Caffeine and Cognitive Task Performance: EEG and EDA Study

• ¹ School of Biomedical Engineering, Science and Health Systems, Drexel University, United States
• ² LeBow College of Business, Drexel University, United States
• ³ Department of Family and Community Health, School of Nursing, University of Pennsylvania, United States
• ⁴ General Pediatrics, Children's Hospital of Philadelphia, United States

Coffee and caffeinated drinks are popular beverages and consumed daily worldwide (Araújo et al., 2015). As a psychoactive stimulant, caffeine has been shown to improve alertness, vigilance, attention, and mood (Araújo et al., 2015). Usually in the form of coffee, caffeine is consumed by over 80% of the United States adult population and is typically expected to enhance cognitive function (McLellan, Caldwell, & Lieberman, 2016). Caffeine consistently improves mood, reaction time and vigilance when alertness is reduced, and given that a basic level of arousal is essential for the performance of any task, it is logical that caffeine is particularly useful in fatiguing circumstances (McLellan et al., 2016). In this study, our aim was to assess the observable effects of caffeine on cognitive task performance via the completion of a task battery before and after coffee consumption. Performance differences on working memory and attention tasks were assessed by comparing groups consuming regular coffee and decaffeinated coffee. Twenty participants (12 females, mean age = 38 years) volunteered for the study. All confirmed that they met the eligibility requirements of being right-handed with vision correctable to 20/20, did not have a history of brain injury or psychological disorder, and were not on medication affecting brain activity. After giving consent, participants were fitted with a wireless 12 channel electroencephalography (EEG) headset (OpenBCI Ultracortex Mark IV) to measure brain electrical activity as well as a wireless electrodermal activity (EDA) sensor (Neulog GSR Logger Sensor NUL-217) on their left hand to assess physiological measures from skin conductance. Subjects were randomly assigned to one of the groups; a caffeinated coffee group and a decaffeinated coffee group. All subjects completed three cognitive tasks in between making hot beverages on beverage machines. The setting for coffee consumption simulated a work environment where employees performed tasks, prepared and consumed hot beverages while on break, and returned to their cubicles to work. The first task participants completed was a mental arithmetic task. Here, one-digit or two-digit numbers were presented to the participant. Participants were instructed to add or multiply numbers mentally and enter the correct response on the screen. They either added or multiplied single digit numbers (2+4 or 2x4) or double-digit numbers (12+45 or 11x13) to increase task difficulty. The next task was a rapid visual processing task (RVP) where digits from 1 to 9 appeared in pseudo-random order on a screen at the rate of 100 digits per minute. Participants were asked to detect target sequences of digits (for example, 2-4-6, 3-5-7, 4-6-8) that appeared with two different levels of difficulty (single digit and triple digit). When the participant saw the target sequence they were asked to respond by pressing enter as quickly as possible. The Stroop paradigm was used for the final task in this battery. Subjects were asked to look at color words (ie. red, blue, green) in two different conditions: congruent, where the word was printed in the color that its name denoted (e.g. "yellow" printed in yellow ink) and incongruent, where the word was printed in a different color than its name denoted (e.g. "yellow" printed in red ink). Preliminary analysis of the behavioral results was done on the improvement in trials 2 and 3 with respect to trial 1 for each participant. Trial 1 was the baseline trial that was performed prior to drink consumption. Trials 2 and 3 were performed after participants consumed either regular coffee (caffeinated beverage) or decaffeinated coffee (control/non-caffeinated beverage). Results indicate that there was accuracy improvement (In trials 2 and 3 with respect to baseline trial 1) as well as correct response time improvement trend in all tasks. The caffeinated beverage significantly improves task accuracy compared to the non-caffeinated beverage for the Stroop task (F1,18=16.5, p <0.001) (fig.1) and a significant difference between groups for correct response time improvement for the Stroop task (F1,76=10.2, p <0.01). Figure 2 depicts the mean change in correct-response-time (lower value is better), and indicates faster response by participants in coffee group. These results confirm the literature that caffeinated beverages help improve accuracy and response time in cognitive tasks when compared to non-caffeinated beverages (Araújo et al., 2015) . Further analysis will be conducted to detect relevant patterns or trends within the EEG and EDA datasets. Figure 1. Comparison of accuracy improvement in trials 2 and 3 during the Stroop task for coffee and decaf groups. Whiskers are Standard Error of the Mean (SEM). Figure 2. Comparison of correct response time changes in trials 2 and 3 during the Stroop task for coffee and decaf groups. Whiskers are SEM.