Visualizing an emotional valence map in the limbic forebrain by TAI-FISH.

A fundamental problem in neuroscience is how emotional valences are represented in the brain. We know little about how appetitive and aversive systems interact and the extent to which information regarding these two opposite values segregate and converge. Here we used a new method, tyramide-amplified immunohistochemistry-fluorescence in situ hybridization, to simultaneously visualize the neural correlates of two stimuli of contrasting emotional valence across the limbic forebrain at single-cell resolution. We discovered characteristic patterns of interaction, segregated, convergent and intermingled, between the appetitive and aversive neural ensembles in mice. In nucleus accumbens, we identified a mosaic activation pattern by positive and negative emotional cues, and unraveled previously unappreciated functional heterogeneity in the D1- and D2-type medium-spiny neurons, which correspond to the Go and NoGo pathways. These results provide insights into the coding of emotional valence in the brain and act as a proof of principle of a powerful methodology for simultaneous functional mapping of two distinct behaviors.