Pedunculopontine tegmental nucleus. Anatomy, functional considerations and physiopathological implications

Pedunculopontine tegmental nucleus is formed by an ensemble of cholinergic and non-cholinergic neurons located in the caudal pontomesencephalic tegmentum, surrounding the superior cerebellar peduncle. It is an integral part of the reticulate formation of the brain stem, with extensive anatomical connections and highly varied functions. By means of ascendant projections that it sends to the thalamus, it intervenes in the waking-sleep cycle. Besides, it constitutes the most caudal nucleus of the neuroaxis, receiving connections from the basal ganglia, for which reason it has attracted the interest of those researchers concerned with the study of these structures. Thanks to its reciprocal connections with the basal ganglia, as well as to its descending projections to different structures of the pons, medulla and spinal cord; it has been related to the control of locomotion. Recently, it has also been considered as a possible centre for the integration of the motor information provided by the dorsal striatum with the motivational or limbic information proceeding from the ventral striatum, to permit its direct access to bulbar or spinal motor centres. In this work we will review its anatomical and functional characteristics, as well as its implication in some diseases of the nervous system such as narcolepsy, progressive supranuclear paralysis, schizophrenia and Parkinson's disease.