Basal Nuclei (Ganglia)

Doctor said he will not go deep within these slides because we will take them in physiology , so he will explain the anatomical structures , and he will go faster in the functions

By : Zaid Al-Ghnaneem

sheet in yellow

Basal Ganglia

• The basal ganglia include the caudate, putamen, and globus pallidusand number of closely related nuclei

• They influence motor system primarily through projections to uppermotor neurons

• Motor deficits depend on the specific nucleus damaged• Understanding the neurochemistry of basal ganglia drives thedevelopment of clinical treatment

and there is other nuclei we will takethem

remember the heirarchy in the last lecture the beggining of motor system, was incerebellum and basal ganglia

Basal Ganglia

• The basal ganglia act as• Brake against involuntary movement• Switch to turn on a fixed action pattern

• Their major output is to the VA of the thalamus• Projects primarily to area 6 (premotor & supplementary motor areas)

important in smoothness of movement , so it is disrupted , there will be movement but

it will not be smooth and it will be hard

یعني مثال بدك تمسك كأس , بدایة الحركة من basal ganglia یعني لو انضربت رح یكون في

تردد في البدایة

there is other functions but we will focus onmotor

output mainly to the ventral anterior nucleus of thethalamus

Basal Ganglia Terminology

• Striatum (neostriatum) = caudate + putamen• Lentiform nucleus = putamen + globus pallidus• Corpus striatum = caudate + lentiform• Basal ganglia = corpus striatum + amygdala• Globus pallidus = pallidum = paleostriatum• Claustrum is some times included with the basal ganglia• Basal ganglia is included by the extrapyramidal system

they are all close to each other

Basal Ganglia: Gross Anatomy 

• Caudate nucleus• Parts• Location• Relations

• Lateral ventricle• Amygdaloid nucleus

parasaggital section

part of lateral wall of lateralventricle

near the end of the caudate nucleus (tail)

• Lentiform nucleus• Parts

• Putamen• Globus pallidus

• Internal (GPi)• External (GPe)

• Shape• Location• Relations

• External & internalcapsules

• Claustrum

Basal Ganglia: Gross Anatomy 

medial to putamenmedial to external one

external capsule is association fiberswhereas internal capsule is projection fibers

after external capsule , close to insula

Basal Ganglia: Gross Anatomy

• Amygdaloid nucleus• Subthalamic nucleus• Substantia nigra

• Pars reticulata (SNr)• Pars compacta (SNc)

• Claustrum

Accessories to basal ganglia :

inferior to thalamus , superior to midbrain , posterior to hypothalamus

not visible in this pic

caudate with putamen it is straitum , the most anterior part of this straitum called ventral striatum , it is the same "nucleus accumbens"

Basal Ganglia Circuitry• Inputs

• Most inputs enter the striatum• From cerebral cortex & thalamus• These inputs are excitatory

• Outputs• Most leave from Gpi & SNr• Most go to VA nucleus of the thalamus,which projects to motor cortex

• The outputs are GABAergic andinhibitory• VA excites motor cortex, leading tomovements

• Increase basal ganglia output will inhibitthe VA and reduce overall movements

we will take function quickly and more info will be taken in physiology

globus pallidus internal & substantia nigra reticulata

Basal Ganglia CircuitryIntrinsic Circuits

• Large number of connections between components of the basalganglia

• Can be grouped into• Direct pathway• Indirect pathway

• These pathways affect the VA activity and thus the motor cortexactivity

The Direct Pathway• From striatum to Gpi

• Uses GABA, which inhibits another GABAergic projection (Gpi to VA)• Disinhibition

• Cortical activity → ↑direct pathway → ↓Gpi activity → ↑ VA activity

• Activity in the direct pathway leads to increased motor cortex activity and increased movements

The Indirect Pathway• Goes from striatum to GPe(GABA) to the subthalamicnucleus (GABA)

• Subthalamic nucleus to Gpi(Glu)

• ↑ activity in the cortex → ↑activity of subthalamic nu. →↑ GPi → ↓ VA activity → ↓motor cortex activity

Basal Ganglia Circuitry• The direct pathway increase movements• The indirect pathway decrease movements• Normal behavior requires a balance between the direct and indirect pathways

• All pathways are uncrossed• Right basal ganglia modulate right cortex and affect movements on the left side of the body

• Acetylcholine is used by the interneurons in the striatum• It affect the output of the direct and indirect pathways• It’s a target for drug therapy

Nigrostriatal Pathway• In the striatum different cell types giverise to the direct and indirectpathways

• Both cell types receive dopaminergicinput from SN pars compacta

• These cells have different receptorsfor DA• For direct pathway, DA excites the

striatal cells• For indirect pathway, DA inhibits the

striatal cells• Thus the nigrostriatal pathway ↑ theactivity of the VA and motor cortex

• PD leads to• ↓ direct pathway activity• ↑ indirect pathway activity• ↓ activity of VA and motor cortex

here in parkinson disease the opposite occur !!

Cerebellum

Cerebellum 

• The cerebellum is essential for normal movements• It affects motor behavior by affecting UMNs• The cerebellum acts as a comparator

• Compares intended movements (data from cerebral cortex)to the actual movements (sensory data)

• Sends corrective signals into the descending motorpathways

important in movements , mostly close in function to basal ganglia

remember basal ganglia was initiator for movementsbut cerebellum for modification of movementsیعني تدارك الحركات الي اصال موجودة نرجع لمثال الكأس , بعد ما مسكتھ حسیت انھ بده یقع فالحركة الي عملتھا حتى مایقع وتداركت الموقف ھاي جایة من الcerebellum

Cerebellar Function

• It affects all movements, it is important in:• Balance• Locomotion• Simple & complex movements• Eye movements, etc.

• Site of motor learning• Important for learning new motor skills and adjusting movements to changingsensory inputs

it has close association with vestibular nuclei for balance during movements

Cerebellar AnatomyGross Anatomy

• Location ….• Relations …..• The cerebellum consists of twohemispheres

• The hemispheres are connectedby vermis

similar to cerebrum , but here the fissure between the two hemisphers is narrow ,, what is this fissure ?? the falx cerebelli

cerebellum composed of cerebellar cortex on the periphery , inside there is white matter , and within the white matter there is also islands of grey matter

Cerebellum: Gross Anatomy• Three main lobes

• Anterior lobePrimary fissure• Posterior lobe (middle lobe)

• Cerebellar tonsilsPosterolateral fissure (uvulonodular fissure)• Flocculonodular lobe

the largest lobe

between anterior and posterior lobe

between posterior and flocculonodular lobe

Cerebellum: Gross Anatomy

Cerebellum: Internal Structure

• Content• Cerebellar cortex (folia) & central nuclei are grey matter• Arbor vitae = tree of life = white matter

the white matter also called arbor vitae or tree of life

Cerebellar Anatomy

• Cerebellum includes a cortex &deep nuclei

• The deep nuclei are the majorsource of output from thecerebellum

• Four nuclei from medial tolateral• Fastigial• Globose• Emboliform• Dentate

Interposed nuclei

the white matter contains 4 nuclei , the fastigial which is the most medial one , Globose and Emboliform called interposed nuclei because they have the same function , and the most lateral one which is Dentate nucleus " Not dentate gyrus!!"

these nuclei , mostly the efferent will exit from them

Cerebellar Cortex

• Cerebellar cortex includes 5cell types in 3 layers

• Five cell types• Inhibitory cells

• Purkinje, basket, Golgi, and stellatecells

• Excitatory cells• Granule cells

• Three layers• Molecular layer• Purkinje cell layer• Granule cell layer

cerebellar cortex efferent is the purkinje , the other layers affect the purkinje

purkinje cells " which is the output (efferent)" it is inhibitoryso if you inhibit it , overall you are exciting :)

Cerebellar Inputs

• Inputs to the cerebellum• Climbing fibers

• From inferior olivary complex(olivocerebellar fibers)

• Decussate• Inferior cerebellar peduncle

• Mossy fibers• All remaining inputs: spinal cord,vestibular n. & nuclei, & pontinenuclei

• Each type of input fibersbranches• Branch to deep nuclei• Branch to cerebellar cortex

Climbing fibers directly affect purkinje.Mossy fibers affect other cells , where these other cells affect purkinje as we said.

Cerebellar Circuit• The basic cerebellar circuitincludes• Main excitatory loop• Inhibitory cortical side loop

The Main Excitatory Loop

• Includes the input and thedeep cerebellar nuclei

• Both the inputs & the cells ofthe deep nuclei are excitatory

The Inhibitory Cortical Side Loop• Serves to modulate the activityin the deep cerebellar nuclei

• Mossy & climbing fibers areinputs to cerebellar cortex• Climbing fibers contact Purkinjecells directly

• Mossy fibers contact granulecells

• Granule cells contact PurkinjecellsOutput of cerebellar cortex(Purkinje fibers) depend on the mossy & climbing fibers

The Inhibitory Cortical Side Loop• Remaining cells (Golgi, basket& stellate) are inhibitoryinterneurons• Alter granule & Purkinje cells

• Purkinje cells (cerebellarcortex output) are inhibitory• Purkinje cells targets

• deep cerebellar nuclei &vestibular nuclei

Thus cerebellar output isdriven by the main excitatoryloop and limited by theinhibitory cortical side loop

Cerebellar Functional Divisions1. Vestibulocerebellum

• Flocculonodular lobe &fastigial nu.

• Balance, eye movements2. Spinocerebellum

• Vermis & paravermal parts ofhemispheres & interposednuclei (emboliform & globose)

• Motor execution3. Cerebrocerebellum

• Lateral hemispheres & dentatenu.

• Motor planning

cerebellum functionally divided to 3 parts

VestibulocerebellumFunction• Balance & eye movementsInputs• Vestibular n. fibers• Vestibular nuclei• Inferior oliveDeep nucleus• Fastigial nucleusOutputs (From fastigial nu. & Purkinje cells)• Vestibular nuclei• Reticular formation• VL of thalamusPart of motor system targeted• UMNs of medial pathwayMajor signs of damage• Staggering or falling, nystagmus

SpinocerebellumFunction• Execution of movement

• Compensates for changes in load, regulates muscle tone, guides limb movement, helps maintain posture

• Organized somatotopically• Head & trunk – vermis• Limbs – paravermal areas

Inputs• Spinal & trigeminal inputs• Inferior oliveDeep nucleus• Fastigial & interposed nucleiOutputs• Vermis

• Reticular formation & Vestibular nu.

• Paravermal• Red nucleus, VL of thalamus & Inferior olive

Part of motor system targeted• UMNs of medial & lateral pathwaysMajor signs of damage• Staggering gait, intention tremor

CerebrocerebellumFunction• Coordination, planning of voluntary movementsInputs• Pontine nuclei (relaying information from sensory &motor cerebral cortex)

• Inferior oliveDeep nucleus• Dentate nucleusOutputs• Red nucleus (to inferior olive, back to cerebellum)• VL of thalamusPart of motor system targeted• Motor cortex (via VL)Major signs of damage• Decomposition of movements

ventrolateral nucleus

Cerebellar PedunclesPeduncle Major inputs to cerebellum

Fibers from:

Major outputs from cerebellum

Fibers to:

Inferior‐ Restiform body

‐ Juxtarestiformbody

Inferior olive (climbing fibers)Dorsal spinocerebellar tractCuneocerebellar tractVestibular nerveVestibular nuclei

Vestibular nuclei

Middle(brachium pontis)

Pontine nuclei (relay inputs from cerebral cortex)

None

Superior(brachium conjunctivum)

Ventral spinocerebellarRostral spinocerebellar

Red nucleusVL thalamusReticular formationInferior olive

as we know there are 3 cerebellar peduncles , every one has it's own contents " inputs and outputs"

divided to 2 parts

Cerebellar Circuitry

Motor cortex

Cerebral Cortex

Spinal cord&Brainstem

Extrafusal

Intrafusal

αγ

Red nu.

Retic. Form.

Sup.Colliculus

VestibularNu.

Lateral systemMedial system

VAVL

Thalamus

Deep nuclei

Cortex

‐++Pontine

nuclei

Vestibularnerve

Inferiorolive

MCP

SCP

ICPCerebellum

UMNs

Blood Supply of Cerebellum• SCA

• Superior cerebellar hemispheres• Superior vermis• Dentate nucleus• Most of white matter• Superior cerebellar peduncle

• AICA• Middle cerebellar peduncle• Flocculus• Anteroinferior surface of thecerebellum

• PICA• Posteroinferior cerebellarhemispheres

• Inferior portion of the vermis• Inferior cerebellar peduncle

Motor cortex

Cerebral Cortex

Spinal cord&Brainstem

Extrafusal

Intrafusal

αγ

Red nu.

Retic. Form.

Sup.Colliculus

VestibularNu.

VAVL

Dorsal thalamus

Deep nuclei

Cortex

‐++Pontine

nuclei

Vestibularnerve

Inferiorolive

MCP

SCP

ICPCerebellum

Striatum

GPeGpiSNr

Globus pallidus

Subthalamicnucleus

Intralaminar nu. Of thalamus

To other UMNs: Retic. Form. & Sup. Coll.

Glu

Glu

Glu

GABA

GABA

GABA

GABA

Basal Ganglia

Upper Motor Neurons

Motor SystemSN compacta

‐

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