Which part of the brain degenerates in Parkinson's disease?

In Parkinson's disease, the primary area of the brain that experiences degeneration is the substantia nigra. This structure is part of the basal ganglia and has a crucial role in movement control. The degenerative changes in the substantia nigra lead to a significant reduction in the levels of dopamine, a neurotransmitter that is essential for transmitting signals that coordinate smooth and controlled movements.

Dopamine deficiency due to the loss of neurons in the substantia nigra results in the hallmark symptoms of Parkinson's disease, such as tremors, rigidity, bradykinesia (slowness of movement), and postural instability. The other brain regions listed, while they may be involved or affected over the course of the disease, do not directly undergo the primary degeneration seen in Parkinson's disease. Thus, the substantia nigra is the key area associated with the pathology of this neurodegenerative disorder.