Differential Recruitment of Competing Valence-Related Amygdala Networks during Anxiety.

The basolateral amygdala (BL) is involved in fear and anxiety, but it is currently unclear how the same network supports these two states. To address this question, we trained rats on appetitive and aversive conditioning in different contexts. Distinct groups of BL neurons displayed increased activity during appetitive (CS-R) versus aversive (CS-S) conditioned stimuli (R cells and S cells, respectively), and they were typically inhibited by the other CS. When the CS-S was presented in the safe context, rats entered a long-lasting, anxiety-like state characterized by increased inter-CS freezing and impaired reward seeking. During this state, a subset of BL cells ("state cells") showed sustained shifts in baseline activity whose time course matched that of the behavioral changes. Many state cells with increased firing rates were S cells, whereas R cells only included state cells with reduced firing rates. Thus, anxiety involves persistent activity changes that are differentially expressed by subsets of valence-specific BL neurons.