August 25, 2023

Dreaming and Brain Waves: How the Left and Right Brain Interact

Professor Omar Ahmed’s lab explores how running, dreaming, and sleep are informed by communication between the left and right brain hemispheres.

In parenting books, Buzzfeed quizzes, and even dating apps, the concept of the left brain and the right brain divides people into simple binaries: creative vs. organized, emotional vs. factual. The science of the human brain, however, tells us that this is a vastly more complex place.

An LSA researcher is leading a lab that is studying brain communication, including the ways that the two hemispheres interact and how that interaction might be related to neurodegenerative disorders and memory loss. Through this research, Professor Omar Ahmed’s lab has discovered how running and REM sleep cause the left and right brain to communicate in a very specific way—something that could have implications for people living with Alzheimer’s disease.

Dreams could hold clues to the research. “We still don’t know the function of dreams, and we don’t know what ends up forming the content of our dreams,” says Ahmed, an associate professor of psychology, neuroscience, and biomedical engineering, who was recently recognized by the U-M Provost’s Neuroscience Scholars Committee. “But our interest in dreaming comes from trying to understand brain regions that are really important for memory.”

Ahmed says that a person’s experiences during the day likely inform what gets remembered during dreaming. And while non-REM sleep has been connected to memory consolidation, REM sleep, or the dream state, is still filled with possibility.

Professor Omar Ahmed examines an image of the retrosplenial cortex on a monitor in his lab. Photos by Scott Soderberg/ Michigan Photography. 

Ahmed sets up an instrument that helps researchers monitor brain activity.

The lab’s findings challenge the dominant belief in the field of neuroscience that the hippocampus is the single most important region of the brain for memory and dreaming. Ahmed says the reality is more complicated. “We’ve seen that the hippocampus gets activated when people and animals sleep, but there is another brain region that is connected,” he says.

That brain region is the retrosplenial cortex, a largely understudied part of the brain that informs a person’s sense of space and time, both in the dream world and in the physical world. “If there is a lesion to this brain region, people cannot remember what happened over the last few years, and sometimes they won’t form new memories either, so it is very similar to the hippocampus,” says Ahmed. “When someone suffers a lesion to this area, due to a stroke or hemorrhage, they simply cannot find their way home and become disoriented.”

The symptoms mirror those seen in Alzheimer’s disease and may provide a greater window into understanding the neurodegenerative disorder. “In the early stages of Alzheimer’s disease, one of the first regions to show altered activity is the retrosplenial cortex,” he says. “So there is clear evidence now that the retrosplenial cortex is impaired in people living with Alzheimer’s disease, perhaps explaining the profound disorientation symptoms associated with Alzheimer’s dementia.”

Splines, Dreaming, and Running

In addition to work on memory and neurodegenerative disorders, the Ahmed lab has made a discovery that is related to dreaming and running. “In studying the retrosplenial cortex, we found a unique brain rhythm that had not been described before,” says Ahmed. “It is way faster than other brain rhythms, 140 times per second. But what is different about this brain rhythm is that it is in perfect anti-phase synchronization across the left and right brain, like a game of neural ping pong across the two halves.” Perfect anti-phase is the difference of 180 degrees between the phase of two waves, or two waves in direct opposition to each other. Ahmed calls this brainwave phenomenon “splines,” named after the teeth on mechanical gears that are also perfectly anti-phase as the gears move each other forward.

“We still don’t know the function of dreams...But our interest in dreaming comes from trying to understand brain regions that are really important for memory.”

The Ahmed lab has tracked how splines are associated with running and dreaming. “We noticed this surprising rhythm, where the left brain and the right brain communicated better when the animals that we were recording ran faster,” says Ahmed. “The same kind of communication happened during dream-like sleep, or REM sleep.”

According to Ahmed, the brain needs to be particularly accurate when someone increases speed while running, because the faster you go, the more likely you are to run into something like a branch. Brain communication must be most accurate at high-risk moments to ensure the runner’s safety by predicting and reacting faster to any surprises in the environment.

As for why that same kind of brain communication goes into overdrive during dream-like sleep, Ahmed believes that it might be associated with making both necessary and random connections. He notes that the high level of the unexpected in dreams could potentially be explained by his lab’s discovery of extremely active neurons in both the left and right brain during splines in REM sleep. The brain in REM sleep could be attempting to foretell what might come next in the dreamscape, just like the runner attempting to avoid a potential branch as they run faster.

Graduate student researcher Megha Ghosh works on her computer while sitting at a lab counter. She is in a lab coat and is reading something on her computer screen. Light above the lab counter illuminates lab equipment along the wall and in cabinets in the background.

Biopsychology student researcher Megha Ghosh works on her computer in the Omar Ahmed lab.

Ahmed, who recently received the 1923 Memorial Teaching Award for outstanding teaching of undergraduates, suggests students and scholars should look for therapies while also considering new natural algorithms used by the brain that “can move the future of artificial intelligence forward.”

He is motivated by the brain’s vastness and the continued potential for new discovery. Ahmed says the human brain is far more efficient, optimal, and powerful at generalized problem solving than modern computers, but he also advises that there are many new horizons in psychology, neuroscience, and engineering.

“What drives me forward every day, in the lab and elsewhere,” he says, “is wanting to discover these amazing ways that our brains can solve problems.”