Directional motion sensitivity in people with Visual Snow Syndrome is modulated by the presence of trailing-type palinopsia

Visual Snow Syndrome (VSS) is characterized by visual perceptual distortions, potentially linked to increased neural excitability. We hypothesized that this hyperexcitability might affect motion direction sensitivity in VSS, particularly in those with trailing-type palinopsia (TTP), an atypical perception of visual motion. Using a spatial suppression paradigm, we assessed motion duration discrimination thresholds for small (1{degrees}), medium (2.5{degrees}), and large (12{degrees}) high-contrast gratings in 23 VSS and 27 control participants. Spatial Suppression Index (SSI) quantified size-dependent increases in duration thresholds. Visual Discomfort Questionnaire scores and VSS symptom ratings including TTP, afterimages, photophobia, etc. were also collected. VSS patients reported higher visual discomfort and perceptual disturbances. However, no group differences were found in duration thresholds or SSI. Notably, higher TTP scores were associated with lower duration thresholds, indicating a facilitatory effect of TTP on motion sensitivity. These findings suggest that visual snow, the core symptom of VSS, is not linked to abnormal directional sensitivity or center-surround suppression associated with visual motion. However, the dependence of directional sensitivity on TTP emphasizes the heterogeneity of VSS, which should be considered in future neurophysiological and clinical models.