Spreading depression is a fascinating phenomenon that can be provoked by ch
emical, electrical or mechanical stimuli of the cortex. Spreading depressio
n-like transient depolarizations are observed in the periinfarct tissue aft
er focal ischemia. The reduction in electrical activity and a negative dire
ct current potential shift propagating over the cortex with a rate of 2-5 m
m/minute are the physiological hallmarks. It is thought that spreading depr
ession and peri-infarct depolarizations might play a role in the pathogenes
is of migraine and stroke. However, these events have never been detected i
n humans. This paper reviews the physiological characteristics of spreading
depression and peri-infarct depolarizations and discusses their potential
role in migraine and stroke.