Localisation Of Function Flashcards
What is localisation of function?
Theory that different areas of the brain are responsible for different behaviours, processes or activities
In the early 19th century what approach did they have regarding the function of the brain? (Later discovered that different areas of the brain were associated with particular and physiological functions I.e. localisation theory
Holistic approach
The brain is divided into 2
Hemispheres:left and right hemisphere. Some of our physical and physiological functions are controlled by a particular hemisphere (lateralisation)
Generally, the left side of the body is controlled by
The right hemisphere and the right side of the body is controlled by left (contralateral)
The outer layer of both hemispheres is called the
Cerebral cortex
What is interesting about the cerebral cortex?
Separates us from lower animals as it is highly developed
Why does the cortex appear grey?
Due to location of cell bodies; hence ‘grey matter’
The cortex of both hemispheres is divided into 4 lobes:
Frontal, parietal, occipital and temporal
What is found in the frontal lobe?
- back of frontal lobe in both hemispheres= motor area
- left frontal lobe = Broca’s area
What is the motor area responsible for?
Voluntary movement on the other side of the body- damage to this area leads to loss of control of fine motor movements
What is Broca’s area responsible for?
Speech production identified in 1880s- damage to Broca’s area leads to Broca’s aphasia = slow speech lacking in fluency and may include stutters
What is found in the parietal lobes?
Front of both parietal lobes= somatosensory area
What is the function of the somatosensory area?
Processes sensory information e.g. touch- the amount of somatosensory area devoted to a particular body part denotes its sensitivity
What’s found in the occipital lobe?
In the occipital lobe at the back of the brain is the visual area
What is the function of the visual area?
Each eye sends information from the right visual field to the left visual cortex and information from the left visual field to the right visual cortex- damage to three left hemisphere for example can produce blindness in part of the right visual fields in both eyes
What’s found in the temporal lobe?
- auditory area
- Wernicke’s area in the back of the temporal lobe
What’s the function of the auditory area?
Analyses speech-based information- damage may produce partial hearing loss (more extensive the damage, the more serious the loss)
What is the function of Wernicke’s area?
Around the same time as Broca’s identified Broca’s area (1880s), Wernicke identified Wernicke’s area responsible for language comprehension- patients with damage to this area had no problem producing speech but severe difficulties understanding it = speech produced was fluent but meaningless
What are the evaluation points for localisation of function?
✅brain scans
❌ phenomenon of neural plasticity
❌ existence of contradictory research
✅ case study evidence
How do brain scans provide support for localisation of function theory?
study of LTM by Tulving et al revealed that semantic and episodic memories located in different parts of the frontal cortex; there now exists a number of highly sophisticated and objective methods for measuring activity in the brain such as fMRI which essentially detects changes in blood oxygenation in areas of the brain- when an area of the brain is more active it requires more oxygen and so causal relationships can be determined between exposure to certain stimuli and responding areas of the brain supporting localisation theory =scientific methods provide sound scientific evidence for localisation of brain function
How is the phenomenon of neural plasticity a challenge to localisation of function theory?
When the brain has become damaged (illness/accident) and a particular function has been compromised or lost, the rest of the brain appears to ‘reorganise’ itself in attempt to recover the lost function; Lashley described this as the law of equipotentiality, whereby surviving brain circuits ‘chip in’ so the same neurological action can be achieved (doesn’t happen every time but there are several documented cases of stroke victims being able to recover those abilities seemingly lost
How does the existence of contradictory research challenge localisation of function theory?
Work of Lashley suggests that higher cognitive functions e.g. processes involved in learning are not localised but distributed in a more holistic way in the brain. Lashley removed between 10-50% of the cortex in rats learning a maze; no area seemed to be more important than the other in terms of the rats’ ability to learn the maze. It seemed the process of learning involved every part of the cortex rather than a particular area= learning too complex to be localised= required involvement of the whole brain
How does case study evidence provide support for localisation of function theory?
Phineas Gage obtained serious brain damage to his frontal lobe after an iron pole was driven through his head and the damage to his brain permanently affected his personality (went from calm and reserved to quick-tempered, rude and “no longer Gage” as stated by bus family and friends). The change in Gage’s temperament following the accident suggests the frontal lobe may be responsible for regulating mood- BUT trauma or other variables could have caused this change so cannot be certain of this
