Localisation and Lateralisation of Functioning in the Brain

Question 1

Outline phrenology.

Answer 1

Early 1800s, Franz Gall proposed that a person’s personality was reflected in the lumps and bumps on the skull which in turn reflected functions of the brain lying underneath the bump.

This isn’t true (not to mention it’s completely unscientific) but he did put forward an interesting idea which we now know to have scientific support; functions were localised to specific regions of the brain. ​

Question 2

What is localisation?

Answer 2

The idea that there are certain brain areas that have specific functions.

E.g. Broca’s area is localised within the left hemisphere’s frontal lobe.

Question 3

What is the corpus callosum?

Answer 3

Bundle of fibres that is essentially a communication pathway between the two hemispheres.

Question 4

What is lateralisation?

Answer 4

The idea that functions within the brain are controlled by either the right or light hemisphere.

E.g. Language centres are lateralised to the left hemisphere.

Question 5

For most people the brain is what? What does this mean?

Answer 5

Contralateral.

This is where the right hemisphere deals with the left hand side of the body and vice versa.

Contra = opposite.

Question 6

Outline how stroke patients support lateralisation.

Answer 6

If a person has a stroke in the motor areas of their right hemisphere the movement in the left hand side of the body will be affected.

Question 7

What is seen in the right visual field is processed by the left hemisphere. Why? Is this only for vision?

Answer 7

This is because of the optic chiasmi, where the optic nerves “crossover”.

It’s also the same for your ears, although auditory information is gathered from both ears, the info from the left ear is predominantly dealt with by the right hemisphere of the brain.

Taste and smell are also contralateral.

Question 8

Why are humans are many other vertebrates contralateral? What is important to know?

Answer 8

The reason is unknown.

Despite this, it is important to remember that our hemispheres are not symmetrical.

Question 9

Outline Clarke et al’s study from 1993.

(Supports lateralisation in the right hemisphere)

Answer 9

Supports lateralisation in the right hemisphere.

This is because a woman with right hemisphere damage demonstrated that the right hemisphere seems to more adept at spatial information. ​

The woman would often get lost, even in familiar situations unless she had verbal instructions which contained distinguishable features (e.g. turn right at the red house).

This suggests that the right hemisphere deals with spatial information.

Question 10

What is the motor cortex?

(Lateralised Brain Regions)

Answer 10

A region of the frontal lobe involved in regulating voluntary movement.

It sends signals to the muscles in the body.

Question 11

Where is the motor cortex located?

(Lateralised Brain Regions)

Answer 11

Located at the back of the frontal cortex in both hemispheres of the brain.

Question 12

What may happen if someone’s motor cortex is damaged?

(Lateralised Brain Regions)

Answer 12

Regions of the motor cortex are arranged in a logical order, meaning if an area of your motor cortex was damaged, you would have difficulty moving and coordinating that part.

Question 13

What is the somatosensory cortex?

(Lateralised Brain Regions)

Answer 13

Where sensory information is processed to produce sensations related to touch, temperature, pressure and pain.

Question 14

Where is the somatosensory cortex located?

(Lateralised Brain Regions)

Answer 14

Located at the front of both parietal lobes.

Separated from the motor area by a ‘valley’ called the central sulcus.

Question 15

What is the primary visual cortex?

(Lateralised Brain Regions)

Answer 15

Receives and processes visual information.

Different regions of the visual cortex are responsible for colour, shape, movement etc.

Question 16

Where is the primary visual cortex located?

(Lateralised Brain Regions)

Answer 16

Back of the occipital lobes.

Question 17

Where is the primary auditory cortex located?

(Lateralised Brain Regions)

Answer 17

Located in the temporal lobes.

Question 18

What is the primary auditory cortex?

(Lateralised Brain Regions)

Answer 18

Auditory centre that analyses sound based information – through ears; contra-lateral effects.

Question 19

What may happen if someone’s primary auditory cortex is damaged?

(Lateralised Brain Regions)

Answer 19

May produce hearing loss; the more extensive the damage, the more extensive the loss.

Damage to Wernicke’s area may affect ability to comprehend language. ​

Question 20

Where are the language centres located?

(Lateralised Brain Regions)

Answer 20

Unlike the other centres which appear in both hemispheres of the brain language centres in the brain are lateralised to the left hemisphere of the brain in most people .​

These include Broca’s Area and Wernicke’s area.​

Question 21

Where is Broca’s area located?

Answer 21

Left Frontal Lobe.

Question 22

Where is Wernicke’s area located?

Answer 22

Left temporal lobe.

Question 23

What is Broca’s area?

Answer 23

A small area responsible for speech production.​

Question 24

What is Wernicke’s area?

Answer 24

A small area responsible for language comprehension.​

Question 25

What was different about Genie’s language centres?

Answer 25

Dichotic listening tasks indicated that she was using her right cerebral hemisphere to process language.

This is unusual as language is normally processed within the left hemisphere.

Question 26

Outline Lenneberg’s study from 1967.

(Supports the idea of a language acquisition (critical period) before the onset of puberty)

Answer 26

Supports the idea of a language acquisition (critical period) before the onset of puberty.

Genie’s use of the right hemisphere for language development might have been a direct consequence of the fact that she did not acquire language before the critical age.

This suggests that there may be a critical period for language acquisition.

This is reinforced by Curtiss (1977).

Question 27

Outline Herasty’s study from 1997.

(Supports the idea that females have proportionally larger Wernicke’s and Broca’s area than males)

Answer 27

Supports the idea that females have proportionally larger Wernicke’s and Broca’s area than males.

This could this perhaps explain the greater ease of language use amongst women.

It also suggests a (beta) gender bias, as before this the male brain had been used as a direct female comparison.

Question 28

Outline the case study of Leborgne, (discovery of Broca’s area).

Answer 28

Leborgne suffered with epilepsy throughout his childhood and eventually lost the ability to speak (although he could say the word “tan”) and was hospitalised at 30 and died there at the age of 51 in 1861. ​

Broca conducted a post-mortem on his brain and found a lesion on the left frontal lobe.

This was the only visible site of damage so he concluded it was the area responsible for the production of speech, based on the deficit Leborgne exhibited. ​

Broca correctly identified the function of that area and the term Broca’s aphasia is used today to describe patients with speech problems. ​

Leborgne’s brain was preserved and kept in Paris – it has been scanned using modern day technology and the area identified as responsible for speech production is correctly localised. ​

Question 29

Outline the discovery of Wernicke’s area.

Answer 29

In 1864, Karl Wernicke, who worked at a hospital in Germany, found that patients who had damage in an area close the primary auditory cortex had specific language impairments.

These included the inability to comprehend language and anomia, which is when someone struggles to find the word they need.

However, Wernicke noticed that these people did have fluent speech, when they could access the words the words quickly.

This led Wernicke to suggest that the area now called Wernicke’s area was important for understanding language and accessing words.

Question 30

Outline the case study of GR.

(Cortical blindness)

Answer 30

She had an operation and started to recover although she had no injury to her eyes, the brain was damaged in the visual cortex, which meant she was cortically blind.

In tests asking her to detect a letter shown on a screen she could not identify the letter but reported an awareness of something, despite seeing nothing.

This is called blindsight, an awareness and accuracy of stimuli, despite ‘seeing’ nothing.

Question 31

Outline Meyer et al’s study from 2010.

Answer 31

Supports the idea that the primary auditory cortex is not just involved with conscious sound, but also with auditory imagery.

This is because they found that when people watch silent films, their primary auditory cortex in both hemispheres will activate if a door is shut with force, for example - they are imaging the bang

Question 32

Outline the case study of Phineas Gage.

(Supports the idea of localisation of functioning in the brain)

Answer 32

Supports the idea of localisation of functioning in the brain.

This is because after the incident he was a very changed man, being hostile, unreliable, and exhibited rude behaviour. He also started swearing lots - something he never did before the accident.

Dr Harlow, a physician who originally treated Gage, believed that there was localisation in the brain and that the area that had been damaged in Gage housed the planning, reasoning and control of the individual.

This was shown to be correct in subsequent research into localisation.

Question 33

Outline the case study of EB.

Answer 33

A young boy who was operated on at the age of 2.5 years to remove a large benign tumour from his left hemisphere.

Virtually all of his left hemisphere was removed, and, at that time, all of his linguistic abilities disappeared too.

He was right handed and it seems that his language localisation was in his left hemisphere.

He underwent an intensive rehab programme and his language abilities started to improve around the age of 5.

They continued to do so over the next 3 years to the point that no problems of language ability were reported.

Question 34

Outline Danelli et al’s study from 2014.

Answer 34

Tested EB at the age of 17 to compare his language abilities with ‘normal’ controls.

They found that his right hemisphere had compensated for the loss of the left hemisphere in that he was functioning linguistically well.

However, there were some minor grammatical problems and he was slower at naming objects in pictures.

This led the researchers to conclude that the right hemisphere had compensated following the intensive programme, but that it was never able to compensate fully.

When scanning EB’s brain, activity was practically identical to the activity of ‘normal’ controls.

This showed that hemispheric lateralisation can be compensated for to at least a basic degree by the non-specialist hemisphere.

Although a case study, this example does show that the brain is able to adapt to profound injury, at least in early childhood.