Children and adolescents at high risk for developing a substance-use disorder (SUD) tend to show deficits in executive cognitive function (ECF).
A study using functional magnetic resonance imaging (fMRI) to assess eye movements in adolescents has found a link between brain functioning and risk for developing an SUD.
Results are published in the March issue of Alcoholism: Clinical & Experimental Research.
“ECF is basically the control center for governing other cognitive processes,” explained Rebecca Landes McNamee, assistant research professor of radiology and bioengineering at the University of Pittsburgh and corresponding author for the study. “For example, in school, ECF would be engaged in the planning and control process required in answering a question; formulating your response, raising your hand, waiting until you are called upon, and stating your answer. A person with low levels of ECF might blurt out the answer. Another example could be interacting with someone on the playground who upsets you. A person with good ECF will think through the actions and consequences of their behavior rather than responding rashly. A person with low levels of ECF may respond with violence.”
McNamee and her colleagues decided to use an antisaccade task to reflect the inhibitory response required in the actions above.
“While this eye-movement task may be more basic in nature than an inhibitory response, it still requires control and response suppression, and is thought to use the same basic mechanisms in the brain as those required in more difficult suppression tasks,” she said. “As response inhibition is something that may be deficient in high-risk children, we thought this task would be a beneficial way to study the workings of basic mechanisms in the brain.”
The researchers employed fMRI with 25 adolescents (15 males, 10 females), ages 12 to 19 years, during a task that required inhibition of an initial eye-movement response as well as a voluntary realignment to an alternate location. The fMRI findings were categorized into regions of activation: total frontal, parietal, occipital, and temporal lobe. Additionally, each subject's neurobehavioral disinhibition (ND) – their ability to control an immediate impulsive response to a given situation – was assessed, and the drug use/histories were determined.
“We found that individuals who exhibit a high amount of ND – that is, do not have a good ability to manage their impulsive responses – have less brain activity in the frontal cortex, the region of the brain responsible for ECF, during the antisaccade task,” said McNamee. “In other words, the regions of the brain responsible for these inhibitory processes engaged less energy in individuals with higher ND scores than those with lower ND scores.”
Normal adolescent development involves an increase in the ability to inhibit impulsive responses, which would be reflected in an increase in brain activation in areas associated with inhibition, said McNamee.