Some decline in a person’s ability to exercise inhibitory control—an important brain function that allows people to suppress actions and resist interference from irrelevant stimuli—is normal with increasing age. But significant change appears to signal incipient brain problems and may make earlier diagnosis of neurodegenerative processes possible, research suggests..
A small study compared 32 healthy older adults to 40 older adults with mild cognitive impairment (MCI), which is characterized by mild impairments in memory, but not at the level to impact independent functioning. Participants underwent screening involving tests of divided attention, working memory, verbal fluency, planning, and inhibitory control—all of which are aspects of executive functioning. According to the report in the September 2012 issue of the Journal of the International Neuropsychological Society, the MCI participants performed significantly worse than the healthy participants on the tests. Every one of the MCI participants demonstrated a deficit in at least one subdomain of executive functioning, and almost half performed poorly on all of the executive function tests. Inhibitory control—which was the most frequently and severely impaired function among participants with MCI—is necessary for making everyday decisions such as resisting temptations and controlling behavior. Because standard screening tests detect impairments in only about 15 percent of people with MCI, the study authors recommend neuropsychological testing in people with mild memory problems to help identify impairments of executive function early on in the disease process so that interventions to slow the progression from MCI to AD may be initiated.
“While some research suggests that inhibitory control may decline even in healthy older individuals due to changes in the brain associated with aging, this small preliminary study suggests that a change in executive functioning—particularly changes that involve deterioration of inhibitory control—may be a sign of early disease process,” says Janet Sherman, PhD, Chief Neuropsychologist and Clinical Director of the Psychology Assessment Center at MGH. “The ability to identify these deficits, which are not readily apparent using routine screening tests, could be an important step in designing more sensitive instruments in AD diagnosis, although further research is required to substantiate these findings.
“It is important to note that more comprehensive neuropsychological evaluations that individuals with MCI sometimes undergo include assessment of executive functions. However, this important domain is not one that is routinely screened.”
Complex cognition and behavior require the ability to suppress information whose processing or expression would interfere with a person’s immediate goals. For example, in a social situation, suppression is the brain function that helps an individual resist the urge to comment on a new acquaintance’s ugly tie or reveal an embarrassing personal secret. This ability to inhibit unwanted thoughts and actions and ignore irrelevant stimuli is thought to be centered in networks within the brain’s prefrontal cortex, a region associated with higher-level cognition. Recent imaging research involving observation of the brains of volunteers who engaged in tests of inhibitory control revealed that, compared to younger adults, older adults showed evidence of declines in inhibitory control that were directly associated with the level of deterioration apparent in this region’s white matter (the networks of myelin-sheathed neuronal axons that allow brain cells to communicate with one another).
In addition to age and neurodegenerative conditions such as MCI, AD, and other dementias (e.g., Lewy body dementia and frontotemporal dementia), loss of inhibitory control is associated with a number of neuropsychiatric disorders, such as attention deficit hyperactivity disorder, autism, obsessive-compulsive disorder, and schizophrenia.
Future treatments of these disorders may well focus on trying to restore this important executive function to normal levels. Meanwhile, there are strategies that can help bolster the capacity to resist unwanted stimuli and improve concentration.
“The ability to ignore distractions as you process information is an essential aspect of paying attention and encoding memories,” says Dr. Sherman. She suggests these tactics to help strengthen inhibitory control and build concentration:
• Meditate: A growing body of research suggests that faculties such as attention and moment-to-moment awareness can be trained through meditation, and result in measurable positive changes in the brain’s white matter involving increased connections and plasticity.
To try meditation for yourself, find a tranquil spot, sit quietly and concentrate on an object of your choice, or on the sound of your own steady breathing. Give it your full attention, bringing your mind gently back whenever it begins to wander. To get maximum mental benefit, try to meditate for at least 20 minutes daily.
• Make focusing a priority: Be aware of the need to concentrate, and form habits that increase your ability to do so. For example, when you’re introduced to someone whose name you wish to remember, stop and think about the person’s name and why it’s important, focus on it, repeat it to yourself and use it in conversation.
• Don’t multi-task: Multi-tasking can impair the amount of attention you can focus in any one endeavor.
• Minimize physical distractions: Eliminate barriers to full concentration, such as physical discomfort caused by excess heat or cold, noise, or distractions such as interruptions by others or a radio broadcast that might make concentration more difficult. Notice what circumstances make concentration easier for you, and apply what you learn.
• Get plenty of rest: Some research suggests that lack of sleep may impair the brain’s inhibitory control. Try to get about seven to eight hours of sleep each night. Sleep is thought to promote activation of attentional networks and increase the ability to form new memories.