A study in Thailand using electroencephalography (EEG) and cognitive tests showed that working memory improved after drinking a caffeinated drink in the morning. Additionally, EEG recordings showed a reduction of alpha wave activity, a type of brain activity often associated with drowsiness, after drinking the caffeinated drink compared to the activity level before. The study was published in Physiology & Behavior.
Caffeinated drinks such as coffee or tea, energy drinks, and others are widely consumed worldwide. People often consume them in the morning to increase vigilance, decrease sleepiness, and stimulate overall attention and arousal. Moderate doses of caffeine have been shown to improve well-being and increase motivation and energy for work without any adverse behavioral effects. A number of recent studies have also shown that just a single dose of caffeine (30-50mg) can affect attention levels.
Another line of recent research has highlighted associations between EEG readings and arousal levels. Notably, researchers have found that a global decrease in the power of the electroencephalographic pattern known as alpha waves corresponds to an increase in arousal. Both were found to occur 30 minutes after consuming a drink containing caffeine in healthy young adults. But is this brain activity associated with changes in cognitive functions such as attention and memory as well?
The authors behind the new study sought to “explore whether a single low caffeine dose as a morning wake-up drink could affect brain wave activity and cognitive function,” explained lead researcher Amornpan Ajjimaporn, an associate professor at Mahidol University.
To answer this question, Ajjimaporn and her colleagues conducted an experiment on 25 healthy young males (average age 21 years) who had been habitually consuming 1-2 or fewer cups of caffeinated coffee or tea or 1 can of caffeinated soda per day.
Participants were randomly divided into two groups. Both groups went through both the experimental treatment and the placebo, but in different order. The experimental treatment consisted of drinking a cup of flavored water to which 50 mg of caffeine were added. The placebo treatment consisted of drinking an equal glass of flavored water, but without added caffeine.
The experiment followed a double-blind procedure, meaning that neither experimenters working with study participants nor the study participants knew whether they were undergoing the experimental or the placebo treatment. Experimenters also asked participants whether they thought that they drank a placebo or a caffeinated drink and reported that 85% of participants could not tell the difference.
The participants visited the laboratory three times. On the first visit, experimenters took various measures – weight, height, body fat percentage, and others. The experiment was carried out on the second visit. “Brain activity was measured for 5 min at rest in a sitting position with eyes closed using electroencephalography (EEG). Subsequently, participants performed two cognitive function tests, i.e., the trail-making test (Trails) A and B and the digit span test,” the researchers explained.
After this, each participant drank his cup of flavored water, either with caffeine or without, depending on the group. Thirty minutes after drinking the water from the cup, participants again underwent brain activity measurements and completed cognitive tests. This was followed by 5 minutes of exercises followed by one more session of brain activity recording and cognitive testing.
A week later the whole procedure was repeated, with the only difference being that the groups switched places. The group that previously underwent the experimental treatment i.e., drank caffeinated water was now given water without caffeine and the former placebo group drank caffeinated water i.e., underwent the experimental treatment.
“The main findings demonstrated that 30 min following caffeine drinking, mean absolute power of the alpha wave appears to diminish whereas a similar pattern, compares to placebo, is exhibited in the delta, beta, and theta wave activity. The cognitive function, i.e., visuomotor processing speed, working memory, and attention were improved after 30 min caffeine drinking and 35 min after 5 min isokinetic exercise,” the researchers wrote. In other words, brain activity indicating drowsiness had decreased and cognitive functioning had improved 30 minutes after ingesting 50 mg of caffeine.
The findings indicate that “commercial drinks with low caffeine doses, the equivalent of an 8-oz cup of instant coffee, a single 1-oz shot of espresso, an 8-oz cup of black tea, a 12oz can of soft drinks, etc., could be able to enhance arousal and improve executive ability (i.e., working memory and inhibition control) after 30 minutes drinking,” Ajjimaporn told PsyPost.
“Interestingly, this is the first study that revealed the inverse correlation between alpha wave activity and cognitive function following a single low-dose caffeine consumption. We found the association between alpha power decreases over the central and occipital cortical areas and better executive functioning,” she added.
The study clearly demonstrates that even a single dose of caffeine can reduce drowsiness and increase cognitive functioning. However, it also has some limitations. Notably, the sample was small and everyone received the same dose of caffeine regardless of weight, resulting in different caffeine concentrations in the body. Also, the study did not measure other aspects of cognitive functioning, such as problem-solving, so it remains unknown whether they are affected by caffeine.
“The study also did not measure other aspects of cognitive functions, such as problem-solving, and decision-making, and as the subjects in this study were only males, future studies can build to obtain gender differences in responses to low doses of caffeine,” Ajjimaporn said.
The paper, “A low- dose of caffeine suppresses EEG alpha power and improves working memory in healthy University males“, was authored by Amornpan Ajjimaporn, Prapan Noppongsakit, Papatsorn Ramyarangsi, Vorasith Siripornpanich, and Rungchai Chaunchaiyakul.
