Answer to Question 1
Patients with Parkinson's disease show low dopamine levels, which leads to the typical trembling and movement problems associated with Parkinson's. When patients receive medication that increases their dopamine level, they (as well as healthy people who receive dopamine) sometimes show an increase in pathological gambling. Gambling is a compulsive disorder that results from impaired impulse control. When dopamine treatment is suspended, these patients no longer exhibit this behavior. This can occur because of the complexities of neurotransmitter symptoms. Neurotransmitters may affect many different brain systems and thus affect a range of behaviors and experiences.
Answer to Question 2
Gazzaniga does not believe that the two hemispheres function completely independently but rather that they serve complementary roles. For instance, there is no language processing in the right hemisphere (except in rare cases of early brain damage to the left hemisphere). Rather, only visuospatial processing occurs in the right hemisphere. Gazzaniga has argued that the brain, and especially the right hemisphere of the brain, is organized into relatively independent functioning units that work in parallel. According to Gazzaniga, each of the many discrete units of the mind operates relatively independently of the others. These operations are often outside of conscious awareness. Although these various independent and often subconscious operations are taking place, the left hemisphere tries to assign interpretations to these operations.