Decerebration is the elimination of cerebral brain function in an animal by removing the

cerebrum The cerebrum, telencephalon or endbrain is the largest part of the brain containing the cerebral cortex (of the two cerebral hemispheres), as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. In ...

, cutting across the

brain stem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is co ...

, or severing certain arteries in the brain stem. As a result, the animal loses certain reflexes that are integrated in different parts of the brain. Furthermore, the reflexes which are functional will be hyperreactive (and therefore very accentuated) due to the removal of inhibiting higher- brain centers (e.g. the facilitatory area of the

reticular formation 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 formation ...

will not receive regulating input from

cerebellum The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cerebel ...

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 extern ...

and the

cortex Cortex or cortical may refer to: Biology * Cortex (anatomy), the outermost layer of an organ ** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain'' *** Motor cortex, the regions of the cerebral cortex i ...

Methods

Decerebration describes the ligation along the neural axis in distinct parts of the brain in experimental animals. Generally: * lower decerebration (the cut is made above the upper border of the pons) * middle decerebration (cut is made through the red nucleus) * upper decerebration (cut is made so the cortical area is removed) Lower decerebration results in a "bulbospinal" animal: reflexes which are integrated within the spinal cord and medulla oblongata are functional, reflexes integrated in midbrain and cortex are absent. With difference to decortication there is pontine transection, thus sparing of the VestibuloSpinal (VS) and ReticuloSpinal (RES). The involved tracts are the corticospinal and rubrospinal tract. decerebration in humans tends to have a worse prognosis than decortication.Harrison's Principles of Internal Medicine, 20e, J. Larry Jameson, Anthony S. Fauci,

Effects

The most obvious accentuation is seen in the tonic labyrinthine reflexes, the otolithic organs mediate input about the gravitational force exerted on the body and the labyrinthine reflex acts on the extensor muscles in order to resist this gravitational force. In an animal where the cortical areas or the midbrain have been "cut off" from the neural axis, this reflex is hyperactive and the animal will maximally extend all four limbs. This phenomenon is known as decerebrate rigidity. In humans, true decerebrate rigidity is rare since the damage to the brain centers it might be caused by usually are lethal. However, decorticate rigidity can be caused by bleeding in the

internal capsule The internal capsule is a white matter structure situated in the inferomedial part of each cerebral hemisphere of the brain. It carries information past the basal ganglia, separating the caudate nucleus and the thalamus from the putamen and the ...

which causes damage to upper motor neurons. The symptoms of decorticate rigidity are flexion in the upper limbs and extension in the lower limbs.

References

{{Reflist * Lange "Review of Medical Physiology", 22nd edition, pp. 202, ff * Guyton and Hall "Textbook of Medical Physiology" 12th Edition. Neurosurgery