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Scientific Dream Interpretation and Analysis |
SP r = √SSxSSy |
|
Scientific Dream Interpretation and Analysis |
SP r = √SSxSSy |
Functions:
Observed Problems:
The cerebellum is involved in the coordination of voluntary motor movement, balance and equilibrium and muscle tone. It is located just above the brain stem and toward the back of the brain. It is relatively well protected from trauma compared to the frontal and temporal lobes and brain stem.
Cerebellar injury results in movements that are slow and uncoordinated. Individuals with cerebellar lesions tend to sway and stagger when walking.
Damage to the cerebellum can lead to:
1) loss of coordination of motor movement (asynergia),
2) the inability to judge distance and when to stop (dysmetria),
3) the inability to perform rapid alternating movements (adiadochokinesia),
4) movement tremors (intention tremor),
5) staggering, wide based walking (ataxic gait),
6) tendency toward falling,
7) weak muscles (hypotonia),
8) slurred speech (ataxic dysarthria), and
9) abnormal eye movements (nystagmus).
Centre for Neuro Skills
For you to perform even so simple a gesture as touching the tip of your nose, it is not enough for your brain to simply command your hand and arm muscles to contract. To make the various segments of your hand and arm deploy smoothly, you need an internal "clock" that can precisely regulate the sequence and duration of the elementary movements of each of these segments. That clock is the cerebellum.
As so often in neurobiology, to understand exactly what the cerebellum does, we can observe patients in whom part of this structure has been destroyed (by a tumour or a stroke, for example). When these patients try to grasp an object, their hands start moving late, advance unsteadily, and either stop before reaching their target, or, often, accelerate past it. In terms of posture, people with damaged cerebellums characteristically display balance problems similar to those found in people who are drunk. In fact, the clumsiness that accompanies excess consumption of alcohol is directly related to its depressive effects on the activity of the cerebellum.
In a healthy person, the cerebellum first receives information about the intended movement from the sensory and motor cortexes. Then it sends information back to the motor cortex about the required direction, force, and duration of this movement Thus this loop involving the cerebellum operates in addition to the loop involving the basal ganglia to regulate the details of motor control.
Another metaphor summarizes the role of your cerebellum rather well: it acts like an air traffic controller who gathers an unbelievable amount of information at every moment, including (to return to our original example) the position of your hand, your arm, and your nose, the speed of their movements, and the effects of potential obstacles in their path, so that your finger can achieve a "soft landing" on the tip of your nose.
The cerebellum appears to play several roles. It stores learned sequences of movements, it participates in fine tuning and co-ordination of movements produced elsewhere in the brain, and it integrates all of these things to produce movements so fluid and harmonious that we are not even aware of them.
To do all this, the cerebellum maintains close communications with the cortex. The motor, somatosensory, and posterior parietal areas of the cortex project massive numbers of axons to the nuclei of the pons, located in the brainstem. The neurons of the pons then project their axons into the cerebellum. This corticopontocerebellar tract forms an extremely dense nerve bundle containing about 20 million axons, just about 20 times more than the pyramidal bundle!
The two hemispheres of the cerebellum then sends signals back to the motor cortex via interconnections in the ventrolateral nucleus (VLc) of the thalamus. The cerebellar hemispheres thus influence the muscles of the arms and legs via the cortex and the lateral motor system.
The two hemispheres of the cerebellum are not divided neatly in two like the two hemispheres of the cerebrum. The medial portion constitutes what is known as the cerebellar vermis. This vermis does not display any lateralization. It projects axons to the brainstem which, via the ventromedial system, help to maintain posture.
More recently, the cerebellum has also been discovered to play a role in sensory information processing as well as in cognitive functioning.
Henri Laborit (1914-1995)