Dr. Julie Schweitzer is an Associate Professor of Clinical Psychiatry at the UC Davis MIND Institute in Sacramento, California. She conducts brain-imaging research on ADHD in children and adults using behavioral- neuropsychological and functional neuroimaging (fMRI) methods. She also studies the correlation between reinforcement in learning strategies in clinical populations. We sat down with Dr. Schweitzer to learn more about her research.
What are the core neurobiological components you’re examining in your brain scan research on ADHD?
Our research attempts to link impairments identified in cognitive, behavioral and motivational functioning with brain activity. We define where we are looking in regard to neurobiology based on what we know is affected on a performance level in functional impairments. The key to functional neuroimaging is looking at the interaction between behavioral performance and its relation to brain activity. Our laboratory is particularly interested in working memory, reward response, self-control and general cognitive control issues.
The prefrontal cortex is commonly identified as the most “malfunctioning” anatomical region responsible for ADHD. Would you agree?
The prefrontal cortex is reliably implicated in ADHD, but we now recognize that other regions are implicated in ADHD and that it is most likely the interaction, or “communication” between brain regions that is most problematic. Furthermore, we know the basal ganglia and cerebellum are also frequently implicated in ADHD as well.
The neurotransmitters, dopamine (DA) and norepinephrine (NE) are implicated in the distractibility and impulsivity typical of ADHD. Would you consider DA or NE as the most responsible for the “ADHD brain”?
Most research has focused on dopamine, thus we don’t really know the extent to which norepinephrine is involved, but clearly both neurotransmitters are implicated in ADHD. To me, the more interesting question is to what degree alterations in the DA or NE system might be implicated in the different presentation types that we classify within ADHD.
What have your brain scans indicated about the pattern of neural activity during cognitive tasks performed by a person with ADHD versus a person without ADHD?
We have conducted several studies demonstrating that ADHD is characterized by both hypo- and hyper-activity in brain functioning in pediatric and adult ADHD and not just hypo-activity, as the earlier research suggested. Our group has also shown that the increased distractibility associated with ADHD may be due to an inability to sufficiently suppress brain activity in a region of the brain called the default attention network, particularly as task difficulty increases.
How much do researchers understand about the neural correlates–or, nervous system correlates–of inhibition and cognitive control processes in ADHD?
There has been a fair amount of research in ADHD and response inhibition. Research into the general area of cognitive control processes in ADHD is definitely growing. Our research suggests that there are impairments in cognitive control in ADHD and these impairments may also differ with subtypes of ADHD. Another interesting area of cognitive control research relates to the imbalance between the network of brain regions engaged during higher order cognitive control and the network of regions (e.g., midline regions, posterior cingulate) that are typically de‑active during the performance of these tasks. These midline regions, also known as default mode regions, are typically de-active during demanding cognitive tasks and tend to be more active during non-cognitively demanding periods. In ADHD we find that children with the disorder have less deactivation than typically-developing children in these default regions, during cognitively demanding tasks. Furthermore, we found that the degree of deactivation related to the difficulty level of the task. We concluded that increased distractibility in ADHD may be due to an inability to sufficiently suppress activity in the default attention network in response to increases in task difficulty.
What is known about the neural correlates of the distractibility characteristic of people with ADHD?
Distractibility does seem to be related to the ability to effectively engage cognitive control. Individuals with ADHD-combined type tend to underuse and overuse parts of their brain, giving a diffused pattern of brain activity. In the inattentive type of ADHD we suspect that distractibility is not associated with over-activity in brain activity, particularly in the motor areas of the brain, where we find it in the combined subtype.
How does fMRI work? What data does it provide researchers on what is happening in an ADHD brain?
Functional MRI works by measuring a subject’s neural activity when they are presented with a task, though data can also be collected during a resting state scan when they are not performing a task. fMRI is based on measures of brain activity by assessing changes in blood flow and oxygenation based on the principle that changes in neuronal activity tend to be associated with changes in brain blood flow and volume. The more active a brain area is, the more oxygenated blood is needed to meet the growing demand. The increase in blood flow can be indirectly measured in relationship to a cognitive or emotionally evocative stimuli presented during the fMRI sessions that relate to ADHD functioning. In ADHD it gives us a physiological measure that helps us understand the relationship between functional deficits in ADHD and an objective, biological measure.
How much is known about the nervous system changes that cause these problems and what are some of the changes specifically?
There have been cross-sectional studies, including some longitudinal research, which primarily examined structural imaging data such as brain volume as it relates to information processing in ADHD. Here at the UC Davis MIND Institute, we are trying to look at nervous system changes in adolescents and adults. We have a hypothesis on the nature of pre-frontal cortical (PFC) development. Typically, the PFC finishes developing during the early to mid-20’s, but in individuals with ADHD we suspect it continues developing for several more years. Interestingly, other laboratories found other regions of the brain mature faster in ADHD. Motor regions appear to develop sooner and we are investigating if reward regions do as well in ADHD. We are interested in the discrepancy between maturation in prefrontal cortical brain regions and the reward center of the brain, the ventral striatum, and whether there is – in essence – a tug of war between the cognitive versus reward regions.
There have been suggestions that sports and physical activity can improve brain function for people with ADHD. What is the clinical evidence around that?
We all want to know how people can channel their extra energy to their advantage. A lot depends on individual. We know that people playing video games or texting and chatting are boosting their dopamine levels, but we also know these are not necessarily the healthiest activities they could pursue. We’d love to do research into finding and identifying a healthy alternative that can be applied globally to the patient population. In the meantime, when a person knows what drives and fulfills them based on their individual interests and history, they’re more likely to find positive ways to use their energy. There are some other laboratories that have been examining the role of physical activity in relation to ADHD.
How can individuals with ADHD with a high creative aptitude harness this strength for their benefit?
The individual has to have some discipline and skill because raw energy is not enough. Achieving success requires skill development. I am interested in how persistence and ambition are cultivated and applied because those are key components to achieving success. In my clinical experience, those with ADHD who are very successful are ambitious and have a goal in mind that they pursued with persistence. Also, being very bright can help, but it is not sufficient. The combination of persistence, ambition, intelligence and talent can make a huge difference. People with persistence are less likely to feel beaten down by obstacles. Without the “stick-to-it” attitude, a person, ADHD or not, will experience difficulties in life later on. Traditional routes may be hard for ADHD people so there are benefits to coaching to help the individual persist and think about other potential avenues.
Rheba Estante is a San Francisco writer working in higher education and pursuing her Master’s degree in Counseling Psychology at Golden Gate University. Known for her compelling articles featuring women’s lifestyle and health issues, she interviews industry leaders ADDA’s E-News, the Potrero View newspaper, and for the SF Women’s Health Examiner for Examiner.com. Learn more about her work on LinkedIn.