Acute effects of alcohol on inhibition

Campbell, Anne Eileen
This thesis set out to investigate whether individual differences in concentrations of the \ud neurotransmitter γ-aminobutyric acid (GABA) could predict the extent of alcohol induced \ud impairment to measures of behavioural inhibition. However, investigations in to the reliability \ud of magnetic resonance spectroscopy (MRS) methods to measure GABA, and of the stop signal \ud reaction time (SSRT) demonstrated that neither measure was sufficiently reliable to be used in \ud correlational research. Instead, this thesis first investigated the effects of alcohol on neuronal \ud oscillations measured by magnetoencephalography (MEG) in the gamma frequency band that \ud are associated with GABA. In response to a visual stimulus alcohol was found to increase \ud gamma power and decrease gamma frequency in the visual cortex. In response to a motor \ud stimulus increases in gamma power were also observed over the motor cortex whilst \ud intoxicated. During resting state recordings alcohol was found to increase power in central, \ud parietal and occipital areas across a number of frequency bands and also to alter activity across \ud functional resting state networks including the fronto-parietal, visual and motor networks. \ud Secondly, alcohol was found to impair behavioural inhibition in line with previous literature. \ud However, this effect was smaller than expected and did not extend from the manual response \ud domain to saccadic responses. It was also found that the stop signal task was not exclusively \ud measuring behavioural inhibition where alcohol also affected action-updating abilities. In the \ud saccadic version of the stop signal task it was found that a saccadic inhibition effect was also \ud present indicating top-down behavioural inhibition is aided by bottom-up automatic inhibition. \ud Altogether this body of work provides a basis for future research wishing to investigate the \ud relationship between acute effects of alcohol on GABAergic functioning and impulsivity in \ud order to better inform intervention and prevention treatments.

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