Language & Hemisphere Function

Question 1

What are the most common types of brain-injuries used to investigate language and the brain?

Answer 1

The most common types of injuries are called cerebro-vascular disorders, such as strokes and cerebral haemorrhages, which lead to localised loss of the brain’s blood supply. Damage is often confined to one of the two hemispheres.

Question 2

What is Broca’s aphasia?

Answer 2

Broca’s aphasia is a loss of expressive speech, although the understanding of speech is intact.

Question 3

What is Wernicke’s aphasia?

Answer 3

Wernicke’s aphasia is an impairment of speech comprehension, whilst speech production still functions.

Question 4

Where are the Broca’s area and the Wernicke’s areas?

Answer 4

The Broca’s area lies in the base of the frontal lobe, the Wernicke’s area lies in the temporal lobe, close to the auditory cortex. Both zones are usually found only in the left hemisphere.

Question 5

What is a conduction aphasia?

Answer 5

A conduction aphasia is damage to the pathways connecting Wernicke’s and Broca’s areas. It leaves speech production and comprehension intact but disconnected.

Question 6

What is a global aphasia?

Answer 6

The destruction of both, Wernicke’s and Broca’s area, is called global aphasia.

Question 7

What is the angular gyrus?

Answer 7

The angular gyrus is in the parietal lobe of the left hemisphere. It is part of our reading and writing system.

Question 8

What is Alexia without agraphia ?

Answer 8

It is pure word blindness and happens when the angular gyrus is disconnected from the visual cortex.
The patient cannot read, although writing is unaffected.

Question 9

What is developmental dyslexia?

Answer 9

It’s the most common form of reading difficulty. There’s no evidence of organic Brian damage, and it may be due to confusion between the hemispheres as language mechanisms are developing.

Question 10

Why do we know much about functions localised to one hemisphere or the other?

Answer 10

Through Roger Sperry’s split-brain patients.
He cut the corpus callosum (major pathway connecting both hemispheres) in order to reduce the severity of chronic epilepsy.
Sperrt devised the divided field technique - without the corpus callosum the stimuli would be confined to the hemisphere to which the stimuli is presented (just one visual field).

Question 11

Why could Sperry test each hemisphere with different stimuli?

Answer 11

He could test each hemisphere with a different stimuli, because the left hemisphere contained speech mechanisms and also controlled the right hand, while the right hemisphere controlled the left hand.

Question 12

What is the basic Modell of hemisphere specialisation?

Answer 12

Hemisphere specialisation divides between verbal and Visuo-spatial processing.
Verbal: left hemisphere- comprehends letters, words, numbers.
Visuo-spatial: right hemisphere- can understand simple words but is better with faces and abstract patterns.

Question 13

Why are Sperry’s split-brain patients not a representative group?

Answer 13

They’ve had severe epilepsy, probably due to brain damage, years of drug treatment, and major brain surgery
(Data needs to be supported with normal subjects).

Question 14

How can Sperry’s divided field technique be modified for normal
subjects?

Answer 14

Pairs of stimuli are presented simultaneously to both hemispheres.
The stimulus reported indicates which hemisphere is superior at processing that type of stimulus.
A left hemisphere superiority leads to faster processing of stimuli in right visual field and vice Versa.

Question 15

What is dichotic listening?

Answer 15

The auditory equivalent of the divided field.

Question 16

Divided field and dichotic listening has been shown what?

Answer 16

Left hemisphere is superior at processing words, letters, digits visually presented, spoken words, and nonsense syllables.
Right hemisphere is superior with faces, abstract patterns, depth perception, environmental sounds, and musical tone.

Question 17

How can we generalise hemisphere function?

Answer 17

The left hemisphere deals better with stimuli that are sequential and need to be analysed into components.
The right hemisphere is specialised to handle stimuli that require parallel processing.
Characteristic stimuli for the two hemispheres would be verbal stimuli and faces respectively.

Question 18

All normal right handers have left hemisphere language. How is the distribution for left handers?

Answer 18

70% have left hemisphere language,
15% have right hemisphere language,
15% have both hemispheres language.

Question 19

What did Annett suggest?

Answer 19

Annett suggested that if you inherit a right shift factor you will be right handed. If you do not inherit a right shift factor, handedness will be determined by random environmental factors, as it is in the rest of the animal kingdom.

Question 20

What is Geschwind proposition?

Answer 20

Geschwind draws attention to higher frequency of left handers developing mental disorder and auto-immune diseases occurring together in males. He proposes that the male embryo can be exposed to high levels of testosterone, and this affects the normal developmental of the hemispheres and the immune system, although there is little evidence of this.

Question 21

Sex differences in behaviour are hard to establish, but generally speaking we can say what?

Answer 21

Males tend to be more aggressive and have better visuo-spatial ability. Females tend to be more affiliative and have superior verbal ability. There is a popular view that female brains are less lateralised than the male brain with respect or language; but differences and variation on any of these measures is much greater between individuals than between sexes.

Question 22

What do studies of brain-damaged patients show in regards to hemisphere function?

Answer 22

The right hemisphere is generally better at perceiving and interpreting emotions if others. Studies on brain-damaged patients suggest that it produces negative emotions, whereas the left hemisphere is responsible for positive emotional states.