The Human Brain : From Neurone to Nervous System

The Main Pathways to and from the Cerebellum

  1. The three main lobes of the cerebellum receive afferent inputs from the vestibular apparatus, the proprioceptive system and the cerebral cortex.

  2. Cortico-pontine (cortico-bulbar) fibres run in parallel with the corticospinal tract and carry copies of motor commands to the pontine nuclei, which relay them to the cerebellar cortex.

  3. These axons also transmit information from association areas of cortex, e.g. the area of parietal cortex concerned with spatial awareness, or the limbic system, concerned with motor responses of an emotional nature, such as flight, fright or fight.

  4. These pathways indicate that cerebellum receives information from all sensory systems - visual auditory, somatosensory - so all signals that can communicate information about movement and the position of the body converge on the cerebellum.

  5. The cerebellum also receives inputs from the proprioceptive system that informs the cerebellum about the precise movements that result from the motor commands. This is carried by the spino-cerebellar systems.

  6. The medullary olive are also involved in signalling information from the proprioceptive and other systems, but this pathway has chracteristic features (see 'climbing fibres') that distinguish it from the ponto-cerebellar pathway (see 'mossy fibres').

  7. The cerebellum acts as a comparator and feeds error signals forward to the cortex. This is a function of the cerebellar cortex, and the error signals are carried by the Purkinje cells to the deep cerebellar nuclei, that communicate with the Red Nucleus of the midbrain, the thalamus, and the cerebral cortex.

  8. The main output pathway sends error signals to the cortex and allows adjustments to be made and ensure that the desired outcome is achieved.

  9. Disorders of the cerebellum lead to involuntary imprecise movements that become worse while performing willed movements.

  10. The cerebellum is also involved in motor memory and learning motor skills.

  11. Key Words: Cerebellum, error detector, comparator, feedback. Motor Learning