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
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
TREATMENT
- LEVODOPA/L-DOPA –>Dopamine cannot enter Blood Brain Barrier but L-Dopa can cross. So, L-Dopa is given as replacement of Dopamine.
- BROMOCRIPTINE –> Synthetic Dopamine Agonist. Can cross BBB.
- ANTICHOLINERGIC – BENZHEXOL — >Inhibits Cholinergic System.
- LEVODOPA + CARBIDOPA –>Carbidopa inhibits conversion of L-Dopa to Dopamine outside BBB, minimizes side effects and prolongs the action of L-Dopa.
- L-DEPRYNYL –>Slows the progression of disease. Inhibits MAO, prolongs Dopamine action.
- 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 GANGLIA | CEREBELLUM |
| No input from spinal cord | Direct input from spinal cord |
| Input from all areas of cerebral cortex | Input 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 side | Affects same side |
‘All change is not growth, as all movement is not forward.’
Concept Maps 