Brain States

Brain states are the distinct macro-scale states the majority of the brain, especially the cortex, exhibits particularly during different behavioral states, a closely related concept.

Commonly defined brain states are:
 * NREM
 * REM
 * Quiet Wake
 * Active Wake

Sources of state modulation
There are at least three sources of state modulation causing different brain states, they include: thalamocortical afferents, corticocortical connections, and neuromodulatory inputs. There's evidence that different states can occur simultaneously in different cortical regions.

Thalamocortical afferents
The thalamus routes a lot of sensory activity to the cortex and is known to provide significant drive to the visual cortex. Spontaneous thalamic activity has also been shown to increase desynchronization, a sign of wake-ness.

Corticocortical connections
These connections are found extensively between different cortical regions.

Neuromodulatory inputs

 * Norepinephrine from the Locus coeruleus
 * Cholinergic inputs from the Basal Forebrain