A. Neurolinguistics and Language Loss
a. The evidence from aphasia
Neurolinguistics, an offspring of psycholinguistics, investigates how the human brain creates and processes speech and language. Human brains have two separate and virtually identical cerebral hemispheres. Anatomically, there are millions of association pathways which connect the left and right hemispheres together so that in normal brains any information in either hemisphere is immediately shared with the other. The brain controls human speech and language without resorting an anatomy text or arranging to view a craniotomy. The location of the control of speech organs and the sensation of speech sounds is in the top part of the brain which controls the lower extremity of the body and vice versa. In an equally counterintuitive manner, the left side of the brain is responsible for the right side of the body and vice versa. It follows that the tops of the motor and sensory cortices take care of the movement and sensation of your feet, and the bottom parts of these two strips are responsible for your head. Language is represented for most people in the left hemisphere, the area of the brain which is crucial for the production and comprehension of human language. A neurologist, Paul Broca, a French physician, named these two locations, motor and sensory, as Broca’s area, who also helped coin the term aphasia, the loss of speech or language due to brain damage. Just behind this area, at the lower portion of the sensory cortex, is Wernicke’s area, named after Broca’s Austrian contemporary, Karl Wernicke.
There are many different types of aphasia, but the classic types are Broca’s aphasia and Wernicke’s aphasia. Broca’s aphasia is characterized by speech and writing which is slow, very hesitant, and in severe cases, completely inhibited. Whereas Wernicke’s aphasia is characterized by speech production and writing are pretty much intact, but because the sensory cortex is damaged, patients experience a great deal of trouble processing linguistic input. In both types and for most cases, aphasia occurs only if either of these two areas are damaged in the left hemisphere of the brain.
b. The surgical evidence
There are two kinds of surgical operation which have a particular bearing on questions of language dissolution. One of these procedures is hemispherectomy. This procedure used to be performed even on adults, but now it is fairly much restricted to children under the age of ten. There is dramatic difference between the effects of this operation on adults and young children when it comes to speech. When an adult undergoes a left hemispherectomy, he or she becomes completely aphasic. Conversely hemispherectomies performed on young children, quite amazingly, do not lead to loss of speech. The effects of neurological damage on linguistic performance are not strictly predictable from anatomical change. In this case, for example, age is a critical factor. The second surgical procedure which also has neurolinguistic relevance is the split-brain operation which was developed in the 1970s to help treat specific and rare cases of severe epilepsy. There are certain severe and singular forms of epilepsy which remain unaffected by pharmacological treatment, and split-brain surgery was developed to spare sufferers from the terrible trauma of major seizures.
Research into aphasia, and studies of hemispherectomy and split-brain patients, has given rise to two superficially contradictory claims about the manner in which the brain processes language. On the one hand, there is irrefutable evidence that for the vast majority of adults, the production and comprehension of speech is located in two closely situated but clearly distinct areas of the left hemisphere, Broca’s and Wernicke’s, and this localization of function is not fully completed until about ten years old. On the other hand, in contrast to these claims about the neurolinguistic primacy of the left hemisphere, research in all areas of language dissolution shows that human linguistic ability does not solely reside in these two relatively small areas on one side of the brain.
B. Speech and Language Disorder
a. Dissolution from non-damaged brain
Language dissolution is the result of operations on the brain. Individual language can deviate significantly from social norms, e.g., stuttering and autism. Stuttering (refers to stammering) is one of the most common articulation problems encountered by speech pathologists. Stuttering is not random: it does not punctuate our speaking spasmodically, like a hiccough. It occurs most frequently on the initial word of a clause; the first syllable of a word, the initial consonant of a syllable, and on stop consonants (like /p/, /t/, /k/). Johnson theory represents the extreme behavioral view and claims that stuttering originates from traumatic events occurring in early childhood when overly sensitive parents (who often themselves were childhood stutterers) and/or primary school teachers are to assiduous in attempting to ensure that the child speaks fluently. The same parent or teacher who criticizes a four-year-old for blurting out ‘P-p-p-please!’ is unlikely to comment on the child’s less than perfectly coordinated way of walking.
Another theory, the Orton/Travis theory, states that stammering is caused by the absence of unambiguous lateralization of speech to the left hemisphere. Neurologically explanation, this latter group of exceptional children often becomes stutters, largely because the brain lacks a fully established primary language center and is therefore indecisive about how to initiate speech. For many language disorders, the disability is not just in the mouth of the speaker but it is also framed by the ears of the listeners. Another disability that is fairly well-recognized though, fortunately, much less common, is autism. Its cause has long been disputed by opposing camps, who have argued for either behavioral or neurological origins, with the letter receiving the most recent support. An autistic infant exhibits a bizarre disregard for human interaction and, in contrast to a normal child, ignores eye and face contact. The autistic infant quickly lags behind in achieving the natural milestones of speech production and within a year or two, the significance of the disease becomes conspicuous. Autism is often referred to as childhood schizophrenia.
b. Language loss arising from inherited disorders
The genes which carry the human heritage of speech are countermanded by an inherited defect that is transported by the same genetic code. Down’s syndrome, a disorder that occurs about once in every 600 births and, along with marked anatomical abnormalities, leaves the child moderately to severely impaired in all cognitive functions. The enlargement of the tongue in Down’s syndrome creates poor articulation, and though comprehension is not significantly affected, expressive speech is hesitant and limited, in a manner reminiscent of Broca’s aphasia.
c. Language loss through aging
Though the humor expressed might diminish proportionally with the age of the recipient, it is true that a reduction physical and mental abilities often does accompany the aging process. Various afflictions, neurological, environment, or hereditary, mean that humans sometimes have the gift of language taken away from them prematurely naturally. The most conspicuous faculty eroded by the aging process is memory, and since language represents a major component of Long Term Memory (LTM). Since access to LTM is capacity limited, it is more logical to assume that the more you have to remember, the easier it is to forget. LTM improved slightly, but after the fifth decade, subject typically forgot one item for every successive decade of life. The memory constraints that may become evident as we get older seem to be due primarily to Short Term Memory (STM) constraints, or limitations on inputting and accessing the material to be recalled. We cannot measure aging directly by chronological years; geriatrics has long taught us that age is more directly a manifestation of health than of the calendar.
Alzheimer’s disease : Appear to involve both hereditary and environmental factors, the brain of an AD patient deteriorates prematurely, and this loss has profound and ultimately injurious effects on every aspects of AD has just begun, but the research which has been undertaken shows that speech and language are not affected in isolation. Linguistic function gradually disintegrates together with those of emotion, cognition and personality. Who wrote more complex composition (i.e. whso used more subordination in their sentences) seemed to have a much better chance of not succumbing to AD compared to those who used simpler sentences structures. Again, the evidence suggests that language is no different from other aspects of human behavior, the more complex the endeavor.