• Brain waves called theta rhythms, shown simultaneously recorded in the hippocampus (grey) and prefrontal cortex (black), are shown reaching peak synchrony (the yellow streak and white blob).

    Brain waves called theta rhythms, shown simultaneously recorded in the hippocampus (grey) and prefrontal cortex (black), are shown reaching peak synchrony (the yellow streak and white blob).

    Image courtesy / Matthew W. Jones

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Brain structures 'tune in' to rhythms to coordinate activity

Brain waves called theta rhythms, shown simultaneously recorded in the hippocampus (grey) and prefrontal cortex (black), are shown reaching peak synchrony (the yellow streak and white blob).


Different brain regions working together may coordinate by locking into an oscillation frequency the way a radio tuner locks into a station, report researchers from the Picower Institute for Learning and Memory at MIT in the Nov. 15 issue of the journal PLoS (Public Library of Science) Biology.

The brain's electrical activity is displayed in the form of brain waves. Matthew A. Wilson, Picower Professor of Neuroscience, and Matthew W. Jones, postdoctoral associate at the Picower Institute, explore how brain waves help different parts of the brain communicate in a broad-based network. When we are focused attentively on a speaker, for instance, brain waves called theta rhythms oscillate in sync throughout our brains. Other rhythms are prominent when we are resting or involved in intense mental activity.

Researchers have found that neurotransmitters -- and antidepressants -- can affect these rhythms. To our brains, the inability to shut down these brain wave communication channels is like having to listen to someone talking who won't shut up, Wilson said. Unsynchronized brain rhythms may be tied to mood disorders or diseases such as schizophrenia, he said.

In the future, analyzing the coordination of patients' brain rhythms at the level of individual neurons and larger networks may help diagnose cognitive disorders, he said.

In the PLoS paper, Wilson and Jones looked at particular theta rhythms in rats. These rhythms are associated with complex behaviors that tap into memory and/or decision-making, such as rats exploring a maze or humans navigating, planning or recalling events.

The MIT researchers' data reveal theta frequency correlation between the memory-centered hippocampus and the decision-making prefrontal cortex when behavioral demands require the two structures to work together and, presumably, communicate. By locking onto certain rhythms, the brain exploits a communication system in which different brain areas can work alone and "tune in" to information from other areas when necessary. This ability to quickly tune information in and out appears to be critical for informed decision-making, Wilson said.

A rat running a maze, for example, needs to integrate spatial information, memory of where the reward is located, route information and rules about how to navigate the space to make the right choice. When its relevant brain structures are all working, its theta rhythms are locked in sync. When these rhythms are not synchronized prior to decision-making, the animals make errors.

"It follows that disruption of such complex cross-structural communication is likely to generate behavioral impairments," Wilson said. "For example, schizophrenia is widely presumed to involve disrupted functional connectivity of the prefrontal cortex. Interestingly, schizophrenic patients also show spatial working memory impairments."

This work is supported by The Wellcome Trust and the National Institute of Mental Health.

A version of this article appeared in MIT Tech Talk on November 30, 2005 (download PDF).


Topics: Bioengineering and biotechnology, Neuroscience

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