One of the guiding principles of memory research in the preceding decades is multiple memory systems theory, which links specific task demands to specific anatomical structures and circuits that are thought to act orthogonally with respect to each other. We argue that this view does not capture the nature of learning and memory when any degree of complexity is introduced. In most situations, memory requires interactions between these circuits and they can act in a facilitative manner to generate adaptive behavior.

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Author Contributions Section: AKR designed the studies, ran experiments, and wrote the manuscript. JCO performed electrophysiological experiments. ZP helped with optogenetic behavioral experiment analysis. FM ran VGLUT2 RNAscope experiments. SG and JT helped with optogenetic experiments. JC, NE and NK helped with behavioral experiments. WZH provided the Adcyap1-2A-Cre mice. RLN made the HSV viruses used in the intersectional viral approach. JW made and provided the PAC1 loxP/loxP and the Adcyap1-EGFP mice. BSK helped with all aspects of electrophysiological experiments and supervised JCO. The electrophysiology experiments were designed by AKR and MSF. MSF supervised all the studies and helped design the experiments and manuscript preparation.

The zebrafish (Danio rerio) is an excellent model system for assessing the effects of toxicant exposure on behavior and neurodevelopment. In the present study, we examined the effects of sub-chronic embryonic exposure to polychlorinated biphenyls (PCBs), a ubiquitous anthropogenic pollutant, on anxiety-related behaviors. We found that exposure to the PCB mixture, Aroclor (A) 1254, from 2 to 26 hours post-fertilization (hpf) induced two statistically significant behavioral defects in larvae at 7 days post-fertilization (dpf). First, during 135 min of free swimming, larvae that had been exposed to 2 ppm, 5 ppm or 10 ppm A1254 exhibited enhanced thigmotaxis (edge preference) relative to control larvae. Second, during the immediately ensuing 15-min visual startle assay, the 5 ppm and 10 ppm PCB-exposed larvae reacted differently to a visual threat, a red ‘bouncing’ disk, relative to control larvae. These results are consistent with the anxiogenic and attention-disrupting effects of PCB exposure documented in children, monkeys and rodents and merit further investigation.