Date on Master's Thesis/Doctoral Dissertation

4-2010

Document Type

Master's Thesis

Degree Name

M. Eng.

Department

Bioengineering

Committee Chair

El-Baz, Ayman Sabry

Subject

Electroencephalography; Visual evoked response; Drug addicts--Research

Abstract

In 2006 it was estimated by the Substance Abuse and Mental Health Service Administration (SAMHSA, 2007) that 19.9 million Americans used illicit drugs, computing to roughly 8.0 % of the United States population. In 2007, there were 2.1 million active cocaine users, comprising 0.8 percent of the population. The National Institute on Drug Abuse (NIDA) estimates that the total expenditure of drug-related complications is greater than 500 billion dollars when healthcare, legal procedures and job loss are considered. Research has shown that prolonged drug use has a profound effect on the EEG recordings of drug addicts when compared to controls during cue reactivity tests. Cue reactivity refers to a phenomenon in where individuals with a history of drug abuse exhibit excessive psychophysiological responses to cues associated with their drug of choice. The goal of this research is to develop gamma band EEG indices to determine the effectiveness of neurofeedback therapies which are thought to offer a non-invasive method of mediating EEG abnormalities resulting from prolonged substance abuse. Method: Ten current cocaine abusers were treated using neurofeedback protocol to simultaneously increase SMR and decrease Theta activity, combined with Motivational Interviewing sessions. Eight of them completed all planned pre and post-neurofeedback cue reactivity tests with event-related EEG recording and clinical evaluations. Cue reactivity tests consisted of a visual oddball task with images from the International Affective Picture System and drug-related pictures. Evoked and induced gamma responses to target and non-target drug cues were analyzed using wavelet analysis and coherence protocols via custom algorithms implemented in MatLab. Results: Outpatient subjects with cocaine addiction completed the bio-behavioral intervention and successfully increased SMR while keeping theta practically unchanged in 12 sessions of neurofeedback training. Neurofeedback treatment resulted in a lower EEG gamma reactivity to drug-related images in a post-neurofeedback cue reactivity test. In particular, evoked gamma showed decreases in power to non-target and target drugrelated cues at all topographies (left, right, frontal, parietal, medial, inferior); while induced gamma power decreased globally to both target and non-target drug cues. Also, long range coherence was found to increase in specified electrode pairings post neurofeedback. Our findings supported our hypothesis that gamma band cue reactivity measures are sufficiently sensitive to functional outcomes of neurofeedback treatment. Both evoked and induced gamma measures were found capable of detecting changes in EEG responses to both target and non-target drug cues. Conclusion: Our study emphasizes the utility of cognitive neuroscience methods based on EEG gamma band measures for the assessment of the functional outcomes of neurofeedback-based bio-behavioral interventions for addictive disorders. This approach may have significant potential for identifying both physiological and clinical markers of treatment progress. These methodologies can also be adapted and used in additional pathologies to provide fast and reproducible evidence of treatment outcomes.

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