Final answer:
The basal ganglia, particularly the striatum, is the area of the brain primarily affected by Huntington's Disease (HD). This leads to its characteristic motor, cognitive, and psychiatric symptoms. As HD progresses, it also impacts the cerebral cortex.
Step-by-step explanation:
The area of the brain primarily affected by Huntington's Disease (HD) is the basal ganglia, specifically a part of it called the striatum. The basal ganglia are a group of nuclei in the brain which are associated with a variety of functions including control of voluntary motor movements, procedural learning, routine behaviors or habits, and emotion.
In the context of Huntington's Disease, the striatum, which is located in the subcortical region of the forebrain, experiences a loss of neurons. This leads to the various motor, cognitive, and psychiatric symptoms associated with HD. As the disease progresses, it also begins to affect other parts of the brain, including the cerebral cortex which plays a key role in memory, perception, and cognition.