The Basal Ganglia

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Functional aspects of cerebellum | Main Anatomy Index | The limbic system

Last updated 30 March 2006

Basal Ganglia

Vu, D. (1998) Basal ganglia [Lecture handouts]. University of NSW. 21 September, 1998.

  1. The caudate nucleus;
  2. The putamen,
  3. The globus pallidus,
  4. The subthalamic nucleus,
  5. And substantia nigra.

Putamen + Globus Pallidus = Lenticular (or lentiform) Nucleus

Caudate Nucleus + Lenticular Nuclei = Corpus Striatum

Caudate Nucleus + Putamen = Neostriatum or Striatum

 

Topography of the Basal Ganglia

Lenticular Nucleus

 

Putamen

 

Globus Pallidus

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Caudate Nucleus

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Connections of the Basal Ganglia

Multiple cortical areas --> corpus striatum --> thalamus --> one of the cortical areas

  1. GPL --> Subthalamic nuclei --> GPM
  2. Striatum --> Substantia nigra --> Striatum
  3. Striatum --> Pallidum --> CM of thalamus --> Striatum

 

Striatum

  1. The cerebral cortex;
  2. The intralaminar nuclei of the thalamus (centromedian, which receives input from the motor cortex);
  3. And the substantia nigra.

 

Cortical Afferent Fibres

Motor and somatosensory cortex --> Putamen

Association areas --> Caudate Nucleus (esp. prefrontal cx --> head of caudate)

Nigral Afferent Fibres

 

Thalamic Afferent Fibres

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Globus Pallidus

Afferents to the Globus Pallidus

 

Efferents to the Globus Pallidus

  1. Fibres related to movement control --> VL/VA
  2. Related to the caudate nucleus and prefrontal cortex --> DM and part of VA
  3. The others --> CM and parafascicular nuclei.
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Subthalamic Nucleus

  1. Interconnections with the globus pallidus;
  2. And some efferent projections to the substantia nigra.

 

Substantia Nigra

  1. A dorsal compact part, containing closely packed, pigmented neurons;
  2. And a reticular part, nearer the cerebral peduncle containing more loosely packed neurons, which are non-pigmented.

 

Reticular Part of the Substantia Nigra

 

Compact Part of the Substantia Nigra

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The Direct Pathway (GABA-Substance P)

Inhibitory to GPM & Substantia nigra --> less inhibition to Thalamus --> movements are facilitated by exciting Premotor and Supplementary motor areas which then project to the Motor cortex

 

Indirect Pathway (GABA-enkephalin)

Inhibitory to GPL --> less inhibition of Subthalamic nucleus --> more excitation of GPM --> more inhibition of Thalamus --> less excitation of Premotor and Supplementary motor areas --> movements are inhibited.

 

Dopaminergic Pathway

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Functional Aspects of the Basal Ganglia

Chorea

 

Sydenham's Chorea

 

Huntington's Disease

  1. Firstly, personality changes;
  2. Then choreiform movements which gradually become more pronounced;
  3. Which are followed by developing dementia.

 

Athetosis

 

Hemiballismus

 

Parkinsonism

  1. A resting tremor, characteristically involving the hands in a "pill-rolling" movement that diminishes during voluntary movement and increases during emotional stress;
  2. The rigidity is caused by increased tone in all muscles though strength is nearly normal and reflexes are not particularly affected;
  3. And difficulty in moving (bradykinesia, or slow movements and hypokinesia, or few movements) is shown by decreased blinking, expressionless face and absence of arm movements associated with walking.
  1. Be uniform throughout a range of movements imposed by the examiner (plastic or lead-pipe rigidity);
  2. Or be interrupted by a series of brief relaxations (cog-wheel rigidity).
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Michael Tam (c) 1998