York U researchers make discovery in brain activity related to memory formation

A team of researchers at York University has identified that a neural activity contributing to memory consolidation during rest is also observed during attentive visual exploration.

A schematic depicting the short-wave ripples (SWR) happening

A schematic depicting the sharp-wave ripples (SWR) happening

Sharp-wave ripples (SWRs) are high-frequency brain rhythms that appear during sleep and are thought to train the brain to remember something while it’s inactive or “offline,” essentially working to strengthen memories. However, recent research out of Professor Kari Hoffman’s Perception & Plasticity Lab indicates SWRs are also associated with attentive focal search.

“We see it popping up where we didn’t expect it,” says Hoffman. “Apparently the brain uses this signal even while it’s working hard to learn solutions to new problems, and not just when it’s offline or at rest.”

Kari Hoffman

Kari Hoffman

Several labs have performed experiments to interrupt these ripples during sleep and inactivity, and have found that interruptions lead to memory deficits. This, says Hoffman, suggests that SWRs are causally related to memory formation.

The ripples, she says, are considered the most synchronous activity in the healthy brain and their rhythm is most closely linked to memory formation.

The new findings out of Hoffman’s lab suggest SWRs may have a similar effect on memory consolidation during active learning, and not just at rest, and therefore could play a new role in memory formation.

Subjects are given a goal-oriented visual search task, similar to the game “Where’s Waldo.” If a ripple happens near the visual target object, the likelihood of finding that object increases.

The work is published in the Journal of Neuroscience, and the first author is Timothy Leonard, a York University PhD student in psychology and a recipient of a Queen Elizabeth II Graduate Scholarship in Science & Technology.

“In the context of ongoing deep brain stimulation clinical trials to alleviate memory decline, this may be an important signal to consider during learning and remembering, and not just while we’re sleeping,” says Hoffman.

The results from the study will also be applied to the lab’s Brain Canada-funded neurorehabilitation research, and researchers will look at the SWR activity in healthy participants and memory-impaired participants during the same tasks.

The goal is to “better understand how memory formation works, in the hope of creating better improving treatments to fight memory decline,” says Hoffman.

The research will continue at the lab with a focus on a real-time closed-loop interruption to see if it has an effect, or a different effect, on active search versus rest.

By Ashley Goodfellow Craig, YFile deputy editor

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