The effect of acute caffeine consumption on performance and brain activity following a *real-life* workday

The stimulant effects of caffeine result in its common consumption by
individuals in an attempt to combat the detrimental effects of fatigue on
performance. However, inconsistent findings regarding the effects of caffeine
on cognitive performance mean that the actions of caffeine on cognition are
unclear. Further, very few studies have examined brain activity underlying
caffeine induced behavioural effects. The present study will use functional
magnetic resonance imaging (fMRI) to investigate the effects of acute caffeine
consumption in the *real life* context of habitual caffeine use on the brain
activity of individuals fatigued by a *real life* workday. Findings will shed
light on the mechanisms whereby caffeine affects behaviour and alleviates
fatigue.
The study also has a much broader research aim to investigate the use of fMRI
as a more sensitive tool for the detection of the effects of nutritional
interventions. Functional MRI has already been demonstrated to be a more
sensitive method for the detection of subtle cognitive impairment following
mild traumatic brain injury, multiple sclerosis, human immunodeficiency virus
and chronic fatigue syndrome. The use of fMRI provided validation of cognitive
complaints in these groups where assessment using neuropsychological tasks
could not. Similarly, it is hoped that fMRI will be able to provide validation
of the subjective fatigue alleviating effects of nutritional interventions by
demonstrating cognitive task related changes in brain activation.

This study aims to determine the effects of acute coffee consumption compared
to consumption of decaffeinated coffee on subjective fatigue and vitality
ratings, neuropsychological performance and brain activity during working
memory and learning tasks. Acute effects will be investigated following a *real
life* workday during which caffeine was consumed according to the participant*s
habitual regime.

The study employs a within-subject design and is a placebo controlled
intervention study.

All participants will be tested twice: once after acute caffeinated coffee
administration (100 mg caffeine, equivalent to 1 cup of coffee) and once after
acute decaffeinated coffee administration (placebo).

Before inclusion in the study, participants will complete a medical
questionnaire and a questionnaire that checks for MRI contraindications and
factors affecting caffeine pharmacokinetics. When included, the participants
will visit the laboratory three times: for a training session (1 hour) and two
test sessions (2 hours each). During each test session participants will
complete questionnaires at three different time points, will perform
neuropsychological tasks outside the MRI scanner (30 min) and two cognitive
tasks (1 hour) inside scanner. The risks related to this study are negligible.