ABSTRACT
Human brain activity displays a wide range of activation patterns during both
normal and abnormal states. Normal states include physical states (such as
sleep, wakefulness, and exertion) as well as mental states (such as calmness,
happiness, and anger). Abnormal states, primarily observed in neurological
disorders and drug-induced imbalances, include seizures (in epilepsy) and de-
mentia (seen in Alzheimer’s disease and Lewy body disease). The list of possi-
bilities is endless. This variety is further compounded by three factors. First,
each state has varying degrees of magnitude which results in varying degrees
and, in some cases, regions of brain activation. Second, brain activity in any
state is modulated by high-level brain functions such as attention and cogni-
tive processing. Third, at any instant of time, the overall brain activity is not
due to any one mental state but rather to a superimposition of a number of
different states.
