Perceptual processing of tastes is performed by the amygdala-cortical loop
Reciprocal connectivity, which generates nonlinear dynamics within a system, should do the same in the taste circuit, which is rife with between-region feedback. Much evidence supports the existence of specific, characterizable within-region dynamics in taste processing, but scant attention has been paid to dynamic inter-region interactions in taste processing. To fill this gap, we apply investigate simultaneous recordings from rodent Gustatory Cortex (GC) and Basolateral Amygdala (BLA), testing specific hypotheses about reciprocal amygdala-cortical interactions. We find that initially GC and BLA responses are independent, but evolve into synchronous, zero-lag ensemble transitions (surprising given the long axons connecting the two regions) within a few hundred milliseconds of taste delivery. Spectral Granger Causality (which infers directional influences) revealed that this tight synchrony also characterizes the system's asymmetric inter-region influences wherein the BLA[->]GC influence is dominant prior to the generation of the behavioral response and the GC[->]BLA influence becomes strong at the time that GC has been shown to release a behavior-relevant signal. To better understand the function of single neurons in this process, we then used Poisson Generalized Linear Modeling to categorize GC neurons in terms of their inferred connectivity. This analysis revealed that GC neurons that both influence and receive influence from BLA - the neurons most deeply embedded in the reciprocal circuit - are the ones most strongly involved in taste processing (quantified as taste-specificity and palatability-relatedness). These results, which are consistent with findings in multiple systems and species, support the notion that taste processing is a function of the amygdala-cortical loop.