Cortical spreading depression is a wave of electrophysiological

Electrophysiology

Electrophysiology is the study of the electrical properties of biological cells and tissues. It involves measurements of voltage change or electric current on a wide variety of scales from single ion channel proteins to whole organs like the heart...

 hyperactivity followed by a wave of inhibition, usually in the visual cortex

Visual cortex

The visual cortex of the brain is the part of the cerebral cortex responsible for processing visual information. It is located in the occipital lobe, in the back of the brain....

.

The term is used by neuroscientist

Neuroscientist

A neuroscientist is an individual who studies the scientific field of neuroscience or any of its related sub-fields...

s to represent at least one of the following cortical processes:

• The spreading of a self-propagating wave of cellular depolarization
  Depolarization
  In biology, depolarization is a change in a cell's membrane potential, making it more positive, or less negative. In neurons and some other cells, a large enough depolarization may result in an action potential...
  
   in the cerebral cortex
  Cerebral cortex
  The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
  
  .
• The spreading of a wave of ischemia
  Ischemia
  In medicine, ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. It may also be spelled ischaemia or ischæmia...
  
   passing through an area of cortex.
• The spreading of a wave of vasoconstriction
  Vasoconstriction
  Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...
  
   following vasodilation
  Vasodilation
  Vasodilation refers to the widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large arteries, smaller arterioles and large veins. The process is essentially the opposite of vasoconstriction, or the narrowing of blood vessels. When...
  
   of contiguous cortical arteriole
  Arteriole
  An arteriole is a small diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillaries.Arterioles have muscular walls and are the primary site of vascular resistance...
  
  s.

The scintillating scotoma

Scintillating scotoma

Scintillating scotoma is the most common visual aura preceding migraine and was first described by 19th century physician Hubert Airy . It is often confused with ocular migraine which originates in the eyeball or socket.-Presentation:...

 of migraine

Migraine

Migraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea...

 in humans may be related to the neurophysiologic

Neurophysiology

Neurophysiology is a part of physiology. Neurophysiology is the study of nervous system function...

 phenomenon termed the spreading depression of Leão

Aristides Leão

Aristides de Azevedo Pacheco Leão was one of the most noted Brazilian biologists and scientists, one of the founders of the Biophysics Institute of the Federal University of Rio de Janeiro and the discoverer of cortical spreading depression, an electrophysiological phenomenon of the central...

.

The spreading depression wave progresses across the cortex at approximately 2 - 5 mm/minute.

Increased extracellular potassium ion

Potassium

Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

 concentration and excitatory glutamate

Glutamic acid

Glutamic acid is one of the 20 proteinogenic amino acids, and its codons are GAA and GAG. It is a non-essential amino acid. The carboxylate anions and salts of glutamic acid are known as glutamates...

 contribute to the initiation and propagation of cortical spreading depression, which is the underlying cause of migraine aura

Aura (symptom)

An aura is a perceptual disturbance experienced by some migraine sufferers before a migraine headache, and the telltale sensation experienced by some people with epilepsy before a seizure. It often manifests as the perception of a strange light, an unpleasant smell or confusing thoughts or...

.