News-Letter

It is commonly believed that the brain is relatively quiet during sleep. Neuroscientists have thought for years that only a few limited areas of the brain are active, particular to the parts of the brain that are responsible for vision.

But a team of researchers anchored at Hopkins have found strong evidence that during REM sleep - the deepest sleep state associated with rapid eye movements and dreaming - our brains are active not only in visual areas, but also in areas that control hearing, smell, touch and balance.

It was previously thought that rapid eye movements sleep (REM), presumably a vision-related event, activated only visual areas of the brain. The new evidence, which implicates several sensory systems, suggests that the activity patterns of the sleeping brain resemble those of the brain when it is awake.

"This is the first report to detect brain activity associated with REMs in areas that control our senses other than sight," lead researcher Charles Hong said.

The team's discovery that the sleeping brain functions similarly when awake has wide implications for future studies of the normal and abnormal brain. Hong said that studying brain systems activated during REM will help researchers better understand brain development in infants.

In addition, studies could aid doctors in the early detection of psychiatric diseases, including schizophrenia and Alzheimer's disease.

"Our findings may provide insight on how our brains work when we are awake," Hong said.

For two nights in a row, the team used fMRIs to scan 11 participants while they slept. Functional Magnetic Resonance Imaging (fMRI) indirectly measures brain activity by recording blood flow.

The participants were monitored by video to determine when the participants fell asleep and when they entered REM sleep, which is often characterized by twitching facial muscles, fingers and toes.

"REM sleep occurs approximately every 90 minutes and lasts about 25 minutes," Hong said. There are a number of benefits to observing the brain during REM sleep. "REMs are task free," Hong said. "The subject does not need to understand or cooperate with instructions given during typical waking studies that ask subjects to perform specific tasks."

This opens the door for REM research on patients who otherwise would not be able to cooperate with conventional waking studies, such as infants or patients with Alzheimer's disease. REM studies are not only more convenient, Hong explained, but also more revealing. "Only six minutes of fMRI data from a participant in the REM study produced robust results."

After obtaining sufficient data from each patient, the researchers analyzed the brain scans for high blood flow levels in localized areas. They found significant activity in areas associated with language, smell, touch and vision.

Activity was also high in "multisensory convergence zones," where sensory information from different areas of the brain is brought together and reassembled.

"Our findings lend great support to the view that the waking brain functions in a similar way to the dreaming brain," Hong said.

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