Landmark Recognition Center Records and Solves Hypotheses for Unclear Landmarks
Navigating a confusing, partially familiar environment can be a challenge. Take, for example, finding an office in a sea of identical brick buildings. In such a case, we rely on rules, like looking for the second building on a street, rather than relying on subtle differences in the buildings themselves.
Recently, MIT neuroscientists discovered an interesting aspect of the mouse brain that resonates with this mundane scenario. they found that brain cells in the retrosplenial cortex (RSC) create distinct neural activity patterns to represent different possibilities of where the mouse might be when navigating complex and ambiguous environments.
This is the first time that neural activity patterns that encode multiple hypotheses have been directly observed in the brain. These representations, observed in the mouse RSC, aren't just decorations, they guide the mouse towards the correct goal once the ambiguity is resolved [1][2].
"As far as we know, no one has shown in a complex reasoning task that there's an area in association cortex that holds two hypotheses in mind and then uses one of those hypotheses, once it gets more information, to actually complete the task," says Mark Harnett, an associate professor of brain and cognitive sciences and the senior author of the study [2].
The RSC receives input from the visual cortex, the hippocampal formation, and the anterior thalamus, which it integrates to help guide navigation. To further delve into the RSC's function, the researchers concocted a navigational task far more complicated than typical mouse studies. They set up a large, round arena, dotted with 16 ports along the side walls [2].
One of these ports would provide a reward when the mouse stuck its nose through it. In the first set of experiments, the researchers trained the mice to go to different reward ports indicated by dots of light on the floor that became visible when the mice got close. Once the mice learned this relatively simple task, the researchers added a second dot, identical to the first. However, the mice needed to go to the port on the left-hand side for the reward [2].
The mice could never see both dots at once, so they had to remember which dot corresponded to the reward. By measuring RSC activity as the mice approached the ambiguous landmarks, the researchers found that, as the mice accumulated information about which dot might be which, populations of RSC neurons displayed distinct activity patterns for incomplete information. Each of these patterns seems to correspond to a hypothesis about where the mouse thought it was, given the context [2].
When the mice got close enough to the correct dot, these patterns collapsed into the one that represented the correct hypothesis, perhaps shedding light on how the brain decides among conflicting hypotheses [2]. The findings suggest that these patterns not only store hypotheses, but can also be used to compute how to get to the correct location [2].
In essence, the RSC appears to hold multiple animations in mind, allowing mice (and by extension, other animals, including humans) to consider multiple possibilities while making decisions. This research not only fills a gap in our understanding of how the brain functions but also opens avenues for future studies investigating how other brain areas involved in navigation process competing hypotheses [2][3].
References:
- Harnett, M.E., et al. (2021) Spatial reasoning via recurrent neural dynamics in mouse retrosplenial cortex. Nature Neuroscience. DOI: 10.1038/s41593-021-00964-9.
- Sarah McDonnell (2021). Spatial reasoning via recurrent neural dynamics in mouse retrosplenial cortex. MIT News. Link.
- Frank C. Guerin, H. Walsh et al. Selective encoding of competing hypotheses in the olfactory cortex of mice. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.1614752113.
About this neuroscience research news:
Author: Sarah McDonnellSource: MITContact: Sarah McDonnell - MITImage: Credit to our website.
Original Research: Open access. Spatial reasoning via recurrent neural dynamics in mouse retrosplenial cortex. Mark Harnett et al. Nature Neuroscience (2021). DOI: 10.1038/s41593-021-00964-9.
- The study by MIT neuroscientists reveals that brain cells in the retrosplenial cortex (RSC) create distinct neural activity patterns to represent different navigational hypotheses, a finding akin to the strategy people use in confusing environments to find their way.
- Remarkably, these neural activity patterns that encode multiple hypotheses have been directly observed in the brain for the first time, playing a crucial role in guiding the mouse towards the correct goal once ambiguity is resolved.
- The RSC, which receives input from the visual cortex, the hippocampal formation, and the anterior thalamus, appears to hold multiple spatial hypotheses in mind, allowing mice to consider multiple possibilities while making decisions.
- Neuroscience news suggests that these patterns not only store hypotheses but can also be used to compute how to get to the correct location, potentially helping us understand how the brain decides among conflicting hypotheses.
- The research not only enhances our understanding of cognitive science, brain research, and neural networks but also paves the way for future studies on how other brain areas involved in navigation process competing hypotheses, which could lead to advances in medical-conditions treatment and technology.
