This study examined how prior taste experience impacts conditioned taste aversion (CTA) learning at the neurobiological level. Rats were either pre-exposed to salty and sour tastes or not, then conditioned to associate a novel sweet taste (sucrose) with illness. Rats with prior taste experience showed stronger CTA learning. Using c-FOS expression as a marker of neural activity, the study found pre-exposed rats had higher c-FOS levels in the anterior insular cortex compared to rats without pre-exposure, whose c-FOS was equal across insular cortex regions. This suggests taste experience changes how the insular cortex processes novel tastes during CTA learning. Future studies will examine the basolateral

1. Conditioned taste aversion (CTA) is a simple adaptive form of animal learning
whereby a food that causes gastric distress is rendered aversive. Previous
research done in the Katz Lab has suggested that experience with salty and sour
tastes can alter a rat’s ability to learn an aversion to a sweet taste; that is to say
that experience with multiple flavors strengthens the rat’s conditioned taste
aversion to a novel taste.
The present study begins our inquiry into the neurobiological underpinnings of
this phenomenon. Using c-FOS, a protein byproduct expressed by recently active
neurons, I have focused on the Insular cortex (IC)-a region known to be involved
in taste learning. Based on previous studies showing an increase in c-FOS
labeling with learning, we hypothesized an increase of c-FOS expression in IC for
rats with prior taste experience. It was initially found that rats who had prior
experience more c-FOS expression in IC. Further investigation showed this result
differed for different sub-regions of IC. Specifically, learning in rats that were not
pre-exposed to a taste array involved an increase in c-FOS expression between
the anterior section and the middle/posterior portion, whereas rats that were pre-
exposed showed an increase in the anterior portion. This led us to conclude that
taste experience changes the way that the Insular cortex processes novel tastes.
• Use c-FOS to examine the Basolateral amygdala's (BLA) role in the described
phenomenon, a region implicated in CTA learning
I would like to thank my mentors Donald Katz ,Veronica Flores, and Sarah Zarmsky
for their guidance in this project. Funding was provided by R01 DC006666-00; R01
DC007703-06; R03 DC014017
Flores, V. L. (2016). "Preexposure to salty and sour taste enhances conditioned taste aversion to novel
sucrose." Learn Mem 23(5): 221-228.
Koh, M. T., E. E. Wilkins and I. L. Bernstein (2003). "Novel tastes elevate c-fos expression in the central
amygdala and insular cortex: implication for taste aversion learning." Behav Neurosci 117(6):
1416-1422.
Schier, L. A., G. D. Blonde and A. C. Spector (2016). "Bilateral lesions in a specific subregion of
posterior insular cortex impair conditioned taste aversion expression in rats." J Comp Neurol 524(1):
54-73.
Experience with an
array of tastes
strengthens CTA
learning
N C
W
è2 days
Chamber
Habituation
3 days of
Pre-exposure
to NaCl and
Citric Acid
Conditioning
to Sucrose
followed by
LiCl Injection
c-FOS in BLA
increases with CTA
learning
Flores et al. 2016
Pre-exposure to an array of tastes
increases c-FOS expression in the
Insular cortex
N=18
N=2
Abstract
The Neurobiology of the Impact of Innocuous Experience on Later Learning
Tamar Parmet1, Veronica L. Flores1, David Levitan2, Madeline Lefkowitz1, Donald B. Katz1,3
Department of Psychology1, Department of Biology2, and the Volen National Center for Complex Sciences3, Brandeis University Waltham, MA 02454
Pre-exposure to salty and sour tastes
Behavioral Paradigm
References
Acknowledgements
Future directions and preliminary data
c-FOS expression appears
to remain constant across
IC with learning (i.e. without
pre-exposure)
Pre-exposure to an array of
tastes changes c-FOS
expression in the anterior
region of IC
Impact of pre-exposure depends on where one looks
in the Insular cortex
c-FOS expression in the Insular Cortex
(Anterior-Posterior)
c-FOS expression is higher in the anterior portion of
IC in rats that were pre-exposed to salty and sour
tastes
Pre-exposure—LiCl: Anterior
Water— LiCl: Anterior
Pre-exposure—LiCl: Posterior Pre-exposure—Saline
Water— LiCl: Posterior Water— Saline
N=16
N=16