Finding your car in a parking lot is based on this newly discovered brain circuit

Summary: A newly discovered brain circuit allows us to focus on what is important in the environment and ignore other sensory stimuli.

Source: UCSF

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

The link, which originates in the prefrontal cortex and extends to the hippocampus, provides evidence of how the upper cognitive regions of the brain refine operations that occur in distant brain areas.

“This circuit is a gateway to understanding how the brain allows the prefrontal cortex to exert up-down regulation of other parts of the brain,” said Vikaas Sohal, MD, PhD, lead author of the study , published on April 28, 2022 a Cell. “It’s a kind of long-acting inhibitory pathway that connects two regions of the brain that had never been seen before.”

The prefrontal cortex (CFP), sometimes referred to as the “general manager of the brain,” controls executive functions such as attention, planning, and decision-making. The hippocampus stores memory and processes spatial information, helping us navigate the environment.

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

“It’s like the PFC is taking all 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 cites the example of a car park as a context in which the PFC exercises this type of top-down control over the hippocampus.

“To remember where you parked, the PFC would tell the hippocampus to pay selective attention to landmarks, and then remember and look for those landmarks when you come back,” Malik said.

Adjust attention using inhibitory neurons

The most unique thing about this circuit is the complex way in which it performs the task of focusing attention: it increases and focuses the activity on specific microcircuits of the hippocampus by deactivating the signals that would otherwise affect these microcircuits.

The result is a very clear signal from the PFC telling the hippocampus what to look for and an extremely clever way to adjust this message as the environment changes.

The team demonstrated this by placing mice in small sand for 10 minutes, where there were a few small objects. As they explored the arena, the mice inspected the objects for a minute or two and then moved on. By observing the brain activity of the mice, the researchers saw that the signals between the two brain regions were synchronized.

When a mouse passed this object again, the researchers were able to see that the signals inside the hippocampus were perfected and improved.

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

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

The newly discovered circuit facilitates the ability to focus on what is important in the environment and ignore other sensory stimuli. The image is in the public domain

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

Dysfunction of the brain circuit may be related to dementia, ADHD

The team wants to have a better idea of ​​the role that this circuit can play in the executive function and what consequences it has when it is not able to do its job effectively. Malik believes that dysfunction in this pathway may be the basis for cognitive problems related to attention or memory, such as dementia, ADHD, or psychiatric disorders.

Your next step toward this goal is to get an idea of ​​how this circuit affects behavior by observing how it works during more complex activities, such as using the information stored in working memory to decide which way to go to find a reward.

Malik believes that this connection from the higher order cognitive part of the brain to the oldest and most universal center of orientation is likely to have a wide influence.

“To operate in a complex environment, to go 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,” he said. “The filtering task of this circuit is absolutely essential.”

See also

This shows a diagram of the study

Financing: This research was supported by NIMH grants R01MH106507 and R01MH117961.

About this neuroscience research news

Author: Robin Marks
Source: UCSF
Contact: Robin Marks – UCSF
Image: The image is in the public domain

Original research: Open Access.
“Top-down control of hippocampal noise signal by long-range prefrontal inhibition” by Vikaas Sohal et al. Cell


Summary

Top-down control of hippocampal noise signal by long-range prefrontal inhibition

Highlights

  • PFC regulates dorsal hippocampus (dHPC) through long-range GABAergic projections (LRG)
  • LRG projections increase feedforward inhibition by targeting VIP interneurons in CA1
  • PFC-dHPC LRG projections enhance object-related spatial encoding in CA1
  • PFC-dHPC LRG projections promote object scanning and CA1-PFC gamma synchronization

Summary

The prefrontal cortex (CFP) is postulated to exert “top-down control” over the processing of information throughout the brain to promote specific behaviors. However, the pathways that mediate top-down control remain poorly understood.

In particular, knowledge about direct prefrontal connections that could facilitate top-down control of hippocampal information processing remains scarce.

Here we describe long-range monosynaptic GABAergic projections from PFC to the hippocampus.

These preferentially inhibit vasoactive interneurons that express intestinal polypeptides, which are known to disinhibit hippocampal microcircuits. In fact, stimulating prefrontal-hippocampal GABAergic projections increases inhibition of early hippocampal feeding and reduces hippocampal activity. live.

The net effect of these actions is to specifically improve the signal-to-noise ratio for hippocampal encoding of object locations and increase object-induced increases in spatial information. Accordingly, activating or inhibiting these projections promotes or suppresses object exploration, respectively.

Taken together, these results shed light on a top-down prefrontal pathway in which long-range GABAergic projections target disinhibitory microcircuits, thus improving the signals and network dynamics underlying exploratory behavior.

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