If you get elbowed in the eye (or get hit on the head as above), you see stars.
See the site
http://www.bio.net/bionet/mm/neur-sci/1996-October/025877.html
for many references
Stein, An Introduction to Neurophysiology
Roe, A. Hahm, J., & Sur, M. (1990). A map of visual space induced in primary auditory cortex. Science, 250, 818-
