Figure 4.

Photo-stimulation of BLA neurons during CS presentation potentiates CS-evoked conditioned approach. A, In Experiment 3a, rats received AAV5-hSyn1-hChR2(H134R)-eYFP or an optically inactive control virus lacking ChR2 (AAV5-hSyn1-eYFP) in the BLA of both hemispheres. Optic fibers were also implanted bilaterally, above virus injection sites. B, Estimated optic fiber placements in the BLA (anteroposterior position is shown in mm relative to Bregma). At least 4 weeks after surgery, rats were water-restricted (2 h/d) and received Pavlovian conditioning sessions where a light-tone CS predicted water (100 μl) delivery (UCS) into a recessed dish. During conditioning sessions, photo-stimulation of BLA neurons was either explicitly paired or unpaired with CS presentation, in independent groups of rats. Control rats included ChR2 and eYFP rats that did not receive photo-stimulations and eYFP rats that received photo-stimulations. C, CS-paired but not CS-unpaired BLA photo-stimulation enhanced CSR/PCSR ratios (ratio of nose-pokes into the water dish during each 5 s CS presentation versus nose-pokes made during the 5 s period preceding each CS presentation). This indicates enhanced Pavlovian learning. n = 3–19/group. *p < 0.05 versus ChR2-Unpaired laser group and control group; ^#p < 0.05 versus control group on the same session; α p < 0.05 versus ChR2-Unpaired laser group on the same session. Values are mean ± SEM.