New Study Reveals Theta Waves Enhance Memory in Primates

Research from the Picower Institute for Learning and Memory at the Massachusetts Institute of Technology (MIT) has revealed that working memory in non-human primates is influenced by theta brain waves, operating at a frequency of 3–6 Hz. This study, published in the journal Neuron, sheds light on how these brain waves help primates detect subtle environmental changes, establishing a link between neural activity and cognitive performance.

The research led by Earl Miller, PhD, a professor of neuroscience and corresponding author of the study, builds on previous findings suggesting that the brain utilizes various frequency waves to perform complex cognitive tasks like working memory. Miller noted that the current research illustrates how these brain waves affect memory performance, stating, “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.”

To investigate working memory, the researchers engaged non-human primates in a video game that displayed an array of colored squares. After a brief interval, the squares disappeared and reappeared with one square changing color. The primates were tasked with identifying the changed square as quickly as possible. The team tracked their reaction times and gaze positions, while also measuring brain wave power across various frequencies and individual neural spikes in the frontal eye fields, a brain region that maps visual input similarly to how it hits the retina.

The study found that the accuracy and speed of the primates’ responses were affected by both the phase of the theta wave at the moment the changed square appeared and the vertical position of that square on the screen. Each location had its own optimal phase of the theta wave for peak performance. Specifically, targets positioned lower on the screen were associated with a later phase of the theta wave for maximum efficiency.

Miller’s previous research has established that alpha and beta frequency waves, ranging from approximately 8 to 25 Hz, help the brain understand task rules and determine when faster gamma frequency waves, above 30 Hz, can be utilized for sensory data encoding. In the context of this study, theta waves appear to coordinate the interaction between beta and gamma waves. During the excitatory phase of the theta waves, beta activity was suppressed, allowing visual information to manifest in neural spiking. Conversely, during the inhibitory phase, beta power increased while spiking activity decreased.

Looking ahead, Miller’s lab is exploring the potential of developing closed-loop analog feedback systems designed to enhance the power of different frequency waves for clinical applications. This research could pave the way for new methods to improve cognitive function in various contexts, particularly those affected by memory impairments.

The findings from this study significantly advance our understanding of the neural mechanisms behind working memory and emphasize the complex interplay between different brain wave frequencies in cognitive processing.