UT study shows why memories flash forward

Emmanuel Briseño

A typical Star Wars marathon may last for many hours, but when it is over, the viewer can recall the experience in a matter of seconds. Recently, UT neuroscience researchers have discovered the mechanism behind this phenomenon.

Postdoctoral fellow researcher Chenguang Zheng, assistant professor Laura Colgin and their colleagues discovered a system that could explain why people are able to design a project or remember a run near the lake in a relatively short time compared to the real-time action. Their research was recently published in the journal Neuron.

“It’s just exciting to think about,” Colgin said. “There could actually be this mechanism that could help explain why we are able to plan things or to remember things in a compressed way.”

The center of memory, emotion and spatial navigation in the brain is called the hippocampus. Place cells, a particular type of neuron in the hippocampus, activate every time a person occupies a different location in their environment.

“There are billions of neurons in the brain,” Zheng said. “They can be activated and help us to work in different kinds of memories for position or behavior.” 

The brain uses waves in different frequencies to communicate with itself. The signals from the place cells are organized within two of these waves, called fast and slow gamma rhythms. Fast gamma rhythms store information in real-time with one piece of information on the peak of each wave. Slow gamma rhythms store multiple pieces of information per oscillation.

Since there is more time between waves in the slow gamma rhythms, more information can be stored, but in less detail.

Colgin said she imagines the signals from the place cells as surfers and the brain waves as ocean waves. The faster the wave is, the sooner it will break, and only one surfer will be able to ride the wave. If the wave is coming in more slowly, more than one surfer will be able to catch the wave before it breaks.

Colgin said the research could have both practical and therapeutic applications.

The research was funded in part by the Office of Naval Research, which is interested in the possibility of being able to decode brain activity for use in computer and human collaborations.  When the computer and human user are not in agreement on a specific decision, the brain activity readings could help determine whether or not the human’s decision should be trusted, Colgin said.

The scientists also expect that the discovery of this mechanism could help people with brain injuries or disorders.

“Gamma rhythms are disrupted in several cognitive disorders, including schizophrenia, autism and Alzheimer’s disease,” Colgin said.

She said she hopes that a better understanding of brain rhythms could lead to new types of therapy for treating these diseases.

“These kinds of techniques have not yet been used for memory disorders, and we can imagine that would be a pretty exciting avenue for future research,” Colgin said.