Priyanka Roy¹ (), Amy Nguyen^2,3, Nicholas Vo^2,4, Arijit Chakraborty^2,5,6; ¹University of Illinois Chicago, ²Midwestern University, ³Pacific University, ⁴Levine Eye Care Center, ⁵University of Waterloo, ⁶Rush University Medical Center

Everyday activities such as physical exercise and drinking caffeinated beverages are known to modulate neuroplasticity, although the interplay between the two is unclear for central nervous system functions, such as visual perception. Previously, we reported (Nguyen et al., 2023) that caffeine selectively enhances dorsal stream function (global motion perception) but does not alter ventral stream function (global form perception) or cortical excitability. This study investigated the interaction between physical exercise and caffeine on dorsal and ventral visual stream functions. Thirty two participants (26±5y) biked for 120 mins at 60% of their maximal heart rate. Participants were randomly assigned to receive either 200 mg of caffeine or a placebo pill an hour through the physical exercise. Motion coherence threshold (MCT) for random-dot-kinematogram and form coherence threshold (FCT) for Glass pattern stimuli were measured sequentially and concurrently within 2-down-1-up adaptive staircases, pre- and post-physical. There was a main effect (F1,31=11.571, p=0.03) of exercise-induced improvement that was modulated by caffeine and the testing method (sequence/concurrent). When measured in sequence, post-exercise, the MCT was improved in both caffeine (pre: 22±7%, post: 11±8%, p=0.01) and non-caffeine (pre: 20±8%, post: 16±8%, p=0.035) groups. There was no change in FCT in either group. When measured concurrently, both MCT (pre: 27±11%, post: 15±7%, p=0.001) and FCT (pre: 31±12%, post: 25±11%, p = 0.02) exhibited a larger improvement in the caffeine group and a slight improvement (MCT, pre: 25±9%, post: 19±7%, p = 0.04; and FCT, pre: 29±10%, post: 25±11%, p=0.043) in the non-caffeine group. Overall, our results indicate an isolated and cumulative beneficial effect of physical exercise and caffeine on dorsal visual stream function. When measured concurrently with the dorsal stream, the additional positive impact on the ventral stream might suggest an influence of the dorsal stream in global form perception through cross-talks between the two streams.