Figure 9.

Schematic summarizing major findings from the present study. (A) Cholinergic inputs to each SOC originate from three areas. One area is the pontomesencephalic tegmentum (PMT), comprising the pedunculopontine tegmental nucleus (PPT) and the laterodorsal tegmental nucleus (LDT). Each SOC receives cholinergic input from both ipsilateral and contralateral PPT and LDT. The second source of cholinergic input to the SOC is from SOC cells themselves. Each SOC receives cholinergic input from neurons within the same SOC as well as from neurons in the contralateral SOC. A third, smaller source is the lateral paragigantocellular nucleus (LPGi). Both ipsilateral and contralateral LPGi project to the SOC. (B) A second finding is that individual cholinergic neurons can send branching axons to innervate the SOC bilaterally. Such collateral projections can arise from cholinergic cells in each of the regions that supply cholinergic innervation to the SOC (for simplicity, projections are shown only from one side).