Davide Frattini¹ (), Mariagrazia Benassi², Tobias Wibble¹, Mattias Nilsson¹, Roberto Bolzani², Tony Pansell¹; ¹Karolinska Institutet, ²University of Bologna

This study explores the impact of concussion on visual temporal resolution processing, particularly in individuals with visually induced motion sickness (VIMS) after concussion. VIMS is thought to stem from changes in the visual cortices involved in motion processing, likely due to neurochemical imbalances and neuronal damage from concussive mechanical forces. The research examines Critical Flicker Frequency (CFF) across various eccentricities of the visual field in concussed individuals, employing CFF as a measure of visual temporal resolution. CFF is defined as the highest frequency at which a flicker is perceived as a steady light, with an increased threshold indicating heightened sensitivity to rapid visual changes. The investigation followed a case-control design, comparing 15 post-concussion syndrome (PCS) patients exhibiting VIMS symptoms with 15 healthy controls. CFF was measured monocularly using an analog modulated LED, with testing conducted at eccentricities of 5, 10, 20, and 40 degrees from the fovea, and the stimulus size was adjusted for retinal ganglion cell density. The results revealed a significant interaction between groups and CFF threshold variability (F(2,136) = 18.216, p < .001). Specifically, while increases in threshold variability in the healthy population were associated with minimal rise in CFF threshold (B = .114, p = .50); in the PCS group, increased threshold variability significantly heightened CFF thresholds (B = .587, p < .001). These findings suggest that the PCS population may exhibit elevated internal noise levels within the visual system, potentially enhancing signal detection temporarily by increasing the probability of neuronal firing at the threshold level. This mechanism aligns with information processing theory and the principles of stochastic resonance. However, such enhancements can also lead to imprecise and exaggerated sensitivity to visual stimuli, or to stimuli that do not have sufficient impulse to spread in the sensory network and affect multisensory integration weights.