Researchers confirm brain region responsible for separating similar memories
September 23, 2016
TORONTO, CANADA – Canadian researchers have discovered the first direct human evidence of a specific brain region responsible for differentiating between similar events in memory, which could help with earlier detection of dementia.
Previous studies conducted with rodents found that the dentate gyrus, a region within the hippocampus, was responsible for event separation, but prior to this study there was no causal evidence within humans.
Senior investigator and associate scientist at Baycrest’s Rotman Research Institute (RRI), Dr. Shayna Rosenbaum, and her research team confirmed this theory when they studied a memory-impaired man (BL) who suffered damage to this brain region as a result of an electrical injury and cardiac arrest. The study’s findings were published in the journal Current Biology on September 22.
“Our day-to-day experiences typically involve routine tasks with subtle changes to the time, place, people or objects involved and our brain has a mechanism to differentiate the overlapping features to remember each distinct experience,” says Dr. Rosenbaum, who is also an associate professor in the Department of Psychology and Centre for Vision Research at York University.
“Due to BL’s injury, he can provide the general aspects or gist of similar past events, but he confuses details from one event with another.”
The study analyzed participants’ performance on recognition memory tests. Participants were shown images of everyday objects for a short period of time. After viewing these objects, they were presented with a different list of images, which included some that were shown before, some that were completely different and some that were similar to previously shown images. Participants were asked to classify these objects as either an image seen before, a new image or a new image that was similar to a previous image. BL was able to identify the items that were studied and to reject novel and different items, but he confused similar new items as studied items.
Based on these findings, more sensitive neuropsychological tests could be developed to assess and diagnose subtle memory impairment issues, such as memory discrimination issues experienced by BL, says Dr. Rosenbaum. Previous studies have shown that people with dementia demonstrate similar memory impairments.
Currently, Dr. Rosenbaum’s research team is developing interventions to offset this memory impairment, which could help treat other neurological conditions, such as Alzheimer’s disease, loss of oxygen to the brain following cardiac arrest, and traumatic brain injury.
“Our study is useful in suggesting a possible mechanism underlying what has been seen in individuals diagnosed with amnestic Mild Cognitive Impairment (aMCI) that affects a person’s memories,” says Dr. Rosenbaum. Currently the cause behind memory issues related to MCI is unclear.
This brain region could also serve as a biomarker for abnormal age-related memory issues that may relate to a higher risk of dementia, which could lead to an earlier diagnosis of dementia.
Research was conducted with support from the Natural Sciences and Engineering Research Council, the Canadian Institutes of Health Research and the European Research Council. Other Baycrest collaborators include Steven Baker, a graduate student at the RRI and the study’s lead author, and Dr. Asaf Gilboa, a scientist at the RRI.
The study’s next steps involve collaborations with Dr. Gilboa and Dr. Claude Alain, RRI assistant director and senior scientist, to study whether this memory differentiation is affected by the way information is presented, such as visual or auditory means.
With additional funding, this research could expand its scope to design preventative and treatment interventions, such as using aerobic exercise, to help treat this memory issue, which also develops in other neurological conditions.
About Baycrest Health Sciences
Headquartered on a 22-acre campus and fully affiliated with the University of Toronto, Baycrest Health Sciences is unique in the world, combining a comprehensive system of care for aging adults and one of the world’s top research institutes in cognitive neuroscience (the Rotman Research Institute). Baycrest’s dedicated centres focus on mitigating the impact of age-related illness and impairment, and offer unmatched global knowledge exchange and commercialization capacity.
About Baycrest’s Rotman Research Institute
The Rotman Research Institute at Baycrest Health Sciences is a premier international centre for the study of human brain function. Through generous support from private donors and funding agencies, the institute is helping to illuminate the causes of cognitive decline in seniors, identify promising approaches to treatment, and lifestyle practices that will protect brain health longer in the lifespan.
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