“We know that impaired functioning in the ECN is linked to an earlier age of drinking onset and higher frequency of drinking, but it was unclear whether this dysfunction occurred before drinking or was a consequence of alcohol use,” said Mr. Clarke. “Our findings suggest [that] reduced prefrontal cortex development predates alcohol use and may be related to future alcohol use disorders.”
A second study examined the levels of impulsivity in relation to the connection between executive control in the prefrontal cortex and the insular cortex, which is involved in processing emotions. Benson Stevens, a graduate student in Georgetown’s Interdisciplinary Program in Neuroscience, used the Drug Use Screening Inventory to establish a high-or-medium risk and a low-risk group, each with 17 participants. Mr. Stevens then administered the CPT test while the participants underwent fMRI. Compared with the low-risk group, high-or-medium-risk participants had reduced connectivity between the prefrontal cortex and the insular cortex.
“Less connectivity predicted higher levels of impulsivity,” said Mr. Stevens. “Importantly, these effects were observed before the onset of alcohol use. The reduced connectivity between these brain regions could be an important factor in adolescent alcohol use, given that reduced inhibitory control has been found to be a factor in alcohol use disorders.”
A third study investigated the relationship between sugar intake, as reported by participants in a food questionnaire, and performance on the CPT and the TD, which measure impulsivity and ability to delay gratification. The CPT was administered while participants were undergoing an fMRI scan.
“We know that, compared with healthy individuals, adults with alcoholism have a stronger preference for sweet tastes, are more impulsive, and are less able to delay gratification,” explained Dana Estefan, a former research assistant in Dr. VanMeter’s laboratory. “We wanted to know if this profile fits youth deemed to be at risk for early alcohol use by the Drug Use Screening Inventory.”
The TD task confirmed the expected relationship; Children with high amounts of added sugar in their diets preferred immediate rewards more than children with lower levels of added sugar in their diets did. The CPT test revealed that individuals with increased sugar intake also showed greater activation in the right superior temporal gyrus and the right insula, which are linked to impulsivity and emotional affect. The hypothalamus was also highly activated in these individuals. This high activation is linked to overeating, reward seeking, and drug addiction, said Ms. Estefan.
“Our findings could potentially mean a positive correlation between impulsivity and sugar intake in adolescents, but more research needs to be done on this,” she added.
In the fourth study, Valerie Darcey, a registered dietitian and a graduate student in the Interdisciplinary Program in Neuroscience, examined the relationship between intake of DHA, an essential omega-3 fatty acid, and impulsivity. DHA, found in cold-water fish, is important for neuronal function.
Ms. Darcey administered a food questionnaire to 81 participants to measure ingestion of DHA and arachidonic acid (AA), which is omega-6 fatty acid found in vegetable oil and foods. Because AA competes with DHA for a place in cell membranes, the more AA a person consumes, the less DHA he or she uses. Ms. Darcey gave participants the CPT test while scanning their brains with fMRI.
“My preliminary findings show that while impulsivity levels are the same for kids with high and low levels of DHA in their diets, the brains of kids with low DHA appear to be more active—working harder to compensate—in a region involved in paying attention to the task and a region that participates in executive function,” she said. “This [result] tells us that the brains of the kids eating less DHA may not be developing like those eating more DHA.”
Patients With Paralysis Walk Using Robotic Exoskeleton and Brain–Machine Interface
Eight patients with paralysis have learned to operate a robotic exoskeleton using a brain–machine interface. The exoskeleton supports the weight of the person inside, is powered by hydraulics, and is operated by a brain–machine interface. Each study participant was able to control walking and kicking in the exoskeleton, according to the findings presented.
“One study participant delivered the inaugural kick of the 2014 FIFA World Cup, demonstrating the system’s reliability,” said senior author Miguel Nicolelis, MD, PhD, Professor of Neurobiology, Biomedical Engineering, and Psychology and Neuroscience at Duke University in Durham, North Carolina. “Our results indicate that brain–machine interface-based control of an exoskeleton could become a rehabilitation tool for severely paralyzed individuals.”
A brain–machine interface extracts and translates motor commands from functional brain areas and sends them to machines that execute the desired movements. To conduct the study, neuroscientists, engineers, and clinicians working with the Walk Again Project designed a wearable robotic exoskeleton. A cap of electrodes on the user’s head captures activity from multiple sensorimotor areas of the subject’s cortex. A computer mounted on the back of the exoskeleton interprets the brain activity and displays a visual representation of that activity on an LED display in the user’s helmet. Based on this display, the user selects movements for the mechanical exoskeleton to perform. Over six months, the researchers conducted 1,152 hours of training for eight individuals living spinal cord injury.