A brief perceptual disturbance, such as a strange light or unpleasant smell. Can be beneficial, as they can give people advance warning before the onset of a migraine or seizure.
Example: A woman sees flashing colored lights to her left for a few minutes before the onset of a severe epileptic seizure.
Grinnell, R. (2008). Aura. Psych Central. Retrieved on April 28, 2015, from http://psychcentral.com/encyclopedia/2008/aura/