The pedunculopontine nucleus (PPN) or pedunculopontine tegmental nucleus (PPT or PPTg) is a collection of neurons located in the upper pons in the brainstem. It lies caudal to the

substantia nigra The substantia nigra (SN) is a basal ganglia structure located in the midbrain that plays an important role in reward and movement. ''Substantia nigra'' is Latin for "black substance", reflecting the fact that parts of the substantia nigra ap ...

and adjacent to the superior cerebellar peduncle. It has two divisions of subnuclei; the pars compacta containing mainly cholinergic neurons, and the pars dissipata containing mainly glutamatergic 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 formati ...

. It was first described in 1909 by

Louis Jacobsohn-Lask Louis Jacobsohn-Lask (born Louis Jacobsohn; 2 March 1863, in Bromberg – 17 May 1941, in Sevastopol) was a German neurologist and neuroanatomist. He studied medicine at the University of Berlin under Heinrich Wilhelm Waldeyer, Rudolf Virchow, ...

, a German neuroanatomist.

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 ext ...

such as the

subthalamic nucleus The subthalamic nucleus (STN) is a small lens-shaped nucleus in the brain where it is, from a functional point of view, part of the basal ganglia system. In terms of anatomy, it is the major part of the subthalamus. As suggested by its name, the ...

substantia nigra pars compacta The pars compacta (SNpc) is a portion of the ''substantia nigra'', located in the midbrain. It is formed by dopaminergic neurons and located medial to the pars reticulata. Parkinson's disease is characterized by the death of dopaminergic neurons ...

, and globus pallidus internus. 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 direct ...

, cerebellum, basal forebrain, 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% consisting o ...

, the supplementary motor area 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 ...

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

Functions

The pedunculopontine nucleus is involved in many functions, including arousal, attention, learning, reward, and voluntary limb movements and locomotion. 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 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 beco ...

References

External links

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