Localisation of the brain Flashcards
What is localisation of the brain?
The theory that different areas of then brain are responsible for specific behaviours, processes or activities
What does the term contralateral mean?
Each hemisphere of the brain (right/left) controls the opposite (contralateral) side of the body. Including both motor and sensory pathways and vision of contralateral visual field
What does the early 19th century holistic theory suggest?
All parts of the brain were involved in processing thought and action
Specific areas of the brain - later linked with specific physical and psychological functions (localisation theory)
Area of the brain (through illness/injury) - function is associated with area with that area is also affected
The brain is divided into two and lateralised, what does this mean?
Some physical and psychological functions are controlled by a particular hemisphere
- Left side of the body is controlled by the right hemisphere and the right side of the body by the left hemisphere
What is the cerebral cortex?
- It covers the inner part of the brain
- 3mm thick, what separates us from lower animals, it is highly developed
- Cortex appears grey due to location of cell bodies (‘grey matter’)
What four lobes is the cerebral cortex of both hemispheres divided into?
Visual cortex (occipital lobe)
Motor cortex
Somatosensory cortex
Auditory cortex
Where and what is the visual cortex in the brain?
- what happens when it is damaged
In the occipital lobe at the back of the brain - the brains visual processing centre, each eye sends info from the RVF to left visual cortex and from the LVF to the right visual cortex
Damage: Leads to partial or complete loss of vision known as cortical blindness. Damage to one cortex can lead to loss of vision in the opposite visual field
Where and what is the somatosensory cortex in the brain?
- what happens when it is damaged
At the front of the parietal lobes. Process sensory info from the skin (touch, heat, pressure e.t.c)
The amount of somatosensory area is devoted to a particular body part denotes its sensitivity
Damage: Loss of sensation, ignoring areas of the body (neglect syndrome), loss of ability in recognising objects by their feel (agnosia). Effects are in opposite side to damage
Where and what is the motor cortex in the brain?
- what happens when it is damaged
At the back of the frontal lobe (both hemispheres) which is responsible for voluntary movement.
Damage: May result in loss of control over finer movements. This occurs on the opposite side of the body to the damage due to contralaterality
Where and what is the auditory cortex in the brain?
- what happens when it is damaged
In the temporal lobe - analyses speech-based information
Damage: May produce partial hearing loss - the more extensive the damage, the more serious the loss
State the two language centres in the brain
Broca’s area
Wernicke’s area
Where and what is the Broca’s area (language centre) in the brain responsible for?
- what happens when it is damaged
Located in the left frontal lobe - responsible for speech production
Damage: Causes Broca’s aphasia which is characterised by speech that is slow, laborious and lacking in fluency - difficulty in finding words and naming certain objects
Missing words -> poor grammar
Where and what is the Wernicke’s area (language centre) in the brain responsible for>
- what happens when is it damaged
Located in the top temporal lobe - responsible for language understanding
Damage: Causes Wernicke’s aphasia produce language but have problems understanding it, so they produce fluent but meaningless speech
Often produce nonsense words as part of the content of their speech
EVALUATION: Individual differences
Certain psychologists argue that the concept of localisation ignores individual differences.
Herasty discovered that women’s Wernicke’s and Broca’s areas are proportionally larger than men’s, which may help to explain why women use language with greater ease than males.
This, however, points to some form of beta bias in the theory; gender differences are overlooked, and changes in the pattern of activity and area sizes seen during different language tasks are not taken into account.
Because of this, research on localisation of function cannot be applied to males and females equally because of differences in brain size and structure, which indicate that various factors need to be taken into account when analysing the sexes.
EVALUATION: Localisation theory is supported by brain scan evidence
Petersen et al used brain scans to show activity in Wernicke’s area during a listening task and in Broca’s area during a reading task
Additionally, Tulving et al.’s long-term memory investigation showed that the prefrontal cortex’s semantic and episodic memory areas are located in different places.
Today, there are several advanced and objective techniques for assessing brain activity, offering reliable scientific proof of the localisation of function.
EVALUATION: Clinical case study research
It demonstrates loss of certain functions if damage is caused to particular areas of the brain e.g Broca and Wernicke’s case studies (aphasia) and Clive Wearing (amnesia)
This suggests functions are localised in these areas
EVALUATION: Counter evidence for case studies
But while case studies provide evidence for the Broca’s and Wernicke’s areas’ functions, more recent research has shown conflicting results.
Tan’s brain was subjected to an MRI scan by Dronkers et al. (2007) in an attempt to confirm Broca’s findings. Even though a region in a organ/tissue (suffered damage)was discovered in the Broca’s area, there was evidence that suggested other locations might have had a role in the speech production failure.
These findings imply that injury to other adjacent areas may be the cause of the abnormalities observed in individuals with Broca’s aphasia and that the Broca’s area may not be the sole location involved in speech production.
EVALUATION: More crucial to look at communication between brain areas
Rather than concentrating on particular brain regions, psychologists argue that it is more crucial to look into how the various brain areas communicate with one another. According to Wernicke, the various brain regions are separate, but for effective functioning, they need to communicate with one another.
As stated by Dejerine, one example of this is a guy who lost his ability to read as a result of injury to the connection between the visual cortex and the Wernicke’s region. This shows that complex behaviours like language are the result of interactions between different areas.
Therefore damage to the localised brain region linked to that particular function may arise from damage to the connection between any two sites. As a result, the localization loses credibility.
