CHAPTER 8 BRAIN AND LANGUAGE

Outline

1. Brain Structure 2. Module theory: Language and

brain 3. Aphasia 4. Summary

1. Brain Structure (1)

Our brain comprises a great number of neurons or nerve cells. Each neuron is connected with each other so that we can think, feel, and put whatever occurs to us into language.

1. Brain Structure (2) Our brain is divided into two cerebral hemispheres

by the corpus callosum: (1) right: for sounds (music, noises), visual space,

logical reasoning, and system cognition. (2) left: verbal reading, writing, arithmetic,

thinking, and time order.

http://poesdeadlydaughters.blogspot.tw/2013/05/right-brain-or-left-brain.html

1. Brain Structure (3)

The phenomenon that each side is respectively responsible for different functions is called lateralization

Other body parts and the brain are in contralaterization

the left brain → the organs in the right of our body

the right brain→ the organs in the left of our body

2. Module theory- Dichotic listening (1-1)

Different sounds are given to the right and the left ears of the subject at the same time.

Given that our left brain is responsible for language, it is natural that our right ear is superior in getting verbal information.

2. Module theory- Dichotic listening (1-2)

If the input sounds to the left ear are musical (melodies, intonation, or tones) but not phonetic segments, then a dichotomy experiment shows that the subjects remember musical melodies.

Different inputs are given to the left and the right ears simultaneously, can help us identify the fact that our right brain and the left ear is responsible for non-phonetic sounds. It is our left brain and the right ear that is responsible for phonetic sounds.

2. Module theory- Brain impaired patients(2-1) Hemiplegic patients: only the left or the

right brain is impaired

Hemidecorticates: left or right brain is entirely cut off.

If a patient gets his/her left brain cut off, then his/her linguistic behaviors are seriously inferior.

2. Module theory- Split brains (3-1)

It is well known that corpus callosum works as a bridge between the left and the right hemispheres of the brain.

what would happen for the information exchange between the right and the left hemispheres?

2. Module theory- Split brains (3-2)

One experiment: the patients whose corpus callosum had been cut off. The left hand of the subject is a tomato, while in the right hand is a banana.

The subject knows that there is a tomato in the left hand, but s/he fails to speak . The information that the right brain gets cannot be transmitted to the left brain

2. Module theory- Gage’s case (4-1)

Gage used to be very polite, but he became hot tempered after an accident.

It was prefrontal cortices that got impaired.

3. Aphasia: Broca’s aphasia

Borca’s aphasia is mainly involved with communications in sound production, so it is also called expressive aphasia.

3. Aphasia: Broca’s aphasia symptoms (1) (1)phonological disorder:

In pronunciation, some sounds are systematically deleted

3. Aphasia: Broca’s aphasia symptoms (2) (1)sound substitution :

Broca’s aphasia patients use fixed sounds to take the place of other sounds

3. Aphasia: Broca’s aphasia symptoms (3) Agrammatism: cannot successfully use

grammatical or morphological structure. They skip function words (prepositions, conjunctions, and pronouns, etc.) quite often.

3. Aphasia: Wernicke’s aphasia

The symptoms: (1) Able to speak quite fluently, with good pronunciation and intonation, but usually

mixed with some nonsense words. (2) Having difficulties in understanding

others’ language.

(3) Difficult in speaking meaningful sentences, and hence raising communication disorder.

3. Aphasia: Wernicke’s aphasia (Example) (P=patient, E= doctor)

→ there was no communication at all

3. Aphasia: Conducting aphasia

Arcuate fasciculus: is responsible for the information

exchange between Broca’s and Wernicke’s areas. If the arcuate fasciculus is injured or broken, conducting aphasia emerges.

3. Aphasia: Alexia

At the area behind Wernickes’a area is angular gyrus, which is specifically responsible for the transforming what we see into what we hear.

Angular gyrus plays a significant role in perception, naming, and reading comprehension. If the angular gyrus is injured, the result is

(a) alexia: unable to read (b) agraphia: unable to write

4. Summary

(1) Two cerebral hemispheres: - left hemisphere and right

hemisphere - in our body it is contralateralization (2) Four arguments are used to support the

module theory:

(a) dichotic listening, (b) brain impaired patients,

(c) split brain, and (d) Gage’s case.

(3) Four types of aphasia: (a) Broca’s aphasia, (b) Wernicke’s aphasia,

(c) conducting aphasia, and (d) alexia.