Figure 1.

Diagrams of stimulation and recording sites. A, A diagram illustrating the circuits present in the sagittal brainstem slice used in this study. Excitatory burst neurons (EBN) are located in the PPRF and project monosynaptically on abducens motoneurons (ABD Mn) and on PH neurons. Stimuli applied to the PPRF also activate descending cholinergic axons from pontomesencephalic areas. See Results for details and references. B, A photomicrograph of a PH neuron stained after intracellular recording. C, A drawing showing the reconstruction of the neuron illustrated in B. This neuron type corresponds to a principal cell (McCrea and Baker, 1985a). The two small arrows indicate initial trajectory of the axon. Scale bars: B, C, 50 μm. NVM, Medial vestibular nucleus.