Caffeine is the most widely consumed psychostimulant. It is often adopted as a tool to modulate brain activations in fMRI studies. However, its pharmaceutical effect on task-induced deactivation has not been fully examined in fMRI. Therefore, the purpose of this study was to examine the effect of caffeine on both activation and deactivation under sustained attention.
Task fMRI was acquired from 26 caffeine naive healthy volunteers before and after taking caffeine pill (200 mg).
Statistical analysis showed an increase in cognition-load dependent task activation but a decrease in load dependent deactivation after caffeine ingestion. Increase of attention and memory task activation and its load-dependence suggest a beneficial effect of caffeine on the brain even though it has no overt behavior improvement. The reduction of deactivation by caffeine and its load-dependence indicate reduced facilitation from task-negative networks.
Caffeine affects brain activity in a load-dependent manner accompanied by a disassociation between task-positive network and task-negative network.
Diagram showing experiment design.
Bar graphs of reaction accuracy and reaction time before and after caffeine ingestion. (a) Mean reaction time at low-load condition, (b) Mean reaction time at high-load condition, (c) Mean reaction accuracy under low-load condition, (d) Mean reaction accuracy under high-load condition.
Low-load condition (attention task) versus baseline brain activation difference. (a) Group level activation difference before caffeine intake, (b) Group level activation difference after caffeine intake, (c) Caffeine-induced changes in low-load task activation versus baseline. Statistical significance level was defined at voxel-wise P < 0.005 and a cluster size of 46 (corrected for multiple comparison using AlphaSim, alpha < 0.05). Red means increased low-load task activation after caffeine intake. The number above each slice indicates slice location in the MNI space. Color bar indicates visualization window for t values.
High-load condition (sustained attention and working memory task) versus baseline brain activation difference. (a) Group level activation difference before caffeine intake, (b) Group level activation difference after caffeine intake, (c) Caffeine-induced changes to high-load task activation versus baseline. Statistical significance level was defined at voxel-wise P < 0.005 and a cluster size of 46 (corrected for multiple comparison using AlphaSim, alpha < 0.05). Red color means increased high-load task activation after caffeine intake. The number above each slice indicates slice location in the MNI space. Color bar indicates visualization window for t values.
High-load condition (sustained attention and working memory task) versus low-load condition brain activation difference. (a) Group level activation difference before caffeine intake, (b) Group level activation difference after caffeine intake, (c) Caffeine-induced changes to high-load versus low-load activation difference. Statistical significance level was defined at voxel-wise P < 0.005 and a cluster size of 46 (corrected for multiple comparison using AlphaSim, alpha < 0.05). Red means greater high-load minus low-load task activation difference after caffeine intake. The number above each slice indicates slice location in the MNI space. Color bar indicates visualization window for t values.
Behavioral Data (Mean and Standard Deviation) of Each Condition before and after Taking Caffeine
Low-load condition | High-load condition | |
---|---|---|
Caffeine | ||
Mean RT (ms) | 419.40 ± 23.80 | 413.00 ± 29.14 |
% Accuracy | 99.51 ± 0.70 | 94.60 ± 1.97 |
Noncaffeine | ||
Mean RT (ms) | 427.20 ± 26.80 | 412.30 ± 26.11 |
% Accuracy RT = reaction time | 99.11 ± 1.25 | 94.31 ± 1.85 |
RT = reaction time
Whole Brain Analysis Local Maxima
MNI coordinates | ||||
---|---|---|---|---|
Cluster size | X | Y | Z | |
Post-caffeine vs. pre-caffeine | ||||
Task vs. control | ||||
L middle temporal gyrus | 53 | –39 | –54 | 21 |
Task vs. baseline | ||||
R middle temporal gyrus | 58 | 48 | –48 | 15 |
R insula lobe | 61 | 39 | –15 | 18 |
L fusiform gyrus | 240 | 27 | –54 | –9 |
R fusiform gyrus | 264 | 3 | 36 | 9 |
L cuneus | 115 | –6 | –84 | 36 |
R calcarine gyrus | 115 | 12 | –66 | 24 |
R inferior occipital gyrus | 131 | 36 | –81 | –3 |
R hippocampus | 210 | 33 | –42 | 3 |
Control vs. baseline | ||||
L lingual gyrus | 252 | –21 | –63 | –6 |
R middle occipital gyrus | 52 | 30 | –93 | –3 |
Local maxima of brain activations on two types of comparison across two types of sessions. “Task” refers to high-load condition, while “control” means low-load condition. L = left; MNI = Montreal Neurological Institute; R = right; vs. = versus