We have previously shown that the central part of the dorsal pallium (Dc) in zebrafish has an important role in recalling the long-term memories of behavioral programs for an active avoidance paradigm. This result suggests that in zebrafish, the pallio-basal ganglia circuit is required for reinforcement learning. Meanwhile it has been reported that the medial part of dorsal pallium (Dm), a presumptive homolog of mammalian amygdala, is involved in retention of the long-term memory of learned fear. Although both two areas, Dc and Dm, are required to recall the active avoidance, there have been little reports how these two areas are functionally or anatomically related.
In this study, using camk2a:GVP; UAS:G-CaMP7 line, we applied in vivo calcium imaging to the dorsal pallium to detect neural activities during retrieval of the behavioral program during the active avoidance. 24 hrs after last training, we measured florescence changes in response to LED stimulation as the CS presentation. In learner fish, neural activities in the Dm and the caudal Dc in addition to the Dc were observed upon the LED stimulation. The neural activities in the Dm preceded that in the Dc. In naive control fish, no signals were observed in these areas. These results suggest that neural activities in the Dc, the Dm and the caudal Dc are involved in a recall of the remote memory of behavioral paradigm.
Now we investigate a correlation of the neural activations among these three areas during a memory retrieval. We also try to measure and compare active neural areas related to different behavior paradigms such as the classical fear conditioning.