Traditional circuits have long been assumed to be the primary means by which the brain processes information, with information traveling directly from one cell to the next. However, a recent study conducted by Salk Professor Thomas Albright and staff scientist Sergei Gepshtein indicates that there is yet another, quite distinct manner in which the brain processes information: by analyzing the interconnections of waves of neuronal activity. To better understand how the brain works, researchers have published their results in Science Advances.
Professor Albright, the Conrad T. Prebys Chair in Vision Research and head of Salk’s Vision Center Laboratory, explains that “we now have a new understanding of how the computational machinery of the brain is working. The model helps explain how the brain’s underlying state can change, affecting people’s attention, focus, or ability to process information.”
How the brain process information
For decades, scientists have known that the brain experiences waves of electrical activity, both during sleep and while it’s awake. When it comes to processing sensory information, such as the sight of light or sound of a bell, ideas on the brain’s processing have focused on sensory information being recognized by specialized brain cells and then shuttled between neurons like a relay.
A single sensory cell’s varied responses to the same stimulus under various environmental conditions could not be explained by the brain’s traditional paradigm. When an animal is especially vigilant, for example, a cell could be triggered in response to a brief flash of light, but if the animal’s attention is elsewhere, the cell will stay dormant.
It is likened to wave-particle duality: the theory that light and matter contain qualities that are both particles and waves, as is the case in chemistry. Light may act like a particle under certain conditions (also known as a photon). It behaves like a wave in other instances.
Waves are dispersed across a large area, whereas particles are concentrated in a single spot. It’s impossible to understand light’s behavior without considering both of these points of view. In the classic concept of brain function, neurons interact to produce neural activity. This notion is similar to the depiction of light as a particle.
‘We’ve found that in some situations, brain activity is better described as interaction of waves, which is similar to the description of light as a wave. Both views are needed for understanding the brain,’ explained Gepshtein, head of Salk’s Collaboratory for Adaptive Sensory Technologies.
The research and its discoveries
It was difficult to explain several sensory cell features seen in the past using the ‘particle’ model of the brain. 139 neurons in an animal model were studied by the researchers in the current study to better understand how the cells coordinated their response to visual input.
Physicist Sergey Savel’ev of Loughborough University collaborated with the researchers to develop a mathematical framework for understanding and predicting the activity of neurons. This was the best method to describe how neurons behaved, they found, rather than individual neurons interfacing with one other.
In contrast to the widely held belief that a single burst of light activates specialized sensory cells, the researchers demonstrated that a scattered pattern of activity, with alternating peaks and valleys of activation like ocean waves, is really produced by many nearby cells.
These waves collide when they are generated concurrently in distinct parts of the brain. There is an even greater surge in activity when two peaks of activity come together than when one peak is met by another trough of low activity. Wave interference is a term for this.
While out in the real world, there are many, many inputs that result in the generation of numerous waves, according to Albright’s theory. A person’s overall response to their environment is determined by the way these waves interact.
In order to validate their mathematical model of how neural waves arise in the brain, the researchers created a visual experiment to go along with it. A tiny, weak line (referred to as a “probe”) was placed on a screen and bordered by other light patterns, and two persons were tasked with seeing it.
The researchers observed that how well participants did this task depended on where the probe located. According to the model, the capacity to detect the probe was raised at certain areas and depressed at others.
What does this mean?
‘Your ability to see this probe at every location will depend on how neural waves superimpose at that location,’ says Gepshtein, who is a member of Salk’s Center for the Neurobiology of Vision. ‘And we’ve now proposed how the brain mediates that.’
Neuronal waves are significantly more important than this visual illusion in describing how they interact. Neuroscientists think similar waves are created and interact in all areas, not simply the region of the cortex responsible for processing visual information. To put it another way, a person’s own thoughts and feelings can alter waves that are formed by sensory stimuli.
Researchers believe this may explain how the brain’s reaction to a stimulus can change from day to day.