The early studies done in this area were by Broca (1861) and Wernicke



(1874). Broca's work included the patient, now known as "tan", who

could only say the word "tan", although his speech comprehension

stayed in tact. The patient died shortly afterwards and autopsy

revealed that he had been damaged in the lower part of the left

frontal lobe. Broca collected eight more cases and concluded that the

identified area was essential in the production and comprehension of

speech. The area is called Broca's area and the condition of damage to

it is called Broca's aphasia.

Wernicke reported a different aphasia. Patients could speak in

organized and grammatical sentences, although what they said seemed to

have little to do with the on going conversation. On the other hand

they seemed to have no understanding of what was spoken to them. On

autopsy, they all had damage to an area at the top of the left

temporal lobe, now known as Wernicke's area.

These speech zones also tally with the sensory and motor cortical

mechanisms. For example, Wernicke's aphasia represents a problem with

speech processing. The spoken word is a sound stimulus which enters

our ear and in transferred as an electrical signal through our nerves

until it reaches the primary auditory cortex in the temporal lobe.

This area is close to Wernicke's area which contains the "word

analyzer". The word analyzer contains the sound patterns of words

that are essential in converting speech into words. If Wernicke's are

damaged the sounds cannot be identified as speech and comprehended.

We humans have a wonderful opportunity to communicate with each other both spoken and written languages, unlike our “smaller brothers" from animal world who can only use some specific signals which are recognized by them only. Language is a very powerful tool that enables us not only to communicate, but also plays a vital part in our brain’s development and simply “working’.

Broca's area is in the frontal lobe and contains the motor cortex.

Speech is a motor process requiring sophisticated control over muscles

of the throat, lips and mouth. Broca's area contains the motor plans

for words. When Broca's damaged the plans cannot be activated

even though the motor cortex is intact.

Speech, reading and writing are also language functions that have a

role in the human brain. Aphasia study showed that the condition was

more common in left hemisphere damage than in right. In contrast to

the symmetry of sensory and motor functions, language functions are

asymmetrical, being more dominant in the left hemisphere. Global

aphasia is when both Broca's and Wernicke's areas are damaged and

"shadowing" experiments in which words are spoken to a subject quickly

and they must repeat them back quickly suggest that a global aphasic

will be unable to "shadow". The accurate fasciculus’s the direct

pathway from Wernicke's to Broca's area. If this is damaged then

conduction aphasia results, which is severe impairment of repetition or

"shadowing". However, normal speech production and comprehension are

less affected. This implies other less direct pathways exist apart

from the direct pathway of accurate fascicules.

Writing, as a motor process is produced from the motor cortex under

the control of the planning centre in Broca's area. The input system,

reading, involves the visual system and a region that contains the

visual pattern of words and is capable of converting visual input into

words. The key region for reading and writing is the angular gyros, on

the borders of the temporal and parietal lobes.

This region contains visual word patterns, the visual pattern is

transmitted to Wernicke's area, where it arouses the auditory form of

the word and comprehension occurs. Pure word blindness occurs when we

have someone able to write a page of coherent and fluent prose, but

who cannot read it back. This syndrome is known as alexia without

agraphia.