Investigating Brain Function in People With and Without Visual Snow Syndrome Using Adaptation to Visual Stimuli

Inclusion Criteria for People with Visual Snow Syndrome: * Between the ages of 18 and 60 years old * Normal (20/25 or better in each eye) or corrected-to-normal vision (MR-compatible glasses will be provided as needed) * Ability to comply with study instructions * Individuals who have a current diagnosis of VSS from a neuro-ophthalmologist or meet diagnostic criteria of VSS (experience of dynamic dots across the visual field persisting longer than 3 months and at least 2 of the following additional visual symptoms: palinopsia, entoptic phenomena, trails behind moving objects, photophobia, or nyctalopia) * Individuals living in Minnesota within 2 hours of the study site Inclusion Criteria for Non-snow Controls: * Between the ages of 18 and 60 years old * Normal (20/25 or better in each eye) or corrected-to-normal vision (MR-compatible glasses will be provided as needed) * Ability to comply with study instructions * Individuals living in Minnesota within 2 hours of the study site Exclusion Criteria for People with Visual Snow Syndrome: * Not being fluent in English or another language for which interpretation/translation services are available * A diagnosed or self-reported intellectual disability * Current substance dependence (besides nicotine), or drug dependence with tolerance or withdrawal within past 12 months * Hallucinogenic substance use within the past 12 months or hallucinogenic substance use within 12 months prior to onset of VSS symptoms * Severe central nervous system disease * Head injury with skull fracture or loss of consciousness for more than thirty minutes * Presence of a physical problem that would render study measures difficult or impossible to administer or interpret (e.g., visual field loss) * Age less than 18 years or greater than 60 years * MRI exclusions (for MR visits only): * Metal in the body that cannot be approved by the CMRR safety committee * Pregnancy * Conditions that affect neuro-hemodynamic coupling * Claustrophobia * Inability to lie still for at least an hour * Weight in excess of 440 lbs * CT scan exclusion only: Research-related radiation exposure within the last 12 months * Any vision anomaly aside from VS or refractive error (e.g., strabismus/ crossed eyes, lazy eyes, color blindness) * Current psychotic episode Exclusion Criteria for Non-snow Controls: * Not being fluent in English or another language for which interpretation/translation services are available * A diagnosed or self-reported intellectual disability * Current substance dependence (besides nicotine), or drug dependence with tolerance or withdrawal within past 12 months * Hallucinogenic substance use within the past 12 months * Severe central nervous system disease * Head injury with skull fracture or loss of consciousness for more than thirty minutes * Presence of a physical problem that would render study measures difficult or impossible to administer or interpret (e.g., visual field loss) * Age less than 18 years or greater than 60 years * MRI exclusions (for MR visits only): * Metal in the body that cannot be approved by the CMRR safety committee * Pregnancy * Conditions that affect neuro-hemodynamic coupling * Claustrophobia * Inability to lie still for at least an hour * Weight in excess of 440 lbs * CT scan exclusion only: Research-related radiation exposure within the last 12 months * Any vision anomaly or refractive error (e.g. strabismus/ crossed eyes, lazy eyes, color blind) * A personal history of VSS symptoms or a diagnosis with VSS * Current psychotic episode