MIT neuroscientists propose a new framework that explains how thought emerges from the coordination of neural activity driven by oscillating electrical fields, known as brain “waves” or “rhythms.”
Watching pixels on your phone under a microscope can be very informative, but it’s not possible if your goal is to understand what an entire video shows on the screen. Cognitive functions are almost identical to those that occur in the brain. A trio of MIT neuroscientists say this can only be understood by observing how millions of cells move in harmony. In a new paper, they lay out the basis for understanding how thought arises from the coordination of neural activity driven by oscillating electric fields, also known as “brain waves” or “rhythms.”
Meaning of brain rhythms
The brain’s rhythms, historically considered merely byproducts of neural activity, are actually critical to its organization, Picower professor Earl Miller and researchers Scott Brincat and Jefferson Roy write in the journal. Current Opinion in Behavioral Science .
Although neuroscientists have gained a great deal of knowledge by studying how individual brain cells are wired and how and when they emit “spikes” to send impulses through specific circuits, there is also a need to evaluate and apply new concepts at the brain rhythm scale. It may involve individual or even multiple areas of the brain.
The field of neuroscience is expanding
“Speech and anatomy are important, but there’s more going on in the brain than that,” says senior author Miller, a faculty member of the Pickaver Institute for Learning and Memory and MIT’s Department of Brain and Cognitive Sciences. “Many functions, especially cognition, occur at a higher level.”
Examining the brain at this scale could include understanding not only healthy higher-level functions, but also how these functions are disrupted during disease, the authors write.
“Many neurological and psychiatric disorders, such as schizophrenia, epilepsy, and Parkinson’s disease, are associated with disruption of primary features such as neuron synchronization,” they write. “We hope that understanding how to interpret and interact with these new features will be critical to understanding cognition as well as developing effective treatments.”
emergence of thoughts
The bridge between the scale of individual neurons and the broader coordination of many cells relies on electric fields, the researchers write. Thanks to a phenomenon called “ephaptic coupling,” the electric field created by the activity of one neuron can affect the voltage of neighboring neurons, creating an alignment between them. Thus, electric fields both reflect and influence neural activity. In a 2022 paper, Miller and colleagues showed through experiments and computer simulations that information encoded in electric fields produced by populations of neurons can be read more reliably than information encoded by the spikes of individual cells. In 2023, Miller’s lab provided evidence that rhythmic electrical fields can coordinate memories across regions.
Role of beta and gamma rhythms
Miller’s laboratory has published numerous studies showing that on this large scale, where rhythmic electrical fields transfer information between brain regions, low-frequency rhythms called the “beta” range originate from deeper layers of the cerebral cortex and regulate brain regions throughout the brain. Strength of gamma rhythms, faster frequency in more superficial layers.
By recording neural activity in the brains of animals participating in working memory games, the lab showed that beta rhythms carry “top-down” signals to control when and where gamma rhythms can encode sensory information, such as images, that animals need to remember. game.
Spatial computing and cognitive control
Some of the most recent data from the laboratory suggests that beta rhythms exert this control of cognitive processes in physical areas of the cerebral cortex, essentially acting as patterns indicating where and when gamma can encode or retrieve sensory information into memory. According to this theory, which Miller calls “Spatial Computation”, beta can determine the general rules of a task (e.g. new numbers when changing the combination) even if the content of specific information changes (such as the forward and reverse turns required to open a combination lock).
Overall, the authors write, this structure also allows neurons to flexibly encode multiple types of information simultaneously; this is a common neural property called “mixed selectivity.” For example, a neuron that encodes the combination number of a lock may also be assigned the specific step of the lock-picking process to which that number relates, depending on which beta patch pattern it is in.
Spatial Coding: New Insights
In the new study, Miller, Brincat, and Roy suggest another advantage consistent with cognitive control based on the interaction of large-scale coordinated rhythmic activity: “subspace coding.”
This idea suggests that brain rhythms organize the multitude of possible outcomes that could arise when, for example, 1000 neurons engage in independent impulse activity. Instead of many combinatorial possibilities, there is actually much less “subspace” of activity because the neurons are coordinated rather than independent. It is as if the impulses of neurons are like a flock of birds coordinating their movements.
Different phases and frequencies of brain rhythms provide this coordination; aligned to reinforce each other or balanced to prevent interference. For example, if sensory information must be remembered, the neural activity representing it may be protected from interference during the perception of new sensory information.
“Thus, organization of neural responses into subspaces can both separate and integrate information,” the authors write.
The impact of brain rhythms on cognition
The ability of brain rhythms to coordinate and organize information processing in the brain is what allows functional cognition to develop on such a scale, the authors write. Therefore, understanding cognition in the brain requires examining rhythms.
“The study of individual neural components (individual neurons and synapses) in isolation has made tremendous contributions to our understanding of the brain and remains important,” the authors conclude. “However, it is becoming increasingly clear that to fully grasp the complexity of the brain, these components must be analyzed together to identify, study and correlate new properties.”
Source: Port Altele
