Coffee consumption, particularly caffeine intake from coffee, decreases connectivity of a region in the brain associated more with passive tasks as opposed to tasks requiring focus and concentration, according to study findings published in Frontiers of Behavioral Neuroscience.
Habitual coffee consumers report increased cognitive performance, work efficiency, and alertness and reduction in fatigue after drinking coffee; however, very limited research has been published on how coffee actually affects the whole-brain network activity.
Researchers in Portugal conducted a study to determine the functional effects of coffee consumption on brain network activity at rest. They recruited 47 Portuguese healthy volunteers (mean age, 30; 31 women) who were habitual coffee drinkers. A habitual coffee drinker was defined as someone who drank at least 1 cup of coffee daily.
These 47 individuals underwent functional magnetic resonance imaging (fMRI) scanning after abstaining from food or caffeinated beverages at least 3 hours before participating in the study. The participants underwent the following 3 fMRI assessments, each of which lasted 7.5 minutes:
- 1 to obtain baseline images
- 1 immediately following coffee intake containing 85 mg of caffeine in 100 mL of water without added sugar
- 1performed 30 minutes after coffee intake
The researchers performed these fMRI scans with the participants at rest, eyes closed and relaxed with their minds allowed to wander freely.
Additionally, the researchers analyzed the effects of caffeine only in a second group of 36 participants (mean age, 32.1; 27 women) who were habitual coffee drinkers. Instead of a coffee drink, these participants were given 100 mL of hot water with the same dose of caffeine mixed in the water. This enabled the researchers to analyze the impact of caffeine only on the activity of specific networks within the brain.
Activity in the left middle occipital gyrus (MOG) within the higher visual network and the right dorsolateral prefrontal cortex within the right executive control network increased after consuming coffee. In contrast, posterior default mode network (DMN) connectivity within the left precuneus decreased after drinking coffee.
The DMN is a network in the brain that contributes to the ability of the brain to respond to external stimuli, especially memory, visuospatial imagery, and self-consciousness. The researchers suggested that the decreased connectivity after both coffee and caffeine intake in this region of the brain at rest may indicate increased readiness of the brain to switch from rest (default mode) to task-oriented functions and processing.
Non-coffee-related caffeine intake reproduced this decreased connectivity of the posterior DMN, but it did not alter activity within the higher visual and right executive control networks as coffee consumption did. The researchers correlated decreased functional connectivity of the DMN with the effect of caffeine on cerebral vascular circulation as caffeine vasoconstricts cerebral blood vessels.
“[C]onnectivity of the posterior DMN is decreased after drinking coffee, while the connectivity in nodes of the higher visual and the right executive control network (RECN) is increased after drinking coffee,” the researchers wrote. “[T]he decrease in the posterior DMN connectivity is replicated by caffeine intake, whereas the alterations observed in the higher visual and the RECN are not.”
Study limitations included lack of a control group of noncoffee drinkers or those who consumed only decaf and the analysis of only resting-state brain connectivity instead of during performance of specific tasks.
Picó-Pérez M, Magalhães R, Esteves M, et al. Coffee consumption decreases the connectivity of the posterior Default Mode Network (DMN) at rest. Front Behav Neurosci. Published online June 28, 2023. doi:10.3389/fnbeh.2023.1176382