Parkinson’s Disease- FLASHBACK
These are slices through the midbrain (like a bread slice). The black “lines” that you see are the substantia nigra (now I think you can tell why it’s called ‘black substance’). The slice on the left is from a patient with Parkinson’s Disease. The slice on the right is from a “normal” brain. As you can see, Parkinson’s involves severe degradation of the neurons in the substantia nigra, resulting in the loss of dopamine to the brain.
From the last post, you know that dopamine promotes movement in both the direct and indirect pathways of the basal ganglia circuitry. This means that when neurons of the substantia nigra die, that excitatory input is lost and so the basal ganglia indirect pathway is overactive and the direct pathway is underactive. This is why Parkinson’s patients experience difficulty moving that progresses as the disease progresses and more of the dopaminergic neurons die.