Abstract
Purpose :
Caffeine, the most commonly used neurostimulant, is known to affect central neural processing mediated by a muscarinic cholinergic system and an upregulation of dopamine. Previous studies suggest that caffeine consumption is associated with increased attention and enhanced motor and sensory behavior. We investigated, through a double-blinded prospective study, whether caffeine alters extrastriate visual processing such as global motion and global form perceptions, which are thought to be the markers of the dorsal and ventral visual streams, respectively.
Methods :
26 participants with normal vision were randomly assigned to the caffeine and control groups. The participants in the caffeine group received a 200 mg caffeine pill, while those in the control group received similar looking rice flour pill. Baseline global motion and global form perceptions were measured using random-dot-kinematogram(100 dots, 6 deg/s, translational up/down motion) and Glass pattern (100 dot pairs, discrimination between concentric and radial pattern), respectively. Using 2-down 1-up adaptive staircases, motion coherence and form coherences thresholds were determined, and thresholds were calculated by averaging the last 10 of 12 reversals. The participants were then administered caffeine/placebo pills and were advised to sit in a quite environment while watching a show on Disney. Global motion and global form perceptions were remeasured after 45 mins to explore any potential effect of caffeine on higher visual processing.
Results :
Post-intervention, participants in the caffeine group had better motion coherence threshold than the baseline (pre-caffeine: 20 ± 9%, post-caffeine: 12 ± 5, p = 0.03). However, the form coherence threshold was not significantly different between baseline and post-intervention (p = 0.48). Similarly, in the placebo group, neither motion coherence (p = 0.31) nor form coherence thresholds (p = 0.63) were different between the two measurements.
Conclusions :
Our results indicate that caffeine selectively enhances the dorsal stream, but not the ventral stream of the extrastriate visual cortex. The fact that caffeine improves performance in detecting visual motion might also have a general implication for other dorsal stream functions, such as object localization, navigation, and visuomotor control.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.