BIO 07 - Localisation of function Flashcards
(21 cards)
What is the localisation of function?
The theory that different areas of the brain are responsible for different behaviours, processes or activities
What is the motor area/cortex?
A region of the frontal lobe involved in regulating all voluntary muscle movement
Where is the motor area/cortex located? And what is its relationship to hemispheres?
- It is located in the frontal lobe of the brain in the precentral gyrus
- Both hemispheres of the brain have a motor cortex
What is the somatosensory area/cortex?
- An area of the parietal lobe that processes sensory information from the skin, muscles and joints related to touch
- Using sensory information, the somatosensory cortex produces sensation of touch pressure, pain and temperature
- It then localises this to specific body regions
Where is the somatosensory area/cortex located? And what is its relationship to hemispheres?
- It is located in the parietal lobe of the brain
- Both hemispheres have a somatosensory cortex on one side of the brain receiving sensory information from the opposide side of the body
What is the visual area/cortex?
- A part of the occipital lobe that receives and processes visual information
- It contains several different areas, each processing different types of visual information such as colour, shape or movement
- Information from the eyes (and the retina) are transmitted to this area of the brain
Where is the visual area/cortex located? And what is its relationship to hemispheres?
- It is located in the occipital lobe of the brain
- There is a visual cortex in each hemisphere
- With each hemisphere receiving its input from the opposide side of the visual field
What is the auditory area/cortex?
It is concerned with the analysis of speech-based information
Where is the auditory area/cortex located? And what is its relationship to hemispheres?
- It is located in the temporal lobe
- There is an auditory cortex in each hemisphere
What is the Wernicke’s area?
- Language centre
- Associated with understanding of speech
- An area of the temporal lobe (encircling the auditory cortex) in the left hemisphere (in most people), responsible for language comprehension
Where is the wernicke’s area located? And what is its relationship to hemispheres?
- It is located in the left temporal lobe
- In the majority of people wernicke’s area is located in the left hemisphere
What is the Broca’s area?
An area of the frontal lobe in the left hemisphere (in most people), responsible for speech production
Where is the broca’s area located? And what is its relationship to hemispheres?
- It is located in the frontal lobe
- It is located in the left hemisphere
Describe the case study of Phineas Gage.
- Whilst working on the railroad in 1948, 25-year-old Phineas Gage was preparing to blast a section of rock with explosives to create a new railway line
- Gage dropped his tamping iron onto the rock causing to the explosive to ignite
- The explosion hurled the metre-length pole through Gage’s left cheek, passing behind his left eye, and exiting his skull from the top of his head taking a portion of his brain with it (most of his left frontal lobe)
- Gage survived but the damage to his brain caused changes in his personality, turning him from calm and reserved to quick-tempered, rude and ‘no longer Gage’ as described by those who knew him
- His case study suggested that the frontal lobe may be responsible for regulating mood
What are the strengths of localisation theory?
- Evidence from neurosurgery
- Evidence from brain scans
What evidence from neurosurgery is there for localisation theory?
- One strength of localisation theory is that damage to areas of the brain has been linked to mental disorders
- Neurosurgery (surgery on the brain) is a last resort method for treating some mental disorders, targeting specific areas of the brain which may be involved
- For example, cingulotomy involves isolating a region called the cingulate gyrus which has been implicated in OCD
- Darin Dougherty et al. (2002) reported on 44 people with OCD who had undergone a cingulotomy
- At post-surgical follow-up after 32 weeks, about 30% had met the criteria for successful response to the surgery and 14% for partial response
- The success of these procedures suggests that behaviours associated with serious mental disorders may be localised
What evidence from brain scans is there for localisation theory?
- Another strength is evidence from brain scans that supports the idea that many everyday brain functions are localised
- For instance, Steven Petersen et al. (1988) used brain scans to demonstrate how Wernicke’s area was active during a listening task and Broca’s area was active during a reading task
- Also, a review of long-term memory studies by Buckner and Petersen (1996) revealed that semantic and episodic memories reside in different parts of the prefrontal cortex
- These studies confirm localised areas for everyday behaviours
- Therefore, objective methods for measuring brain activity have provided sound scientific evidence that many brain functions are localised
What are the limitations of localisation theory?
- Counterpoint to brain scans through rat study
- Language may not be localised just to Broca’s and Wernicke’s area
- Case studies lack generalisability
What evidence is there that language may be organsied holistically in the brain?
- One limitation is that language may not be localised just to Broca’s and Wernicke’s areas
- A recent review by Anthony Dick and Pascale 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 was 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
- This suggests that, rather than being confined to a couple of key areas, language may be organised more holistically in the brain, which contradicts localisation theory
How does the rat study counter the evidence from brain scans for localisation theory?
- A challenge to localisation theory comes from the work of Karl Lashley (1950)
- Lashley removed areas of the cortex (between 10% and 50%) in rats that were learning the route through a maze
- No area was proven to be more important than any other area in terms of the rats’ ability to learn the route
- The process of learning seemed to require every part of the cortex rather than being confined to a particular area
- This suggests that higher cognitive processes, such as learning, are not localised but distributed in a more holistic way in the brain
How do the case studies supporting localisation of function lack generalisability?
- Unique cases of neurological damage support localisation theory, such as the case of Phineas Gage
- However, there are problems with case studies. It is difficult to make meaningful generalisations from the findings of a single individual
- Also, conclusions drawn may depend on the subjective interpretation of the researcher
