" Different parts of the brain are responsible for different functions. When they are attacked by neurodegenerative disorders such as Parkinson’s disease or Alzheimer’s disease, the way those different parts of the brain are attacked, at what time course and to what extent, will have an impact as to how you would look clinically. The well-known part of the brain that is susceptible to Parkinson’s pathology early in the disease is called the nigrostriatal pathway. That’s part of the basal ganglia and that’s why motor symptoms such as slowing, losing some coordination, dexterity, becoming stiff, losing balance and sometimes tremor are oftentimes the early motor manifestations of Parkinson’s disease and not so much dementia or cognitive impairment. But that doesn’t mean that higher order parts of the brain like the frontal lobe or the temporal lobe, which includes the hippocampus and other networks, are immune to Parkinson’s. They are not involved early on. They are relatively resistant to the underlying pathological process. They are only going to be involved later in the disease and not to the same extent as for instance in Alzheimer’s, where they are affected and attacked early on in the disease and to a greater extent. "