Pedunculopontine nucleus

The pedunculopontine nucleus (PPN) (or pedunculopontine tegmental nucleus, PPTN) is located in the brainstem, caudal to the substantia nigra and adjacent to the superior cerebellar peduncle. It is composed by a wide variety of neurochemical cell types, including cholinergic, glutamatergic and GABAergic cells. In the classical sense, the PPN is considered to be one of the main components of the reticular activating system.

Projections
One of the distinctive characteristics of the PPN is the wide range of its projections. PPN neurons send their axons to several targets in the thalamus, basal ganglia, cerebral cortex, basal forebrain, and lower brainstem. A particularly interesting area for the study of PPN projections is the basal ganglia, due to the high level of interconnectivity between them. The complex receives direct afferences from the medial pallidum.

Functions
The PPN is involved in many functions, including arousal, attention, learning, reward, and locomotion. It is also implicated in the generation and maintenance of REM sleep.