Basal Ganglia




Connections of Basal Ganglia (Direct & Indirect Pathways)

NIGROSTRIATAL PATHWAY
Modulation of Direct and Indirect pathways by Nigrostrial Pathway

CONNECTIONS OF BASAL GANGLIA
NEURAL CONNECTIONS OF BASAL GANGLIA

FUNCTIONS OF BASAL GANGLIA

PLANNING & PROGRAMMING –> Discharge starts even before commencement of movement.

EXECUTION OF MOTOR TIMING, INTENSITY & SEQUENCES –> Basal Ganglia gets input from cortex projects back to cortex (Prefrontal, premotor, Supplementary motor area). These Corticospinal & Corticobulbar neurons influence Proximal & Distal limb.

MUSCLE TONE –> Inhibits tone, decreases stretch reflex (BG LESION – HYPERTONIA).

COGNITIVE FUNCTION –> Connects to Prefrontal & Orbitofrontal Cortex.

SPEECH –> Lesion in Lt head of Caudate Nucleus – causes DYSARTHRIA

In lower animals, higher centre for MOTOR ACTIVITY.

DISEASES OF BASAL GANGLIA

Basal Ganglia disorder

PARKINSONISM / PARKINSON’S DISEASE/PARALYSIS AGITANS/ SHAKING PALSY

Named after James Parkinson (English Physician) -1817.

Has both HYPOKINETIC & HYPERKINETIC features.

Loss of PARS COMPACTA neurons of Substantia Niagra that leads to loss of DOPAMINE in NIGROSTRIATAL Pathway.

Imbalance between Excitation & Inhibition

FEATURES OF PARKINSONISM

TREATMENT

  1. LEVODOPA/L-DOPA –>Dopamine cannot enter Blood Brain Barrier but L-Dopa can cross. So, L-Dopa is given as replacement of Dopamine.
  2. BROMOCRIPTINE –> Synthetic Dopamine Agonist. Can cross BBB.
  3. ANTICHOLINERGIC – BENZHEXOL — >Inhibits Cholinergic System.
  4. LEVODOPA + CARBIDOPA –>Carbidopa inhibits conversion of L-Dopa to Dopamine outside BBB, minimizes side effects and prolongs the action of L-Dopa.
  5. L-DEPRYNYL –>Slows the progression of disease. Inhibits MAO, prolongs Dopamine action.
  6. Surgical treatment –>
    • Implantation of dopamine secreting tissue (adrenal medulla, foetal striatal tissue)
    • Surgical lesion  :
      • VA, VL Nuclei
      • Globus Pallidus
      • Use of pacemaker

Difference between Cerebellum and Basal Ganglia

BASAL GANGLIACEREBELLUM
No input from spinal cordDirect input from spinal cord
Input from all areas of cerebral cortexInput only from Motor areas.
Output is more widespread, reaches prefrontal & all premotor areas.Restricted to premotor & primary motor cortex.
Few connections with brainstem.Has rich connections with brainstem.
LESIONS               LESIONS
Usually causes HYPERTONIA (Rigidity)Causes HYPOTONIA
Tremors at rest. Disappears with activity. Intentional tremor. Disappears with rest & reappears with exercise/movt.
Lesion affects opposite sideAffects same side
Difference between Cerebellum and Basal Ganglia

All change is not growth, as all movement is not forward.’

Ellen Glasgow

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