Total Recall: UT Researchers Shed Light on Memory


Let’s say it’s the morning of your first day of college. You’ve memorized your schedule, mapped out your route, and taken off 20 minutes early. But when you actually set foot on campus, you’re lost. Without reference points and out of time, you accidentally take a seat in a graduate physics class.

Then two days later, you wake up with only five minutes to spare, run out the door, and arrive on time like a pro. You barely even thought about how to get to the right building. This ability to recall locations in less than an instant is the focus of some UT researchers’ latest study.

Assistant professor of neuroscience Laura Colgin and the researchers from her lab recently co-authored a study addressing how place cells, or brain cells that become active when an animal enters a particular environment, code spatial information. Published in the January edition of the journal Neuron, the nearly two-year-long study shows evidence of a mechanism that compresses information needed for memory retrieval.

By studying rats, the researchers looked at the presence of gamma rhythms, which are a type of brainwave thought to be related to conscious perception, during different activities. They found that different gamma rhythm frequencies indicated different brain activities. Colgin says if a gamma rhythm was fast, “activequietactivequietactivequiet,” then the animal was immediately experiencing a location. But with a slow gamma rhythm, “active…quiet…active…quiet,” then the animal was recalling information about a location.

“If the animal is actually in that location, then the cells can just receive all the process sensory information from the environment,” Colgin says. “Or the cells could say ‘we’ve learned this environment before so we can just retrieve that memory of what’s coming up.’”

Although it might seem counterintuitive that fast memory recall would coincide with a slow gamma rhythm, Colgin says the way to understand it is to imagine a group of surfers on the beach, all lined up and ready to catch a wave. If a wave is coming in fast, only one surfer will be able to catch it before it breaks. But if a wave comes in slowly, it continues to build, allowing more surfers to ride the wave together.

“Since there were multiple surfers surfing per wave, even though the waves were moving in more slowly, you’d be able to move through the line more quickly within a certain amount of time,” she says.

Colgin and her team believe their research could have larger implications with regard to human health, though she stresses that until their work can be done on humans, they can’t be fully certain. In several cognitive disorders, such as Alzheimer’s disease, autism spectrum disorder, and schizophrenia, gamma rhythms are disrupted. The researchers are studying the gamma rhythms of animal models with these diseases, observing which mechanisms are distorted.

“That might give us some insight into cognitive impairments that patients have,” she says. “And then we can test various manipulations that can counteract these disorders.”

Illustration via Allan Ajifo on Flickr


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