March 13, 2020
A recent Baycrest study found a severe deficit in inhibitory control in people with mild cognitive impairment (MCI), a preclinical stage of Alzheimer’s disease. “These findings have important practical implications for dementia screening and diagnosis,” says Dr. Nicole Anderson, senior scientist at Baycrest’s Rotman Research Institute (RRI) and director of Baycrest’s Ben and Hilda Katz Inter-Professional Research Program in Geriatric and Dementia Care.
Inhibitory control is the ability to ignore irrelevant thoughts and actions to achieve our current goals. It’s what allows us to focus on traffic instead of the news on the radio while driving, or to tune out others’ conversations when talking to a friend.
“Like memory, inhibitory control is a critical cognitive process in everyday life, and it’s also one of the most noticeable impairments in Alzheimer’s disease,” says Dr. Rachel Rabi, post-doctoral fellow at the RRI and lead author of the study. “But unlike memory, it has received little clinical attention in people with MCI, even though many of them go on to develop Alzheimer’s.”
In this study, published in Neuropsychology Review, the scientists analyzed a total of 66 published studies on the topic, representing 2,184 individuals with MCI and 3,049 healthy older adults. The selected studies tested individuals with MCI as well as healthy older adults on tasks commonly assumed to measure inhibitory control.
One such task is the “go-no go” task. In this task, participants may be instructed to respond as quickly as possible to white shapes, but not pink shapes, on a screen. The white shapes then appear much more frequently than the pink shapes, meaning that when they see a pink shape, participants have to suppress the automatic urge to respond. Another commonly used test is the Stroop task, in which participants view the names of colours printed in non-corresponding ink. For example, the word “yellow” may be printed in blue. Participants then have to indicate the ink colour (blue) and avoid reading the word (yellow).
Across tasks and studies, the scientists found significantly worse inhibitory control in those with MCI compared to the healthy adults.
“The fact that we reviewed so many studies on this topic means we can be quite confident in our results,” says Dr. Rabi. “And since we’re seeing such severe impairments in inhibitory control in people with MCI, we really need to be including inhibition tasks in clinical tests used to assess people’s cognitive status.”
The study’s results could also help us better understand memory deficits in MCI. “We know people with MCI have impairments in memory, but successful memory performance also requires the inhibition of irrelevant information. Therefore, it’s possible that inhibitory deficits in MCI contribute to the memory deficits in this population,” adds Dr. Rabi.
In addition, this study’s findings could lead to the development of programs that address inhibitory functions in people with MCI. “Existing programs for people with MCI primarily focus on memory,” says Dr. Anderson. “However, our findings suggest that it would be beneficial to include other approaches, such as RRI Senior Scientist Dr. Brian Levine’s Goal Management Therapy, which helps people stay focused on their goals.”
As a next step, the scientists are looking at electrical activity in the brains of people with MCI. They want to see whether changes in inhibitory control can be seen at the brain level before they show themselves in behaviour.
This work was made possible with support from the Alzheimer’s Society of Canada and the Natural Sciences and Engineering Research Council of Canada (NSERC).
With additional funding, the researchers could further examine the deficits in cognition that occur with MCI. They could also investigate possible interventions for people with impairments in inhibitory control.
Baycrest is a global leader in geriatric residential living, healthcare, research, innovation and education, with a special focus on brain health and aging. Baycrest is home to a robust research and innovation network, including one of the world’s top research institutes in cognitive neuroscience, the Rotman Research Institute; the scientific headquarters of the Canadian Consortium on Neurodegeneration in Aging, Canada’s largest national dementia research initiative; and the Baycrest-powered Centre for Aging + Brain Health Innovation, a solution accelerator focused on driving innovation in the aging and brain health sector. Fully affiliated with the University of Toronto, Baycrest provides excellent care for older adults combined with an extensive clinical training program for the next generation of healthcare professionals. Through these initiatives, Baycrest has remained at the forefront of the fight to defeat dementia as our organization works to create a world where every older adult enjoys a life of purpose, inspiration and fulfilment. Founded in 1918 as the Toronto Jewish Old Folks Home, Baycrest continues to embrace the long-standing tradition of all great Jewish healthcare institutions to improve the well-being of people in their local communities and around the globe. For more information please visit: www.baycrest.org
About Baycrest’s Rotman Research Institute
The Rotman Research Institute at Baycrest 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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