Date Thesis Awarded

5-2015

Document Type

Honors Thesis

Degree Name

Bachelors of Science (BS)

Department

Neuroscience

Advisor

Josh Burk

Committee Member

Pamela Hunt

Committee Member

Randolph Coleman

Abstract

Decision-making, especially when rewards are probabilistic, influences our lives on a daily basis and can be affected in some psychological disorders. Thus, understanding the neural basis of decision-making is important to understand how this processing occurs under “normal” conditions and to develop potential targets for treating conditions in which decision-making is affected. Projections from the basal forebrain release acetylcholine in all cortical areas. These projections are damaged in Alzheimer’s disease and there has also been interest in this pathway with respect to attention deficit/hyperactivity disorder (ADHD) and schizophrenia. Rats were trained in a probability-discounting task in which the animal choses between a small reward available 100% of the time or a larger reward available 100%, 33%, or 17% of the time. The subjects then received cholinergic lesions to the orbitofrontal cortex using 192IgG-saporin; sham-surgery, or no surgery. Cholinergic lesions to the OFC lead to more risky behavior in the subjects, causing the lesion animals to choose the large reward at higher rates than the control animals especially when the large reward was at 17% availability. Differences in lesion and sham-lesion groups did not reach significance, while lesion and nonsurgical groups showed significant differences, indicating that surgery may have been a large factor in changes seen in task performance.

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