Neuroanatomy Lecture 22

Cerebellar Anatomy

Functions of the Cerebellum

motor planning, comparator, motor learning

Motor Planning

aids the cortex in motor planning

Comparator

compares intended movement with actual movement and corrects errors

Motor Learning

circuitry changes with experience (neurons), modifies movements so there are fewer errors the next time a given movement is made

Cerebellar Lesions Cause

uncoordinated movements, impaired balance, inability to change/update motor programs

Cerebellar Lesions DO NOT CAUSE

paralysis

Small Bumps on the Cerebellum

folia

Lines on the Cerebellum

folium

Flocculonodular Lobe

sits in between the anterior and posterior lobe of the cerebellum

Folia

parallel folds running along the outer surface of the cerebellar cortex

Gray Matter in Folia

gray matter is exterior to white matter except in the deep cerebellar nuclei

Deep Cerebellar Nuclei

groups of cell bodies (gray matter) inside the white matter of the cerebellum

Deep Cerebellar Nuclei Input/Output

Input: receives input from collaterals of axons projecting to the cerebellar cortex

Output: output from the cerebellar cortex goes to these nuclei and neurons in these nuclei are the output of the cerebellum

Cerebellar Peduncles

cerebellum is connected to the brainstem via 3 cerebellar peduncles (superior, middle, inferior)

Divisions of the Cerebellum Dorsal View (3)

moving out laterally: vermis in the very center, intermediate hemisphere, lateral hemisphere

Know the different nuclei in deep cerebellar nuclei

look at diagram!

Vestibulo-cerebellar Pathway

receives input from vestibular system (cranial nerve 8 and the vestibular nuclei), then goes to flocculonodular lobe and then to the oculomotor and vestibular brainstem nuclei, deals with balance

Oculomotor Brainstem Nuclei

coordinate reflexive eye movements

Vestibular Nuclei

send information to the spinal cord to control proximal muscles used in balance

Damage to the Vestibulo-cerebellar Pathway Causes… (3)

Nystagmus (repetitive eye movement), disturbances of equilibrium, truncal ataxia (difficulty sitting or standing without support)

Spino-cerebellar Pathway: Vermis Division (spinocerebellar tract)

receives input from proximal musculature, goes to the vermis, then the fastigial nuclei of the deep nuclei, functions for error correction during movement of proximal muscles

Damage to the Spino-cerebellar Pathway: Vermis Division Causes… (3)

gait ataxia (struggle with walking), dysarthria (slurred/slow speech), hypotonia (lack of muscle tone)

Spino-cerebellar Pathway: Intermediate Division (spinocerebellar tract)

receives input from distal musculature and the motor cortex (pontine nuclei), goes to the intermediate hemispheres, then to the interposed nuclei of deep nuclei, functions for error correction during movement of distal muscles

Damage to the Spino-cerebellar pathway: Intermediate Division Causes… (4)

limb ataxia (distal parts), dysmetria (trouble reaching accurately), intention tremor (hand gets close to something and shakes), hypotonia (lack of muscle tone)

Dysmetria

errors in smoothness and direction of targeting movements; patients tend to over or undershoot objects, closer the movement gets to the target the more irregular the movement (intention tremor)

Cerebro-cerebellar Pathway (corticopontine tract/pontine nuclei)

receives input from primary somatosensory cortex, supplementary and pre-motor cortices, primary motor cortex, and primary visual cortex and visual areas of parietal cortex, goes to the lateral hemisphere, then the dentate nuclei of the deep nuclei which goes to the thalamus and the premotor cortex

Cerebro-cerebellar Pathway (corticopontine tract/pontine nuclei) Functions

skilled movements, dexterous movements, complex movements, assists premotor cortical regions in selecting efficient motor programs

Damages to the Cerebro-cerebellar Pathway (corticopontine tract/pontine nuclei) Causes… (3)

delayed initiation and termination of movement (not smooth and takes longer because has to coordinate), dysmetria, dysdiadochkinesia (inability to perform a series of rapid alternating movements, can also affect repeating speech)

Short-term Effects of Alcohol on Cerebellum

lack of coordination, unsteady gait, slurred speech

Lhort-term Effects of Alcohol on Cerebellum

permanent damage to cerebellum that affects movement in the lower limbs, causes wide staggering gait (vermis which is center piece)

Alcohol Affect on Cerebellar Structure

mainly affects vermis in anterior lobe, cellular dgeneration (loss of Purkinje fibers)

What is special about the Intermediate Division of the Spino-cerebellar Pathway

neurons go to cerebellum which gets info about what happens vs what should happen and it compares the two to make changes, corticospinal tract neurons go up to cortex before other places, corticopontine tract also sends neurons to cerebellum because limbs are more coordinated via the pons

Physiological Tremor

normal; minor but exacerbated by stress or anxiety

Parkinsonian Tremor

resting tremor (3 Hz), usually hands/arms

Essential Tremor (benign familial tremor; 4-8 Hz)

not progressive, doesn’t affect other things, tremor occurs when muscles are “under load” and usually in the hands but can sometimes be head/neck muscles, can involve intention tremor as well

Intention Tremor

occurs near the end of a movement