The cerebral origin of the alpha rhythm.

The EEG alpha rhythm was recorded from 8 isolated canine brains in the absence of orbital contents, drug effect, or pulsatile cerebral blood flow. Abrupt shift to hypoxic perfusion, with maintenance of other perfusion variables, resulted in a loss of alpha coincident with a fall in CMRO2 and rise in oxygen deficit. It is concluded that the alpha rhythm reflects neural electrical activity, and that sources in the eye muscles or in cardiac-induced electromechanical properties of the brain may be rejected.