Neuronal circuits in the brain 'sense' our inner state

Date:
July 15, 2020
Source:
Technical University of Munich (TUM)
Summary:
How decisions are made and how behavior is controlled is one of
the most important questions in neuroscience. The neurotransmitter
dopamine plays a central role in all of this. Scientists looked
into the role that dopamine plays in the decision-making process
and in controlling movement.



FULL STORY ========================================================================== Animals have an innate preference for certain scents and
tastes. Attractive scents are linked to things like good food. Less
attractive scents -- that of spoiled food, for example -- instinctively
give the animal a signal which says: "There could be danger here!" When
it comes to taste, all animals have similar preferences: Sugars and
fats are perceived positively, whereas a bitter taste is perceived
rather negatively.


==========================================================================
In order to be able to make such evaluations, we need signals in the brain
that tell us "This is good" or "This is bad." The dopaminergic system
in the brain, better known as the reward system, plays an important role
in these evaluations.

Understanding what happens in the brain Neurons that produce dopamine,
known as dopaminergic neurons, play a role in a range of diseases,
from addictive behavior and obesity to Parkinson's disease.

In addiction or obesity, the reward system signals can be too strong or
also too weak. In Parkinson's disease, dopaminergic neurons degenerate,
and this affects the control of motor functions.

To learn more about the processes in the brain, basic research is
essential.

Ilona Grunwald Kadow, Professor of Neural Control of Metabolism at the
TUM School of Life Sciences in Weihenstephan, and her team are conducting research on the fly Drosophila melanogaster.

Neuroscientists often use this fly as a model because its neuronal
networks are much simpler than those of humans. Using genetic tricks, scientists can turn individual network components on and off or change
them. This enables the researchers to understand the principles
of neuronal circuits that underlie the functions of more complex
brains. "Dopamine plays a very similar role in the brain of humans and insects," explains the scientist.



========================================================================== Further clarifying the effect of dopamine Dopamine is one of the most intensively studied signals in the brain. It is involved in both cognitive (e.g. motivation, reinforcement, goal-oriented behavior, motor control
and movement, decision-making and learning) and more basic functions
(e.g. reproduction and nausea).

How dopamine contributes to the various aspects of neural circuit
functionality and behavior is an open question, but it is believed
that dopaminergic neurons use different activity patterns to send a
signal to the brain about what the body needs and senses. "We have now investigated the activity of the dopaminergic neurons in greater detail,"
said Ilona Grunwald Kadow. The team developed a custom 3D-imaging method
based on in-vivo calcium imaging, as calcium is a good indicator of
neuronal activity.

Neurons react flexibly and individually Using this method, the research
team was able to show that the activity of a network of dopaminergic
neurons reflects both the innate preferences for smell and taste as well
as the physiological state of the organism.



==========================================================================
In addition to sensory stimuli such as smell or taste, dopaminergic
neurons also record information as to whether an organism is moving or
not. The neurons can respond to both internal behavioral states and
external signals, bring them together, and use this to support both
cognitive and motor processes.

"By doing that, the neurons can react flexibly and individually to the
most important information -- such as smell, taste, but also hunger
or one's own movement. This is important to reach a balanced decision,
because an external sensory signal can sometimes mean something good or
bad, depending on an organism's condition," says Prof. Grunwald Kadow.

Surprising results The researchers were surprised that dopaminergic
neurones behave quite differently in different animals. The scientists speculate that this might explain individual preferences and behavioral differences between individuals.

In addition, the researchers found that the movement of the animal not
only activates these dopaminergic neurones, but also other areas of
the brain that actually have nothing per se to do with movement. This
provides starting points for further research, for example what role
movement plays in general when reacting to an environmental stimulus.


========================================================================== Story Source: Materials provided by
Technical_University_of_Munich_(TUM). Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. K.P. Siju, Vilim Stih, Sophie Aimon, Julijana Gjorgjieva, Ruben
Portugues, Ilona C. Grunwald Kadow. Valence and State-Dependent
Population Coding in Dopaminergic Neurons in the Fly Mushroom Body.

Current Biology, 2020; 30 (11): 2104 DOI: 10.1016/j.cub.2020.04.037 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200715111420.htm

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