Functional Differences in the Work of Brain Hemispheres - Essay Example

Discuss the differential roles of the left and the right hemispheres and individual differences in functional lateralization The difference in the anatomy of the brain leads the right and left hemisphere to perform different functions, and functional lateralisation forms the basis for the differences in the performance of individuals in specific circumstances. The brain is anatomically partitioned into two halves; the left and the right hemispheres. Certain functions are localized to one hemisphere while other functions are balanced between the two hemispheres. The differences in brain anatomy and function are related to lateralization with the assumption that the right and left hemispheres are more asymmetrically controlled in men than in woman. Therefore men are more lateralized and women are considered to utilize both the hemispheres to a larger extent while performing various tasks. It is claimed that certain skills like spatial and mathematical capability improves with lateralization while women enjoy advantage for verbal test because they use both the hemispheres equally (Lee 2005 p.138). Despite gender differences, lateralisation also involves individual differences due to the difference in the composition of the brain cells. Hemispheric specialization is a classic dichotomy that suggests that the right hemisphere concerns visuo-spatial abilities and the left hemisphere is associated with linguistic abilities. However, this does not mean that the distribution of hemispheric functions does not make the right hemisphere irrelevant to language or the left hemisphere ignorant of processing non-linguistic data. Novelty-routinisation continuum is an approach that explains hemispheric specialization of functions that argues the basic reasons for the lateralisation of cerebral responsibilities. The theory proposes that the left hemisphere is crucial for the processing of routinised cognitive decisions and pre-existing representations and the right hemisphere is crucial for the processing of new cognitive situations that has no pre-existing strategies or codes. The traditional assumption thus becomes an extraordinary case of this basic principle (Malloy & Duffy 2001 p.83) The novelty routinisation approach gives emphasis to individual differences with the theory that the cognitive novelty of one may be a familiar concept to another that can be explained through a dynamic approach instead of a static theory that details hemispheric specialization or laterlisation. Hemispheric specialization tends to vary with individuals at varying stages of skill development. The dominance of left hemisphere is not uniformly strong for all factors of language processing. The advantage of left hemisphere is evident while using consonants than while using vowels, for abstract words when compared to concrete words, for long words when compared to short words and for low frequency words when compared to high frequency words. The outcome of early hemidecortication proposes that the complete development of verbal skill does not require the left hemisphere. Early hemidecortication in the left hemisphere allows the subsequent progress of phonemic inequity between real words, and not between phonologs or pseudowords. The early hemidecoritcation in the left also allows the progress of propositional analysis though it is restricted to interference build on general logical constraints and lexical information as against to the explicit approval of syntax. The hemidecortication also allows the progress of a large auditory lexicon though only to a restricted categorical linkage between lexical items. Therefore, the right hemisphere has a vital role in the creation of the reference base of the code and the left hemisphere is specifically significant for the rule centred internal derivations contained in the code (Malloy & Duffy 2001 p.84). The left hemisphere specializes in language and is responsible for evaluating consonant sounds, examining grammatical categories, process rapidly varying acoustic events and classifies objects according to standard linguist based categories. Until recently, the right hemisphere was considered an inferior organ that lacks any special functions to its credit. It is now proved that the right hemisphere performs special roles and leads the mediation of a number of cognitive tasks. The task is defined as those that require processing, recognition, detection and memory of information and does not let the right hemisphere to linguistic analysis and detection (Molfese & Segalowitz 1988 p.209). Though the right hemisphere lacks the capability to support speech, it offers adequate substrata for limited factors of the linguistic process comprising the comprehension of spoken vocabulary. The right hemisphere has a crucial role in evaluating the prosodic that differs from the syntactic or semantic features of language. This proves the cognitive ability of the right hemisphere. There are several studies in neuropsychology that evaluates the cerebral specialization for the expression, experience and perception of emotional state. Research indicates that the right hemisphere performs a leading role in the intervention of negative emotions and the left hemisphere intervenes in processing positive emotions. However, there are other research that reverses this evidence and still other research reveals that right hemisphere intervenes in the processing of both negative and positive emotional states (Molfese & Segalowitz 1988 p.210) Individual differences in functional lateralization One of the major issues concerned with lateralization is individual differences. The differences are analysed on the basis of left handers and right handers and their organization of language. It was believed till the 1940’s that in left handers, the right hemisphere was dominant than the left hemisphere for speech organization. However, latest research shows that in majority of left handers, two third or more of the left hemisphere plays a dominant role for speech with a similarity in the right hemisphere role in right handers. Latest research also reveals that there are individual differences among homogenous groups like right handers. For example, normal right handed adults vary in their characteristic methods of hemisphere arousal with certain individuals exhibiting phasic right hemispheric arousal and others exhibiting left hemispheric arousal. In a specific research the individual differences are derived on the basis of crucial differences in the methods of performance in the observation of chimeric faces in an open viewing task. Other methods used to find differences include gaze deviation. It is usual for a person to move the eyes towards the right for questions related (Molfese & Segalowitz 1988 p.210) to verbal analysis (indicating greater arousal of the left hemisphere) and the eyes are moved towards the left for questions related to spatial relation analysis (greater arousal of the right hemisphere). Neuropsychologists have coined the term hemisphericity to refer to this kind of probable dimension of individual differences that arise from the depth of conception of the problem. The individual method of performance is related to variables like occupation or college major with a view that left hemisphericity is over represented among people with occupations or academic disciplines that are highly related to linguistic logical skills as in lawyers, and right hemisphericity is considered to be prominent among people whose work requires greater amount of spatial-artistic capabilities as in artists. The conclusion of the research is however inconclusive. Certain findings are consistent though the differences are meagre and are usually difficult to repeat. It is found that despite the cognitive style or line of work individuals in general cannot be defined in simple terms as right or left brained. Research indicates that lateral specialization is a developing process that increases with age from no or limited specialization during infancy to complete specialization during adolescence or adulthood. There is also contrasting evidence which indicates that cerebral hemispheres are functionally and structurally different for individuals even during early infancy and irrespective of the several neurobehavioral and neurological changes that occur over time, the amount of lateralization does not change (Molfese & Segalowitz 1988 p.211). Functional lateralisation extensively determines the type of material that can be recognized or memorized by each part of the cerebrum. This phenomenon is due to the form or code in which the stimulus is interpreted by the brain and the memory is decided by the method (p.29) through which it is developed and then transformed. Since the left and the right hemisphere process information differentially, the method through which information is developed is also likely to be lateralised. Therefore certain forms of information is developed or stored by the left versus the right cerebrum. For instance, it is perceived that the left hemisphere maintains the recall and encoding of verbal memories and the right cerebrum plays the leading role in the non verbal, visual spatial and emotional memory processing. In case the left temporal lob is destroyed it will result in the impairment of verbal memory processing because the right brain has no ready storage of this kind of information and the left brain undergoes a complex state for remembering and storing non-linguistic information. There is unilateral storage of memory traces in a normal brain rather than the storage of memory traces in both hemispheres. Further when a hemisphere learns and acquires experiences or stores information it is not necessary that this information are accessible to the other hemisphere because one hemisphere has no option to access the details stored in the other part. A hemisphere can obtain access to the information stored in the lateralised memories of the other hemisphere by activating the memory banks of the latter through corpus callosum (Joseph, 1990 p.30). Lateralisation of memory can affect the behavioural function in several ways because one hemisphere has the capacity to store and experience specific information in memory and later respond to specific situation based on those memories that may perplex or surprise the other brain. It may be concluded that it is not necessary that one hemisphere can always obtain access to the information stored in the other part of the brain (Joseph, 1990 p.31). Functional lateralization occurs when there are hemispheric differences between the two hemispheres in the structure of the brain even at cell level. Functional laterlisation has gained relevance with the research of Geschwind and Levitsky that revealed that the left hemisphere is composed of an enlarged area known as the planum temporale situated on the temporal lobe’s mesial surface. While locating this region in the sylvian fissure, one can view the enlarged superior factor of the temporal lobe. The region is specifically significant for language and is larger in the left hemisphere. The right hemisphere is composed of a smaller planum temporale with a double sized Heschl’s gyrus. The right and the left Heschl’s gyri play a crucial role as primary auditory sensory region and has similar roles in developing auditory stimuli. Individual differences are further attributed to the difference in the shape and size of the hemispheres and the varying inclinations of the size and slope of the sylvian fissure. Asymmetry of cerebral function is also supported by the anatomy of the brain. The difference in size of plannum temporale has a good relation for handedness when compared to differences in language (Andrewes 2002 p.274). It may be concluded that the left and the right hemisphere dominates in performing differing task and the individual differences due to lateralisation is attributed to the difference in the composition of the brain cells. Reference Andrewes, D.G. 2002 Neuropsychology: From Theory to Practice Philadelphia: Psychology Press, 2002 Joseph, R. 1990 Neuropsycholog, neuropsychiatry, and behavioral neurology New York: Springer, 1990 Lee, J.W. 2005 Psychology of gender identity New York: Nova Publishers Molfese, D.L. & Segalowitz, S.J. 1988 Brain lateralization in children: developmental implications New York: Guilford Press, 1988 Malloy, P. & Duffy, J.D. 2001 The frontal lobes and neuropsychiatric illness Virginia: American Psychiatric Pub Read More