Linking Brain and Behavior: Reflections on Neurodegenerative Diseases and Fetal Neural Transplantat

Linking Brain and Behavior: Reflections on Neurodegenerative Diseases and Fetal Neural Transplantation

Neurodegenerative diseases are caused by malfunctions within the motor sector of the nervous system. These malfunctions, which are caused by the presence or absence of hormones, are a direct result of neural cell deterioration within the brain. Thus, biological problems of the brain, or rather predicaments arising between cellular connections within the brain, and the treatment of such conditions, illustrate how the brain organizes movement and behavior (11).

The brain is the body's communication headquarters. It obtains a myriad of information from various parts of the sensory system and processes this information in an organized fashion. It then relays sensory input to different parts of the motor system. Such messages from the brain dictate specific muscular and behavioral patterns. Thus, this neural system is highly depended on a cause and effect system, where the slightest offset to the assembly-line fashion of cellular interaction results in major behavioral abnormalities(11). Moreover, there are two particular areas of the brain that are specifically related to motor malfunctions: the substania nigra and the striatum (the caudate nucleus and the putamen). The cells of the nigra synapse with cells of the striatum, which serves as the controller of motor functions such as walking, balance, and muscular movement. Information from the nigra cells passes through the synapses with the aid of a specific hormone, dopamine, which is a significant chemical transmitter in the brain. Because the existence of dopamine is essential to the function of the substania nigra, it is also essential for the various muscular activities controlled by the striatum, such as walking, balance, etc (9).

Neurodegenerative diseases, like Parkinson's Disease and Huntington's disease, thus, illustrate two very different behavioral patterns that are subsequently caused by two opposite and extreme biological abnormalities, where the nigra-striatum neural communication assemblage is hampered. Parkinson's disease (PD) results from a depletion in the amount of dopamine produced by the brain. At the onset of the disease, dopamine-secreting cells of the substania nigra, either because of genetic factors or environmental toxins, experience mass cell death. Thus, the nigra cells are unable to form synapses through which they secrete and relay dopamine to the striatum in a neural circuit within the basal ganglia (11). The striatum is also a coordination center for chemical messengers. When there is a decrease in dopamine levels, the striatum experiences a chemical imbalance (2).