The role of the gustatory cortex in incidental experience-evoked enhancement of later taste learning

  1. David Levitan2,5
  1. 1Department of Psychology, Brandeis University, Waltham, Massachusetts 02454, USA
  2. 2Department of Biology, Brandeis University, Waltham, Massachusetts 02454, USA
  3. 3Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02454, USA
  4. 4National Center for Behavioral Genomics, Brandeis University, Waltham, Massachusetts 02454, USA
  1. Corresponding authors: dbkatz{at}brandeis.edu; levitand{at}brandeis.edu
  1. 5 These authors contributed equally to this work.

Abstract

The strength of learned associations between pairs of stimuli is affected by multiple factors, the most extensively studied of which is prior experience with the stimuli themselves. In contrast, little data is available regarding how experience with “incidental” stimuli (independent of any conditioning situation) impacts later learning. This lack of research is striking given the importance of incidental experience to survival. We have recently begun to fill this void using conditioned taste aversion (CTA), wherein an animal learns to avoid a taste that has been associated with malaise. We previously demonstrated that incidental exposure to salty and sour tastes (taste preexposure—TPE) enhances aversions learned later to sucrose. Here, we investigate the neurobiology underlying this phenomenon. First, we use immediate early gene (c-Fos) expression to identify gustatory cortex (GC) as a site at which TPE specifically increases the neural activation caused by taste-malaise pairing (i.e., TPE did not change c-Fos induced by either stimulus in isolation). Next, we use site-specific infection with the optical silencer Archaerhodopsin-T to show that GC inactivation during TPE inhibits the expected enhancements of both learning and CTA-related c-Fos expression, a full day later. Thus, we conclude that GC is almost certainly a vital part of the circuit that integrates incidental experience into later associative learning.

  • Received July 14, 2018.
  • Accepted September 7, 2018.

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