Left vs Right Brain

Left vs right brain concepts are discussed as though they are obvious rudimentary concepts within psychology. However, left-right brain psychology is not an academic concept and grossly misrepresents how the brain works.

Left vs Right Brain

➡ The Two Hemispheres Are Not Even Connected

What left/right brain concepts are reaching for is what is called brain lateralization. This term means that a certain cognitive function is specific to one hemisphere of the brain; brain functions being lateralized to one region. The brain has two major hemispheres and a brain stem. The two sides are connected by a few fissures but most notably the corpus callosum. Some sources will claim that the hemispheres are completely independent and separated with no connections at all.  This is absurd as a simple image search for corpus callosum will show otherwise.

Each Hemisphere is Entirely Responsible for Certain Behaviors

The next argument would be to say that behaviors are specific to one hemisphere; that they are lateralized. There is a lot of evidence in the scientific community and a lot of it will admit that further research might reveal lateralization. I have yet to find an article that actually shows lateralization but does shoe predominance, which is the next venue for debate. However, let us look at some examples of what I mean:

“We have found marked anatomical asymmetries between tile upper surfaces of the human right and left temporal lobes. The planum temporale (the area behind Hesch’s gyrus) is larger on the left in 65 percent of brains; on the right it is larger in only 11 percent. The left planum is on the average one-third longer than the planum. This area makes up part of the temporal speech cortex, whose importance is well established on the basis of both anatomical findings in aphasic patients ans cortical stimulation at operation.”

+ Human Brain: Left-Right Asymmetries in Temporal Speech Region

– This article, trying to demonstrate speech lateralization, shows a predominance of the left temporal lobe. However, it is still evident that both hemispheres interact in order to facilitate the function.

“Reviews research on brain damage, psychiatric disorders, and normal emotion, which has shown the importance of the right hemisphere’s holistic and nonverbal conceptualization to emotion. Studies of hemispheric asymmetries in psychiatric patients have suggested the importance of specific and apparently lateralized arousal systems in the brain that support the differential cognitive capacities of the 2 cerebral hemispheres. The operation of these arousal systems seems to vary closely with the individual’s affective state. Research on emotional effects of unilateral lesions has suggested that the hemispheres may be specialized not just for the kind of emotion but for its valence, positive or negative. Research issues and methods in this area are still at an early stage of development, yet it seems clear that further research on the lateralization of emotion should reveal how emotional processes are at one level dependent on basic neurophysiological activation processes and at another level intrinsic to the differential forms of conceptualization of the 2 cerebral hemispheres. (3½ p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)”

+ Lateral brain function, emotion, and conceptualization.

– In this case, the study is looking at nonverbal perception of emotion. In this case, there is evidence that predominance is taken for certain emotions, but still interactive. Furthermore, the article suggests that further research ought to be invested in for lateralization, implying that there may be strong correlations, but not locality.

While these are the consistent results in scientific inquiry, there are some originating significant results that initially caused reason for thinking there is lateralization:

* Broca’s Area: This area of the brain, mostly in the left hemisphere, is responsible for speech production. However, it is now noted that this region shares a significant contributor in the right hemisphere. While it is predominantly in the left hemisphere, it still relies on communication with the right hemisphere.

* Wernicke’s Area: Dominantly responsible for understanding writing and language. This region is predominantly in the left hemisphere. However, it is now shown that this region is connected with other regions within the right hemisphere and different lobes of the brain (not just the temporal)

To further demonstrate this point, if a behavior is only relying on one hemisphere of the brain, then we ought to be able to separate the two hemispheres and have no interference in regular functions. However, split-brains often have significant behavioral changes, challenges, and debilitating effects. While split-brains can compensate for the loss and operate normally at times, it is definitely apparent that there are handicaps and distinguishing differences. Let’s look at some sources:

“Tested 4 commissurotomy patients (described in a previous study by J. Levy et al; see record 1973-11433-001) for ability to match tachistoscopically presented stimuli with pictures in free vision, according to either structural appearance or functional-conceptual category. Patients were given ambiguous, structural, or functional instructions on any given run of trials with simultaneous double stimulus input to the 2 cerebral hemispheres. With ambiguous instructions, appearance and function matches were performed by the right and left hemispheres, respectively. When instructions were specific, appearance instructions tended to elicit appearance matches and right-hemisphere control. When function instructions were given, left-hemisphere control and function matches tended to be elicited. In 3 of the 4 patients, however, there was a significant number of dissociations between controlling hemisphere and strategy of matching. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)”

+ Metacontrol of hemispheric function in human split-brain patients.

– This study is looking at how split-brains problem-solve ambiguous situations or how they respond when given instructions on how to solve ambiguous situations. For a significant amount of the time, there was significant amount of challenges to strategic problem-solving.

There are further sources, offline, suggesting that memory deficits are obvious in split-brains. This suggests that both hemispheres are required for accurate recollection and short-term memory tests. Furthermore, split-brains have grammatical and vocabulary challenges indicating a dependent relationship between the hemispheres for linguistic operations as a whole.

+ Tramo MJ, Baynes K, Fendrich R, Mangun GR, Phelps EA, Reuter- Lorenz PA, Gazzaniga MS (1995): Hemispheric specialization and interhemispheric integration: Insights from experiments with commissurotomy patients. In: Epilepsy and the Corpus Callosum 2. Reeves AG, Roberts DW, eds. New York: Plenum, pp. 263-295

+ Kandel E, Schwartz J, Jessel T. Principles of Neural Science. 4th ed. p1182. New York: McGraw–Hill; 2000. ISBN 0-8385-7701-6

Thus, it cannot be the case that a hemisphere is completely responsible for such gross behaviors. If this were the case, split-brains would not have such significant deficits. Furthermore, there is a plethora of evidence demonstrating predominance.

➡ Okay so left/brain predominance

In this case, we can say that there are predominant regions for behaviors. However, we cannot let that exaggerate to locality or lateralization. It is definitively evident that, while a behavior may be predominantly functioning in a region, it is still dependent on other regions for complete functionality. As an analogy, a guitar may make music predominantly from the pickups, but definitely not entirely. The entire guitar is responsible for producing its sound.

At length, it is easy to see how left/right brain concepts come to rise. We must appreciate how dynamic and complex the brain is instead of trying to grossly mis-represent and simplify it. The brain is far more complex than a simplistic chart of functions to a certain side. If anything, the lobes of the brain ought to be focused on for their specific functionality, not hemispheres.

What do you think…?

~

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