New tests and variations on older ones help define executive control while they anchor basic work on psychiatric disease.
|Jason Brandt, Ph.D.|
We all know people like this. They sprout with promise as children, but with coming of age and social expectations, they don't bloom. They may be too casual about rules or responsibilities. Or they can't plan ahead. Or their houses become temples to clutter. People with poor executive control over cognition can have quite chaotic, disturbed lives, says neuropsychologist Jason Brandt. So the value in figuring out what's going on, he says, is enormous.
Linking abnormal executive behavior to flaws in the brain is trendy,'says Brandt, whether they come from developmental problems' as in ADD from neurologic diseases like Alzheimer's or from events like traumatic brain injury. The idea is sound, he adds, but we see problems in many of those studies: They lump executive control (EC) into one vague category.
Brandt, who heads Hopkins Division of Medical Psychology, has researched EC for more than a decade. Because his group's forte is neuropsychological assessment, he and colleagues use a number of paper-and-pen tests, including several Brandt has developed, to evaluate patients with Huntington's disease, stroke, Parkinson's, head trauma and epilepsy, among others. They monitor a variety of cognitive disturbances, including EC, but for reasons Brandt explains, knowing about executive control may help us learn the most about mental illness in general.
Q. Myths persist in executive control studies, don't they?
A. Yes. One is where it exists. We used to confine EC to the frontal lobes, but that's simply not correct. Patients with cerebellar disease as far as you can get from the frontal cortex often show executive difficulties. Surprisingly, they often display the same symptoms as those with frontal damage. That's because the frontal cortex is so interconnected in the brain that even injury elsewhere can perturb its circuits.
Myth two is that EC is a single quality. I doubt that?' s so. Instead, we think, it's a construct. It encompasses a number of distinct cognitive abilities planning, problem solving, creativity. Think of it as the CEO of General Motors who's responsible for the big picture: He oversees people who make the cars or order materials or do advertising, adjusting things when necessary, bringing flexibility.
Q. How many abilities?
A. There are six we're looking into, and developing tests that will tell us if they're distinct. Decision-making and judgment form one category. Applying a rule to explain something and being able to shift it as circumstances shift is another.
Q. Don't we have tests of executive function?
A. Yes, many are excellent, but they may not pick out specific processing problems. Or they're too hard! The gold standard Wisconsin Card Sorting Test, for example, has people arrange cards according to one rule; then the rule changes. Not easy! Patients who have anything wrong with the brain often do poorly on it. So we're aiming for simple and specific.
Q. Like what?
A. (Scribbles out tick-tack-toe.) Like this! Tick-tack-toe is international and nonverbal. I've seen patients quite impaired with dementia able to do it. It doesn't require new learning, yet it clearly demands a strategy, planning, and obeying a set of rules. We've developed a way to administer and score it that evaluates those strategies. Now we're validating it in people with neurodegenerative disease. If only it didn't sound so silly! Another executive test involves intentionally completing sentences with a word that makes no sense. That tells us how well patients can block ingrained responses.
Q. Where's this leading?
A. We're hoping patterns might surface in these six EC varieties, distinct for different diseases,that might be predictive. Right now, we have a grant to study older people with mild cognitive impairment. Does the appearance of certain types of executive glitches tell who will go on to Alzheimer's disease and who won't?
We think each EC category reflects a different underlying brain circuitry. So damage to specific circuits say, one between the orbital frontal cortex and the subcortical brain, may translate to risk-taking, which we'd detect and measure. Evaluating categories also gives a way to measure treatment success. This neuropsychological 'technology' is rewarding, of course, but it's also tremendously fun to carry out!