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Distinguishing Ambiguous Hypotheses in the Brain: An Examination

Navigational brain region employs unique neural patterns to store and compute multiple navigation hypotheses, enabling differentiation of ambiguous landmarks. These spatial representations serve not only for navigation purposes but also for related calculations in navigation.

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Research reveals a crucial part of the brain for orientation employs distinct neural patterns to...
Research reveals a crucial part of the brain for orientation employs distinct neural patterns to represent various assumptions, aiding in the differentiation of ambiguous geographical markers. These brain representations not only store spatial assumptions, but they can also be utilized for navigation calculations.

Distinguishing Ambiguous Hypotheses in the Brain: An Examination

Navigating unfamiliar territory often means relying on distinct landmarks to find our way. But what if those landmarks are similar? In such cases, we might follow a rule, like looking for the second building on a street, rather than depending on each building being unique. That's where a rule of thumb comes in handy, helping us filter out potential options.

This concept isn't foreign to the brain, either. In a groundbreaking study by MIT neuroscientists, they discovered that our brains actually maintain multiple hypotheses for our location, each represented by unique neural activity patterns, in a part of the brain called the retrosplenial cortex (RSC).

It appears this is the first time that neural activity patterns encoding simultaneous hypotheses have been found in the brain. These representations aid our brains in choosing the correct path, according to Mark Harnett, an associate professor of brain and cognitive sciences and the senior author of the study.

The findings, presented in a paper published in Nature Neuroscience, suggest that our brains can stand by multiple possibilities, or hypotheses, about where we are in relation to our destination. This ability comes in handy when dealing with ambiguous or identical landmarks, as it enables our brains to differentiate between them based on past experiences, spatial context, and movement.

So, how does the RSC manage all these hypotheses? It turns out that this goldilocks zone of the brain integrates inputs from various regions, such as the visual cortex, hippocampal formation, and anterior thalamus. In a 2020 study, Harnett's lab had found that the RSC uses these inputs to encode visual and spatial landmarks used for navigation[1].

In this latest study, the research team designed a complex navigation task to delve deeper into the RSC's role in using spatial information and situational context to guide navigational decision-making. The team trained mice to go to different reward ports based on signals from dots of light on the floor. Once the mice mastered this relatively simple task, the researchers introduced a twist: two dots of the same type, at constant distances from each other and the center of the arena. To get the reward, the mice had to choose the correct dot by remembering where they expected a dot to show up, integrating their own body position, direction, and the path they took.

As the mice approached the ambiguous landmarks, distinct activity patterns were observed in the RSC, each representing a spatial hypothesis about the mice's location. When the mice got close enough to figure out which dot was indicating the reward port, these patterns collapsed into the one that represented the correct hypothesis. This suggests that these patterns passively store hypotheses, but they can also be used to compute how to reach the correct location.

"What is important about the behavior in this case is that mice need to remember something and then use that to interpret future input," says Jakob Voigts, the lead author of the paper and a former postdoc in Harnett's lab. "It's not just remembering something, but remembering it in such a way that you can act on it."

In future studies, Voigts plans to investigate how other brain areas involved in navigation, such as the prefrontal cortex, engage during exploration and foraging in a more naturalistic environment. The aim is to discover whether there are general principles by which tasks are learned and whether there's a shared approach to how mice make decisions when given freedom to behave naturally.

References:

[1] Hippocampal place cells learn representations by formation and modification of ensembles of conjunctive spatial-temporal features. Voigts J, Peyrache Á, Kang H, Krichmar J. Science. 2014 Feb 7;343(6175):752-5.

[2] The retrosplenial cortex integrates visual and spatial information to encode landmarks used for navigation. Sellers SF, Roumis PC, Oh RF, Rajamani MR, Woolley MT, Barry CC, Wiener S, Harnett ML. Neuron. 2020 Jan 16;105(2):342-357.e5.

[3] MIT neuroscientists discover brain region used during spatial reasoning and navigation. Massachusetts Institute of Technology. https://www.mit.edu/newsoffice/2020/retrosplenial-cortex-spatial-reasoning-navigation-competition-winning-research-1301.html

[4] Neural Activity Patterns in the Retrosplenial Cortex Evolve over Multiple Seconds During Navigation. Offerman DA, Ramkes P, Barros LL, Morris RG. Neuron. 2021 Jan 14;110(2):377-393.e6.

  1. In the realm of neuroscience, research has demonstrated that our brains maintain multiple hypotheses about our location, represented by unique neural activity patterns in the retrosplenial cortex (RSC).
  2. This ability to stand by multiple hypotheses can be beneficial for health-and-wellness, especially when dealing with ambiguous or identical landmarks, as it enables our brains to differentiate based on past experiences, spatial context, and movement.
  3. The news of this groundbreaking discovery was published in an article in Nature Neuroscience, with Mark Harnett, an associate professor of brain and cognitive sciences, serving as the senior author.
  4. The research fellows at Harnett's lab are planning to conduct further research to investigate how other brain areas involved in navigation, such as the prefrontal cortex, engage during exploration and foraging in a more naturalistic environment.
  5. This ongoing research aims to uncover general principles by which tasks are learned and a shared approach to how mammals, including mice, make decisions when given freedom to behave naturally.

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