Localisation of function in the brain Flashcards
What is localisation of function?
- The theory that different areas of the brain are responsible for specific behaviours, processes or activities
Before Broca’s & Wernickes areas were discovered what theory did psychologists have on the brain?
Generally supported the hollistic theory
- That all parts of the brain were involved in the processing of thought & action
What are the areas of the brain that are localised?
(carry out specific functions,behaviours or activities)
- Visual centres
- Auditory centres
- Motor cortex
- Somatosensory cortex
- Language centres (Broca’s & Werncike’s areas
What is the celebral cortex?
- The outer covering of the surface of your brain
- Carries out essential functions of your brain such as, memory, thinking, learning etc.
What is lateralisation?
- Where some of our physical & psychological functions are controlled/ dominated by a particular hemisphere
What is the cortex of both hemispheres subdivided into?
Subdivided into 4 centres called the ‘lobes’:
* Frontal lobe
* Parietal lobe
* Occipital lobe
* Temporal lobe
Found in both hemispheres of the brain
‘lobe’ is part of an organ that is separate in some way than the rest
What is the motor area?
Region in (back of) frontal lobe which controls voluntary movement in the opposite side of the body
What could happen if you damage your motor area?
May result in a loss of control over fine movements
What is the somatosensory area?
- Where sensory information from the skin (e.g. touch,heat pressure etc.) is represented
At (the front) of both parietal lobes
Separated from motor area by a ‘valley’ called central sulcus
What is the visual area?
- Part of occipital lobe (at back of brain) that recieves & processes visual information
Each eyes sends info from right visual field to left visual cortex & from left visual field to right visual cortex
What happens if there is damage to the left hemisphere in terms of the visual area?
Can produce blindness in part of right visual field of both eyes
What is the auditory area?
Located in temporal lobes & concerned with the analysis of speech-based information
What hemisphere is language linked to?
The left hemisphere
What did Paul Broca identify?
A small area in the left frontal lobe responsible for speech production
What does damage to Broca’s area cause?
- Causes Broca’s aphasia which is characterised by speech that is slow, laborious & lacking in fluency
Who was Broca’s patient tan?
- Broca encountered a patient known as “Tan,” who had lost the ability to speak but retained other cognitive functions after suffering a stroke.
- Despite being unable to articulate anything other than the word “tan,” patient seemed to understand language reasonably well.
Following Tan’s death,
Broca conducted post-mortem & noticed a lesion in the left frontal lobe
What did Karl Wernicke discover?
- Identified a region (Wernickes area) in left temporal lobe being responsible for language understanding
Was describing people who had no problem producing language but severe difficulties understanding it
What is Wernickes aphasia?
Results when Werncke’s area is damaged:
* Ppl who have Wernicke’s aphasia will often produce nonsense words (neologisms) as part of the content of speech
What was Hubels & Weisels visual cortex experiment with the cats?
- Carried out an experiment on kittens & adult cats in 1963 which proved that the visual cortex develops during a critical period early in life.
- First, they prevented visual stimulation in one eye by sewing up one eye of each kitten.
- Several months later, they unstitched the eye.
What were Hubel & Weisel’s findings?
- Looking at brains of the kittens under microscope, they found that ocular dominance columns for the stitched up eye had shrunk that & the ocular dominance columns for the open eye had expanded
- Suggesting that the columns for the open eye had taken over the columns that were not being stimulated (i.e. the neurons in the visual cortex had switched dominance).
- Found that adult cats retained their normal vision after having their eye stitched closed for several months & their ocular dominance columns remained unchanged.
Repeated experiment on young and adult monkeys and achieved the same results.
How can Hubel & Weisel’s findings be applied to humans?
- Since visual cortex in cats and humans is similar (they both contain ocular dominance columns), H & W results can be applied to humans.
Means that humans need to receive visual stimulation from both eyes during early periods of life for their visual cortex to develop normally
What is the homoculus man?
Related to density of sensory receptors- receptors on the skin
* The more we use a part of our body the bigger the body part
hence oversized hands,lips, tounge & gentials
What happened to Phineas Gage?
- Whilst working on railroad in 1848 25yr old Phineas Gage was preparing to balst a section of rock with explosives to create a new railway line
- During process, Gage dropped his tamping iron onto the rock causing explosive to ignite
- Explosion hurled the meter-length pole through Gages left cheek, passing behind his left eye & exiting his skull from the top of his head taking a portion of his brain with it- most of his left frontal lobe
What was the aftermath of Gage after his accident?
- Incredibly he survivied but damage to his brain had left a mark on his personality
- Had turned from someone who was calm & reserved to someone who was quick tempered & rude
Accident suggested that frontal lobe may be responsible for regulating mood
Give one strength of localisation theory.
There is research evidence to support the concept that functions are localized in the brain
* Broca
* Wernicke
* Phineas Gage
Some of this research is very modern and is highly scientific
HOWEVER…
Some of the research is very old and lacks scientific credibility
Some research shows that higher-order functions are not localised
Give another strength of localisation of function
Another strength- Evidence from brain scans supports idea that many everday brain functions are localised
* Steven Petersen et al (1988) used brain scans to demonstrate how Wernickes area was active during listening task & Brocas areas was active during reading task
Give one limitation of localisation of function?
- Langauge may not be localised just to Broca’s & Wernicke’s areas
- Recent review by Dick & Tremblay (2016) found only 2% of researchers think that language in the brain is completely controlled by Broca’s & Wernicke’s area
- Imaging techniques icluding FMRI seems to show language function is distributed far more holisitcally in brain than first thought
for example: so-called language streams have been identified across the cortex including brain regions in right hem
