By Kamil Wiśniewski, Aug. 12th, 2007
Neurolinguistics is a branch of linguistics dealing mainly with the biological basis of the relationship of the human language and brain. Although the very name of this science was coined relatively recently, the issues investigated by it were analyzed already in the nineteenth century. The first attempts to account for the parts of brain responsible for the ability to produce speech were made on the basis of unfortunate accidents in which people suffered some damage to head and brain, thus enabling scientists to exclude the damaged brain parts from linguistic investigations if the injured remained capable of language production.
Since that time on the basis of posthumous analysis of brains of people with some language dysfunctions it has been determined that the left hemisphere of the brain plays a major role in language comprehension and production, and especially some of its areas that are more or less above the left ear. In the following picture of the left hemisphere of the human brain the grey areas indicate the parts of brain responsible for language recognition and production:
The part marked as (1) is known as Broca’s area or ‘anterior speech cortex’ and as it has been discovered it is responsible for speech production. Interestingly, damage made to the same spot on the right hemisphere of the brain does not cause any language-related problems, therefore only the part of the left hemisphere is connected with linguistic abilities.
Posterior speech cortex, or as it is usually described Wernicke’s area, in the picture marked (2) is responsible for speech comprehension. This fact has been stated after the examination of a group of subject who had enormous difficulties with the understanding of speech.
The largest part of the brain marked in the picture is the motor cortex (3) and it is responsible for the muscular movements. The part of motor cortex that is close to the Broca’s area is responsible for the articulatory muscles of jaw, face, as well as tongue and larynx. Part (4) in the picture shows arcuate fasciculus which is the bundle of nerve fibers connecting Wernicke’s and Broca’s areas.
When all the above mentioned parts were described it was proposed that brain activity connected with the perception and production of language would follow certain patterns. Thus, it is claimed that speech is perceived by the Wernicke’s area, then the signal is transferred through arcuate fasciculus to Broca’s area. Afterwards, the signal goes to the motor cortex to articulate the word.
However, such a sophisticated system sometimes fails us in everyday conversations when it is difficult to remember a well known word. In situations like that speakers often claim that they have the word at the tip of the tongue. Studies show that in fact speakers can often tell how many syllables the word has, or what sound it begins with, and in some tests they produce similar words which led neurolinguists to believe that the word-storage may be organized on the basis of phonological information.
There are some other similar phenomena analyzed by neurolinguists, such as the slip of the tongue for example. The slip of the tongue is an unconsciously made error in which the (usually) initial sounds of a few words are interchanged. One other type of mistakes often made in conversations is the slip of the ear which can be described as hearing a words as a different word which might not have been said. It is said that such mistakes are in fact slips of the brain which is trying to process and organize the linguistic information.
Moreover, neurolinguistics deals with various language disorders known as ‘aphasia’ which is impairment of language functions because of some brain damage leading to difficulties in either producing or understanding linguistic forms. There are different aphasias depending on the language impairment and the damaged part of brain. Thus Broca’s aphasia is characterized by a reduced amount of speech, slow pace of speaking and distorted articulation. Wernicke’s aphasia is characterized by quite fluent, yet incomprehensible speech and difficulties in finding appropriate words. Conduction aphasia is connected with damage to arcuate fasciculus and it is connected with mispronouncing words, disrupted rhythm, large number of hesitations and pauses.
Yule G. 1996. The study of language. Cambridge: CUP.