Revising Prior Assumptions – Recent Research Directly Associates Brain Oscillations with Memory Functions

by Tatsuya Nakamura
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Theta oscillations in brain and memory

A new study indicates that rhythmic electrical activity in the brain, or oscillations, are principally driven by memory functions, challenging earlier theories. The research highlights that theta oscillations in the hippocampus were more frequently observed when individuals were engaged in recalling events rather than in experiencing them firsthand. This emphasizes the central role of memory in driving theta oscillations and suggests possible avenues for addressing cognitive impairments and brain injuries.

These insights could lay the foundation for therapeutic approaches aimed at mitigating cognitive deficits and enhancing memory function.

Generated within neurons, rhythmic patterns of electrical activity, known as oscillations, have been a subject of much debate within neuroscience, particularly concerning what primarily triggers these signals. Researchers at the University of Arizona found that the act of recalling events could elicit these oscillations more prominently than the experience of the events themselves.

Published in the scientific journal Neuron, the study focused specifically on theta oscillations. These waves appear in the hippocampus during activities like exploration, navigation, and sleep—a region of the brain integral to the capacity to recollect the past.

Before this investigation, prevailing thought was that external environmental factors were more instrumental in influencing theta oscillations, according to Arne Ekstrom, professor of cognition and neural systems at the University of Arizona’s Department of Psychology and the senior author of the study. However, Ekstrom and his team found that internally generated memories are, in fact, the primary catalyst for theta activity.

“Remarkably, theta oscillations in humans were found to be more frequent during the act of memory recollection than during direct experience of events,” said Sarah Seger, the lead author of the study and a graduate student in the Department of Neuroscience.

The outcomes of this research may offer significant contributions to treatment modalities for patients suffering from cognitive impairments and brain injuries, including those caused by seizures, strokes, and Parkinson’s disease, stated Ekstrom. The use of memory to internally stimulate and consequently drive theta oscillations could lead to incremental enhancements in memory over time.

The study was a collaborative effort involving researchers from the University of Texas Southwestern Medical Center in Dallas, including neurosurgeon Dr. Brad Lega and research technician Jennifer Kriegel. The team worked with 13 patients preparing for epilepsy surgery, monitoring them via implanted brain electrodes to detect sporadic seizures. Theta oscillations in the hippocampus were recorded for the study.

Participants engaged in a virtual reality experiment in which they navigated through a virtual city. The researchers paused the experiment upon the participants’ arrival at the intended location and asked them to mentally retrace their navigational path. The research team found that theta oscillations were more frequent and sustained when participants were merely recalling the route compared to when they were navigating through it initially.

As a means of compensating for cognitive impairments, cognitive training and rehabilitation could be deployed, Ekstrom suggested.

“In future, the research will also explore how theta oscillations behave in patients who are freely moving as opposed to bedridden, thereby examining the relationship between free navigation and memory in the context of brain oscillations,” Ekstrom added.

“Having the capability to directly juxtapose oscillations present during the original experience with those during subsequent recollection is a considerable advancement for designing new experiments and comprehending the neural underpinnings of memory,” commented Seger.

Reference: “Memory-related processing is the primary driver of human hippocampal theta oscillations” by Sarah E. Seger, Jennifer L.S. Kriegel, Brad C. Lega and Arne D. Ekstrom, published on 18 July 2023 in Neuron.
DOI: 10.1016/j.neuron.2023.06.015

The research received funding from the National Institutes of Health.

Frequently Asked Questions (FAQs) about Theta oscillations in brain and memory

What is the main finding of the new research published in the journal Neuron?

The central finding of the new research is that theta oscillations in the brain are primarily driven by memory functions, as opposed to external experiences. This challenges previous beliefs that considered the external environment to be the main factor influencing these oscillations.

Who conducted this research and where was it published?

The research was conducted by a team from the University of Arizona in collaboration with researchers from the University of Texas Southwestern Medical Center. The study was published in the scientific journal Neuron on 18 July 2023.

What specific brain region does the study focus on?

The study focuses on theta oscillations that occur in the hippocampus, a region of the brain that plays a crucial role in memory.

How could this research impact therapies for cognitive impairments and brain injuries?

The findings suggest new avenues for developing therapeutic approaches aimed at treating cognitive impairments and brain injuries. By understanding that memory is the primary driver of theta oscillations, treatments may be designed to stimulate these oscillations for cognitive enhancements.

What methods were used in the study?

The study used a virtual reality experiment involving 13 patients who were preparing for epilepsy surgery. Electrodes were implanted in their brains to record theta oscillations in the hippocampus as they navigated through a virtual city and later recalled the route.

Who funded this research?

The research was funded by the National Institutes of Health.

What are the future plans for this line of research?

Arne Ekstrom, the senior author of the study, plans to conduct future research in freely walking patients to examine the relationship between free navigation and memory in the context of brain oscillations.

Is this study significant for understanding the neural basis of memory?

Yes, the study is significant as it allows researchers to directly compare oscillations present during the original experience with those during subsequent recollection, providing new insights into the neural basis of memory.

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