BASAL NUCLEIBASAL NUCLEI

(Basal Ganglia)(Basal Ganglia)

Basal Nuclei ComponentsBasal Nuclei Components

Substantia nigra (within the midbrain)Substantia nigra (within the midbrain)Subthalamic nuclei (diencephalon)Subthalamic nuclei (diencephalon)Corpus striatumCorpus striatumRed nucleus (?)Red nucleus (?)Claustrum (?)Claustrum (?)Nucleus accumbens (?)Nucleus accumbens (?)

Corpus StriatumCorpus Striatum

Composed of caudate nucleus + lentiform Composed of caudate nucleus + lentiform nucleus:nucleus:

Striatum = caudate nucleus + putamen.Striatum = caudate nucleus + putamen.

Pallidum = globus pallidus.Pallidum = globus pallidus.Putamen + globus pallidus = lentiform Putamen + globus pallidus = lentiform

nucleus.nucleus.Controls large subconscious movements Controls large subconscious movements

of the skeletal muscles.of the skeletal muscles.The globus pallidus regulates muscle tone.The globus pallidus regulates muscle tone.

Corpus StriatumCorpus Striatum

Corpus Striatum(Telencephalon)

Striatum Pallidum

Caudate Nucleus Putamen Globus Pallidus

Substantia Nigra SubdivisionsSubstantia Nigra Subdivisions

Dorsal pars compacta:Dorsal pars compacta:

Has melanin containing neurons and Has melanin containing neurons and dopaminergic neurons.dopaminergic neurons.

Ventral pars reticularis:Ventral pars reticularis:

Has iron-containing glial cells.Has iron-containing glial cells.

Has serotonin and GABA (no melanin).Has serotonin and GABA (no melanin).

Substantial NigraSubstantial Nigra

Substantia NigraMesencephalon

DorsalPars compacta

VentralPars reticularis

Melanin containing neurons Dopaminergic neurons

Iron-containing glial cellsSerotonin and GABA

Input NucleiInput Nuclei

Striatum Striatum Caudate nucleusCaudate nucleusPutamen Putamen Nucleus accumbensNucleus accumbens

Receive widespread input from:Receive widespread input from:NeocortexNeocortexIntralaminar nucleiIntralaminar nucleiSubstantia nigraSubstantia nigraDorsal raphe nucleusDorsal raphe nucleus

Input NucleiInput Nuclei

Striatum projects to:Striatum projects to:Globus pallidusGlobus pallidusSubstantia nigraSubstantia nigra

Pars reticularisPars reticularis

Via gabaminergic fibersVia gabaminergic fibersMotor and sensory cortices project to Motor and sensory cortices project to

putamen.putamen.Association areas of all lobes project to Association areas of all lobes project to

caudate nucleus.caudate nucleus.

Output NucleiOutput Nuclei

Globus pallidus (medial part)Globus pallidus (medial part)Substantia nigra:Substantia nigra:

Pars reticularisPars reticularisVentral pallidumVentral pallidumFibers project to:Fibers project to:

VA/VL nucleiVA/VL nuclei

Mostly inhibitoryMostly inhibitory

General Core CircuitGeneral Core Circuit

Cerebral cortex to:Cerebral cortex to:Striatum to:Striatum to:Globus pallidus to:Globus pallidus to:Thalamus to:Thalamus to:Portions of motor cortex to:Portions of motor cortex to:Upper motor neuronsUpper motor neurons

Basal Ganglia ConnectionsRed = excitatory; Black = Inhibitory

Motor areas of cerebral cortex

Ventrolateralthalamus Putamen

Globus pallidusexternus

Outputnuclei Subthalamic

nuclei

Substantia nigracompacta

LateralActivationpathways

Pedunculo-Pontinenuclei

Reticulospinal and Vestibulospinal

pathways

Thalamic FasciculiThalamic Fasciculi

Ansa lenticularis:Ansa lenticularis:

Consists of fibers from dorsal portion of Consists of fibers from dorsal portion of globus pallidus.globus pallidus.

Loops under internal capsule.Loops under internal capsule.

To VA/VL complex.To VA/VL complex.

Thalamic FasciculiThalamic Fasciculi

Lenticular fasciculus:Lenticular fasciculus:

Consists of fibers from ventral portion of Consists of fibers from ventral portion of globus pallidus.globus pallidus.

Passes across the internal capsule.Passes across the internal capsule.

To VA/VL complex.To VA/VL complex.

FunctionsFunctions

Basal nuclei set organism’s level of Basal nuclei set organism’s level of responsiveness to stimuli.responsiveness to stimuli.

Extrapyramidal disorders are associated Extrapyramidal disorders are associated with basal nuclei pathology:with basal nuclei pathology:

Negative symptoms of Negative symptoms of underresponsiveness:underresponsiveness:

AkinesiasAkinesiasi.e. Parkinson diseasei.e. Parkinson disease

Positive symptoms of over-responsiveness:Positive symptoms of over-responsiveness:Choreas, athetoses, ballismsChoreas, athetoses, ballismsi.e. Huntington’s choreai.e. Huntington’s chorea

Dopamine Neuronal SystemDopamine Neuronal System

Consists of nigrostriatal fibersConsists of nigrostriatal fibersFrom pars compacta of substantia nigraFrom pars compacta of substantia nigraTo striatumTo striatumDopaminergic Dopaminergic