Why Cognitive Training Helps Increase Broader Mental Acuity

Cognitive training exercises can help older adults maintain or improve certain mental skills, such as memory and attention. Such training can also lead to improvements in cognitive abilities not specifically trained for, according to recent research from The University of Texas at Dallas.

A new brain-imaging study by scientists in the Center for Vital Longevity sheds light on the underlying brain mechanisms that might be responsible for such beneficial crossover effects.

"Our examination of brain function during certain tasks suggests that if you're cognitively normal, training yourself on improving the speed at which you switch between tasks - which relies heavily on how quickly you process information - can be very beneficial in helping maintain your cognitive functions," said Dr. Chandramallika Basak, associate professor of psychology in the School of Behavioral and Brain Sciences and corresponding author of a study published in the Aug. 1 issue of Human Brain Mapping.

In a clinical trial conducted with participants at UT Dallas and the University of Iowa, 129 cognitively healthy adults ages 65 to 85 were tested on various cognitive tasks, such as general cognition, mental processing speed, attention and memory. Then the participants underwent a functional MRI (fMRI), during which they performed single tasks as well as switching between multiple tasks.

The fMRI measured blood-oxygen-level-dependent (BOLD) signals, which show the amount of oxygen available in a region during each moment of testing of a specific mental task. Those results indicated which regions were activated more when subjects performed multiple tasks compared to performing only one task, or when switching between tasks versus repeatedly doing the same task.

"The results imply that the older you are, the more you activate the right prefrontal regions during multitasking between two types of numerical judgments. But the greater your risk of Alzheimer's disease is, the more you activate the left somatosensory parietal regions."

Dr. Chandramallika Basak, associate professor of psychology in the School of Behavioral and Brain Sciences

"Measuring the BOLD signals allows us to investigate the brain regions that are associated with specific types of cognitive control," Basak said. "Some signal patterns had an impact beyond the scanned task, generalizing to tasks of executive control or general cognition, while others did not."

Based on the brain activation patterns, the researchers could predict how a subject would perform on unrelated cognitive tasks.

"Activation of specific age-sensitive brain regions during various task-switching scenarios indicates that training at task-switching may be responsible for documented improvements in other cognitive abilities," Basak said. "Few attempts have been made to look at what the brain activations during an fMRI task tell us about not only performance on the current task, but also other seemingly unrelated cognitive tasks. Such studies can help us theorize the underlying neural mechanism of broad enhancements from cognitive training."

The tests revealed that in older adults' activation of the right middle frontal brain was detrimental to performance at task-switching, whereas activation in the inferior frontal and caudate nucleus regions was related to faster processing speed during task-switching. Crucially, however, activations of these regions did not predict performance on other tasks.

But other regions did.

"FMRI activity in other brain regions involved in aspects of task-switching not only predicted improved performance on task-switching, but also positively predicted better performances on a working memory task and general cognition, and faster processing speed," Basak said. "These regions included multiple hub regions of cognitive control as well as regions associated with motor processing.

"Together, these results suggest that activations in the left frontoparietal brain associated with task-switching generalize to other cognitive tasks - both easy and complex."

Processing speed might be the basis of that transfer to other tasks, Basak said. This speed can decline beginning as early as age 35.

"Processing speed seemed to underlie many brain-behavior relationships," said Paulina Skolasinska MS'21, PhD'24, lead author of the study and a graduate of Basak's Lifespan Neuroscience and Cognition Lab now working as a postdoctoral research associate at McGill University. "Perhaps this is a cognitive function that might be targeted for future interventions."

The study's results also support the dedifferentiation hypothesis of brain aging, which posits that regions of the brain that normally are specialized to perform distinct tasks become less selective in their responses to different types of stimuli.

"The more that older adults activate left prefrontal regions, the better they perform on task-switching and other unrelated cognitive tasks. In contrast, the more they activate similar areas on the other side of the brain, the poorer their task-switching performance," Basak said. "We believe this right-side activation reflects a reduced ability to process information due to the aging brain's dedifferentiation."

The study's outcomes point to two concurrent correlations that may delineate differences between healthy and dysfunctional aging.

"The results imply that the older you are, the more you activate the right prefrontal regions during multitasking between two types of numerical judgments," Basak said. "But the greater your risk of Alzheimer's disease is, the more you activate the left somatosensory parietal regions. So, while both increases in brain activations occurred in our participants, they imply two different aging patterns.

"Because of this, brain activation patterns of normal older adults versus those at-risk of Alzheimer's disease are informative in determining whether future cognitive training can impact these activation patterns differently."

Other authors include Shuo Qin PhD'19, a former researcher in Basak's lab who is now at the National University of Singapore; Dr. Michelle Voss of the University of Iowa; and Dr. Hyun Kyu Lee of Posit Science. The clinical trial was funded by a grant (R44-AG047722) to Lee from the National Institute on Aging, a component of the National Institutes of Health.