Cholinergic cells in the laterodorsal tegmental nucleus (LDTg) and the posterior component of the pedunculopontine tegmental nucleus (PPTg) project to the VTA [19,20] where they modulate the activity of DA neurons and reward processing [21–26]. The anterior portion of the PPTg sends cholinergic projections to the substantia nigra [20]. Together with glutamate fibers, the ACh connection from the LDTg to the VTA forms a loop between the midbrain DA cells, the pons and the PFC. The ACh input onto DA cell bodies (in the VTA) is therefore a critical link for gating information flow through the mesocorticolimbic and mesostriatal systems.
