UC Riverside spider expert reveals the good, the bad, and the ugly about the eight-legged arachnids — and tells us how to deal with truly scary spiders.

Prions, long studied by UCSF professor and Nobel laureate Stanley Prusiner, build up in the brain to cause Alzheimer's and other dementias. Now they're linked to post-traumatic stress disorder in combat veterans and in the brain damage of athletes who have suffered repeated concussions.