Figure 8. Proposed model of DRN^5-HT network at the population- and single-cell level.

A large fraction of serotonergic neurons in the dorsal raphe nucleus is modulated by emotional salience. More cells respond to emotionally salient stimuli than to neutral stimuli, and activity scales with relative salience. At the network level, discrete ensembles are highly correlated over long timescales. Single cells respond to diverse combinations of individual stimuli with some constraints by valence and sensory modality. Projection-specific subpopulations contain the full complement of response types but in weighted proportions. Arrows represent the populations of cells responding to sucrose (blue), first social interaction (green), exploratory behavior in the elevated plus maze (yellow), and footshock (red).