Cholinergic projection sites of the nucleus of tractus diagonalis.

The cholinergic projection sites of the basal portion of the nucleus of the tractus diagonalis (td) were studied following bilateral stereotaxic lesions. Choline acetyltransferase (ChAT) activity was measured in various cortices, hippocampus and amygdala. Significant decreases in ChAT activity were observed in the anterior and posterior cingulate cortex, the frontal cortex, occipital cortex, hippocampus and dentate gyrus. It is concluded that (1) the hippocampus is innervated by the basal portion of the td and not from the medial septal nucleus, (2) the td contains cholinergic cell bodies which project widely to the cortex and hippocampus. It is suggested that these cholinergic projections have important influences on emotional behavior via connections with the cortex and limbic system.