It is possible to take mental damage instead of physical damage. This can happen from:
•Psionics
•Toxins ( or mis-used pharmaceuticals)
•Certain diseases
•Magic and specifically failed magic.
Willpower can be added to base dice for the damage divisor.
Willpower is also used for calculating the Grace Period for mental tasks.
RCM’s and Guest Stars can substitute any mental ability dice (IQ, WP or PE) for base dice when suffering from mental damage.
A KO or mortal blow of Mental Damage could justify amnesia or insanity.