By Samantha Montoya and University of Minnesota research team
A study from Visual Snow Initiative (VSI) collaborators at the University of Minnesota provides new insight into the neural mechanisms of Visual Snow Syndrome (VSS). Researchers have demonstrated that visual snow is susceptible to the motion aftereffect —a phenomenon where, after staring at a moving pattern, stationary images appear to move in the opposite direction.
Objective
In Visual Snow Syndrome (VSS), the visual field is covered with flickering specks, likely caused by spontaneous activitiy in the visual system. Researchers hypothesized that this activity originates early in the visual pathways and tested its reach to motion-selective areas using the motion aftereffect.
Methods
11 VSS participants adapted to high-contrast drfiting grating moving in opposite directions, then judged motion in their visual snow on a blank screen, pressing a button when the motion on both sides appeared the same. The grating duration varied (1.6-45 sec), and a control condition with a stationary square wave pattern confirmed typical motion aftereffects for external stimuli.
Results
After adaption, most participants (10/11) reported that their visual snow moved in the oppostie direction of the gratings, as expected. Longer adapter durations led to longer-lasting illusions, with a linear relationship on a log-log axis, consistent with established motion aftereffect research
Conclusions
Visual snow is susceptible to the motion aftereffect, usggesting that the neural activitiy producing visual snow reaches motion selective neurons involved in perceiving the motion aftereffect, which are believed to include the V5/MT. If visual snow arises before area V5/M, our findings suggest that this activity is propagated forward through the visual pathways.
This shows that visual snow perception can be influenced by biasing motion-selective neurons, and future studies can use this approach to explore the neural mechanisms of visual snow. Pinpointing the neural origins of visual snow may facilitate the development of novel treatment approaches targeting specific visual brain areas or networks.
