The pedunculopontine nucleus (PPN) or pedunculopontine tegmental nucleus (PPT or PPTg) is a collection of neurons located in the upper

pons The pons (from Latin , "bridge") is part of the brainstem that in humans and other bipeds lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum. The pons is also called the pons Varolii ("bridge of Va ...

in the brainstem. It lies caudal to the substantia nigra and adjacent to the superior cerebellar peduncle. It has two divisions of subnuclei; the pars compacta containing mainly

cholinergic Cholinergic agents are compounds which mimic the action of acetylcholine and/or butyrylcholine. In general, the word " choline" describes the various quaternary ammonium salts containing the ''N'',''N'',''N''-trimethylethanolammonium cati ...

neurons, and the pars dissipata containing mainly

glutamatergic Glutamatergic means "related to glutamate". A glutamatergic agent (or drug) is a chemical that directly modulates the excitatory amino acid (glutamate/aspartate) system in the body or brain. Examples include excitatory amino acid receptor agonis ...

neurons and some non-cholinergic neurons. The pedunculopontine nucleus is one of the main components of the

reticular activating system The reticular formation is a set of interconnected nuclei that are located throughout the brainstem. It is not anatomically well defined, because it includes neurons located in different parts of the brain. The neurons of the reticular formatio ...

. It was first described in 1909 by Louis Jacobsohn-Lask, a German

neuroanatomist Neuroanatomy is the study of the structure and organization of the nervous system. In contrast to animals with radial symmetry, whose nervous system consists of a distributed network of cells, animals with bilateral symmetry have segregated, defi ...

Projections

Pedunculopontine nucleus neurons project axons to a wide range of areas in the brain, particularly parts of the

basal ganglia The basal ganglia (BG), or basal nuclei, are a group of subcortical nuclei, of varied origin, in the brains of vertebrates. In humans, and some primates, there are some differences, mainly in the division of the globus pallidus into an exter ...

such as the subthalamic nucleus, substantia nigra pars compacta, and

globus pallidus internus The internal globus pallidus (GPi or medial globus pallidus; in rodents its homologue is known as the entopeduncular nucleus) and the external globus pallidus (GPe) make up the globus pallidus. The GPi is one of the output nuclei of the basal gang ...

. It also sends them to targets in the

thalamus The thalamus (from Greek θάλαμος, "chamber") is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the thalamus to the cerebral cortex in all directions, ...

, cerebellum,

basal forebrain Part of the human brain, the basal forebrain structures are located in the forebrain to the front of and below the striatum. They include the ventral basal ganglia (including nucleus accumbens and ventral pallidum), nucleus basalis, diagonal b ...

, and lower brainstem, and in the

cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consistin ...

, the

supplementary motor area The supplementary motor area (SMA) is a part of the motor cortex of primates that contributes to the control of movement. It is located on the midline surface of the hemisphere just in front of (anterior to) the primary motor cortex leg representa ...

and

somatosensory In physiology, the somatosensory system is the network of neural structures in the brain and body that produce the perception of touch (haptic perception), as well as temperature (thermoception), body position (proprioception), and pain. It i ...

and motor cortices. It receives inputs from many areas of the brain. It both projects to and receives input from most parts of the basal ganglia, with the exception of the substantia nigra pars compacta (which it projects to but does not receive input from), and the

substantia nigra pars reticulata The pars reticulata (SNpr) is a portion of the substantia nigra and is located lateral to the pars compacta. Most of the neurons that project out of the pars reticulata are inhibitory GABAergic neurons (i.e., these neurons release GABA, which is ...

(which it receives input from but does not project to).

Functions

The pedunculopontine nucleus is involved in many functions, including arousal, attention, learning,

reward Reward may refer to: Places * Reward (Shelltown, Maryland), a historic home in Shelltown Maryland * Reward, California (disambiguation) * Reward-Tilden's Farm, a historic home in Chestertown Maryland Arts, entertainment, and media * "Rewa ...

, and voluntary limb movements and

locomotion Locomotion means the act or ability of something to transport or move itself from place to place. Locomotion may refer to: Motion * Motion (physics) * Robot locomotion, of man-made devices By environment * Aquatic locomotion * Flight * Locomo ...

. While once thought important to the initiation of movement, recent research suggests a role in providing sensory feedback to the

. It is also implicated in the generation and maintenance of REM sleep. Recent research has discovered that the pedunculopontine nucleus is involved in the planning of movement, and that different networks of neurons in the pedunculopontine nucleus are switched on during real and imagined movement.

Parkinson's disease

Research is being done on whether

deep brain stimulation Deep brain stimulation (DBS) is a neurosurgical procedure involving the placement of a medical device called a neurostimulator, which sends electrical impulses, through implanted electrodes, to specific targets in the brain (the brain nucleus ...

of the pedunculopontine nucleus might be used to improve the gait and postural difficulties found in

Parkinson's disease Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms becom ...

References

External links

* {{Authority control Pons