Social communication using language is an incredible ability that humans have. Currently there are more than 6000 languages being used in the world, where each has its own unique phonological system to combine sounds to make words or morphemes, as well as a syntactic system to combine words and morphemes to form meaningful phrases.
There are various theories for the origin of human language. According to American linguist and philosopher Noam Chomsky, “some random mutation took place, maybe after some strange cosmic ray shower, and it reorganized the brain, implanting a language organ in an otherwise primate brain.” Although caution must be taken in taking any theory too literally, it has been widely accepted that the production of language probably coincides evolutionarily with the increase in brain volume of humans.
Language is coordinated in the brain. It controls both the composition of cognitive meaning as well as the mechanics of speech production. Even though our current knowledge on the neurological basis of language is limited, brain lesion studies and utilization of modern imaging techniques helped us in understanding some of the organizational differences in language processing.
In the 19th century neuroscientists working on patients with different brain lesions discovered two brain areas that are important for language: Broca’s and Wernicke’s area. Lesions in these brain areas causes severe aphasia, meaning “speechlessness”, which is a language disorder that results with problems in comprehension or formulation of language. The observations of different functions of these regions allowed neuroscientists to understand that language is processed in different locations of human brain.
The first area to be discovered was Broca’s area. It is located in the posterior inferior frontal gyrus of the dominant hemisphere (left hemisphere in 95% of right handed and 60% of left handed people). The area was named after Pierre Paul Broca, a French physician, surgeon and anatomist, who reported impairments in language production in some of his patients who had lost the ability to speak. In Broca’s aphasia, patients usually understand what is being said to them, but cannot speak themselves. In other words they know what they want to say but cannot figure out how to say it. The affects on language can be seen in difficulty in finding words, producing normal-sounding rhythm and formulating correct syntax.
Wernicke’s area is located in the posterior section of superior temporal gyrus in the dominant hemisphere (mostly left hemisphere as described above). The area was was named after Carl Wernicke, a German neurologist and psychiatrist, who realized that not all language deficits were equal and not all were due to damage to Broca’s area. In Wernicke’s aphasia, sometimes called fluent aphasia, patients usually have impaired language comprehension, whereas the produced speech has relatively normal rhythm and syntax. So they are able to produce speech, but it is mostly meaningless.
Interestingly both Broca’s and Wernicke’s aphasia also affect people who use sign language, similar to their effect on spoken language. Patients with Broca’s aphasia sign slowly with incorrect grammar, but understand when other people sign. Patients with Wernicke’s aphasia sign fluently however with little meaning, and have difficulty understanding when other people sign. The effect of the brain lesions on both spoken and sign language is very important since it indicates that these areas are responsible for not just the ability to perform the mechanics of producing speech, but for the ability to use language.
Broca’s aphasia patient explaining a problem with his leg
Wernicke’s aphasia patient having difficulty producing meaningful words
Wernicke’s aphasia patient having difficulty producing meaningful speech
Image source: Flickr