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  • From cerebral cortex (all parts )to striatum
  • From the centromedian nucleus of thalamus to striatum
    so the afferents to the basal ganglia end in the striatum



  1. Mainly from the internal segment of globus pallidus to the ventro lateral, ventroanterior and centromedian nuclei of thalamus
  2. From substantia nigra to the thalamus
  3. Inside connection

    (dopaminergic) this is the nigro striatal pathway . The neurotransmitter is dopamine


    ii. GABA ergic                 

    iii. Striatum globus pallidus (internal and external segment)




A: direct pathway – causes disinhibition of thalamus (and stimulation of cortex)

B: Indirect pathway -
causes inhibition of thalamus (and inhibition of cortex)

(dopamine (nigro striatal pathway ) stimulates A and inhibits B )

The appropriate balance between the direct and indirect pathway maintains a suitable excitatory tone within the cortical motor pathway. The additive effect of the nigro striatal pathway provides an excitatory bias to the basal ganglia loop (note that there is a closed – loop connection between the cerebral cortex and basal ganglia ) (Also note that in the basal ganglia, the circuits through the subthalamic nucleus is an important regulator of basal ganglia output that normally maintains movement in a smooth and appropriate state)

Functions of basal ganglia

1.  Planning and programming of movements


2.  Role in cognitive processes (especially that of the caudate nucleus)


3.  ON/OFF Controller of movement


4.  Helps in learning of Skilled movements


Lesion of Basal ganglia

  1. Hemiballismus à due to lesion in subthalamic nucleus
  2. Huntington’s disease/chorea:- Due to abnormal gene à many times repeating codon, CAG- “The abnormal movements are believed to be caused by loss of most of the cell bodies of GABA-secreting neurons in the caudate nucleus and putamen (=  Striatum)  and acetyl choline secreting neurons in many part of the brain”
  3. Parkinson’s disease (Paralysis agitans) Q\ - “results from widespread destruction of that portion of the substantia nigra Q, the pars compacta, that sends dopamine-secreting nerve fibers to the caudate nucleus and putamen (= striatum) - C/F — Cog-wheel or lead pipe rigidity, Involuntary tremor (3-6 cycles/sec) and Akinesia.
  4. Athetosis (Writhing movement) à due to lesion in the globus pallidus.

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