Localisation of function in the brain

Question 1

Localisation of function is the idea that

Answer 1

specific areas of the brain are associated with specific functions

Question 2

The Case Study of Phineas Gage
(Macmillan, 2002)

Answer 2

Phineas Gage was a railway worker in the USA, whose job required him to use dynamite to blast a clear path for railway track construction.
One day, Gage was using a tamping iron (metal rod) to bed the dynamite in place and it caused a spark, causing the dynamite to blow up.
The rod blasted through Phineas’ left cheekbone and out through the top of his head.

Question 3

The Case Study of Phineas Gage (Macmillan, 2002)
Findings

Answer 3

Immediately after the accident Phineas was conscious and could speak.
Though he recovered physically, he changed psychologically:
Before the accident, he was calm and well-mannered
Following the accident, he exhibited unreliable, quick-tempered, hostile, rude and sexually inappropriate behaviour. He also used vulgar language.

Question 4

The Case Study of Phineas Gage (Macmillan, 2002)
Support for localisation in the brain:

Answer 4

The damaged area is thought to be responsible for functions such as planning, reasoning and control.

Question 5

The Case Study of Phineas Gage (Macmillan, 2002)
Evaluation

Answer 5

The accounts of Gage’s behavioural changes are based largely on anecdotal reports that are not substantiated by the little evidence there is.
There’s little doubt that Gage sustained extensive frontal lobe damage in the accident, but we’ll never know the true extent of the damage.

Question 6

What are the strengths and limitations of case study research?

Answer 6

Strengths
Case studies can be used to investigate instances of human behaviour that are rare and that would be unethical to investigate experimentally.
Case studies provide rich, detailed data that provides an in-depth understanding of a single individual.

Limitations
It is difficult to generalise from individual cases such as Phineas, because each one has unique characteristics (lacks population validity).
Researcher bias - researchers may lack objectivity, as they become familiar with the case, which may affect their interpretation of behaviour.
Ethical issues – confidentiality Many cases are easily identifiable due to unique characteristics.

Question 7

The brain is contralateral (in most people):

Answer 7

The right hemisphere deals with the left side of the body and vice versa.
e.g. movement on the left side of the body is controlled by the… right hemisphere

Taste and smell are also contralateral: taste from the left side of the tongue and smells from the left nostril are processed by the right hemisphere.

Question 8

The Motor Cortex

Answer 8

The motor cortex of the brain is located in the frontal lobe (adjacent to the central sulcus) of the brain and is responsible for movement.

Both hemispheres have a motor cortex –>
The motor cortex on one side of the brain controls the muscles on the opposite side of the body.
A motor cortex is required in both hemispheres to be able to move both sides of the body.

The motor cortex is responsible for complex/fine movements, not basic actions such as coughing or crying.

The motor cortex communicates with the body to bring about movement by sending messages (via the motor neurons) to the muscles via the brain stem and spinal cord.

Question 9

Different parts of the motor cortex exert control over different parts of the body:

Answer 9

This diagram shows the approximate position of the neurons designated to specific areas of the body.

There is no relationship between the size of the area of the body and the number of neurons involved.

It is the complexity of movement in the area that dictates how many neurons are needed
– movement in the face and hands involves more neurons.

Question 10

The Somatosensory Cortex

Answer 10

Somatosensory refers to ‘sensation of the body’.
The somatosensory cortex perceives touch/detects sensations from different regions of the body.
It is located in the parietal lobe of the brain along the postcentral gyrus.

Both hemispheres have a somatosensory cortex –>
The somatosensory cortex on one side of the brain receives sensory information from the opposite side of the body (via sensory receptors in the skin, which communicate information to the brain through sensory neurons).

The somantosensory cortex produces sensations of touch, pressure, pain and temperature.
Touch-sensitive areas of the body: face, lips and hands

Question 11

The Visual Cortex

Answer 11

The visual cortex is the main visual centre, located in the occipital lobe at the back of the brain.

It spans both hemispheres, with the right hemisphere receiving input from the left visual field and vice versa.
Light enters the eyes and is received by the retina, hitting the photoreceptors (rods/cones) at the back of the retina.

Nerve impulses then travel down the optic nerve to the brain, where they are received by the thalamus.

The thalamus acts as a relay station, transmitting information to the visual cortex.

Question 12

The visual cortex contains several different areas, each processing different types of visual information, such as colour, shape or movement

Answer 12

Area V1 is necessary for visual perception:
Individuals with damage to V1 report no vision of any kind: conscious vision, visual imagery while awake or in their dreams (Hurovitz et al., 1999)

Question 13

Research (Bridgeman and Staggs, 1982):

Answer 13

Individuals with damage to Area V1 may show ‘blindsight’
Individuals appear qualitatively blind, in that they report no vision, but they can locate objects in a visual field by pointing at them.
This suggests that some of the processing in the visual cortex is not conscious.

Question 14

Overgaard et al. (2008)

Answer 14

Overgaard et al. (2008) conducted a case study about a 31 year old woman, known as GR, who experienced ‘blindsight’, following damage within her visual cortex, which occurred as a result of a brain haemorrhage.

Question 15

Overgaard et al. (2008)
How did the researchers test this and what did they find that demonstrated the existence of the condition in her?

Answer 15

In tests asking her to detect a letter shown on a screen, she could not identify the letter, but she did report an ‘awareness of something’, despite seeing nothing.
There was found to be a significant relationship between awareness of stimuli and accuracy. GR was argued to have blindsight.
This suggests that there may be two types of vision, one conscious and the other unconscious.

Question 16

The Auditory Cortex

Answer 16

The auditory cortex is located within the temporal lobes of both hemispheres and is responsible for analysing and processing acoustic information e.g. loudness, tempo, pitch.
It receives information from both ears via two pathways that transmit information about what the sound is and its location.
Information from the right ear primarily goes to the auditory cortex in the left hemisphere and vice versa.

The auditory pathway:
Cochlea – sound waves are converted to nerve impulses, which travel via the auditory nerve to the
Brain stem – basic decoding i.e. duration/intensity of sound
Thalamus – further processing of auditory stimulus and relay station
Auditory cortex – sound is fully recognised and results in appropriate response

Question 17

Damage to the primary auditory cortex does not lead to total deafness:

Answer 17

Sounds can still be heard but if they require complex processing i.e. music, this ability is no longer present.

Question 18

Research evidence (Meyer et al., 2010):
Auditory cortex

Answer 18

The primary cortex also processes auditory imagery.
When people watch silent films, their primary auditory cortex in both hemispheres will activate if a door is shut with force because they imagine the bang.

Question 19

The Case Study of Leborgne:

Answer 19

Paul Broca (a French neurosurgeon) treated Mr. Leborgne, who suffered from epilepsy and eventually lost the ability to speak.
He nicknamed Mr. Leborgne, “Tan”, because this was the only syllable he could express.
A post-mortem study of Tan’s brain identified a lesion in the frontal lobe of the left hemisphere

Question 20

Broca’s/Expressive Aphasia

Answer 20

Patients have problems producing speech (poor speech fluency - speech is limited mainly to short utterances of less than four words);
Nouns and verbs often appear unaffected, whereas prepositions (e.g. ‘of’, ‘to’) and conjunctions (e.g. ‘and’) cannot be spoken;
Language comprehension is relatively preserved, making reading possible, but writing may be limited

Question 21

Left HemisphereLanguage Processing: Wernicke’s area

Answer 21

In 1874, Carl Wernicke discovered:
Wernicke’s area: responsible for understanding language

Located in the posterior portion of the temporal lobe in the left hemisphere

Question 22

Wernicke’s/Receptive aphasia:

Answer 22

Patients with a lesion in Wernicke’s area can speak fluently, but are unable to understand language (poor comprehension);
Speaking: often what they say doesn’t make a lot of sense; patients often produce made up words
- sentences are syntactically incorrect
- they are unaware;
Reading: patients struggle to extract meaning from text;
Writing: patients struggle to write meaningful sentences

Question 23

The Relationship Between Broca and Wernicke’s Areas

Answer 23

Wernicke proposed that language involves separate motor and sensory regions located in different cortical regions…
The motor region - located in Broca’s area - is close to the area that controls the mouth, tongue and vocal cords.
The sensory region - located in Wernicke’s area, is close to regions of the brain responsible for auditory and visual input (when listening and reading)

Input from these regions is transferred to Wernicke’s area
where it is recognised as language and associated with meaning
There is a neural loop (the arcuate fasciculus) running between
Broca and Wernicke’s area.

Question 23

Language Processing

Answer 23

Fast and easy way to remember the difference between the two types of aphasia:

Broca = Broken (articulate, but broken/slow/deliberate/simple speech) – patients have control of speech, but lack fluency

Wernicke = Wacky (words make no sense) – patients have fluent speech, but poor language comprehension

Both areas are located in the left hemisphere:
Broca’s in frontal lobe
Wernicke’s in temporal
Alphabetically, front to back.