward specific individuals within a social context.
Social memory engram neurons in vCA1 maintain stable representations of individual identity.
Following social defeat, synaptic connectivity from vCA1Trpc4 neurons to BLARspo2 neurons (fear neurons) is strengthened, leading to increased responses of BLA neurons to the aggressor. Downstream, NAcD2R neurons exhibit amplified and synchronized population activity, enabling the updating of negative valence and the selective avoidance of harmful individuals (specific social avoidance).
Abstract
Social animals recognize familiar conspecifics and selectively avoid harmful ones. As social relationships shift, continuous updating of social valence is essential, yet the underlying neural mechanisms remain unclear. Here, by artificially transforming a previously neutral conspecific into an aggressive one, we show that valence updating depends on enhanced synaptic connectivity and physiological changes within the hippocampal ventral CA1 (vCA1)–basolateral amygdala (BLA)–nucleus accumbens (NAc) circuit. Following defeat, social memory engram neurons in the vCA1 strengthened their connections with BLA neurons carrying negative valence. The vCA1–BLA–NAc neural circuit flexibly regulates adaptive social behaviors.
