Mar 28, 2019 in Medicine

Nervous System Research

This essay reviews the latest research on the construction of the nervous system and its role in shaping behavior. It examines the work of scientists in the recent years, considers the methods that were used in the experiments, and analyzes the conclusions and the alternative views of other researchers.

In the last decade, research of the nervous system began to develop much faster than in previous years. Of course, this is due to the significant achievements by the progress in the field of machinery and equipment, which allow penetrating into the depths of the human body, in particular, its nervous system. In this decade, the results of the demonstration of the “ventral language pathway” were investigated a lot of times (Nouet, Gatignol, & Duffau, 2007). According to them, the functions and multiple possibilities of the pathways as the most of the previous practice results have been expanded and replicated. Despite this, the very existence of paths causes the distrust of many scientists, and the controversies surrounding their origin do not subside for several centuries. 

A number of researchers have presented the series of works, dedicated to the functional and structural appointments of four tracts of ventral 'semantic' language network, which differ significantly from the classical understanding of their neuroanatomical origins. Some of the controversies, surrounding this topic in the past, have caused the confusion in the terminology and a lack of such definition as a "lingua franca". The neuroimaging methodologies, using MR tractography and diffusion tensor imaging (DTI), allow to study the nervous system more wider and deeper. A special interest in these works is to consider the brain as a system, which is capable for neutral functional integration, where the white matter tracts are able to exchange the information with the incredible speed overcoming the distant parts of the brain. In addition, these studies offer to reconsider the interrelation of the white matter connectivity and the neural network for the language.

  The advanced theories differ from the pathway “dorsalonly” of Geschwind model, which belongs to the classical concepts of the neurology and, at the moment, is the fundamental knowledge about the contemporary models of the language operation. Furthermore, the ventral route in the context of the correlating between the damaged tracts and the neurological dysfunction causes the increased interest of the entire community of scientists. Departing from the strict localization of anatomy, such a system resembles the Wernicke approach and the disconnection syndromes described by Geschwind. 

There exists a definite correlation between the neuropsychiatric conditions and the damage of the white matter tracts in the temporal lobe of the brain. For example, abnormal functioning of the inferior fronto-occipital (IFOF) and uncinate (UF) induces a state of schizophrenia (Fujino, Takahashi, Miyata, Sugihara, Kubota, Sasamoto, et al., 2014), and abnormal fractional anisotropy in the UF causes depression (Aghajani, Veer, Meens, van den Bulk, Rombouts et al., 2013). Another surprising discovery was the thinning of the temporopolar and the reduction between the white matter tracts, which previously were connected (such as ILF or UF). It was found in the patients with the semantic dementia not in the traditional areas of the brain for the dementia as previously assumed. Sometimes, the low semantics is related with the disruption of the UF and IFOF work after the stroke; at the same time, the AF connects with the impaired repetition. However, despite the submitted studies, such linking of the neuropsychiatric disorder with the functioning of the white matter is sufficient courageously, because the nervous system is a complex structure of a number of subsystems the anatomical representation of which will help to improve the diagnosis and prognosis of symptoms. In this regard, other scientists consider the structure of the four paths that are associated with the ventral language pathway and located in the temporal lobe of the brain. Such scientists as Bajada, Lambon, and Cloutman (2015) do not adhere to the consensus on the functional and structural qualities of each of the tracts; therefore, there are many controversies and debates over the accuracy of their starting and ending points. However, compared to the ventral semantic language network, the most biologists agree that these tracts occupy a central place. 

The modern studies have used the four basic methodologies that undoubtedly have their own advantages and disadvantages, but all together, they act very effectively. Among these methods, it is necessary to distinguish the diffusion MRI tractography which was mentioned earlier, the gross dissection, the tracer studies, and the polarized light imaging (PLI). However, scientists remind that none of the methods can fix completely accurate structure of the nervous system and the functioning of the white matter. 

Moreover, both the scientists who belong to the classical school and the modern one, agree that the ventral language pathway is located in the temporal lobe areas (Patterson & Hodges, 1994). That is why a number of studies are aimed at exploring the ways of the white matter underlying in the language function. The MR tractography and the methods mentioned above are able to show the location of the new ways, i.e. branches from the four most important pathways – IFOF, UF, ILF, and MdLF (Ebeling & Cramon, 1992). In spite of this, the specific description of their function is not developed to a satisfactory extent. The follow-up studies are needed to provide a detailed description of their work, and accordingly – the evolutionary development in favor of the further discoveries. 

In conclusion, this essay has touched the researches related to the correlation between the white matter and the frontal lobes of the human brain. It has explored the methods that were used during the experiments as well as the advantages and disadvantages of such studies. In addition, this work has examined the contradictions, which have arisen in the particular segments in the presented researches. 

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