Parkinson's Disease Analysis

Parkinson’s disease (PD) is the second most common neurodegenerative disease in the country. It is characterized by tremor, rigidity, bradykinesia, and impaired muscular coordination (Wei et al., 2014). It affects approximately 50 out of every 100,000 people over the age of fifty. PD can occur sporadically, but affects one third of people who have two or more first-degree relatives with the disease (Duffy, 2005, p. 190). Several systems are affected in the population of those with Parkinson’s disease. These systems include cognition, phonation, articulation, language, and respiration. When cognition is affected, it is difficult for people with PD to think quickly, follow internal cues, or understand complex sentences (Friederici et al., 1999).

The basal ganglia (BG) are responsible for a variety of functions, specifically providing adequate voluntary motor activity. They are an organized network, where different parts are activated for specific functions and circumstances. The motor circuit of the basal ganglia is the focus in this disease because PD is mainly thought to be a movement disorder (Obeso et al., 2008). Therefore, the level of the brain within the Central Nervous System that underlies the disorder is the cerebral cortex, and some subcortical structures. The cerebral cortex is the outer layer of the brain that is essential for higher mental and behavioral functioning. Underneath the cerebral cortex is where axons connect to and from the cortex and where interconnected clusters of cell bodies, like the basal ganglia, are located (Stirling, 2000, p. 61). The basal ganglia receive input from cortical areas, and transmit that input to the motor cortex through the thalamus, in order to permit movement. The substantia nigra is interconnected with the nuclei of the basal ganglia. Some connections are excitatory and some are inhibitory. The pars compacta part of the substantia nigra is where dopamine is produced. When there is a depletion, or low levels of the neurotransmitter dopamine in the substantia nigra, the balance of the output from the basal ganglia to the motor cortex is altered (Byrne

Due to these imbalances, pathophysiological changes in the basal ganglia thalamo-cortical loops are said to trigger key symptoms of Parkinson’s disease (Timmermann & Fink, 2011). When there is a loss of dopaminergic neurons, the ultimate result is the lack of movement. This is because the balance between direct pathway excitation of the cortex and indirect pathway inhibition of the cortex is leaned in favor of the indirect pathway, with a consequent inhibition of motor cortex areas. Ultimately, the reason for the poverty of movement seen in Parkinson’s becomes clear because normally the nigrostriatal pathway would excite the direct pathway and inhibit the indirect pathway. However, the loss of this input causes and imbalance with favor to activity in the indirect pathway. Therefore, the internal segment globus pallidus neurons are abnormally active, inhibiting the thalamic neurons. The lack of thalamic input causes the motor cortex neurons to be reduced in excitement, and the motor system is not able to execute the motor activity in response to a person’s desire to conduct movement (Byrne & Dafny, n.d; Heneka et al.,