This paper reflects the research and thoughts of a student at the time the paper was written for a course at Bryn Mawr College. Like other materials on Serendip, it is not intended to be "authoritative" but rather to help others further develop their own explorations. Web links were active as of the time the paper was posted but are not updated.
Biology 202, Spring 2005
First Web Papers
A person's need to communicate and form close and complex relationships with other people is one of the most well studied of all the human behaviors. Its applications can be seen in almost all the major fields of social science, sometimes being the sole focus of a specific subfield (i.e. social psychology). Although these fields often deal with the effects and benefits that communication with others can have on an individual, when it comes to the natural sciences, biologists are only interested in its most observable manifestation, language. One of the most recent trends of thought in neurobiology is the idea that all of human behavior, thought, and emotion originate from the lump of matter that sits atop our body, the brain. When applied to the study of language, this assertion requires that two conditions are met: 1) that there must be an anatomical area of the brain that is responsible for language in humans and 2) that this area of the brain must be different for people who speak different languages.
For determining the validity of the first condition, it was often more valuable to use a backwards technique of discovery. For example, researchers would examine cases in which there was a loss or inability to communicate through language and find out what cause the problem rather than performing experiments on patients without language impairments. It is assumed that the area of the brain that was damaged was responsible for the ability that the patient lacked. Now let us pick apart the processes involved with communication through language, starting with the comprehension of spoken language.
The first step in this process is the physical recognition of the sound waves produced by produced by another's speech. This is a very detailed and complex process whose specifics are not entirely relevant to the comprehension of language. However, it is important to keep in some of the details, such as the fact that the sensory information received by the organs of our inner ear through sound waves is processed on the sensory cortex in the temporal lobe (1). Knowing this, it makes sense that the portion of the brain responsible for the comprehension of spoken language be located in the temporal lobe of the brain. This area, named Wernicke's area after the neurologist that discovered it, was first identified in a patient who suffered from what is now referred to as Wernicke's Aphasia (2). This is a condition often associated with a brain lesion in Wernicke's area in which the patient, although he is able to speak, is unable to understand the speech of others. In fact when the patient does speak, it is with meaningless, unrelated sentences whose words often do not relate to one another. Surprisingly, however, they tend to have little trouble with the grammar of their sentences (2).
Once speech is comprehended and interpreted, one then gathers their thoughts in an attempt to produce a response in the form of spoken language. Just as with Wernicke's area, the location Broca's area, the region of the brain responsible for the act of speaking, is determined by its function. It is located near the area of the motor cortex responsible for the muscles in our face because the production of speech would not be possible without the physical movement of our tong and mouth (1). Paul Broca, for whom the region is named after, made his discovery after performing an autopsy on one of his patients who had suffered severe brain damage to it. "Tan", the name given to the patient because that was the only word he could say, had no trouble understanding someone speak but could not do it himself. In some cases of Broca's Aphasia, the patient may be able to produce slurred speech; however, it is usually expressed in very poor grammar (i.e. it will be missing the –ed ending to words in the past tense) (2).
Now that we have covered the basics of spoken language, we can turn our attention to understanding and construction of written language. Once again, the idea of anatomic specificity is maintained with the angular gyrus, the brain region responsible for written language, being located in the brain's occipital lobe near the visual cortex (2). This is expected because one's ability to read and write is directly related with their visual perception. Recently, problems with the angular gyrus have been linked to conditions that result in poor reading or writing activities. More specifically, it is thought that low activity levels in this region in the brains of people with dyslexia (difficulty with reading) and agraphia (inability to write) has caused them to use other, less efficient areas of the brain to perform these tasks (3).
We now turn our attention to the second condition. There has been some support for the idea that people with different behavior related to language also have differences in brain structure and the way that they process and produce language. For example, recent findings have found that bilingual children who are bilingual have a larger amount of grey matter in the brain areas responsible for language when compared to people who only speak one language (4). There also seems to be a specific pattern of lateralization of these language centers between right and left handed people (they are located on the left hemisphere for right handed people and vise-versa for left handed people) (2). This pattern of specialization between the two hemispheres as far as language is concerned seems to deteriorate as people get older and they begin using both sides more equally.
This evidence, however, does not account for differences in brain anatomy and function in the language areas of two people who speak different languages. In fact, it has been shown that there is little or no difference between the two. Although this fact would seem to contradict our initial contention that all behavior results from processes in the nervous system, one must consider an important fact about all languages that was discovered by Noam Chomsky. Chomsky's nativist theory of language states that all languages have a universal grammar, syntax, and follow a general organizational patter. Furthermore, Chomsky believes that these laws of language are "hard-wired" into our brains from birth as language acquisition devices (LAD) (5). The fact that all languages are understood, spoken, and written using the same basic rules explains why the brains of two people who speak different languages would not appear different. There is no need for a specialized brain region for each language if they are all, at their root, the same. An important correlation to the nativist theory proposed by Eric Lenneberg is the idea that there is a critical period for the learning of language. If a language (it does not matter which one) is not learned before this period and the proper neural connections are not formed, it then becomes impossible for the individual to ever learn a language (5).
After having resolved this issue, we can confidant that our original assertion, that the behaviors associated with language are a product of our brain and its neural connections, is a step in the right direction in understanding the role of the nervous system in relation to human behavior. We were able to identify the specific areas of the brain that were responsible for language and were able to show that differences in behavior in relation to languages caused (or were caused by) differences in brain anatomy and processing. And in the cases that these behavioral differences did not correspond to anatomical differences, we were able to explain why.
1)sparknotes neurobiology webpage,
2)website created by Dr. C. George Boeree,
3)the Society for Neuroscience webpage about dyslexia,
4)article posted on the UCSF website,
5)the Wikipedia site about language acquisition and Noam Chomsky,
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