CAMBRIDGE, Mass. — The brain continues to be a fascinating organ that keeps neuroscientists on its toes. Researchers from the Massachusetts Institute of Technology (MIT) have made a pioneering discovery involving the brain’s cortex — the outer layer responsible for complex functions such as thought, memory, and emotion. The team has identified distinct patterns of electrical activity within the cortex’s six layers, findings that hold true across various brain regions and several animal species, including humans.
The cortex’s layered structure, visible under a microscope, has long fascinated scientists. Now, for the first time, researchers have shown that these layers exhibit unique patterns of electrical oscillations.
At the heart of this research is the observation that neuron activity in the cortex’s upper layers is dominated by fast-moving gamma waves, while deeper layers are characterized by slower alpha and beta waves. This consistency across different species and brain regions suggests these waves play a critical role in brain function.
“When you see something that consistent and ubiquitous across cortex, it’s playing a very fundamental role in what the cortex does,” says study senior author Earl Miller, the Picower Professor of Neuroscience and a member of MIT’s Picower Institute for Learning and Memory, in a university release.
The study also touches on the potential link between the imbalance in these oscillations and brain disorders such as epilepsy and ADHD, drawing an analogy to an orchestra where a single out-of-sync instrument can disrupt the entire performance.
To conduct their research, neuroscientists analyzed data from various sources, including human patients undergoing surgical procedures, using advanced electrodes that record activity from all cortical layers simultaneously. This data was processed with a novel computational algorithm, termed FLIP (frequency-based layer identification procedure), allowing precise mapping of which layer each signal originated from.
This large-scale analysis revealed a consistent pattern of layered activity across all examined species and cortical areas, underscoring the fundamental nature of this mechanism within the cortex.
“We did a mass analysis of all the data to see if we could find the same pattern in all areas of the cortex, and voilà, it was everywhere,” notes study lead author Diego Mendoza-Halliday, a research scientist at MIT. “That was a real indication that what had previously been seen in a couple of areas was representing a fundamental mechanism across the cortex.”
Researchers propose that this spatial organization of oscillations helps the brain integrate new sensory information with existing memories and processes, a balance crucial for cognitive function. Imbalances in these oscillations could lead to various neuropsychiatric disorders, offering new avenues for diagnosis and treatment.
“The consequence of a laminar separation of these frequencies, as we observed, may be to allow superficial layers to represent external sensory information with faster frequencies, and for deep layers to represent internal cognitive states with slower frequencies,” explains study senior author André Bastos, an assistant professor of psychology at Vanderbilt University. “The high-level implication is that the cortex has multiple mechanisms involving both anatomy and oscillations to separate ‘external’ from ‘internal’ information.”
Looking ahead, the team aims to further explore these oscillation patterns across different brain regions.
“Our hope is that with enough of that standardized reporting, we will start to see common patterns of activity across different areas or functions that might reveal a common mechanism for computation that can be used for motor outputs, for vision, for memory and attention, et cetera,” says Mendoza-Halliday.
The study is published in the journal Nature Neuroscience.