The pontine tegmentum is a part of the pons

Pons

The pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it...

 of the brain

Brain

The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

 involved in the initiation of REM sleep. It includes the pedunculopontine nucleus

Pedunculopontine nucleus

The pedunculopontine nucleus 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...

 and the laterodorsal tegmental nucleus

Laterodorsal tegmental nucleus

The laterodorsal tegmental nucleus is a nucleus situated in the brainstem, spanning the midbrain tegmentum and the pontine tegmentum...

, among others, and is located near the raphe nucleus and the locus ceruleus

Locus ceruleus

The locus coeruleus , is a nucleus in the brainstem involved with physiological responses to stress and panic. It was discovered in the 18th century by Félix Vicq-d'Azyr....

.

The trapezoid body

Trapezoid body

The trapezoid body is part of the acoustic pathway. It is a bundle of fibers and cells in the pontine tegmentum. It consists of fibers arising from the ventral cochlear nucleus. A collection of nerve cells inside forms a trapezoid nucleus. The superior olivary nucleus is situated on the dorsal...

 is part of the pontine tegmentum.

Function

In animal studies, lesions of the pontine tegmentum greatly reduce or even eliminate REM sleep. Injection of a 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...

 agonist

Agonist

An agonist is a chemical that binds to a receptor of a cell and triggers a response by that cell. Agonists often mimic the action of a naturally occurring substance...

 (e.g. carbachol

Carbachol

Carbachol , also known as carbamylcholine, is a drug that binds and activates the acetylcholine receptor. Thus it is classified as a cholinergic agonist. It is primarily used for various ophthalmic purposes, such as for treating glaucoma, or for use during ophthalmic surgery...

), into the pontine tegmentum produces a state of REM sleep in cats.

PET

Positron emission tomography

Positron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...

 studies seem to indicate that there is a correlation between blood flow in the pontine tegmentum, REM sleep, and dream

Dream

Dreams are successions of images, ideas, emotions, and sensations that occur involuntarily in the mind during certain stages of sleep. The content and purpose of dreams are not definitively understood, though they have been a topic of scientific speculation, philosophical intrigue and religious...

ing .

Pontine waves (P-waves, or ponto-geniculate-occipital waves) are brain wave

Brain wave

* Brain Wave, a science fiction novel by Poul Anderson* a neural oscillation* a layman term for the electric fields measured by Electroencephalography...

s generated in the pontine tegmentum. They can be observed in mammals, precede the onset of REM sleep, and continue throughout its course. After periods of memory training, P-wave density increases during subsequent sleep periods in rats. This may be an indication of a link between sleep

Sleep

Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles. It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than...

 and 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...

.

External links

• http://pathcuric1.swmed.edu/PathDemo/cns1/cns1140.htm
• http://isc.temple.edu/neuroanatomy/lab/atlas/panfc/
• http://www.sci.uidaho.edu/med532/pons.htm