Biopsychology: localisation of function and hemispheric lateralisation

Question 1

Define localisation

Answer 1

the theory that specific areas of the brain are associated with particular physical and psychological functions

Question 2

The human brain can be viewed as being formed of three concentric layers:

Answer 2

1. The central core
2. The limbic system
3. The cerebral cortex

Question 3

Define homeostasis

Answer 3

the process by which the body maintains a constant physiological state.

Question 4

What is the central core area of the brain?

Answer 4

This regulates our most primitive and involuntary behaviours such as breathing, sleeping or sneezing.
It contains the brain stem and includes structures such as the hypothalamus – in the midbrain.
It regulates eating and drinking as well as regulating the endocrine system in order to maintain homeostasis.

Question 5

What is the limbic system area of the brain?

Answer 5

This contains the parts of the brain involved in controlling our emotions (like the amygdala).

Around the central core of the brain, interconnected with hypothalamus, it contains structures such as the hippocampus; key roles in memory.

Question 6

What is the cerebral cortex area of the brain?

Answer 6

This regulates our higher intellectual processes.
It is the outermost layer of the brain and appears grey because of the location of cell bodies (hence “grey-matter”).
The cerebral cortex is made up of the left and right hemispheres connected by a bundle of fibres called the corpus callosum which enables messages to enter the right hemisphere to be conveyed to the left hemisphere and vice versa.

Question 7

Each hemisphere is further divided into four lobes:

Answer 7

1. The frontal lobe
2. The parietal lobe
3. The occipital lobe
4. The temporal lobe

Question 8

Define hemispheric lateralisation

Answer 8

he dominance of one hemisphere of the brain for particular physical and psychological functions.

Question 9

Within the four lobes, specific smaller areas have been identified. The named areas on the spec are:

Answer 9

• The motor cortex (in the frontal lobes)
• The somatosensory cortex (in the parietal lobes)
• Visual cortex (in the occipital lobes)
• Auditory cortex (in the temporal lobes)

Question 10

What are the two language centres?

Answer 10

• Wernicke’s area
• Broca’s area

Question 11

Where is the motor cortex?

Answer 11

Both hemispheres of the brain have a motor cortex.

It is located in the frontal lobe.

Question 12

What does the motor cortex do?

Answer 12

The primary motor cortex is responsible for the generation of voluntary motor movements.
The process of motor movements is contralateral.
This means that the primary motor cortex on the right frontal lobe controls movement on the left side of the body and vice versa.
This means that any damage to one side of the brain in this area (e.g. through a stroke) will affect the control of movement on the opposite side of the body.

Question 13

How is the motor cortex organised?

Answer 13

Somatotopically
This is the point-for-point correspondence of an area of the body to a specific point on the central nervous system.
Areas which are finely controlled (e.g. the hands) have larger portions of the cortex whereas coarsely controlled areas (e.g., the trunk) have smaller portions.

Question 14

Where is the somatosensory cortex?

Answer 14

Both hemispheres of the brain have a somatosensory cortex, with the cortex on one side of the brain receiving sensory information from the opposite side of the body. This means that, like the primary motor cortex, it is contralateral.

It is located in the parietal lobe.

Question 15

What does the somatosensory cortex do?

Answer 15

The primary somatosensory cortex detects sensory events arising from receptors in the different areas of the body.
Using sensory information from the skin, the somatosensory cortex produces sensations of touch, pressure, pain and temperature, which it then localises to specific body regions.

Question 16

How is the somatosensory cortex organised?

Answer 16

Somatotopically
This is the point-for-point correspondence of an area of the body to a specific point on the central nervous system.
Areas which have more sensory receptors (e.g. the hands) have larger portions of the cortex whereas areas with less sensory receptors (e.g., the legs) have smaller portions.

Question 17

Where is the visual cortex?

Answer 17

The primary visual centre in the brain is located in the visual cortex.
This is in both hemispheres within the occipital lobe of the brain.

Question 18

What does the visual cortex do?

Answer 18

Visual processing begins in the retina, at the back of the eye, where light enters and strikes the photoreceptors (rods and cones).
Nerve impulses from the retina are then transmitted to the brain via the optic nerve.
The right hemisphere receives its input from the left-hand side of the visual field and vice versa.

Question 19

How is the visual cortex organised?

Answer 19

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

Question 20

Elaborate on damage to the visual cortex?

Answer 20

Damage to the visual cortex can cause loss of vision (called cortical blindness).
However, visual perception also requires additional input from neighbouring cortical areas (secondary visual areas) and damage to these areas can lead to loss of specific areas of visual perception.
E.g. prosopagnosia – loss of the ability to recognise familiar faces or identify faces at all.

Hurovitz et al. (1999) found that damage to Area VI (a specific area within the visual cortex) leads to a complete loss of ALL vision including visual imagery in dreams.

Question 21

Where is the auditory cortex?

Answer 21

Where is it?
Most of this area lies in the auditory cortex within the temporal lobes in both hemispheres of the brain.
Like the other areas, the auditory process is contralateral with information from the right ear travelling primarily to the left auditory cortex and vice versa.

Question 22

What does the auditory cortex do?

Answer 22

What does it do?
The auditory centre in the brain is concerned with hearing.
The auditory pathways begin in the cochlea in the inner ear, where sound waves are converted to nerve impulses. These travel to the brain stem where a basic decoding takes place (e.g. the duration and intensity of a sound) before moving on to the thalamus and the finally the auditory cortex where the sound is recognised and interpreted.

Question 23

What happens with damage to the auditory cortex?

Answer 23

What does it do?
Damage to the auditory cortex produces difficulties in processing and understanding sounds rather than total deafness (e.g. there may be an inability to perceive a certain pitch).

Question 24

Evaluation strength for localisation of function: supporting research from case studies

Answer 24

P: There is research support from human clinical case studies of the loss of specific abilities after restricted brain damage.

E: For example, receptive aphasia following damage to Wernicke’s area and amnesia following damage to specific areas of the hippocampus.

E: HM damaged his hippocampus during surgery for epilepsy and created irreversible damage to memory.

L: This suggests that localisation of functioning is supported by real life evidence.

Question 25

Evaluation strength for localisation of function: supporting research from case studies from brain scans

Answer 25

P: There is also supporting evidence for localisation of function from brain scans.

E: For instance, Buckner and Peterson (1996) used brain scans to reveal that semantic and episodic long term memories reside in different parts of the prefrontal cortex. Similarly, research by Maguire et al. (2000) suggests navigational skills reside in the posterior hippocampal regions.

E: These studies confirm localised areas for everyday behaviours.

L: Therefore, these objective methods for measuring brain activity have provided sound scientific evidence that many brain functions are localised to specific areas.

Question 26

Evaluation limitation for localisation of function: contradictory research

Answer 26

P: However, a challenge to localisation theory comes from the work of Lashley (1950) contradicting these findings.

E: Lashley removed areas of the cortex (between 10%-50%) in rats that were learning the route through a maze. No area was proven to be more important than any other area in term of the rats’ ability to learn the route.

E: The process of learning seemed to require every part of the cortex rather than being confined to a particular area.

L: This suggests that higher cognitive processes, such as learning, are not localised, but distributed in a more holistic way in the brain.

Question 27

Evaluation limitation for localisation of function: research into plasticity

Answer 27

P: The Plasticity of brain function argues that localisation of function is largely incorrect.

E: More recent research into the plasticity of the brain shows that key areas for key functions can be changed in the light of injury / functional recovery after brain injury.

E: It may be the case that simpler functions are likely to be more localised in the brain, eg motor control but more sophisticated aspects of the brain can swap and change if necessary.

L: This could mean suggestions that the brain is highly localised is overstated by research.

Question 28

Describe hemispheric lateralisation with example of L/R functions

Answer 28

Some brain functions are found only in one hemisphere and this is known as hemispheric lateralisation.

Overall, the left hemisphere appears to focus on detail and will be more active on tasks where an individual is asked to identify small details.

Conversely, the right hemisphere appears to process overall patterns and shows more activity when individuals are asked to make sense of e.g., a whole picture.

Question 28

Name some tasks that the L hemisphere operates with one in detail

Answer 28

-Mathematics
- Analytical skills
- Reasoning and decision making
- Linear thinking and sequencing

Language: For most people their language processing is done in the left hemisphere, although this is not always the case (approximately 96% of right handers and 70% of left handers have left hemispheric dominance for language).

Question 29

Name some tasks the R hemisphere operates with one detailed example

Answer 29

• Musical ability (i.e., rhythm)
• Creativity / arts
• Imagination and daydreaming
• Nonverbal cues
• Holistic thinking

Spatial relationships: The right hemisphere also appears to be dominant for spatial functions like finding your way. People with damage to the right hemisphere may have difficulties with spatial tasks such as remembering a route.

Question 30

Name two language centres lateralized to the left hemisphere

Answer 30

• Broca’s area
• Wernicke’s area

Question 31

Describe Broca’s area

Answer 31

Broca, a French neurosurgeon, identified a ‘language centre’ in the posterior (back) portion of the frontal lobe of the left hemisphere (Broca 1865). This area is believed to be critical for speech production.
Broca found that patients (firstly Patient Tan) with deficits who could understand language but could not speak or write had lesions in their left frontal hemisphere whereas patients with damage in these areas in the right hemisphere did not have the same language problems.
Interestingly not all words are equally affected, nouns and verbs often seem to be fine. Conjunctions and prepositions have major problems. E.g. with Broca’s aphasia you couldn’t read ‘to be or not to be’ but could read ‘two bee ore knot two bee’.

Question 32

Describe Wernicke’s area

Answer 32

Wernicke’s area is in the posterior portion of the left temporal lobe. Whereas Broca’s patients could understand language but not speak, patients with a lesion in the Wernicke’s area could speak but were unable to understand language. This is called Wernicke’s aphasia.
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 and hence is involved in speech production.
The sensory region, located in Wernicke’s area, is close to regions of the brain responsible for auditory and visual input. Input from these regions is thought to be transferred to Wernicke’s area where it is recognised as language and associated with meaning.

Question 33

How do Broca’s area and Wernicke’s area work together?

Answer 33

Broca’s area and Wernicke’s area work together to process and produce language.
There is a neural loop (called the arcuate fasciculus) running from Broca’s area (responsible for the production of language) and Wernicke’s area (responsible for the processing of spoken language).
Damage to both Broca’s and Wernicke’s areas may lead to global aphasia which is an inability to understand or to produce speech.

Question 34

Evaluation point for hemispheric lateralisation: Limitation: Research Methodology

post-mortem

Answer 34

P: Much of the evidence for Wernicke’s Broca’s areas comes from post-mortem studies which investigate the brain after death.

E: Although this may help to pinpoint areas of the brain involved in different functions, it is not possible to then refine the understanding of these functions by getting the participant to do further tasks.

E: Also, these effects may be specific to the individuals concerned and may not be generalisable to others.

L: This suggests that more modern methods of brain imaging (fMRI) will prove to be more useful and continue our understanding of the brain.

Question 35

Evaluation point for hemispheric lateralisation: Limitation: Disputing Research

Answer 35

P: Research has found that lateralisation patterns shift with age.

E: Some research has found clear differences between young children’s brains and adult brains with regards to lateralised abilities.

E: Szaflarski et al (2006), found most tasks generally become less lateralised in healthy adulthood.

L: This suggests that conclusions on localised and lateralised functioning need to take into account the role of AGE and EXPERIENCE.

Question 36

Evaluation point for hemispheric lateralisation: Limitation: Disputing Research for language being lateralised

Answer 36

P: Furthermore, more recent research suggests that language may not be confined to just Broca’s and Wernicke’s area, or lateralised to one hemisphere.

E: A recent review by Dick and Tremblay (2016) found that only 2% of modern researchers think that language in the brain is completely controlled by Broca’s and Wernicke’s areas. Advances in brain imaging techniques, such as fMRI, mean that neural processes in the brain can be studied with more clarity than ever before. It seems that language function is distributed far more holistically in the brain than first thought. So-called language streams have been identified across the cortex, including brain regions in the right hemisphere, as well as subcortical regions such as the thalamus.

L: This suggests that, rather than being confined to a couple of key areas, language may be organised more holistically in the brain, which contradicts lateralisation theory.

Question 37

Evaluation point for hemispheric lateralisation: Evaluation: Supporting Research

Answer 37

P: There is research to support lateralisation. This is shown by Sperry’s pioneering split brain research.

E: Sperry found that the left hemisphere is more geared towards analytic and verbal tasks, whilst the right is more adept at performing spatial tasks and music.

E: This suggests that the two hemispheres do have seperate functions, with the left being the analyser whilst the right is the synthesiser.

L: This suggests that …

Question 38

Evaluation point for hemispheric lateralisation: Evaluation: Sperry’s Research Methodology

Answer 38

P: A strength of Sperry’s procedure was that by using a mixture of quasi- experiments and clinical case studies, he was able to combine qualitative and quantitative approaches.

E: As the quasi-experiment is a quantitative method of data collection, it provides information in the form of numbers and frequencies, and so can be easily analysed statistically. On the other hand, the case study is a qualitative method of data collection which is concerned with describing meaning.

E: This means that a combination of methods allows for the collection of statistically reliable information to be enhanced by information about the research participants.

L: …

Question 39

What’s the background of split brain research?

Answer 39

In cases of severe epilepsy, one drastic solution for those who had not been helped by conventional medicine is to have surgery to disconnect the two sides of the brain.
This then restricts the epileptic seizures to only one hemisphere and reduces the severity of the attack.
This had mixed results.
Split brain patients are those who have had the connection between the left and right hemisphere severed.
In other words, their corpus colussum (the bundle of nerve fibres called commissural fibres) has been cut.
This is called a cerebral commissurotomy.
These people have proved useful to psychologists interested in studying how the different hemispheres function.
Normally, the two hemispheres share information.
In split-brain patients, this does not happen so when the eyes visual fields are restricted (info sent very briefly only to one visual field) the differences between left and right hemisphere functioning can be seen.
Although importantly in everyday life they do not show problems as the eyes are constantly moving!

Question 40

Split Brain Research: Opportunistic Research

Answer 40

The psychologists researching hemispheric functioning using split brain patients did not sever the corpus callosum of the epileptic patients themselves.
It WAS NOT done for the PURPOSE of the research.
The researchers merely took advantage of the fact that this operation had been done to allow them to investigate the effects.
If they then designed high controlled studies, what type of experiment would this be?

Question 41

Split Brain Research: The Process

Answer 41

Split brain research uses a split visual field.
Pts are sat in front of a screen and asked to gaze at a fixed point in the centre of the screen.
Visual stimuli are projected onto the screen either to the right or left visual field at a very high speed so the Pt has no chance to move their head and is only able to process the image in the visual field where it was placed.

Question 42

Split Brain Research: Roger Sperry
Words projected to LVF (to right hemisphere).

Answer 42

What was done: Words projected to LVF (to right hemisphere).

Testing: Verbal responses to language.

Finding: Words not registered. Pt’s would say they saw nothing.

Conclusion: Left hemisphere responsible for language (so words need to be presented to RVF in order to be registered).

Question 43

Split Brain Research: Roger Sperry

Words (e.g., fork) projected to LVF (to right hemisphere).

Answer 43

What was done: Words (e.g., fork) projected to LVF (to right hemisphere).

Testing: Physical responses to language.

Finding: Left hand (controlled by RH) was placed behind a screen with objects. Pt’s could feel around and select the correct object DESPITE being unable to verbally report it.

Conclusion: Right hemisphere does have some language ability for understanding words if not for speech.

Question 44

Split Brain Research: Roger Sperry
A different face presented to each hemisphere at the same time. Pt’s given a set of faces and asked to select those they had seen.

Answer 44

What was done: A different face presented to each hemisphere at the same time. Pt’s given a set of faces and asked to select those they had seen.

Testing: Matching abilities in response to pictures.

Finding: Pt’s chose the one presented to the RH, indicating its role in identifying faces and shapes.

Conclusion: Right hemisphere is responsible for visuospatial tasks.

Question 45

Evaluation point for split brain research: strength Practical applications

Answer 45

A strength of split brain research is that it has useful practical applications enabling a greater understanding of the differing functions of the hemispheres and adding to the unity of the consciousness debate.
For instance, we now know that language is largely processed in the left hemisphere…

This allows our scientific understanding of the brain to move forward from split brain research.

Question 46

Evaluation point for split brain research: lacks generalisability

Answer 46

The split brain research lacks generalisibility as there was a limited number of participants (only 10-15 have been subjected to systematic study).
In addition, the participants varied considerably in age, gender and handedness as well as the age at which they developed epilepsy and the degree of drug therapy they had experienced before their operation. All factors that will affect behaviour.
This implies split brain research…

Question 47

Evaluation point for split brain research: hard to establish cause and effect

Answer 47

The split brain patients were often compared to neurotypical controls, but these people often had no history of epilepsy (i.e. not matched pairs) and therefore this could be a potential confounding variable as a history of epilepsy would affect general behaviour.
This means it is harder to establish ___________ and ___________ and there could be other explanations for split brain findings , such as…

Question 48

Evaluation point for split brain research: uses standardised procedures

Answer 48

A strength of split brain research is that they use highly specialised and standardised procedures.
Sperry presented visual information to one hemispheric field at a time, asking participants to stare at a given point, the ‘fixation point’. The image projected would be flashed up for a one-tenth of a second, meaning the split-brain patient would not have time to move their eye across
the image and so spread the information across both sides.
This allowed Sperry to vary aspects of the basic procedure and ensured that only one hemisphere was receiving the information at a time.
Thus, he developed a very useful and well-controlled procedure.