Pedunculopontine nucleus
Encyclopedia
The pedunculopontine nucleus (PPN) (or pedunculopontine tegmental nucleus, PPTN or PPTg) is located in the brainstem, caudal to the substantia nigra
and adjacent to the superior cerebellar peduncle. It has two divisions, one containing cholinergic
neurons, the pars compacta, and one containing mostly glutamatergic neurons, the pars dissipata. The PPN is one of the main components of the reticular activating system
.
such as the subthalamic nucleus
, substantia nigra pars compacta, and globus pallidus internus. It also send them to targets in the thalamus
, cerebellum
, basal forebrain
, and lower brainstem, and in the cerebral cortex
, the supplementary motor area
and somatosensory and motor cortices
.
It receives inputs from the areas of the basal gangla to which it projects with the exception of the substantia nigra pars compacta to which it projects but does not receive, while it receives but does not project to the substantia nigra pars reticulata.
, 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 cerebral cortex
. It is also implicated in the generation and maintenance of REM sleep.
of the PPN might be used to improve the gait and postural difficulties found in Parkinson disease.
Substantia nigra
The substantia nigra is a brain structure located in the mesencephalon that plays an important role in reward, addiction, and movement. Substantia nigra is Latin for "black substance", as parts of the substantia nigra appear darker than neighboring areas due to high levels of melanin in...
and adjacent to the superior cerebellar peduncle. It has two divisions, one containing cholinergic
Cholinergic
The word choline generally refers to the various quaternary ammonium salts containing the N,N,N-trimethylethanolammonium cation. Found in most animal tissues, choline is a primary component of the neurotransmitter acetylcholine and functions with inositol as a basic constituent of lecithin...
neurons, the pars compacta, and one containing mostly glutamatergic neurons, the pars dissipata. The PPN is one of the main components of the reticular activating system
Reticular activating system
The reticular activating system is an area of the brain responsible for regulating arousal and sleep-wake transitions.- History and Etymology :...
.
Projections
PPN neurons project axons to a wide range of areas in the brain, particularly parts of the basal gangliaBasal ganglia
The basal ganglia are a group of nuclei of varied origin in the brains of vertebrates that act as a cohesive functional unit. They are situated at the base of the forebrain and are strongly connected with the cerebral cortex, thalamus and other brain areas...
such as the subthalamic nucleus
Subthalamic nucleus
The subthalamic nucleus is a small lens-shaped nucleus in the brain where it is, from a functional point of view, part of the basal ganglia system. Anatomically, it is the major part of subthalamus. As suggested by its name, the subthalamic nucleus is located ventral to the thalamus. It is also...
, substantia nigra pars compacta, and globus pallidus internus. It also send them to targets in the thalamus
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
, cerebellum
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
, basal forebrain
Basal forebrain
The basal forebrain is a collection of structures located ventrally to the striatum. It is considered to be the major cholinergic output of the central nervous system . It includes a group of structures that lie near the bottom of the front of the brain, including the nucleus basalis, diagonal band...
, and lower brainstem, and in the cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
, the supplementary motor area
Supplementary motor area
The supplementary motor area is a part of the sensorimotor cerebral cortex . It was included, on purely cytoarchitectonic arguments, in area 6 of Brodmann and the Vogts...
and somatosensory and motor cortices
Motor cortex
Motor cortex is a term that describes regions of the cerebral cortex involved in the planning, control, and execution of voluntary motor functions.-Anatomy of the motor cortex :The motor cortex can be divided into four main parts:...
.
It receives inputs from the areas of the basal gangla to which it projects with the exception of the substantia nigra pars compacta to which it projects but does not receive, while it receives but does not project to the substantia nigra pars reticulata.
Functions
The PPN is involved in many functions, including arousalArousal
Arousal is a physiological and psychological state of being awake or reactive to stimuli. It involves the activation of the reticular activating system in the brain stem, the autonomic nervous system and the endocrine system, leading to increased heart rate and blood pressure and a condition of...
, attention
Attention
Attention is the cognitive process of paying attention to one aspect of the environment while ignoring others. Attention is one of the most intensely studied topics within psychology and cognitive neuroscience....
, learning
Learning
Learning is acquiring new or modifying existing knowledge, behaviors, skills, values, or preferences and may involve synthesizing different types of information. The ability to learn is possessed by humans, animals and some machines. Progress over time tends to follow learning curves.Human learning...
, reward
Reward system
In neuroscience, the reward system is a collection of brain structures which attempts to regulate and control behavior by inducing pleasurable effects...
, and voluntary limb movements and locomotion
Animal locomotion
Animal locomotion, which is the act of self-propulsion by an animal, has many manifestations, including running, swimming, jumping and flying. Animals move for a variety of reasons, such as to find food, a mate, or a suitable microhabitat, and to escape predators...
. While once thought important to the initiation of movement, recent research suggests a role in providing sensory feedback to the cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
. It is also implicated in the generation and maintenance of REM sleep.
Parkinson disease
Research is been done on whether deep brain stimulationDeep brain stimulation
Deep brain stimulation is a surgical treatment involving the implantation of a medical device called a brain pacemaker, which sends electrical impulses to specific parts of the brain...
of the PPN might be used to improve the gait and postural difficulties found in Parkinson disease.