A functional MRI study of the distributed neural circuitry of learning and reward

The aim of this research project was to study the neural substrates involved in processing rewarding stimuli. Evaluation of the magnitudes of reward is one of the fundamental aspects of goal directed behavior, and studies have shown that this process involves the midbrain dopamine system. Work by C. R. Gallistel has shown that the reward magnitude of electrical stimulation to structures within this system increases with increasing current and frequency. In this study, operant conditioning with intracranial self-stimulation of the medial forebrain bundle (MFB) was used to correlate the rewarding quality of a stimulus with variations of its current amplitude (Part 1) or electrical pulse frequency (Part 2). For Part 2, a saturation frequency, which is the point at which increasing stimulus frequency does not elicit a more vigorous operant response, were established for each of the responsive subjects. Functional magnetic resonance imaging (fMRI) with blood oxygenation level dependent (BOLD) contrast was then used to evaluate the brain activation in response to behaviorally characterized electrical stimuli. High resolution anatomical images revealed that subjects with electrode tips positioned within 1 mm of the midline of the MFB tended to demonstrate reward-seeking behavior. Timecourses were plotted for imaging voxels in areas exhibiting BOLD responses in Part 1 and Part 2.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Nuclear Engineering

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Awai, Alexandra F

Advisor dc:contributor.advisor

• Alan Jasanoff.

• Nuclear Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/34457

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/34457