New research from a new University of Toronto faculty member is providing valuable insight into how the brain works to retain memory — and it could help treat patients with memory impairment.
Alexander Barnett, an assistant professor in the Department of Psychology in the Faculty of Arts & Science, and a team of researchers have found that a vital part of the brain that helps retain memory — the hippocampus — may have more dynamic interactions with the rest of the brain than previously thought, particularly when it comes to event boundaries, the start and end of a memory.
“At event boundaries, the hippocampus actually peaks in activity, reliably. What’s even more remarkable is at those moments, what we see is that the hippocampus is communicating with other regions of the brain,” Barnett says.
“And the more it communicates with those regions, the better people’s memory is for the events that just happened, and it’s really specific to these event boundary time points.”
The hippocampus needs to get information fed into it in order to do its job. When it’s disconnected, it’s almost like it’s not getting that information that it needs in order to lay down new memories.
A collaborative study between Barnett and researchers from the University of California, Davis, have found that the hippocampus’ increased activity at event boundaries may play a key role in better identifying exactly when those with memory impairments experience difficulty.
The hippocampus is a seahorse-shaped bundle of neurons located deep within the brain’s temporal lobe. With the help of signals from other neurons in the brain, the hippocampus is essential to forming long-term episodic memory — but tends to be disconnected from other areas of the brain for those with memory impairment.
Previously, researchers believed that the hippocampus continuously had to receive information from the rest of the brain in order to always make new memories. This left the relationship between the hippocampus and the neocortex — that part of the brain that processes cognition, emotion and sensory perception — overlooked.
“The hippocampus needs to get information fed into it in order to do its job. When it’s disconnected, it’s almost like it’s not getting that information that it needs in order to lay down new memories,” Barnett says.
Barnett’s research focuses on how alterations in network communication impact populations with memory impairment. He uses functional MRI to scan brain activity and combines this research with new theories from cognitive psychology to understand short-term and long-term memory.
To gain a deeper understanding of connectivity between the hippocampus and neocortical regions, researchers tested two groups. Each watched the same 15-minute cartoon movie. One group was told to indicate when they feel a meaningful event had ended and when another begun by clicking a button — essentially marking event boundaries.
Meanwhile, the second group was not given this instruction and watched the same movie as one would a television show, while in an MRI scanner.
By understanding how the brain functions normally, maybe we can use that to help boost memory in populations that are having memory difficulties.
Researchers found that both groups indicated the same event boundaries throughout the movie. An MRI scan of the second group indicated that the hippocampus increases in activity at event boundaries.
To test memory, researchers have typically used techniques such as asking patients to memorize and recite a list of words, for example. But that may have actually been insufficient.
Barnett explains that episodic memory, the memory of everyday events, helps our brains know what to expect in certain situations, like going out for dinner, for example. It was believed that the hippocampus was always working with the rest of the brain to store episodic memories. This new study suggests that the hippocampus only needs to encode memories when new events occur.
“It would be unnecessary for the hippocampus to be constantly encoding new information all the time, rather than just these special opportune moments where the hippocampus needs to communicate in order to form these new memories,” Barnett says.
Findings from this study may also help researchers determine behavioural interventions to help increase patient attention at event boundaries. This, in turn, might help reduce memory impairment, Barnett says.
“One question is, do we do this all the time or do we try to focus on these very particular moments when we think new events are being laid down into long-term memory.”
“By understanding how the brain functions normally, maybe we can use that to help boost memory in populations that are having memory difficulties.”