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Home , Caudate nucleus, Corticobulbar tract, Direct pathway, Nucleus accumbens, Pars compacta, Putamen

The

SMA Posterior S1 M1 Anterior Posterior PMA parietal Prefrontal

Basal Ganglia Loop

Thalamus VLc VLo Overview 1 Caudate N. Accumbens Red

Cerebellar Loop Cerebellar Nuc. Subthalamic nuc. Inf. Sup. & Inf. Olive Colliculi

Vest. Retic.

Nuc. Form. Spinocerebellar Tr. Spinocerebellar

Vest. Retic. Rubro Cortico- Tecto- Spinal Spinal Spinal Spinal Spinal Tr. Tr. Tr. Tr. Tr.

Anterior Posterior

1 SMA Posterior S1 M1 Posterior PMA parietal Prefrontal

Basal Ganglia Loop

Thalamus VLc VLo Pons Overview 1 Caudate Putamen N. Accumbens Red Globus pallidus Cerebellum

Cerebellar Loop Cerebellar Nuc. Substantia nigra Subthalamic nuc. Inf. Sup. & Inf. Olive Colliculi

Vest. Retic.

Nuc. Form. Spinocerebellar Tr. Spinocerebellar

Vest. Retic. Rubro Cortico- Tecto- Spinal Spinal Spinal Spinal Spinal Tr. Tr. Tr. Tr. Tr.

Areas of the Nervous System Involved in Movement

Upper Motor Association Cortex Association Cortex

Thalamus Thalamus

Basal Ganglia Cerebellum

Lower

Muscle

2 Motor loop of the basal ganglia

Nuclei of the Basal Ganglia

Input Intrinsic Output Caudate

Putamen Globus pallidus – external segment Globus pallidus – Substantia nigra pars internal segment compacta Substantia nigra pars Ventral reticulata Ventral pallidum

Ventricles Thalamus Caudate Putamen Globus Pallidus

3 Coronal Section

Corpus Callosum Cingulate Gyrus

Lateral Ventricle Caudate (head)

Septum Pellucidum

Claustrum Putamen Nucleus Accumbens Optic Chiasm

4 Coronal Section

Caudate Nucleus Putamen Internal Capsule Thalamus Globus Pallidus Pars Externa Pars Interna

Amygdala

BCP p.479

5 Simplified box diagram of basal ganglia loop Substantia nigra

Output nuclei Input nuclei Thalamus Globus pallidus Caudate n. pars interna Ventral lateral n. (all lobes) BasalPutamen Ganglia CircuitryVentral pallidum Ventral anterior n. N. accumbens Substania nigra Medial dorsal n. Direct route

Globus pallidus Subthalamic pars externa nucleus

Indirect route

Corticospinal /

General Circuitry of the Basal Ganglia Direct and Indirect Pathways

Substantia Nigra

Direct route

Cerebral cortex (all lobes) Input nuclei Output nuclei Thalamus

Indirect route

Globus pallidus Subthalamic Frontal lobe pars externa nucleus

The (Skeletomotor)

Substantia nigra pars compacta D1 Cortex

Thalamus E I Globus pallidus I M1, S1 pars interna Premotor Putamen VA, VL Substania nigra cortex pars reticulata

Low Spontaneous High Spontaneous M1, SMA, PMA

E E I I E: Sign Preserving – “disinhibitory”

6 The Indirect Pathway (Skeletomotor)

Substantia nigra pars compacta Cortex D2

Thalamus Globus pallidus M1, S1 E I pars interna Premotor Putamen VA, VL Substania nigra cortex pars reticulata I E I Globus pallidus Subthalamic M1, SMA, PMA pars externa nucleus E

E I I E I E: Sign Inverting – “inhibitory”

Skeletomotor Loop

Substantia nigra Inhibition Excitation pars compacta

Thalamus Globus pallidus M1, S1 pars interna Premotor Putamen VA, VL Substania nigra cortex pars reticulata Direct pathway

Globus pallidus Subthalamic M1, SMA, PMA pars externa nucleus

Corticospinal/corticobulbar tract

Direct path excites thalamic target Indirect path inhibits thalamic target neurons

DopamineX (SNc) ? Direct path Indirect path

Dopamine is thought to facilitate movement by both exciting direct path and inhibiting indirect path

7 Normal Diseased

SNc

Parkinson’s disease (Paralysis Agitans)

Loss of SN pars compacta (SNc) inputs to the basal ganglia increases inhibition of voluntary movement

Hypokinetic signs (impoverished movement)

Major impairment initiating movements – akinesia Reduction in the extent and speed of movements – bradykinesia Postural deficits

Resting (shaking palsy, resembles pill rolling) Expressionless , infrequent blinking – mask facies Characteristic limb stiffness – lead pipe or cogwheel rigidity

Disorders of the basal ganglia: disturbances of tone: dystonia abnormalities of movements: dyskinesia

Upper Motor Neuron signs Extrapyramidal signs

•Increased tone in specific •General increased tone across muscle groups all muscles •Clasp-knife response •Cogwheel rigidity •Hyperreflexia •Reflexes ~normal •Weakness (paresis) •Slowed/limited movement, but not particularly weak •Positive signs (tremor, ballism, , )

8 Ballismus / “Releases” Indirect pathway thalamus Cortex Thalamus Globus pallidus M1, S1 E Putamen pars interna I Premotor Substania nigra VA, VL cortex pars reticulata I E Globus pallidus I Subthalamic M1, SMA, PMA pars externa nucleus E

Caused by vascular accidents affecting the subthalmamic nucleus

Loss of excitatory influence of subthalamic nucleus reduces output of GPi, which in turn releases thalamus of inhibition

Leads to exaggerated, large amplitude movements: hyperkinesis

Dyskinesias due to degeneration of the (Huntington’s disease)

Substantia Nigra

Cerebral cortex (all lobes) Input nuclei Output nuclei Thalamus

Direct route X Globus pallidus Subthalamic Frontal lobe pars externa nucleus

Indirect route Normal Diseased

Chorea / Choreiform Movements

Involuntary, sudden, frequent, and purposeless jerks of the extremities, head, and trunk

9 Athetosis / Athetoid Movements

Combination of symptoms characterized chiefly by a more or less constant mobility of the extremities and an inability to retain them in any fixed position

Treatment of basal ganglia disorders such as PD

Dopamine replacement (levodopa) MAO inhibitors (e.g. selegiline) prolong action of dopamine Surgical lesions: (reduces rigitidy) thalamotomy (relieves tremor) Fetal nigral transplantation

Drug MPTP, a heroin like compound, destroys DA neurons, and has been used to develop a experimental model of

10 Implantable Components

Patient Component

System Start-up Requirements

Cortical origin Input nucleus Output nuclei Thalamus / SC Posterior parietal Caudate SN, reticulata VA Prefrontal Additionalnucleus GP, internaloops MD

Frontal & Oculomotor loop Suppl. eye fields

Posterior SN, reticulata parietal Caudate VA GP, interna Premotor nucleus MD

Association loop Prefrontal

Ventral pallidum Temporal Ventral striatum SN, reticulata MD (n. accumbens) GP, interna VA

Ant. cingulate Limbic loop Orbitofrontal

SMA S1 M1 Posterior PMA parietal Prefrontal

Basal Ganglia Loop

Thalamus VLc VLo Pons Overview 1 Caudate Putamen N. Accumbens Red Globus pallidus Cerebellum

Cerebellar Loop Cerebellar Nuc. Substantia nigra Subthalamic nuc. Inf. Sup. & Inf. Olive Colliculi

Vest. Retic.

Nuc. Form. Spinocerebellar Tr. Spinocerebellar

Vest. Retic. Rubro Cortico- Tecto- Spinal Spinal Spinal Spinal Spinal Tr. Tr. Tr. Tr. Tr.

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