This process, known as spreading depolarisation or spreading depression
, is marked by hyperactivity in the neurons, followed by a sudden silence.
A chemical process in the brain known as cortical spreading depression
helps to explain the increased risk of stroke in migraine patients.
The low-frequency brainwave linked to migraines and epilepsy is known as cortical spreading depression
(CSD) and is currently best studied by placing electrodes directly on the surface of the brain.
Migraine is thought to be a neurovascular disease, which is activated due to changes in the modulating nociceptive inputs from the raphe and locus coeruleus nuclei in the brainstem or a cortical spreading depression
In 1994, Leo proposed the theory of cortical spreading depression
to explain the mechanism of headache with aura.
This study suggested that an electrophysiological event such as cortical spreading depression
generated the aura in the human visual cortex.
They found that adding basic conservation principles to the older models immediately demonstrated that spikes, seizures, and spreading depression
were all part of a spectrum of nerve cell behavior.
Migraine attacks, like epileptic seizures, may be triggered by excessive neocortical cellular excitability; in migraine, however, the hyperexcitability is believed to transition to cortical spreading depression
rather than to the hypersynchronous activity that characterizes seizures.
Another piece of evidence was cortical spreading depression
(CSD), a wave of electrical "silence" in the brain that follows electrical stimulation, spreading out from the point of stimulation in a predictable pattern.
Furthermore, we already have headache at the onset of aura, and that does seem to conflict with the idea that you have to have a [cortical] spreading depression
to activate the trigeminovascular system to cause headache.
Dr Charles said that migraines show cortical spreading depression
(CSD), when dramatic waves of activity spread across the surface of the brain.
Later researchers connected the phenomenon to a migraine aura, reasoning that the flickering light that patients see could occur as the cortical spreading depression
crosses the visual center at the back of the brain.