Cns basal ganglia

BASAL GANGLIA

Basal Ganglia (Nuclei)

• Group of deep, interrelated subcortical N

• Accessory motor system that • Functions usually not by itself but in close

association with cerebral cortex & corticospinal motor control system

• Most input signals from: cerebral cortex• Most output signals back to: cerebral cortex

Anatomy– Caudate– Putamen– Globus

pallidus– Substantia

nigra– Subthalamic

nucleus

Anatomy Overview

Anatomy

The Putamen Circuit – Executing Patterns of Motor Activity

The Putamen Circuit - Functions

• Putamen circuit + cerebral cortex• Controls complex patterns of motor activity

– Writing, Cutting paper with scissors, Hammering nails – Shooting a basketball through a hoop, passing a football,

Throwing a baseball – Most aspects of vocalization – Controlled movements of the eyes – And virtually any other skilled movements

The Putamen Circuit - Lesions

• Globus Pallidus: • Spontaneous, continuous writhing movements of a hand, an

arm, the neck, or the face – Athetosis

• Subthalamus: • Sudden flailing movements of an entire limb –

Hemiballismus

• Putamen: • Flicking movements in hands, face, & other parts of body –

Chorea

• Substantia Nigra: • Common and extremely severe disease of rigidity, akinesia,

and tremors - Parkinson’s disease

The Caudate Circuit – Cognitive Control of Sequences of

Motor Patterns

– Cognition • Most motor

actions occur as a consequence of cognition

• Caudate nucleus is pivotol

The Caudate Circuit

• Timing and Scaling of movements

BG Circuit - Neurotransmitters

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• What was common between Yasir Arafat, Muhammad Ali & Adolph Hitler?

Parkinson’s Disease

• Degenerative disorder of basal ganglia

• Dopamine depletion results from:• Degeneration dopamine nigrostriatal system• Antipsychotic drugs that block dopamine receptors• Toxic reaction to a chemical agent

» The Northern California drug dealer!*

• Severe carbon monoxide poisoning

Parkinson’s Disease – Clinical

• Tremor (involuntary tremor)– Affects distal segments of limbs (hands and feet; head,

neck, face, lips, tongue; or jaw)– Characterized by rhythmic, alternating flexion &

contraction movements (4-6 beats/minute)– Disappears during voluntary movement– Start unilateral- spread bilateral

• Rigidity – Resistance to movement of both flexors & extensors

throughout the full range of motion– Most evident during passive joint movement

» involves jerky, cogwheel-type movements requiring considerable energy

– Start unilateral- spread bilateral

Parkinson’s Disease – Clinical• Bradykinesia (slowness of movement)

• Movements:– Are slow to initiate & perform– Difficult to stop– Are stiff & staccato in character instead of smooth

• While walking:– Walking and turning en bloc is difficult

» Freezing spells– take small, shuffling steps without swinging arms

• Posture:– Lean forward to maintain center of gravity– Loss of postural reflexes – fall (often backward)

• Masked face:– Emotional & voluntary facial movements become limited– Loss of blinking reflex – Failure to express emotion

• Throat:– Tongue, palate, and throat muscles – rigid

» Drooling common• Speech:

– slow and monotonous, without modulation and poorly articulated

Parkinson’s Disease – Clinical

• Advanced Parkinsonian features:• Dementia (similar to Alzheimer’s disease) • Falls • Fluctuations in motor function • Neuropsychiatric disorders• Sleep disorders

Parkinson’s Disease – Treatment

• Nonpharmacologic• Group support • Education• Daily exercise, adequate nutrition • Botulism toxin injections

• Pharmacologic• Antiparkinson drugs act by:

– Increasing functional ability of underactive dopaminergic system

» Increase dopamine levels (levodopa)» Augment release of dopamine (amantadine)» Function as dopamine agonists (bromocriptine)» Inhibit metabolic breakdown of dopamine (selegiline)

– Reducing excessive influence of excitatory cholinergic neurons» Anticholinergic drugs

Parkinson’s Disease – Treatment

• Surgical• Thalamotomy or pallidectomy performed using

stereotactic surgery

Overall Motor Control