Recovery from Stroke: New research on hidden deficits from stroke

This following is the third in a three-part series with Susan Jackson and Susan Kemper:

Dual tasking is an energy drain

The human brain has only so much capacity for multiple power demands. This is particularly true for stroke survivors. It's like living in a beautiful old house. You just can't run the vacuum cleaner and a window air conditioner at the same time -- or you'll blow a fuse.

"Our patients tell us they can't focus on driving and listen to the radio -- they have to turn the radio off," said Jackson. This is a classic dual-tasking dilemma. There just aren't enough amps.

Scientists at the University of Kansas recently documented that older adults who've had a stroke can't effectively dual-task. "When they try to talk and walk at the same time, we are seeing problems with coherence. They can't finish their sentences," said Susan Kemper, a distinguished professor of psychology and gerontology. Screening out TV noise, walking, using their hands -- these "tasks" all affected their ability to sort through ideas and talk.

The study by Susan Kemper and Ruth Herman from the KU Gerontology Center and Joan McDowd, Patricia Pohl and Susan Jackson at the KU Medical Center was published in the journal Aging, Neuropsychology and Cognition in 2003.

The findings of this study -- funded by the National Institute on Aging -- came as a surprise. All the participants had been given a clean bill of health. They were two or more years into recovery and had sailed through the standard tests for stroke. "But when they were faced with dual tasks," said Kemper, "they looked like they had aphasia and motor impairment." "Functional competency measures tend to test one activity at a time," explained Susan Jackson, "but the changes in a stroke patient's cognitive reserve capacity is apparent when he does two things at once."

In other words, a patient may not be considered aphasic, but under certain conditions he may struggle with the symptoms. Because communication is so important to quality of life, this study makes the case for rehab services regardless of the diagnosis.

What is cognitive reserve capacity?

Walking and talking seem like natural companions -- something we do so routinely we can hardly believe it's a power drain. But no matter our age or health, something has to go when we do two things at once, says Susan Kemper. "Can you rub your tummy and pat your head in perfect rhythm? Of course not. What is surprising is some people can in fact do multiple things at once -- without costs -- like airplane pilots."

It is our cognitive reserve capacity that powers complex tasks like reasoning and problem solving. It enables a good pilot to focus on a stream of visual and auditory inputs while steering a complicated machine. It holds all the pieces of information in the mind, sorts and prioritizes for coordinated action.

With advancing age, accompanied by changes in eyesight, balance, and attention, there are just too many demands on our cognitive resources. And individuals who survive a stroke will find they have surprising limitations when they try to do two things at once.

Simple awareness of the challenges can help. "Don't just assume your father isn't hearing you," said Kemper. "Try turning off the TV so he can focus on your conversation."

This is the third in a three-part series with Susan Jackson and Susan Kemper -- scientists at the Schiefelbusch Institute for Life Span Studies at the University of Kansas:

Part 1: Aphasia and rehabilitation
Part 2: What is Speech-Language Therapy Like?
Part 3: New Research on Hidden Deficits from Stroke


Kemper, S., Herman, R., and Lian, C. The costs of doing two things at once for young and older adults: Talking while walking, finger tapping and ignoring speech or noise. Psychology and Aging.

Kemper, S., McDowd, J., Pohl, P., Herman, R., and Jackson, S. Revealing language deficits following stroke: The cost of doing two things at once. Aging, Neuropsychology and Cognition.

Lindenberger, U., Marsiske, M., Baltes, P.B. (2000). Memorizing while walking: Increase in dual-task costs from young adulthood to old age. Psychology and Aging 15, 417-436.