Summary: A recent study examines how the brain creates coherent cognitive maps of spaces and identifies the crucial role that sleep plays in this process. While “place tissues” in the brain mark particular locations, weaker geographical cells create a detailed cognitive map of these points.
According to research, sleep allows the brain to join locations and encapsulate them in a psychological geography, allowing it to process these maps more accurately. This finding highlights the value of both gentle and delicate neural activity in improving our ability to plan and navigate in our surroundings.
Important Information:
- Poorly Geographic Cells: These cells connect discrete spot memories into a cognitive map, necessary for navigation.
- Role of Sleep: Sleep develops and strengthens neurological relationships, enhancing mental tracking.
- Mental Maps: These maps offer graphic depictions of spaces, enabling emotional exploration and planning.
Origin: Picower Institute at MIT
Your investigations of new cities expose you to numerous unique locations on the first day of your trip. Although the memories of these locations ( such as a stunning backyard on a quiet side street ) are immediately inescapable, it may take a few days before you have enough sense of the area to point a more seasoned visitor to that same location and perhaps to the café you discovered nearby.
A recent study by MIT researchers at The Picower Insitute for Learning and Memory in animals provides fresh evidence for how the mind creates coherent mental drawings of entire places and emphasizes the crucial role that sleep plays in this process.
Researchers have long been aware that the brain uses neurons in a place known as the brain to recall certain locations. When an animal is at the location that the synapse is tuned to recall, so-called “place tissues” can actually start to trigger.
However, having a mental concept of how they all relate in a constant total geography is more helpful than having markers for specific areas.
Although these” cognitive maps” were first proposed in 1948, researchers have remained unsure of how the mind came to construct them.
The ability to make subtle but significant changes in the activity of tissues that are only weakly attuned to individual locations but that increase the resilience and elegance of the hippocampus ‘ processing of the entire space, according to a new study published in the December edition of Cell Reports.
With rest, the article’s analyses indicate, these “weakly geographic” cells extremely enrich neural community engagement in the brain to link together these places into a cognitive map.
” On moment 1, the mind doesn’t represent the area really well”, said lead author Wei Guo, a research scientist in the facility of senior author , Matthew Wilson, Sherman Fairchild Professor in The Picower Institute and MIT’s Departments of Biology and Brain and Cognitive Sciences.
” Neurons represent individual locations, but together they don’t form a map. But on day 5 they form a map. All of these neurons must work together in a coordinated ensemble if you want a map.
Mice mapping mazes
For about 30 minutes a day for several days, Guo and Wilson and labmates Jie” Jack” Zhang and Jonathan Newman gave mice simple mazes of various shapes to explore them freely. Importantly, the mice were not directed to learn anything specific through the offer of any rewards.
They just wandered. Previous research has demonstrated that mice naturally exhibit “latent learning” of spaces after a number of days of this unrewarded experience.
Guo and his colleagues created artificial neural networks to flash when a buildup of calcium ions made them electrically active, to understand how latent learning manifests.
They not only recorded the flashes of the neurons when the mice were actively exploring, but also while they were sleeping. Wilson’s lab has shown that animals , “replay”  , their previous journeys during sleep, essentially refining their memories by dreaming about their experiences.
Analysis of the recordings revealed that the place cells ‘ activity started to develop and continued to grow steadily over the course of several days of exploration. This activity alone would not be sufficient to explain how a cognitive map or latent learning develop over a period of days.
Guo expanded his analysis to more subtly enigmatic and mysterious activity of cells that were not so spatially tuned, in contrast to many other studies where scientists only examine the strong and clear activity of place cells.
He discovered that many of the “weakly spatial” cells gradually correlated their activity with activity patterns among other neurons in the network using an emerging method called “manifold learning.”
As this was happening, Guo’s analyses showed, the network encoded a cognitive map of the maze that increasingly resembled the literal, physical space.
” Although not responding to specific locations like strongly spatial cells, weakly spatial cells specialize in responding to ‘ ‘ mental locations,’ ‘ i. e., specific ensemble firing patterns of other cells”, the study authors wrote.
This weakly spatial cell can act as a bridge between these locations if a weakly spatial cell’s mental field includes two subsets of strongly spatial cells that encode distinct locations.
In other words, the weakly spatial cells ‘ activity is likely to combine the various locations represented by the place cells into a mental map.
The need for sleep
Studies by Wilson’s lab and many others have shown that memories are consolidated, refined and processed by neural activity, such as replay, that occurs during sleep and rest.
Therefore, Guo and Wilson’s team sought to determine whether weak spatial cells contribute to latent cognitive mapping by requiring sleep.
To accomplish this, they allowed some mice to take a three-hour siesta between each new maze and two times during the same day. Some mice were given permission to sleep, while others were denied. The ones who did, however, showed a marked improvement in their mental map, whereas those who were not allowed to sleep did not.
Not only did the network encoding of the map improve, but also measurements of the tuning of individual cells during demonstrated that sleep assisted cells in becoming more attuned to both places and network activity patterns, so called “mental places” or “fields” ( also known as “mental places” ) or “fields” ).
Mental map meaning
The” cognitive maps” the mice encoded over several days were not literal, precise maps of the mazes, Guo notes. Instead they were more like schematics. Their advantage is that they give the brain a topology that can be explored mentally without having to reside in a particular location.
For instance, once you’ve created a cognitive map of the area around your hotel, you can organize your excursion the following morning ( for example, you could picture eating a croissant at the bakery you found a few blocks west and then imagining putting it on one of those benches in the park along the river ).
Indeed, Wilson suggested that the weakly spatial cells ‘ activity may be obscuring salient non-spatial information that provides additional meaning to the maps ( i .e., the concept of a bakery is not spatial, even if it is closely related to a particular location ). However, the study did not examine any particular behaviors among the mice or any landmarks within the mazes.
Wilson said that future studies can look into what kind of information they might be incorporating into the animals ‘ sense of their surroundings now that the study has determined that weakly spatial cells make a significant contribution to mapping. We appear to think that the places we live in are more than just a collection of discrete locations.
In this study, we focused on natural behavior and found that significant neural plastic changes at the ensemble level still occur during freely exploratory behavior and subsequent sleep, in the absence of reinforcement,” the authors claimed.
” This form of implicit and unsupervised learning constitutes a crucial facet of human learning and intelligence, warranting further in-depth investigations”.
The study was supported by the National Institutes of Health, The Picower Institute for Learning and Memory, and The Freedom Together Foundation.
About this news from neuroscience and sleep
Author: David Orenstein
Source: Picower Institute at MIT
Contact: David Orenstein – Picower Institute at MIT
Image: The image is credited to Neuroscience News
Original Research: Open access.
” Latent learning drives sleep-dependent plasticity in distinct CA1 subpopulations” by Matthew Wilson et al. Cell Reports
Abstract
Latent learning drives sleep-dependent plasticity in distinct CA1 subpopulations
Without requiring additional instruction, the brain can convert experiences into” cognitive maps,” a type of implicit memory, through a process known as latent learning.
We use hippocampal neurons in mice to study its neural mechanisms as they undergo latent spatial mapping. We find that the high-dimensional neural state space gradually changes into a low-dimensional manifold that resembles the physical environment over time.
This transformation occurs as a result of sleep-related neural reactivation of navigational experiences.
Additionally, we discover a subset of hippocampal neurons that, instead of creating place fields in a novel setting, maintain weak spatial tuning but gradually become correlated with other neurons.
The ensemble code transforms from a low-dimensional manifold that effectively connects distinct place fields of place cells into a map-like structure as a result of the elevated correlation’s introduction of redundancy.
These findings point to a potential mechanism by which the hippocampus may learn spatial maps at latent speed.
