The effect of stress and alcohol on prefrontal cortex activity and cognitive performance in undergraduate students

Dwyer, Rebecca Suzanne (2022) The effect of stress and alcohol on prefrontal cortex activity and cognitive performance in undergraduate students. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Background: High stress exposure has been related to an increase in alcohol intake, and research has shown that both alcohol consumption and high stress levels affect brain function. Brain vulnerability to alcohol and stress is heightened during the development period, which in humans extends to the third decade of life. University students require a healthy brain for good academic performance, however, increased stress levels due to financial pressures, continuous academic demands, and student lifestyle may affect brain development and have detrimental consequences on cognitive performance. Aim: The research within this thesis aimed to investigate the effects of acute stress, perceived stress in the month prior, and average monthly units of alcohol consumption in the month prior on executive function and prefrontal cortex activity in undergraduate students aged between 18-30 years old. Methods: Three empirical studies were conducted. This comprised of two laboratory-based experiments including a pilot study (N=26) and a larger scale laboratory study (N=96), and finally an online study (N=88). These studies included measures of i) executive function (EF) under stress [Wisconsin Card Sort Task (WCST), Trail Making Task (TMT), Stroop Task, and Symbol Digit Modalities Task (SDMT)], ii) subjective stress and iii) perceived stress and average monthly units of alcohol consumption. In addition, both laboratory-based studies assessed brain activity during EF performance (using a functional near-infrared spectroscopy device), and the pilot study assessed physiological stress (electrodermal activity and heart rate) during exposure to acute stress. Results: The effects of both stress and alcohol appear to be domain and task-dependent. While stress induced immediately before EF performance (acute stress) increased EF performance in the Stroop task (response inhibition) the opposite effect was found for overall perceived stress experienced in the prior month. Interestingly, perceived stress (but not acute stress) improved performance in the TMT, a task related to cognitive flexibility but only in the online study. Despite the differential effect on EF performance, both acute and perceived stress increased activity in the prefrontal cortex during EF, specifically in the right dorsolateral prefrontal cortex. Unexpectedly, increased levels of average monthly units of alcohol consumption were related to increased performance in TMT A, Stroop B, and the SDMT in the laboratory study, while a similar increase in performance was found in TMT A in the online study. Furthermore, increased levels of average monthly units of alcohol consumption were related to increased activity in areas across the prefrontal cortex during the performance on some tasks such as Stroop B. Conclusion: The findings from this thesis conclude that stress and alcohol impact on domains of executive functioning are EF-task and EF-domain-dependent. Increases in prefrontal cortex activity due to exposure to stress and alcohol may indicate an increased neural effort to perform tasks under pressure, indicative of a compensatory mechanism to facilitate performance.