A recent study published in the journal Neuron highlights the role of theta-frequency brain waves in the visual working memory of non-human primates. Conducted by researchers at the Picower Institute for Learning and Memory at the Massachusetts Institute of Technology (MIT), the study sheds light on how these brain waves, oscillating at 3-6 Hz, may influence the detection of subtle environmental changes.
The findings provide a deeper understanding of the brain”s mechanisms for managing visual working memory while also addressing the limitations and variability in performance. Led by Earl Miller, PhD, a professor of neuroscience and the study”s corresponding author, the research builds on prior work suggesting that the brain utilizes waves of varying frequencies to perform complex cognitive tasks.
Miller noted, “It shows that waves impact performance as they sweep across the surface of the cortex. This raises the possibility that traveling waves are organizing or even performing neural computation.”
In the study, non-human primates participated in a video game designed to analyze their working memory. They viewed an array of colored squares that vanished and then reappeared after a brief interval, with one square displaying a different color. The primates had to quickly identify the altered square. Researchers monitored their gaze and reaction times, alongside measuring brain wave activity across various frequencies and individual neural spikes in the frontal eye fields, an area of the brain responsible for processing visual information.
The accuracy and speed of the primates” responses were found to be influenced by the phase of the theta wave at the moment the modified square reappeared, as well as its vertical position on the screen. Each height corresponded to a specific theta phase where performance peaked; notably, lower target squares aligned with later phases of the theta wave.
Previous research from Miller”s lab has revealed that alpha and beta frequency waves (approximately 8-25 Hz) help the brain comprehend task rules while regulating the use of faster gamma frequency waves (30 Hz and above) for sensory data encoding. In this latest study, theta waves appeared to mediate the interaction between beta and gamma waves. During the theta wave”s excitatory phase, beta activity was suppressed, leading to increased neural firing in response to visual stimuli. Conversely, during the inhibitory phase, beta activity surged while neural firing diminished.
Miller”s team is currently exploring the development of closed-loop analog feedback systems aimed at enhancing the efficacy of brain waves at different frequencies for potential clinical applications.
