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The Basal Ganglia. Maryann Martone, Ph. D. NEU257 2/22/2011. What are the basal ganglia?. Depends on whom you’re talking to: Anatomical: Non-cortical nuclei in the forebrain Caudate nucleus, putamen, nucleus accumbens, amygdala, globus pallidus

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the basal ganglia

The Basal Ganglia

Maryann Martone, Ph. D.

NEU257

2/22/2011

what are the basal ganglia
What are the basal ganglia?
  • Depends on whom you’re talking to:
    • Anatomical: Non-cortical nuclei in the forebrain
      • Caudate nucleus, putamen, nucleus accumbens, amygdala, globus pallidus
    • Functional: Richly interconnected set of nuclei in the forebrain and midbrain
system view
System View
  • Dorsal Striatum
    • Caudate nucleus
    • Putamen
  • Ventral Striatum
    • Nucleus Accumbens
    • Olfactory Tubercle
  • Globus Pallidus
    • Internal segment
    • External segment
    • Ventral pallidum
  • Subthalamic nucleus
  • Substantia nigra
    • Pars compacta
    • Pars reticulata
  • Pedunculopontine nucleus**

Striatum

Other Terms:

Archistriatum

Paleostriatum

Neostriatum

slide5

Caudate Nucleus

    • C shaped structure (“tail”)
    • Lateral wall of lateral ventricle
    • Head, body and tail
slide6

Caudate nucleus

  • Putamen
  • Nucleus accumbens
  • Internal capsule
  • External capsule
  • Extreme capsule
  • claustrum
  • Septum pellucidum
  • Insular cortex
  • Corpus callosum
slide7

Caudate nucleus

  • Putamen
  • Globus pallidus external
  • Globus pallidus internal
  • Ventral pallidum
  • Anterior commissure
  • Substantia innominata
  • Internal capsule
  • Lentiform nucleus**
slide8

Head, body, tail of caudate

  • anterior and temporal horn of lateral ventricle
  • Globus pallidus internal and external
  • Internal capsule, anterior and posterior limbs
slide9

Caudate nucleus (body and tail)

  • Putamen
  • Globus pallidus
  • Subthalamic nucleus
  • Substantia nigra
    • Pars compacta
    • Pars reticulata
slide10

Globus pallidus external

  • Globus pallidus internal
  • Subthalamic nucleus
  • Substantia nigra
slide11

Subthalamic nucleus

  • Substantia nigra
  • Ventral tegmental area
slide13

Globus pallidus and entopeduncular nucleus

vs.

Globus pallidus (external) and Globus pallidus (internal)

slide14
“Chemical Neuroanatomy” was very important in increasing our understanding of basal ganglia structures
  • Use of different histochemical and immunocytochemical stains revealed more extensive striatal structures than previously thought
  • Also caused revised views of basal ganglia structures in non-mammals and pointed to considerable homologies between birds, mammals and reptiles

From Zhou et al., Nature Neuroscience, 4, 1224 - 1229 (2001) 

functions of the basal ganglia
Functions of the basal ganglia
  • Extrapyramidal motor system
  • Motor planning, sequencing and learning
  • Activity of striatal neurons is not sufficiently explained by the stimuli presented or the movements performed, but depends on certain behavioral situations, certain conditions or particularly types of trials
      • -sensory stimuli but only when the elicit movements
      • -instruction cues (go-no go)
      • -memory related cues
      • -reward (especially ventral striatum)
      • -self-initiated moves
  • Basal ganglia distinguished from cerebellum by connections with limbic system
diseases of the basal ganglia
Diseases of the Basal Ganglia
  • Parkinson’s:
    • Akinesia
    • Bradykinesia
    • Resting tremor
    • Rigidity
  • Huntington’s disease
    • Chorea
    • Psychiatric disturbances
    • Dementia
cytoarchitecture
Cytoarchitecture
  • Main neurotransmitter in basal ganglia is GABA
  • 95% of neurons in neostriatum are medium spiny neurons (rodent)
    • Contain GABA
    • Principal neurons: project to globus pallidus and SNpr
    • Subpopulations are distinguished by peptides, neurotransmitter receptors and connections
    • Receive bulk of afferent input
  • Several populations of interneurons
    • aspiny
    • ACh, GABA/parvalbumin, GABA/calretinin; GABA/NPY/NADPH/Somatostatin

From Groves, Brain Res. 286: 109, 1983

the neostriatal mosaic
The Neostriatal Mosaic
  • Neostriatum divided into two compartments: patch (striosome) and matrix
  • First described by Ann Graybiel in 1978 using AChE stain
  • Not visible in Nissl stains (“hidden chemoarchitecture”)
  • Define input/output architecture of neostriatum

From Holt et al., 1997, JCN

connections
Connections
  • Afferents (striatum):
    • Cerebral cortex (entire cortex)
    • Thalamus (intralaminar and midline nuclei)
    • Amygdala (basolateral nucleus)
    • Raphe, substantia nigra pars compacta, VTA
  • Efferents (Gpi, VP, SNpr)
    • Ventral tier nuclei of thalamus
    • Superior colliculus
    • Lateral habenular nucleus
slide20

All regions of cerebral cortex project to the basal ganglia, but output of basal ganglia is directed towards the frontal lobe, particularly pre-motor and supplementary motor cortex

basic circuit of basal ganglia

+

+

Gpe

+

Subth

Basic Circuit of Basal Ganglia

Cerebral Cortex

Neostriatum

Gpi/SNpr

VA/VL thalamus

Connections of afferents and within basal ganglia are largely non-reciprocal

some numbers rat
Some numbers (rat)
  • 2.8 million neurons in caudoputamen
  • 46,000 neurons in Gpe
  • 3200 neurons in Gpi
  • 26,000 neurons in SNpr
    • Oorschot (1996)
    • Significant convergence of input from striatum to target nuclei
disinhibition
Disinhibition

From Chevalier and Deniau, TINS 13:277, 1990

direct vs indirect pathways
Direct vs indirect pathways
  • Different populations of spiny neurons
  • Enkephalin vs substance P
  • D1 vs D2 receptors

From Graybiel, A. Neural Networks, Am J Psychiatry 158:21, January 2001

facilitation vs inhibition of movement
Facilitation vs inhibition of movement

Albin RL, Young AB, Penney JB.The functional anatomy of basal ganglia disorders.Trends Neurosci. 1989 Oct;12(10):366-75.

  • Akinetic disorders: overactivity in the indirect pathway
    • Dopamine increases activity in the direct pathway and decreases activity in the indirect pathway
    • Loss of dopamine decreases activity in the direct pathway and increase activity in the indirect pathway
      • Increased activity in the indirect pathway = increased activity in the direct pathway = increased inhibition on thalamus
  • Hyperkinetic disorder: overactivity in the direct pathway
    • Projections to the Gpe degenerate early in HD = removal of inhibition = increased activity of indirect pathway
    • Increased activity of indirect pathway = increased inhibition of subthalamic nucleus = decreased excitatory drive on direct pathway = decreased inhibition on thalamus
slide26

Inhibit

Hypokinetic

Release

Hyperkinetic

functional subdivisions
Functional subdivisions
  • Sensorimotor
    • Putamen + globus pallidus/SNpr
    • SNpc
  • Association
    • Caudate nucleus + globus pallidus/SNpr
    • SNpc
  • Limbic
    • Nucleus accumbens + ventral pallidum
    • VTA

From Parent, TINS 13: 254, 1990

neostriatal mosaic and input output organization
Neostriatal Mosaic and Input/Output Organization
  • Most inputs to the neostriatum terminate in a patchy fashion (“matrisomes”)
  • Input from a given cortical region terminates over an extended anterior-posterior extent
  • Functionally related cortical areas project to the same patches
  • Output neurons to a given efferent subregion are also arranged in patches
  • Neurons in patches project to both Gpi/SNpr and GPe
slide29

Cortex

Neostriatum

Gpi/SNpr

“divergent-reconvergent processing”

From Graybiel et al., The basal ganglia and adaptive motor control, Science, 265: 1826, 1994