Motion Induced Blindness
You probably noticed that the yellow dots seem to wink in and out -- most people see this effect. It works best in dim lighting. If you had difficulty seeing this effect above, please try an improved example of the MIB illusion.
This illustration is not traumatic, but -- at least metaphorically -- it illustrates a dissociative process of intermittently not knowing whether a traumatic event "really happened".
The Motion Induced Blindness illusion was discovered by Yoram Bonneh. Work by Jack Pettigrew at University of Queensland suggests that this illusion results from a rivalry for dominance between the left and right hemispheres at the parietal lobe. When the right hemisphere is dominant, you see the yellow dots; when left hemisphere gains dominance, the yellow dots disappear.
On the other hand, this illusion may work similarly to some dissociative experiences. Our right hemisphere sees the world more as it really is, while the left hemisphere sees the world as we want it to be (Tucker & Luu, 2012) -- and suppresses sensory information that conflicts with what it believes "ought" to be. Paul Valent discusses the implications this issue for trauma therapy, in a presentation on this site about the right brain as a substrate for reforging psychoanalytic and trauma therapies.
Bonneh, Y. S. et al. (2001). Motion-induced blindness in normal observers. Nature, 411, 798-801. (Letters).
Funk & Pettigrew (2003). Does interhemispheric competition mediate motion-induced blindness? A transcranial magnetic stimulation study. Perception, 32, 1328-1338.
Valent, P. (2001). The right brain as a substrate for reforging psychoanalytic and trauma therapies. Presented at the ASTSS/NCPTSD Annual Conference, Canberra, Australia. March 2001.
Tucker, D. & Luu, P. (2012). Cognition and Neural Development. New York: Oxford University Press.