The entire brain experiences slow, sustained waves of electrical activity when you sleep, much like the waves on a still ocean. That mental state is referred to as “slow wave sleep” by researchers. The electrical activity pattern is altered upon awakening to resemble more random noise. However, postdoctoral fellow Yianling Shi, assistant professor Tatiana Engel, and its colleagues at Cold Spring Harbor Laboratory (CSHL) discovered that there are patterns in the noise. The huge rolling sleep waves were shown to have smaller, quicker, more localized counterparts in the visual processing area of a monkey brain. How alert that region of the brain is reflected in the forms and dynamics of these local waves. The wave patterns may hold a key to understanding sleep, anesthesia, and attentiveness, according to the experts.
The visual cortex, which processes visual information, functions like a television screen that assembles an image from a series of dots, or “pixels,” to form a picture. Each brain pixel is made up of a column of cooperating neurons. Unstimulated columns can be either electrically active and responsive to stimuli (referred to as “On”) or inert and resistive to electrical activity (referred to as “Off”). Visual information (a stimulus) is registered as a significant electrical spike when it comes into contact with a “On” visual column. However, if visual information enters a column when it is “Off,” it may not be at all recorded.
Engel and Shi discovered that the waves become shorter and more choppy when monkeys are paying attention to a stimulus. They conducted this research in partnership with Kwabena Boahen, Tirin Moore, and Nicholas A. Steinmetz of the University of Washington. In contrast to when the animal is paying attention to something else, “On” and “Off” states flicker across visual cortical columns triggered by this stimulus more quickly and in a smaller region. But why would a conscious, alert brain wish to turn its informational columns off and miss something? Engel has several theories:
Keeping neurons in the ‘On’ state all the time is energetically costly. Another reason is that if we were always receptive to information, we may become overwhelmed; the ‘Off’ state could help suppress irrelevant information.
Researchers may be able to better understand how the brain reacts to medications and illness as a result of the finding that electrical noise exhibits pattern variations with various brain states. Additionally, machine learning researchers may adopt the skillfully designed noise tactics used by monkey brains, which are particularly adept at processing visual information, to enhance artificial brains.
Cortical state dynamics and selective attention define the spatial pattern of correlated variability in neocortex.Yan-Liang Shi, Nicholas A. Steinmetz, Tirin Moore, Kwabena Boahen, Tatiana A. Engel.
Published: February, 2022
DOI: 10.1038/s41467-021-27724-4