Neuro Lecture 10: Basal Ganglia + Cerebellum

Do the basal ganglia and cerebellum initiate movement?

No, they MODULATE movement (it is initiated by the primary motor cortex)

This structure controls starting, stopping, timing of slow ramp movements by facilitating or inhibiting other movement structures

Basal ganglia

This structure modulates postural reflexes, coordinating fast movements

Cerebellum

What are the 3 components of the basal ganglia?

Input, output, instrinsic?

Putamen (input)

Caudate nucleus (input)

Globus pallidus (instrinsic= external + subthalamus; output=internal)

The caudate and putamen are called what?

Striatum

The putamen and globus pallidus make up what?

Lenticular nuclei

This is part of the substantia nigra and a major input of the basal ganglia as well as a source of dopamine

Pars compacta

What are the inputs of the basal ganglia (2)?

Most of cortex (motor + somatosensory)

Substantia nigra

What are the outputs of the basal ganglia?

Motor cortices and brainstem

What are the functions of the basal ganglia (2)?

Monitors motor and somatosensory info

Procedural memory

What are the regulatory loops between basal ganglia structures (4)?

S.O.P.L

1. Skeletomotor

2. Oculomotor

3. Pre-frontal

4. Limbic

This loop controls degree and force of movement

Skeletomotor

This loop controls spatial perception with eye movements

Oculomotor

This loop controls executive function with motor planning

Pre-frontal

This loop controls motivation and emotional responses with movement

Limbic

Lack of spontaneous movements slowing of voluntary movements

Hypokinesia

Involuntary, spontaneous movements

Hyperkinesia

Uncontrollable movements (often jerky)

The individual movements ‘make sense’, appear purposive, but are completely involuntary

Progressive, appearance in mid 40’s, fatal

Pathology:

• Wasting of caudate and putamen (no regulation of GP)

• Dementia is a component in 50% of cases

Huntington’s chorea/disease - ex. of hyperkinesia

Rigidity

Bradykinesia - poverty and slowness of movement

Ex. Parkinson’s

Hypokinetic dyskinesias

Bradykinesia, tremors & rigidity

Pathology: Loss of pigmented cells within the Substantia nigra affecting dopamine transmission

Parkinson’s Disease

These are examples of what?

• Chorea (brief, irregular, involuntary)

• Athetosis (continuous, slow, flowing, writhing)

• Dystonia (chorea/athetosis which occurs after sustained muscle contractions)

• Ballismus (‘flinging’)

• Tic

Hyperkinetic dyskinesias

Twice as many neurons as cerebral cortex

Input from cortex and feedback to cortex.

Input from many brainstem systems

And from ascending somatosensory and descending motor tracts.

Cerebellum

The older system of the cerebellum modulates what reflexes?

What 3 main tracts? No what tract?

Postural reflexes

Spinocerebellar, vestibulospinal, and reticulospinal

No cerebellar-spinal tract

The newer system of the cerebellum modifies what movements?

Rapid + ballistic movements

The gyri of the cerebellum

Increases the size and space of cerebellum

Folia

Separating the hemispheres at the midline portion of the cerebellum

Information regarding gross coordination, posture, and locomotion

Vermis

Small anterior portion of the cerebellum

Information regarding balance, oculomotor control, and posture

Flocculonodulus

Separates anterior and posterior lobes

On superior portion of the cerebellum

Primary fissure

Separates posterior lobe into superior and inferior portions

Along the transverse midline of the cerebellum

Horizontal fissure

Separates the flocculonodulus from the cerebellar hemispheres

Along the posterior aspect of the flocculonodulus

Posterolateral fissure

Information regarding motor planning, fine coordination, manipulation and muscle tone

Cerebellar hemispheres

Receiving afferent information and projecting efferent cerebellar information

Within the white matter (on either side of the vermis) of the cerebellum

Beneath the folia

Deep nuclei

These enter and exit the cerebellum via the cerebellar peduncles

Cerebellar axonal fibers

Controls efferents from cerebellum to thalamus, red nucleus

Superior cerebellar peduncle

Controls afferents to cerebellum from contralateral pons

Middle cerebellar peduncle

Controls afferents to cerebellum from spinocerebellar tracts and vestibular system and others

Inferior cerebellar peduncle

The cerebellum influences what side of the body?

The cortex?

Cerebellum - ipsilateral

Cortex - contralateral

What are the 6 major cerebellar pathways, what do they control?

Call Vibes And Post Cool Reels

Cerebrocerebellar (motor cortex)

Vestibulocerebellar (balance)

Anterior Spinocerebellar (lower body)

Posterior Spinocerebellar (lower body)

Cuneocerebellar (upper body)

Rostral spinocerebellar (upper body)

What is the order of the cerebrocerebellar afferent pathway (afferent info from cortex to cerebellum)?

Cortex

Internal capsule

Cerebral peduncles

Pons nuclei

Cross at pons fasciculus?

Middle cerebellar peduncle

Deep nuclei

Cerebellar hemispheres

The cerebellar hemispheres control what 3 things?

1. Motor planning

2. Fine coordination + manipulation

3. Muscle tone

What is the order of the cerebrocerebellar efferent pathway (efferent info from cerebellum to cortex)?

Cerebellar hemisphere

Deep nuclei

Superior cerebellar peduncle

Cross to the contralateral red nucleus (midbrain)

Thalamus (VL)

Cortex

Cerebrocerebellar dysfunction includes what 5 things?

D. D. A. I. H

1. Dysmetria (under or overshoot in coordination)

2. Dysdiadochokinesia (problem with rapid alternating movements)

3. Ataxia (generalized problems with coordination)

4. Intention tremors (during deliberate movements)

5. Hypotonia (decrease in tone)