Re-mapping taste in the brain
New study reveals that the cortex

Date:
November 12, 2020
Source:
Stony Brook University
Summary:
A new study found that the map of neural responses mediating taste
perception does not involve, as previously believed, specialized
groups of neurons in the brain, but rather overlapping and spatially
distributed populations.



FULL STORY ==========================================================================
What happens in our brain that makes us experience the sweet taste of
a donut or the bitter taste of tonic water? What are the patterns of
neural activity responsible for the perception of taste? A new study
from Stony Brook University found that the map of neural responses
mediating taste perception does not involve, as previously believed, specialized groups of neurons in the brain, but rather overlapping and spatially distributed populations.


==========================================================================
The findings, to be published in Current Biology, counter an influential
but controversial theory based on studies suggesting that there is a topographic map in the gustatory cortex that is responsible for our
perception of taste.

According to this theory, the gustatory cortex has "hot spots" of neurons
whose activation leads to the perception of certain tastes. The new study
by Stony Brook researchers demonstrates such a simple map of taste does
not exist in the cortex of behaving animals.

When we taste food, neural activity propagates from the tongue to the
brainstem and up to the cerebral cortex region known as the gustatory
cortex. Activation of the gustatory cortex contributes to our perception
of taste and flavor.

Early imaging experiments provided evidence in favor of the theory
of taste coding that postulates the existence of spatially localized
clusters of neurons encoding specific tastes. These clusters, also
known as "hot spots" form a map of taste on the gustatory cortex, with
an hot spot for "sweet," one for "bitter," one for "salty," and one for "savory." According to this model of taste function, the activation of
one cluster would correspond to the sensation of a specific taste.

"Our experiments demonstrate there is not a map with hot spots in the
gustatory cortex of behaving animals," says Alfredo Fontanini, MD,
PhD, lead investigator and Chair of the Department of Neurobiology and
Behavior in the College of Arts and Sciences and Renaissance School of
Medicine at Stony Brook University.

"Instead, each taste is represented by spatially distributed ensembles of neurons sprinkled across the cortex. Neurons can represent one or many
taste sensations and form what is called an ensemble code. Basically,
neurons act very much like instruments in an orchestra playing different
notes forming a chord." The researchers demonstrated this activation repeatedly in behaving mice sampling different tastes from a spout. They
used calcium imaging to determine how taste and task-related variables
are represented in alert licking mice.

With the experiments they collected data on how various taste stimuli
evoke responses from neurons in the gustatory cortex. They found that
some neurons respond to a single taste and other to multiple.

An analysis of the distribution of responses over multiple spatial scales demonstrated that taste representations are distributed across the cortex,
with no sign of spatial clustering or topography as would be expected with
a map of the gustatory cortex corresponding specific taste sensations.

"Our findings are important because they address one of
the basic organizing principles of brain function," explains
Dr. Fontanini. "Topographical maps are a pervasive feature of brain organization. Demonstrating that the spatial organization of taste
responses is not as simple as previously believed makes us re-evaluate the neurobiological processes underlying taste perception and taste-related
brain functions." The researchers conclude that their overall data
provides evidence for a distributed neurobiological brain process when it
comes to taste, a coding scheme differing from the topographical brain organization of visual, somatosensory and auditory systems and similar
to olfaction.

The research was supported in part by the National Institutes of Health's National Institute on Deafness and Other Communication Disorders (NIDCD),
grant number R01DC018227 and R21DC017681.


========================================================================== Story Source: Materials provided by Stony_Brook_University. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Ke Chen, Joshua F. Kogan, Alfredo Fontanini. Spatially Distributed
Representation of Taste Quality in the Gustatory Insular Cortex of
Behaving Mice. Current Biology, 2020; DOI: 10.1016/j.cub.2020.10.014 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/11/201112134649.htm

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