The term telencephalic DA cell group refers to a population of cells immunoreactive for dopamine and tyrosine hydroxylase that are broadly distributed in the rostral forebrain, including such structures as: substantia innominata, diagonal band, olfactory tubercle, piriform cortex, striatum (at levels rostral to the anterior commissure), claustrum, and deep cortical layers of all gyri of the frontal lobe rostral to the head of the caudate nucleus; the cells are also numerous in intervening white matter, including the external capsule, extreme capsule and frontal white matter. They are found in the rodent, the macaque and the human ( Dubach-1994 ).