Racial Differences in Brain Activity

Archive for the ‘secondary zones’ tag

Affected Speech Hearing

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In the previous post we began speaking about patients with affected secondary zones. To such patients 'dot' sounds like 'tot', 'lot' or 'cot'. The patient can neither distinguish these words when he hears them nor pronounce them correctly, and he has difficulty whenever he has to say these words in a conversation. Failing to find the appropriate word, he tries to find a substitute, for example, 'the thing you do your hair with' for 'comb', or 'land without water' for 'desert'. In the most serious cases patients have so many 'difficult' words and make so many mistakes in pronouncing them, that their speech becomes quite incomprehensible.

Naturally, if one cannot sense the differences between the words 'dot', 'tot' and 'cot', one's faculty to understand speech is generally affected. A curious but so far unaccountable fact is that such patients find it especially hard to identify nouns, and their speech mostly consists of link words, prepositions, adverbs, verbs and all kinds of words expressing relationship.

Another curious fact is that when speech hearing is affected, people do not become tone-deaf. Several cases have been recorded where gifted composers lost their speech hearing and the faculty to speak as a result of a serious illness, but were still able to write music and successfully continued their creative work. On the other hand, a lesion of the corresponding zones in the right cerebral hemisphere does not affect the patient's speech, but may make him tone-deaf.

Written speech is also affected in the case of injury to the secondary zones of the acoustic analyser. The patients can copy or write such familiar words as 'mother' or 'moon', sign their name and reproduce such common letter codes as OK or IOU, but they become completely incapable of writing a note or even a few lines of dictation coherently. Their ability to read is also affected. They can recognize and understand some very familiar words or phrases, but become incapable of reading separate letters, syllables or less familiar words.

Written by brainer

January 5th, 2010 at 12:46 pm

Difficulty in Understanding Speech

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Human speech consists of complex sounds of an involved pattern. To be able to speak, it is not enough to have good hearing. To a baby in its first months speech is nothing more than a kind of a noise. To master speech, a child must learn to single out from a flow of sounds the essential features, or the phonemes. What one needs to perceive speech is not so much a keen ear as an ear trained to the system of a particular language.

If you do not know a foreign language, you will not be able to distinguish the individual elements of that language in the flow of sounds. You will not be able to repeat the words and phrases you hear, let alone understand them.

It is an interesting and important fact that this process is performed not merely by the acoustic regions of the brain, but also by the articulatory organs, which take part in the utterance of speech sounds, and by the corresponding motor regions of the brain. Even adults, although they usually do not realize it, do not perceive speech eiiher by sounds or visual appearance (written text), but by so-called kinaesthetic perception, a vague, inner sensation arising in the muscles and tendons of the articulatory organs during speech.

Acoustic information is analyzed in the temporal lobes of the cerebral cortex. Like all the other analysers in the human brain, the temporal lobes of the cortex consist of the primary or projection zones, to which the nerve fibres from each ear come, and the secondary zones which receive information not from the periphery, but that already processed by the primary zones.

If the primary zones have been affected by disease, the patient will have hearing trouble. It is quite a different matter if the secondary zone of the left hemisphere is damaged. The hearing is practically intact, but speech hearing is gravely affected. They cannot distinguish d from t, b from p and z from s. Obviously, they fail to identify phonemes and consequently have difficulties in understanding words.

Written by brainer

January 3rd, 2010 at 12:46 pm