Functional Anatomy of the Basal Ganglia• Four main nuclei

striatum, globus pallidus, subthalamic nucleus, & substantia nigra

• Two general frameworks– Anatomically-based physiological models

• Direct vs indirect pathway controling motor output– Systems/behavioral level

• Functional classification according to behavioral distruption caused by focal lesions

– Parallel Cortico-BG-cortical loops• Major inputs: neocortex & substantia nigra• Major output: neocortex via thalamus

Overview: Basal Ganglia & thalamus

Herrero et al (2002) Figure by MIT OCW.

Striatum = Caudate nucleus and putamenPallidum = Ext. and Internal segments of globus pallidus

Cerebral Cortex

Caudate

Putamen

Globus Pallidus

(Substantia Nigra)

Hippocampus

Amygdala

White Matter

Midbrain dopamine InputsSN: Substantia NigraVTA: ventral tegmental areaSC: sup. ColliculusRD: red nucleus Section of brainstem

stained for tryosinehydroxilase (DA)

Glutamate Input:Cortex

Organizing principlesProximity

Topograpic projections from motor/somatosensory cortices to putamen

LongitudinalTrans-striatal projections from association cortices to caudate

Tripartate pattern

Saint-Cyr (2003) J. Int. Neuropsych. Soc.Figure by MIT OCW.

Tripartate input/output organization“The neurologist’s, psychologist’s & psychiatrist’s basal ganglia” (Saint-Cyr, 2003)

Neurologists movement disorders Psychologists cognitive operationsPsychiatrists behavioral & emotional disorders

Nakano et al. (2000)

CN

CN

Put

IC

GPe

GPi

STN

CM

PfVAmc

VApc

VLo

Motor

Associative

Limbic

Figure by MIT OCW.

Multiple parallel loop model• Alexander et al (1986) proposed as many as five

separate cortico-BG-cortical circuits

1. Motor2. Oculomotor3. Cognitive4. Lateral frontal5. Emotional

• Complete segregation unlikely given anatomy• Main point: The basal ganglia isn’t just a motor

structure

Middleton & Strick (2000)

Cognitive Sensory

Planning,workingmemory

Spatialworkingmemory

Objectworkingmemory

Visualrecognition,

discrimination

9 46 12 TE

VApcVAmc VAmcVApc

MDmfVAmcMDmf

VAmcMDmf

GPi GPi GPiGPi

SNprGPi

SNprSNpr SNprSNpr

M1 SMA PMv FEF

VLo VLo VLoVLm

Movementparameters

Internally-guided

movements

Externally-guided

movements

EyeMovements

Skeletomotor Oculomotor

Function

Corticalarea

Thalamicnucleus

Outputnucleus

Figure by MIT OCW.

Major Output:Thalamus

Herrero et al (2002)

MAJOR OUTPUT: Thalamus

SomatosensoryCortex

Motor Cortex

Premotor Cortex

Prefrontal

Primary Visual Cortex

Primary Auditory Cortex

Cingulate Gyrus

Central Sulcus

Calcarine Sulcus

I

MD

VA

VLa

VLp

VPL

MGNLGN

Pulv

Figure by MIT OCW.

Basic Neuropathology

Dauer & Przedborski (2003)Figure by MIT OCW.

Lewy Bodies

• Intraneuronal inclusions• Stain positively for synuclein & ubiquitin• Found in SN, locus coeruleus, nucleus basalis,

cerebral cortex, & olfactory bulb

Cortico-BG-Cortical Circuitry

Herrero et al (2002)

SO+SI SO+SI

STN STN

Met-Enk Met-Enk

PutPut

GPe GPe

GPi GPi

SPSP

DA

Cerebral Cortex Cerebral Cortex

DA

D2

SNpc

SNpr SNpr

SNpc

D1D1

D2

CONTROL PARKINSONIAN SYNDROME

+

++

+

_

_

_

_

_

Figure by MIT OCW.