AD (728x60)

Monday, 1 October 2012

Brain and Language

Share & Comment

BRAIN AS A LANGUAGE ORGAN


            That language is manifested in spoken and written forms through the works of speech organs and fingers —and in the case of sign language, through gesture— has caused a common assumption that the biological basis of language lies in the throat, the ear and the fingers.  However there are some people who have vocal cords working properly and good manual dexterity, yet they do not have the abilities to comprehend and produce language in a coherent and grammatical manner due to brain damage or a genetic issue.  Although language can be represented by sounds and alphabets circulating out there, “language exists in the brain.” (Laka et al. of Basque Research Team, 2008).  The biological basis for language processing is the brain.    
Human cerebrum, consisting of a subcortex and a cortex (the outer layer), is divided into left and right hemispheres. The functional characteristics of brain as a language organ lie in the cortex and the two hemispheres.  The center of human speech and language processing has been localized in the cortex (Plontke, 2003: 2).  In most adults, lateralization of language skills takes place in the perisylvian area of the left hemispheric cortex. Only the human species uses cortex for communication. The signals of animal systems of communication seem to be controlled by the subcortex, the area which in humans controls similar inborn response signals such as laughter, crying and involuntary emotive reflex called Tourette’s syndrome, for example the utterance “uhmm”.  Other parts used in language processing are parts of the temporal lobe, which is nearby the left hemisphere, for storing and retrieving meanings; the parietal lobe for mediating speech and motor representation; and the angular gyrus for integrating different sources for example understanding lexical phrases and idioms (Li in Landau, 2009).
This paper focuses on one part of the brain that plays a dominant role in language production and comprehensionthe left hemisphere of the cerebral cortexparticularly Broca’s area and Wernicke’s area.  It also discusses some evidence for the left hemisphere being the dominant language processor, and explains about the structural and functional features of Broca’s and Wernicke’s areas, how the two areas work in unison and cognitive loss of language (also known as aphasia, or dysphasia in British English) resulting from damages to these areas.
One of the reasons why language process happens in the left hemisphere is that language is a linear process. According to Vajda, sounds and words are uttered one after another in a definite progression, not in multiple directions simultaneously. Even among natural left-handers whose right brain is more dominant (in about 12.5 % of any human population), language skills are localized in the cortex of the left hemisphere. In cases where damage to the left hemisphere happens in childhood, language may be prevented from localizing there. It is still unidentified why, in about one in fifty healthy adults, language localizes in the right hemisphere of the brain. However, there is immense physical evidence showing the left hemisphere as the language center in adults, some of which are as follows.
1.      70% of adult patients with damage to the left hemisphere will experience at least some cognitive language loss in a variety of ways, while only 1% of adults with damage to the right hemisphere experience any permanent language loss.
2.      The language centers in the left hemisphere of humans actually make the left hemisphere bulge out slightly in comparison to the same areas of the right hemisphere. The same evidence was found in Homo neanderthalus and Homo erectus skulls, thus neurolinguist have called humans the lopsided ape
3.      If sodium amytal is injected into the left carotid artery, which services blood to the left hemisphere, language skills are temporarily disrupted (Wada, 1949).  If the entire left hemisphere is put to sleep, a person can think but cannot talk.
4.       If an electrical charge is sent to certain areas of the left hemisphere, the patient has difficulty talking or involuntarily utters a vowel-like cry.  An electrical charges to the right hemisphere produces no such effect (Pinker in Smallwood, 2010).
The studies of which specific areas of the left hemisphere are involved in the production and processing of particular aspects of language result from the study of aphasics (i.e. people who suffer from aphasia (Harley, 2001: 96).  There are two basic types of language loss, each of which is associated with damage to either Broca’s area or Wernicke’s area in the perisylvian area in the left hemispheric cortex.
Broca's area is in the frontal portion of the left perisylvian hemisphere which seem to be involved in grammatical processing, speech articulation and producing sounds. Damage to this area is called Broca’s aphasia, causing the patient difficulty in oral production.  Broca's aphasics can comprehend verbal messages but face great difficulty speaking in a grammatical way.  They tend to utter only isolated content words; this is a sign that they lose morphological and syntactic connectedness.  Grammar is destroyed; the lexicon more or less preserved intact. For these two reasons, this type of language loss is also known as emissive, agrammatical aphasia.
Wernicke's area in the lower posterior part of the perisylvian region controls comprehension of words, the selection of content words and semantics.  They can produce long, grammatically well-formed, even syntactically complex spoken utterances, but the content does not seem to respond specifically to their interlocutor.  Wernicke's aphasics also experience difficulty in comprehension or extracting meaning from a context. They speak incessantly, giving little chance to others to speak, and tend to use jibberish words such as “whatchamacallit" instead of true content words.  Because they have low level of auditory comprehension and speak in a way that other people find hard to understand, their affliction is also known as jargon, receptive aphasia.
When a normal person speaks, his mind uses both Broca’s and Wernicke’s areas simultaneously. His neurons of Wernicke's area select sounds, words or lexical chunks while his neurons of Broca's area combine these units according to the abstract, functional rules of morphology, syntax and phonology—to produce utterances. Broca's and Wernicke's areas are actually connected by a neural band of tissue hidden in the brain, called perisylvian area. It is still contested among neurolinguists, however, whether this perisylvian area is the exact location of language organ in humans. It seems to be the spot in a normal brain where language skills in most adult are localized as the brain matures.
An exception to this theory applies to some adults whose language skills seem to be localized in slightly different areas of their brain. Broca's area does not always control grammar and Wernicke’s area does not always control semantics. This is why damages to Broca's area does not always cause the typical agrammatic aphasia; and damage to Wernicke's area does not always cause the typical jargon and babbling symptoms of Wernicke's aphasia.
To sum up, language is brain stuff.  Neurolinguists’ studies over decades have shown that in most normal adults, language processing happens in their left hemisphere of the brain, involving the works of neurons in Broca’s and Wernicke’s areas and a connecting neural tissue called perisylvian area.

References:

Basque Research (2008, June 30). How Does Language Exist In The Brain?. ScienceDaily. Retrieved from http://www.sciencedaily.com/releases/2008/06/080630093618.htm on April 20, 2012.
Harley, T. 2001. The Psychology of Language From Data to Theory: Second Edition. East Sussex: Psychology Press, Ltd.
Landau, E. 2010. From brain to language to accent. Retrieved from http://thechart.blogs.cnn.com/2010/09/23/from-brain-to-language-to-accent/  on April 20, 2012.
Plontke, R. (2003). Brain and language. Chemnitz University of Technology. Term paper, p.2.
Smallwood, F. 2010. Language and the brain. Retrieved from http://musingsofscience.wordpress.com/2010/04/26/language-and-the-brain/ on April 15, 2012.
Vajda, E. Brain and Language. Retrieved from http://pandora.cii.wwu.edu/vajda/ling201/test4materials/language_and_the_brain.htm  on April 21st, 2012.
Wada, J. (1949). A new method for the determination of the side of cerebral speech dominance. A preliminary report of the intra-carotid injection of sodium amytal in man. Igaku Seibutsugaki, 4, 221-222.


Tags:

About the author

Hening is a laid-back ENTP (by upbringing) and a solar-Scorpio-and-lunar-Sagittarius (by birth). She believes that thrifting is an art form that helps rewire our brain circuits for the better.

 

CLIENTS (2001-2019)

SMS/Text only: +1 (646)2 333 400

Copyright © Hening Dian Paramita as TRAVELINGUIST. | Templateism