New Study Reveals Theta Brain Waves Influence Memory in Primates

Research from the Picower Institute for Learning and Memory at the Massachusetts Institute of Technology (MIT) has unveiled a significant link between theta brain waves and working memory in non-human primates. Published in the journal Neuron, the study titled “Working memory readout varies with frontal theta rhythms” explores how these brain waves, oscillating at a frequency of 3–6 Hz, contribute to the ability to detect subtle changes in visual environments.

The research confirms the hypothesis that the brain employs different wave frequencies to facilitate complex cognitive functions. According to Earl Miller, PhD, a professor of neuroscience and the study’s corresponding author, “This raises the possibility that traveling waves are organizing or even performing neural computation.” The findings provide clarity on how visual working memory operates and why its performance can vary among individuals.

To examine this phenomenon, researchers engaged non-human primates in a video game designed to test their working memory. In the game, an array of colored squares briefly appeared on a screen, only to disappear shortly after. Following a one-second delay, the array reemerged, with one square altered in color. The primates were tasked with identifying the changed square as quickly as possible. Throughout the experiment, researchers monitored the animals’ gaze positions and reaction times, while also measuring brain wave power across various frequencies and individual neural spikes in the frontal eye fields.

The study revealed that the primates’ accuracy and speed were influenced by the phase of the theta brain wave at the moment the square changed color, as well as the vertical position of the square on the screen. Each height on the screen corresponded to a specific phase of the theta wave that maximized performance. Notably, lower target squares aligned with later phases of the theta wave, impacting the timing of optimal performance.

Previous investigations from Miller’s laboratory have indicated that brain waves in the alpha and beta frequency range (approximately 8-25 Hz) regulate the cognitive understanding of task rules and dictate when faster gamma frequency waves (above 30 Hz) can be employed for sensory data encoding. In this latest study, theta waves appeared to mediate the interaction between beta and gamma waves. During the excitatory phase of theta, beta waves were suppressed, allowing visual information to emerge in neural spiking activity. Conversely, during the inhibitory phase, beta power increased while spiking activity decreased.

The implications of this research extend beyond basic neuroscience. Miller’s team is actively developing closed-loop analog feedback systems intended to enhance the power of various brain wave frequencies for potential clinical applications. Such advancements could pave the way for innovative therapies targeting cognitive impairments in humans.

This study is a significant step toward understanding the intricate workings of memory in non-human primates and highlights the potential for future applications in enhancing cognitive function through brain wave manipulation.