cerebellum

Examples of cerebellum in the following topics:

• Parts of the Cerebellum

  • The cerebellum, which looks like a separate structure attached to the bottom of the brain, plays an important role in motor control.
  • The cerebellum is separated from the overlying cerebrum by a layer of leathery dura mater.
  • Like the cerebral cortex, the cerebellum is divided into two hemispheres.
  • Schematic representation of the major anatomical subdivisions of the cerebellum.
  • Superior view of an "unrolled" cerebellum, placing the vermis in one plane.

• Somatic Sensory Pathways to the Cerebellum

  • The ventral and dorsal spinocerebellar tracts convey proprioceptive information from the body to the cerebellum.
  • The ventral spinocerebellar tract conveys proprioceptive information from the body to the cerebellum.
  • The ventral spinocerebellar tract then enters the cerebellum via the superior cerebellar peduncle (connects the cerebellum to the midbrain).
  • These axons ascend to the pons where they join the superior cerebellar peduncle to enter the cerebellum.
  • The anterior and posterior spinocerebellar tracts are the major somatosensory pathways communicating with the cerebellum.

• Modulation of Movement by the Cerebellum

  • The cerebellum is important for motor control—specifically coordination, precision, and timing—as well as some forms of motor learning.
  • The cerebellum is a region of the brain that plays an important role in motor control.
  • The cerebellum does not initiate movement, but it contributes to coordination, precision, and accurate timing.
  • The strongest clues to the function of the cerebellum have come from examining the consequences of damage to it.
  • This means that the cerebellum, in contrast to the cerebral cortex, cannot generate self-sustaining patterns of neural activity.

• Functions of the Cerebellum

  • Cerebellar function was once believed to be motor-specific, but newer findings suggest the cerebellum is also involved in higher-level brain processing.
  • Examining the consequences of damage to the the cerebellum provides the strongest clues to its function.
  • Additionally, correlation studies have shown interactions between the cerebellum and non-motor areas of the cerebral cortex.
  • This was expressed in one of the first books on cerebellar electrophysiology, The Cerebellum as a Neuronal Machine by John C.
  • Damage to the upper part of the cerebellum - gait impairments and other problems with leg coordination (ie, ataxia). 

• Functions of the Cerebellum in Integrating Movements

  • The cerebellum differs from most other parts of the brain in that the signal processing is almost entirely feedforward—that is, signals move unidirectionally through the system from input to output, with very little recurrent internal transmission.
  • This feedforward mode of operation means that the cerebellum, in contrast to the cerebral cortex, cannot generate self-sustaining patterns of neural activity.
  • As Eccles, Ito, and Szentágothai wrote, "This elimination in the design of all possibility of reverberatory chains of neuronal excitation is undoubtedly a great advantage in the performance of the cerebellum as a computer, because what the rest of the nervous system requires from the cerebellum is presumably not some output expressing the operation of complex reverberatory circuits in the cerebellum, but rather a quick and clear response to the input of any particular set of information."
  • In the human cerebellum, information from 200 million mossy fiber inputs is expanded to 40 billion granule cells, whose parallel fiber outputs then converge onto 15 million Purkinje cells.
  • This schematic illustration of the structure of zones and microzones in the cerebellum shows three levels of magnification.

• Pons

  • The pons is a relay station between the forebrain and cerebellum that passes sensory information from the periphery to the thalamus.
  • It is above the medulla, below the midbrain, and anterior to the cerebellum.
  • The white matter of the pons includes tracts that conduct signals from the cerebrum down to the cerebellum and medulla, and tracts that carry the sensory signals up into the thalamus.
  • These connect the cerebellum to the pons and midbrain.
  • During embryonic development, the metencephalon develops from the rhombencephalon and gives rise to two structures: the pons and the cerebellum.

• Ataxia

  • Ataxia is a nonspecific clinical manifestation implying dysfunction of the parts of the nervous system that coordinate movement, such as the cerebellum.
  • Cerebellar ataxia is ataxia that is due to dysfunction of the cerebellum .
  • The cerebellum is responsible for integrating significant amounts of neural information that is used to coordinate ongoing movements and to participate in motor planning.
  • Focal lesions - Any type of focal lesion of the central nervous system (such as stroke, brain tumur, multiple sclerosis) will cause the type of ataxia corresponding to the site of the lesion: cerebellar if in the cerebellum, sensory if in the dorsal spinal cord (and rarely in the thalamus or parietal lobe), vestibular if in the vestibular system (including the vestibular areas of the cerebral cortex).
  • Ataxia may depend on hereditary disorders consisting of degeneration of the cerebellum and/or of the spine; most cases feature both to some extent, and therefore present with overlapping cerebellar and sensory ataxia, even though one is often more evident than the other.

• General Organization of the Somatosensory System

  • This neuron's ascending axons will cross, or decussate, to the opposite side of the spinal cord or brainstem and travel up the spinal cord to the brain, where most will terminate in either the thalamus or the cerebellum.
  • Regarding posture, the tertiary neuron is located in the cerebellum.
  • Somatosensory information involved with proprioception and posture is processed in the cerebellum.

• Grey and White Matter

  • Both the cerebrum and cerebellum have an outer additional layer of gray matter.
  • Grey matter is distributed at the surface of the cerebral hemispheres and cerebellum, as well as in the depths of the cerebrum, cerebellar, brainstem, and spinal grey matter.

• The Brain

  • At the rear of the brain beneath the cerebrum and behind the brainstem is the cerebellum.
  • These same structures are present in other mammals, although the cerebellum is not so large relative to the rest of the brain in non-human mammals.
  • Distinguish between the cerebellum, cerebral cortex, and brain stem regions of the brain