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INCA: Impulsivity Neural Correlates in ADHD
Brian Barnett
E-mail address: [email protected]
I.
Please briefly describe the overarching research problem. Why is it a problem? Why does this problem warrant academic
research? Who cares?
Attention deficit hyperactivity disorder is characterized by inattention and impulsivity that negatively affects one’s ability to
concentrate, form relationships, and moderate behavior (National Institute of Mental Health, 2007). This neurobehavioral
disorder is controversial; the major sources of disagreement arise over its legitimacy as a disorder, its frequency of diagnosis,
how to diagnose it, and its method of treatment (especially in children). Because of all of these unknowns, it is as likely that
some people are suffering through a debilitating condition because they have not been diagnosed or treated properly as it is that
some are being treated with dangerous and addictive stimulants for a disorder they might not have (Zwi, Ramchandani, and
Joughin, 2000). Research into the neural bases of ADHD could help to formulate a concrete diagnosis of the disorder, which
would help to reduce both of the aforementioned undesirable situations. If a specific area of the brain and its activity is
associated with ADHD, then this information would be instrumental in diagnosing patients with ADHD in a consistent and
empirical manner. This research would benefit children, as they form the largest pool of diagnosed patients and are most
susceptible to the effects of the current forms of ADHD medication. In addition, teachers and parents would be able to more
effectively influence the development of their children if they were able to surely identify which children have ADHD and which
do not.
National Institute of Mental Health. (2007). Attention Deficit Hyperactivity Disorder. Retrieved from
http://web.archive.org/web/20071018052052/http://www.nimh.nih.gov/health/publications/adhd/complete-publication.shtml
Zwi, M., Ramchandani, P., Joughin, C. (2000). Evidence and belief in ADHD. British Medical Journal,
321,975-976.
II.
Please describe the current direction of research on this problem (including two scholarly references).
A number of behavioral disorders, including ADHD, have been linked to the failure of mechanisms to control or inhibit actions.
Stop-signal tasks (the type that is proposed for the research of this topic) have gained popularity in the fields of neuroscience and
psychology; they are able to assess how inhibition affects an action that has been initiated with temporal precision. Research has
shown that ADHD leads to slower inhibition response times, which is counterintuitive to a hyperactivity disorder, but makes
sense in the context that ADHD reduces inhibitions and as a result, also reduces ability to react to impulses and control them
(Eagle and Baunez, 2010). Another study proposes that psychological functions or lack therof can act as endophenotypes
(markers in between genes and symptoms) for ADHD. What this means is that though ADHD does not have a definite genetic
basis and its symptoms are not universal, behavior can be used as a determinant of its existence. Stop-signal tasks were found to
incorporate the prefrontal cortex and specifically the right inferior frontal cortex; furthermore, the basal ganglia is associated
with response inhibition as well as modulation systems (Aron and Poldrack, 2004). These studies show that ADHD has a
measurable effect on inhibition and has some neural basis; this provides a starting point from which the proposed research
project can be carried out. The stop signal task is experimentally shown to provide significant information about behavioral and
neural activity and will be instrumental to the success of the project.
Aron, A. & Poldrack, R. (2004). The Cognitive Neuroscience of Response Inhibition: Relevance for Genetic
Research in Attention-Deficit/Hyperactivity Disorder. Society of Biological Psychiatry, 57, 1285-1292.
Eagle, D., & Baunez, C. (2010). Is there an inhibitory-response-control system in the rat? Evidence from
anatomical and pharmacological studies of behavioral inhibition. Neuroscience & Biobehavioral Reviews, 34(1), 50-72.
III. Please describe the proposed research project description (to address an aspect of the problem cited above). How will the team
carry out the research? What methodologies and methods will the team use? What data are most important to collect?
The research project involves obtaining a set of at least 8 rats, lesioning their brains with an established model of ADHD,
inserting electrodes into specific areas of the brain, performing stop-signal tasks to observe neural activity, and analyzing this
activity to make conclusions about the neural basis of ADHD. Rats will be relatively easily acquired after the IACUC research
protocol forms are filled out to ensure their ethical usage. Existing research shows that lesioning the nucleus accumbens, anterior
cingulate cortex, and medial prefrontal cortex provides a model of ADHD in the brain of rats. This surgery, in combination with
the insertion of electrodes into the brain, does not need to be performed by a professional; with the proper training, the research
team will be able to safely and effectively complete these tasks. The rats will need to be trained to perform the stop-signal task,
which is just a matter of putting them through the task until they remember the proper responses. The stop-signal task has a wellestablished methodology and has many modules of alteration that can best fit the data that needs to be collected. This data
includes the activity levels of neurons of the brain at very specific time periods, which will provide information about the neural
basis of the effects of ADHD. After this data is collected, it will be analyzed with appropriate computer software and conclusions
such as the effect of ADHD on the stop-signal task can be made. The rats in the study will be euthanized and their brains will be
removed and sliced so that more information about the regions of the brain involved in the research can be gained. Each member
of the team will have to come into the lab for some amount of hours a week and this is dependent on the number of members in
the group. Responsibilities will include training the rats, performing surgeries, putting the rats through the trials, compiling data,
and taking care of the rats.
IV. Potential research question(s):
What is the neural basis of attention deficit hyperactivity disorder and
V.
Additional considerations:
A. Please comment on this project’s feasibility (considering time, cost, and staffing). Your initial impressions based on your
two sources are fine for the first vote, but Part B will need to be completed for the project to be eligible for the second
vote.
This project is feasible because the stop-signal task only requires equipment already on-campus and all of the work can
be completed by a few researchers, let alone an entire Gemstone group. Not only is most of the necessary equipment
already on campus, but since the project deals with a human behavioral disorder, grant funding from sources such as
HHMI will be available. The proximity of the laboratory and the type of research involved provides the team with the
opportunity to develop a well-rounded and complete research project instead of focusing all of its resources on data
collection. The research data can be collected in less than one semester, which will allow the team to collect more
supplementary data as needed. No additional staffing besides the mentor and the team members will be required.
B. Are you aware of any potential mentors within the campus or community? If so, please list their name(s) and position(s):
Dr. Matthew Roesch is a professor in the Psychology department and NACS and already performs behavioral research
on rats with the stop-signal task. He expresses interest in being a mentor for this project.
VIII.
In order for this topic to be eligible for the second vote, you must discuss (vet) its feasibility with a faculty member on
campus and write a summary of his or her opinion regarding the project’s worth and feasibility. Project sheets that have not been
vetted by a suitable expert will NOT be eligible to move forward in the process.
A. Name of expert who vetted the project:
__Matthew Roesch_________________________________________________
B. Title of expert who vetted the project:
_____Assistant Professor_______________________________________________
C. Date the project was vetted by the expert: __3/29/11__________________________________________________
D. Was the project vetted by email, phone, or an in-person conversation?
_______In person_____________________________________________
E. A summary of the expert’s comments regarding the feasibility of the project (e.g., time, money, logistics, staffing):
This project is feasible. The Roesch lab has the necessary equipment to perform these experiments and is already training rats
on a version of the stop-signal task. The Roesch lab is funded by grant money from NIDA and start up funds from the
university. Graduate students and lab technicians that are also interested in the project will be available during the course of
the study.
F. A summary of the expert’s comments regarding the worthiness of the project (Who cares? Is it academically
rigorous? Does it have the potential to make a worthwhile contribution to the field? Is it worth doing?):
Understanding the neural correlates of impulsivity is a critical issue in today’s society. Drug addicts and children with
ADHD, as well as patients with several other mental disorders, can be characterized as being overly impulsive. A better
understanding of how the brain governs impulsivity might lead to better treatments for these disorders.
G. A summary of the expert’s overall assessment. Should this project be allowed to move forward? If so, what changes are
necessary?
The project should move forward as planned.