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The effects of caffeine and caffeine withdrawal on measures of mood, cognition, and functional magnetic resonance imaging

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The effects of caffeine and caffeine withdrawal on measures of mood, cognition, and functional magnetic resonance imaging
Addicott, Merideth
Caffeine is a widely used neurostimulant that exerts its effects by antagonizing adenosine receptors in a competitive fashion. Caffeine has been considered to have net benefits on mood, reaction time, and cognitive performance. However, chronic caffeine use can result in tolerance to some of its stimulant effects and symptoms of withdrawal, such as headache and fatigue, which can appear after 12 hours of abstinence. The reversal of the negative withdrawal effects in chronic caffeine users has been proposed to outweigh any net benefits of caffeine. The acute effects of caffeine were investigated among moderate habitual caffeine consumers in an abstained state following 30 hours of caffeine abstinence, and in a normal caffeinated state following normal caffeine use. It was hypothesized that the effects of caffeine on measures of mood, cognition, and functional imaging would be greater in an abstained state than in a normal caffeinated state. Caffeine research frequently relies on self-report measures of caffeine consumption in order to quantify levels of chronic exposure. However, the accuracy between different self-report methods has not been compared. The first experiment compared a retrospective interview and a prospective diary of caffeine use against salivary caffeine concentrations obtained during normal caffeine use. It was determined that both the interview and the diary are valid methods of estimating actual caffeine concentrations among individuals who report consuming less than 600 mg/day. Moderate daily caffeine consumers who experienced withdrawal symptoms were included in the second experiment. Measures of self-reported mood, choice reaction time, selective attention, and memory were obtained on 4 separate days: after the administration of caffeine or placebo in an abstained and a normal caffeinated state. Withdrawal symptoms were reported in the abstained state, and caffeine had a greater positive effect on mood and choice reaction time in the abstained, than in the normal state, as hypothesized. However, measures of selective attention and memory were not negatively affected by abstention and caffeine improved these measures in both states. These results show limited support for the withdrawal reversal hypothesis. Lastly, the effects of caffeine and withdrawal on the blood oxygen level dependent (BOLD) signal were investigated using functional imaging. Since the effects of caffeine on the traditional measure of the BOLD response have been inconsistent, time course parameters were extracted in an attempt to separate neural and vascular influences. Changes in cerebral blood flow, salivary caffeine concentrations, and response time to a visual-motor task predicted different parameters of the BOLD response using a multivariate regression analysis. Differences between the abstained and normal state were not apparent in the time course parameters. However, the results of this experiment suggest that these parameters are a sensitive and useful measure for the study of psychoactive drugs that have concomitant neural and vascular effects, such as caffeine.
Weiner, Jeffrey (committee chair)
Laurienti, Paul (committee member)
Liguori, Anthony (committee member)
Porrino, Linda (committee member)
Maldjian, Joseph (committee member)
2009-12-02T18:23:53Z (accessioned)
2010-06-18T18:58:50Z (accessioned)
2009-12-02T18:23:53Z (available)
2010-06-18T18:58:50Z (available)
2009-12-02T18:23:53Z (issued)
Neuroscience (discipline)
http://hdl.handle.net/10339/14799 (uri)
en_US (iso)
Wake Forest University
Release the entire work for access only to the Wake Forest University system for one year from the date below. After one year, release the entire work for access worldwide. (accessRights)

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