Cerebellum

The cerebellum sits atop the brainstem straddling the medulla -pontine junction and anchored to the pons through three cerebellar peduncles. I accounts for approximately 25% of the brain volume. It evolved out of the vestibular system over 450 million years ago before the first vertebrates as a rudimentary appendage of the brainstem. As more visual, proprioceptive, somesthetic, and complex auditory stimuli was received and demanded additional processing, it gradually increased in size. As species became bipedal increasingly complex demands were placed on the anterior cerebellum in order to coordinate gait and upper as well as lower limb movements. This gave rise to the evolution of the neocerebellum (including the dentate gyrus and the cerebellar hemispheres).

While most commonly associated with motor movements and smoothness of those movements, the cerebellum has been implicated in cognitive, emotional, sensory, motor and speech processing. It communicates with almost all regions of the neuroaxis, with the exception of the striatum. Neuroplasticity has been demonstrated, as have learning and memory functions. It has been postulated that this structure may serve as an integrative interface for cognition, emotion, motor functioning and memory. It has also shown significant influences on "autonomic functions, conditioned learning, visual spatial skills, linguistic processing, mental imagery, cognitive flexibility, sensory discrimination, classical conditioning, verbal memory, attention, and emotional states have been noted.”

**Structure** The structure of the cerebellum can be subdivided in several different ways. Functionally it may be subdivided into three lobes: the anterior, posterior and flocculonodular lobes--each of which can be further subdivided into 10 lobules. It may also be divided according to three longitudinal zones – the lateral zone which receives information from the motor and somesthetic cortex via the pons, the medial zone which receives vestibular, visual, and auditory input, and the intermediate zone which receives input from the spinal cord and the motor cortex. Divisions may also be made phylogenetically and functionally. The archicerebellum (which includes the flocculonodular lobe), the paleocerebellum (or anterior lobe) which influences autonomic and emotional activity, and the most recently eveolved neocerebellum which includes the posterior lobe and detate gyrus and influences motor, somatic, and cognitive activities such as neocortical information processing.

Fulton and Dow subdivided the cerebellum in accordance with the symptoms produced when injured: Vestibulocerebellum in the vicinity of the flocculonodular lobe producing symptoms of the vestibular system (e.g. head tilt, circling gait, nystagmus) Spinocerebellum: in the vicinity of the anterior lobe producing symptoms of abnormal spinal control over walking, i.e. impaired gait without impaired reaching Cerebrocebellum: in the vicinity of neocerebellum producing symptoms of impaired reaching and clumsiness suggesting impairments in voluntary motor control

As noted above, rich connections exist with almost all regions of the forebrain and telencephalon, with the exception of the striatum. These are primarily through a number of feedfoward and feedback loops involving the corticopontine and pontocerebellar thalamocrotical pathways. These include afferents that convey tactile, auditory and visual impulses, including those which essentially reconstruct and maintain somesthetic images of the body in different lobules. Most of these signals are carried via mossy fibers, which are generally excitatory and utilize glutamate as a neurotransmitter, and synapse with Golgi cells whose axons (parallel fibers) excite Purkinje cells. Purkinje cells are all innervated by climbing fibers from the brainstem which also use glutamate as a neurotransmitter. These impulses appear to counter one another and can give rise to long term potentiation, or long term depression which can impact learning capacity. In addition, Purkinje cells also receive norepinephrine the locus ceruleus and serotonin from the raphe nucleus.

**Motor Functions** In the regulation of motor control the cerebellum exerts a tonic and stabilizing influence that aids to coordinate, smooth, fine tune, and maintain timing of motor movements. Neuron firing rates vary rate during movement, increasing and then decreasing, suggesting that they are modulating these movements. Activity in some deep nuclei, such as the dentate of the neocerebellum, become active prior to movement and prior to activation of the frontal motor cortex and can fire by just thinking about making a movement. The dentate gyrus controls voluntary actions and direction of movement which involves multiple joints and the upper limbs. Dystaxia, predominantly in the legs can result from cerebellar dysfunction. This can often appear to others as if the individual is heavily intoxicated. Indeed, in additional to trauma, alcholism and nutritional deficiencies can result in damage to the cerebellum and cause such dystaxia. Motor related disturbances including tremor, nystagmus, gait disturbances, incoordination, and postural instability can be common following an injury.

When an individual acquires new skilled movements, such as when playing a guitar or a piano, it requires conscious control of motor functioning and strong neocortical activity while the cerebellum plays a minimal role. As one practices, less conscious attention, and one's "motor memory" becomes more of a component, the cerebellum receives neocortical signals via the pons and begins to increase its participation and slowly learn the necessary movements. Over time the cerebellum may begin to acquire primary control over the task, operating subconsciously, with little or no help from the cerebrum and the conscious mind which are free to do and think about other things. Lesions can abolish the acquisition and retention of conditioned responses. In this, compound movements are more severely effected that simple movements. It has been argued that the cerebellum appears to learn automatic and habits, not acting to form memories per se. Rather, that these are simply step-by-step motor sequences being carried out. This is further substantiated by studies showing stimulation of the fastigial nucleus, vermis, and superior cerebral peduncle may elicit motor operations such as biting, chewing and swallowing movements without eliciting any actual hunger or seeking food. The neocerebellum in particular maintains rich interconnections with forebrain motor areas, in particular, the motor thalamus, which relays these impulses to motor areas 4 and 6 in the frontal lobe and the somatosensory areas of the parietal lobe.

The lateral cerebellum appears to be involved in regulating the timing of sequential movements with injury causing difficulty with timing and rhythm. Abormalities in the rate, range, and force of movement are demonstrated as deficiencies in finger to nose testing. ex: when asked to touch the physicians finger and then their own nose, the patient's arm and hand may sway and miss on both count. Irregularities in acceleration and deceleration of movement are also common, possibly due to programming errors. Limb extension may be arrested prematurely, such that the target/objective is attained by a series of jerky stop and go movements. When asked to touch their nose, they may do it in two stages: By lifting the arm to nose level, then by bringing the fingers to the nose. Movements may become ballistic, being too quick, and failing to slow down or the limb overshoots the mark and the error is corrected only by a series of secondary movements. When asked to make movements as fast as possible, however, they will often do so slower than normal.

//Differential Diagnosis in sensory abnormalities (dystaxia):// If the individual performs more poorly due to the loss of visual input (closing the eyes) rather than the symptoms is due to loss of visual guidance (removing visual cues) and visual and proprioceptive input rather than cerebellar damage. The cerebellum is able to equilibriate only if it has proper proprioceptive information.

In post-injury symptoms lateralized cerebellar signs limited to one half of the body are due to lesions (infarct, neoplasm or abscess) affecting only one of the cerebellar hemispheres. Bilateral cerebellar signs are likely a result of toxic-metabolic, demyelating, or other degenerative diseases.

<span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">What is referred to as "cerebellar gait" typically demonstrates as a wide based gait, steps being characteristically unsteady, irregular, uncertain, and of variable length. If mild, these may only be noticeable when the individual is tired. If severe the patient may not be able to stand without assistance. Symptoms may include: <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Loss of muscle tone <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Incoordination of volitional movements <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Intention tremor <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Minor degrees of muscle weakness <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Fatigability <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Disorders of equilibrium including nystagmus are common features.
 * <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">Cerebellar Gait **

<span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">The neocerebellum contributes to and is concerned with cognitive functioning including language. The right cerebellum (interconnected with the left cerebral hemisphere) becomes activated when asked to produce verbs in response to nouns. The cerebellum also becomes activated when reading aloud vs. looking at words. Moving the mouth without speaking also activates the cerebellum, whereas internal (silent) speech without motor movement does not.
 * <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">Language Functions **

<span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">Those with cerebellar injuries may display disturbances on verbal paired associates tests. With severe injuries some may display an intial mutism. This may be due to brainstem compression involving the periqueductal gray. They may also be a result of the extensive interconnections between the left cerebellum and the right cerebral hemisphere whereby there are disruptions on neocortical processing and/or afferents as they pass through the brainstem in route to the cranial nerves. It is also possible that these disturbances are due to the complex cognitive processes being performed by and within the cerebellum.

<span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">Speech can also be affected and become dysarthric following an injury. This is particularly true with left-sided damage. If there is a rapid and acute onset, one may become transiently mute. Cerebellar dysarthric speech may be of two types: <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Slowed and slurred, particularly when required to repeat sounds ("ga ga ga") <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Scanning dysarthria with variable intonations as words are broken up into syllables some of which are explosibly uttered (i.e. ballistic speech).
 * <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">Ataxic Speech **

<span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">Motor tasks may be inhibited when visual cues generally used to guide movement are eliminated. Lesions in the left neocerebellum (which is interconnected with the right hemisphere) have also been shown to have mild difficulty in performing cognitive-spatial operations in three dimensional space. This is presumably due to connections with the hippocampus.
 * <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">Vision and Visuo-spatial Functions **

<span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">**Emotional Activity** <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">Injury and electrical stimulation of this brain region have shown emotional responses including triggering rage reactions and constant states of hyperactivity. Stimulation of the paleocerebellum will elicit these rage like reactions including threat, attack, and autonomic changes including alterations in arterial pressure, heart rate, piloerection, dilation of the pupils, urination, gastrointestinal changes, and the production of sleep-like EEG spindles, but they seem to remain undirected and, at best, semi-purposeful (i.e. "sham rage."). Activation of the anterior cerebellum may also increase blood pressure, heart rate, respiration, and inhibit gastromotility. The posterior cerebellum has the exact opposite effect. Removal of the cerebellum does not eliminate these or other emotional behaviors however and should connections with the amygdala and hypothalamus become severed, cerebellum stimulation ceases to have an influence on these functions.

<span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">For these reasons, the emotional responses of the cerebellum tend to be primarily attributed to the rich interconnections maintained between the cerebellum and the limbic system, specifically the amygdala, hippocampus, hypothalamus, septal nuclei, nucleus accumbens, and substantia nigra. It is hypothesized that the cerebellum may exert an inhibitory influence on these nuclei. Fibers from the hypothalamus appear to terminate in all layers of the cerebellar cortex which in turn project to the lateral, dorsal medial and anterior hypothalamus; structures implicated in the rudimentary aspects of emotion, including sexuality and control over the autonomic nervous system. Emotional and affective behavior with autonomic changes also appear to be influenced by direct connections with the brainstem. In this regard it "modulates the systemic circulation and profoundly influences cerebral blood flow and metabolism, and initiates long-term protection of the brain from ischemia". This neuroprotective mechanism has been demonstrated through stimulation reducing focal cerebral infarction volume by 50% due to its dramatical influence on arterial pressure.

<span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">“Childhood mania” has been associated with cerebellar dyplasia and more recently, abnormalities in the cerebellum have also been implicated in the pathogenesis of cases of schizophrenia and autism, as well as post-injury/surgery mutism and highly abnormal emotional behavior which often resolves after a few days or weeks. Joseph notes that monkeys reared under deprived conditions displayed abnormal electrophysiological activity in the cerebellum (dentate gyrus) as well as the septal nuclei while also displaying autistic behavior and that these findings are significant given the cerebellum being an outgrowth of the vestibular system, and that insufficient social-emotional or physical stimulation may also result in insufficient vestibular activation. Joseph goes on to note that up to 50% of patients diagnosed as psychotic or schizophrenic display cerebellar abnormalities, including atrophy of the vermis or tumors and approximately 50% of those who are psychotically depressed show a similar pattern of cerebellar abnormality. Stimulation of the paleocerebellum (i.e. the vermis) can induce electrophysiological desychronization in the thalamus, anterior cingulate, amygdala, hippocampus, orbital frontal lobes, midbrain reticular formation, hypothalamus, and the ventral striatum; nuclei that have been implicated in the genesis of psychotic and emotional disturbances. It has been reported that electrical stimulation of the vermis can relieve chronic and intractable psychotic disturbances in over 90% of those treated. Presumably this is due to the effects of cerebellar activity on the limbic system. It has also been reported that cerebellar stimulation may decrease limbic system seizure activity, whereas ablation will result in enhanced limbic system seizures.

<span style="color: #000000; font-family: "Times New Roman",serif;">**The Cerebellum – Pathology and Symptoms** <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Dysarthria <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Vertigo <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Hypotonia <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Intention tremor <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Abnormalties in force, accuracy, range, and rate of goal directed voluntary movements <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Asynergia: Lack of motor coordination <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Dysdiachokinesia: Inability to make rapid alternating movements of the limb. <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Involuntary motor sequences || <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Disrupted visually guided tracking movements and determination of movement trajectory: past pointing; distances are incorrectly judged <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Dysmetria: Falling short or going to far when attempting to touch or grasp an object <span style="color: #000000; font-family: "Times New Roman",serif;">-Nystagmus: <span style="font-family: "Times New Roman",serif;">involuntary slow and fast rhythmic lateral eye movements usually to the side of the lesion <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Difficulty with paired verbal testing || -Increased ”rage response” (semi-purposeful/”sham”) -Hyperactivity -Autonomic function dysregulation (heart rate, blood pressure, respiration, gastromotility, etc) -Possible schizophrenia psychoses -Possible autstic-like symptoms ||
 * Motor Movement || Visual and Verbal || Emotional ||
 * <span style="color: #000000; font-family: "Times New Roman",serif; font-size: 9pt;">-Gait ataxia

<span style="color: #000000; font-family: "Times New Roman",serif;">**Acupuncture Considerations** <span style="font-family: TimesNewRomanPSMT,serif;">A number of points have demonstrated by fMRI studies a correlation to brain activity in the temporal lobes <span style="font-family: TimesNewRomanPSMT,serif; font-size: 6pt;">10 **Activating:** <span style="font-family: TimesNewRomanPSMT,serif;">Cerebellum General: LR-3, GB-40, GB-34, GB-39, LI-4 **Deactivating:** <span style="font-family: TimesNewRomanPSMT,serif;">N/A <span style="font-family: TimesNewRomanPSMT,serif;">George Soulie De Morant 13 notes indications for brain regions according to his extensive studies of the medicine in China prior to the communist revolution when much of the information was either politically streamlined or lost. According to his studies points had been found to influence the cerebellum. LU-8 LU-10 LU-11 LI-6 ST-5 ST-11 ST-15 ST-20
 * Tonifying ||
 * LU-7

ST-33 SP-6 SP-7 SP-9 SP-21 HT-6 HT-8 SI-3 BL-30 BL-50 BL-56 BL-57 KI-5 KI-6 KI-10

KI-13 KI-17 KI-19 KI-20 KI-22 KI-26 PC-1 PC-2 PC-6 PC-7 TW-6

TW-15 GB-24 GB-32 GB-34 LR-5 (Opposite: if insufficient, spasms: tonify; if excess, weakness: disperse) LR-8 LR-9 LR-10

LR-13 CV-16 CV-17 CV-21 CV-22 GV-4 GV-6 GV-17 GV-23 ||

<span style="color: #000000; font-family: TimesNewRomanPSMT,serif;">BL-65 <span style="color: #000000; font-family: TimesNewRomanPSMT,serif;">TW-10 <span style="color: #000000; font-family: TimesNewRomanPSMT,serif;">LR-2 ||
 * Dispersing ||
 * <span style="color: #000000; font-family: TimesNewRomanPSMT,serif;">LU-5

<span style="color: #000000; font-family: "Times New Roman",serif;">**Points in the Cerebellar Region** <span style="font-family: "Times New Roman",serif; font-size: 9pt;">These are essentially the same points as located near the brainstem as the two structures lie in similar posterior positions along the scalp.