Finding your car in a parking lot relies on this newly discovered brain circuit
'CEO of the brain' focuses attention on the most relevant stimuli in the environment

Date:
May 3, 2022
Source:
University of California - San Francisco
Summary:
When exploring a new environment, mice make use of a unique
long-distance connection in the brain that prompts them to
pay attention to the most salient features of the environment,
according to new research. The link, originating in the prefrontal
cortex and stretching to the hippocampus, provides evidence of how
the brain's higher cognitive regions refine operations occurring
in distant brain areas.



FULL STORY ==========================================================================
When exploring a new environment, mice make use of a unique long-distance connection in the brain that prompts them to pay attention to the most
salient features of the environment, according to new research from UC
San Francisco.

The link, originating in the prefrontal cortex and stretching to the hippocampus, provides evidence of how the brain's higher cognitive
regions refine operations occurring in distant brain areas.


========================================================================== "This circuit is a gateway to understanding how the brain allows the
prefrontal cortex to exert top-down regulation of other parts of the
brain," said Vikaas Sohal, MD, PhD, senior author on the study, published
April 28, 2022, in Cell.

"It's a type of long-range, inhibitory pathway connecting two brain
regions that hasn't been seen before." The prefrontal cortex (PFC),
sometimes thought of as the "CEO of the brain," controls executive
functions like attention, planning and decision making. The hippocampus
stores memory and processes spatial information, helping us to navigate
the environment.

The newly discovered circuit facilitates the ability to focus attention
on what's important in the environment and ignore other sensory stimuli,
said the study's lead author, Ruchi Malik, PhD.

"It's as if the PFC is taking in all of this sensory information and
saying 'Hey, hippocampus, we're here in this particular context, so pay attention to this particular information right now,'" Malik said.

She gives the example of a parking lot as a context in which the PFC
exerts that kind of top-down control over the hippocampus. "To remember
where you parked, the PFC would tell the hippocampus to selectively pay attention to landmarks, and then recall and seek out those landmarks
when you return," said Malik.



========================================================================== Fine-Tuning Attention by Inhibiting Neurons Most unique about this circuit
is the complex way that it accomplishes the task of focusing attention:
it heightens and focuses activity in specific microcircuits of the
hippocampus by turning off signals that would otherwise tamp down those microcircuits. The result is a very clear signal from the PFC telling
the hippocampus what to attend to, and an extremely deft means of fine-
tuning that message as surroundings change.

The team showed this by putting mice into a small arena for 10 minutes,
where there were a few small objects. While exploring the arena, the
mice would inspect the objects for a minute or two, and then move on. By looking at activity in the brains of the mice, the researchers saw that
the signals between the two brain regions synchronized.

When a mouse passed that object again, the researchers could see that
the signals within the hippocampus were refined and enhanced.

"There was this dialogue happening; the hippocampus was mapping the
locations of objects in space and the PFC was instructing the hippocampus
on the relevance of each location," said Malik.



==========================================================================
The team also found that data indicated which neurons were firing at a
given time and identify where the mouse was at that moment, confirming
that brain activity changes as the mouse approaches or investigates an
object that the PFC has deemed important.

This suggests that as the hippocampus is mapping the environment, it is
also becoming fine-tuned to produce certain patterns of neural activity
when the prefrontal cortex detects that the mouse is approaching an
important target such as a new object.

Dysfunction of Brain Circuit May Be Linked to Dementia, ADHD The team
would like to get a better sense of the role this circuit might play in executive function, and what the consequences are when it's not able to
do its job effectively. Malik believes that dysfunction in this pathway
may underlie cognitive issues related to attention or memory, such as
dementia, ADHD or psychiatric disorders.

Their next move toward that goal is to get a sense of how this circuit
impacts behavior by looking at how it functions during more complex
activities, like using information stored in working memory to decide
which path to follow to find a reward.

Malik thinks it's likely that this connection from the higher-order,
cognitive part of the brain to the more ancient and universal wayfinding
center may exert broad influence.

"To operate in a complex environment, to go look for food or rewards
and then come back, you need to be able to pay attention to specific
stimuli and arrange them in space in a precise way," she said. "The
filtering job of this circuit is absolutely essential." This research
was supported by NIMH grants R01MH106507 and R01MH117961.


========================================================================== Story Source: Materials provided by
University_of_California_-_San_Francisco. Original written by Robin
Marks. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Ruchi Malik, Yi Li, Selin Schamiloglu, Vikaas S. Sohal. Top-down
control
of hippocampal signal-to-noise by prefrontal
long-range inhibition. Cell, 2022; 185 (9): 1602 DOI:
10.1016/j.cell.2022.04.001 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/05/220503141313.htm

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