Anatomy of language processing

Mark HarjuMark Harju

Most components for language Most components for language processing are located in the left processing are located in the left hemispherehemisphere

Left= dominant language hemisphereLeft= dominant language hemisphere Nearly all right-handed peopleNearly all right-handed people Two-thirds of leftiesTwo-thirds of lefties The cortical area most involved in the The cortical area most involved in the

left hemisphere is central around the left hemisphere is central around the sylvan fissuresylvan fissure

The two most traditionally distinct areas areThe two most traditionally distinct areas are Wernicke’s areaWernicke’s area

The two most traditionally distinct areas areThe two most traditionally distinct areas are Wernicke’s areaWernicke’s area Broca’s areaBroca’s area

Wernicke’s area comprises a region that includes:Wernicke’s area comprises a region that includes: the posterior part of the superior temporal gyrusthe posterior part of the superior temporal gyrus parietooccipitotemporal junction, including the angular parietooccipitotemporal junction, including the angular

gyrusgyrus

Wernicke’s area is concerned with the Wernicke’s area is concerned with the comprehension of spoken language. comprehension of spoken language.

The angular gyrus has to do with comprehension The angular gyrus has to do with comprehension of written language of written language

Broca’s area comprises a region covering the Broca’s area comprises a region covering the posterior part of triangular gyrusposterior part of triangular gyrus

Opercular gyrus in the inferior frontal gyrus Opercular gyrus in the inferior frontal gyrus

Broca’s area is concerned with speech Broca’s area is concerned with speech productionproduction

Within Broca a vocalization program is Within Broca a vocalization program is formulatedformulated

This program transmits to the face, tongue, This program transmits to the face, tongue, vocal chords, and pharynx areas of the vocal chords, and pharynx areas of the motor cortex for execution of speech. motor cortex for execution of speech.

It is also connected with the supplementary It is also connected with the supplementary motor area, which is concerned with the motor area, which is concerned with the initiation of speech. initiation of speech.

Broca and Wernicke are connected by the Broca and Wernicke are connected by the arcuate fasciculusarcuate fasciculus

A fiber bundle pathway, necessary for A fiber bundle pathway, necessary for repetition of spoken language repetition of spoken language

The cortical areas are used in sequence The cortical areas are used in sequence when processing language.when processing language.

For example, if you were reading aloud you For example, if you were reading aloud you would need to involve your visual cortex, would need to involve your visual cortex, located in your occipital lobelocated in your occipital lobe

You would also need your primary motor You would also need your primary motor cortex to use your face, tongue, vocal cortex to use your face, tongue, vocal chords, and pharynx to speakchords, and pharynx to speak

…….And your supplementary motor cortex in .And your supplementary motor cortex in order to initiate speech.order to initiate speech.

The output from the visual cortex goes to The output from the visual cortex goes to the angular gyrus, where it links the image the angular gyrus, where it links the image of the written words to language.of the written words to language.

Then to Wernicke’s area where the words Then to Wernicke’s area where the words are processed and given meaningare processed and given meaning

Then through the arcuate fasciculus to Then through the arcuate fasciculus to Broca’s area, where the vocalization of the Broca’s area, where the vocalization of the words is formulatedwords is formulated

Then the vocalized program is delivered to Then the vocalized program is delivered to the primary motor cortex, and initiated into the primary motor cortex, and initiated into speech by a signal to the supplementary speech by a signal to the supplementary motor cortex. motor cortex.

Another example Another example

In the case of speaking words you hear, you In the case of speaking words you hear, you would need to involve would need to involve

In the case of speaking words you hear, you In the case of speaking words you hear, you would need to involvewould need to involve

The auditory cortex to hear the wordsThe auditory cortex to hear the words

The primary motor cortex to use your faceThe primary motor cortex to use your face

And the supplementary motor cortex to tell And the supplementary motor cortex to tell your face to start talking.your face to start talking.

Boom. You are saying what you have Boom. You are saying what you have heard.heard.

A quick word on language in the right A quick word on language in the right hemispherehemisphere

Corresponding areas have been Corresponding areas have been measured as metabolically active in measured as metabolically active in right hemisphere during speechright hemisphere during speech

This is believed to be linked with This is believed to be linked with melodic function of speech (prosody)melodic function of speech (prosody)

This may explain some cases of autism or This may explain some cases of autism or brain damage where the subjects are unable brain damage where the subjects are unable to speak yet are able to singto speak yet are able to sing