Amygdala-cortical interactions in taste perception and learning

Brandeis University, Waltham MA

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Abstract

The neural system underlying conditioned taste aversion (CTA) is, like all systems underlying perceptual learning, highly complex—learning-relevant regions, most notably including basolateral amygdala (BLA) and gustatory cortex (GC), work together to make learning happen. While most research to date has focused on the role of each individual region in learning, rather than their influence on each other, my lab’s work is a direct investigation of inter-neuronal and inter-regional interactions during taste learning. This work has demonstrated that the coupling between BLA and GC taste responses is important for both basic taste processing and for CTA learning: blocking transmission in the BLAàGC pathway interferes with the coherent emergence of palatability-related information in GC ensemble taste codes (information that appears relatively late in GC responses), and keeps learning from happening; it is therefore reasonable to propose that activity in BLAàGC axons is vital for learning-related plasticity in those GC ensemble responses—that is, in the changes to late-appearing palatability-related coding. The experiments proposed here will build upon this foundation, and on recent work by collaborators, to test this overarching hypothesis. First we will acutely and selectively silence BLAàGC axons, and test whether this perturbation blocks learning- and behavior-linked changes in GC population responses. We will then test whether recently-identified learning-related transcription changes occurring in BLAàGC projection neurons are necessary for the induction and maintenance of GC taste response plasticity caused by CTA. Finally, we will test whether intrinsic excitability in the connection between BLA and GC—which appears to be increased in mice that fail to learn, and decreased in projection neurons that are involved in learning—is the parameter controlling learning-related changes in GC network activity. Together, these experiments will be the first to directly and specifically relate cellular/molecular plasticity processes to the emergent dynamics of network function in vertebrates. In the process, they will reveal new facets of the neural mechanisms of a more general experiential phenomenon that affects (sometimes adversely) all mammals including humans.