localisation of function

Question 1

what is localisation of function?

Answer 1

• theory that different areas of the brain are responsible for specific processes or activities
• if a certain area of the brain becomes damaged through illness or injury, the function associated with that area will also be affected

Question 2

how is the cerebrum divided?

Answer 2

2 symmetrical halves called the left and right hemisphere

Question 3

what is lateralisation?

Answer 3

the idea that some of our physical and psychological functions are controlled or dominated by a particular hemisphere

Question 4

what is activity on the left or right-hand side of the body controlled by?

Answer 4

• activity on the left-hand side of the body is controlled by the right hemisphere
• activity on the right-hand side of the body is controlled by the left hemisphere

Question 5

what is the cortex of both hemispheres divided into?

Answer 5

4 centres called lobes

Question 6

what are the four lobes of the brain?

Answer 6

• the frontal lobe
• the parietal lobe
• the occipital lobe
• the temporal lobe

Question 7

what is a lobe?

Answer 7

• a part of an organ that is separate in some way from the rest
• each lobe in the brain is associated with different functions

Question 8

describe the motor area

Answer 8

• back of frontal lobe in both hemispheres
• controls voluntary movement in opposite side of body

Question 9

what might damage to the motor area result in?

Answer 9

loss of control over fine movements

Question 10

describe the somatosensory area

Answer 10

• at the front of both parietal lobes
• separated from the motor area by a ‘valley’ called the central sulcus
• where sensory information from the skin (eg. related to touch, heat, pressure etc.) is represented
• the amount of SA devoted to a particular body part denotes its sensitivity
  > eg. receptors for our hands and face occupy over half of the area

Question 11

describe the visual area

Answer 11

• in the occipital lobe at the back of the brain
• each eye sends information from the RVF to the left visual cortex and vice versa
• therefore, damage to the LH can produce blindness in part of the RVF in both eyes

Question 12

describe the auditory area

Answer 12

• in the temporal lobes
• analyses speech-based information

Question 13

what may damage to the temporal lobe result in?

Answer 13

• partial hearing loss
• the more extensive the damage, the more extensive the loss
• damage to a specific area of the temporal lobe, wernicke’s area, may affect the ability to comprehend language

Question 14

describe broca’s area

Answer 14

a small area in the left frontal lobe responsible for speech production

Question 15

what does damage to broca’s area result in and describe the condition

Answer 15

• broca’s aphasia
• characterised by speech that is slow, laborious and lacking in fluency
• difficulty with prepositions and conjuctions (a, the and etc.)

Question 16

describe broca’s most famous patient

Answer 16

• ‘tan’
• this was the only word he could say

Question 17

describe wernicke’s area

Answer 17

region in the left temporal lobe which is responsible for language understanding

Question 18

describe wernicke’s aphasia

Answer 18

• caused when wernicke’s area is damaged
• can produce language but severe difficulties understanding it
• the speech they produce is fluent but meaningless
• produce nonsense words (neologisms) as part of the content of their speech

Question 19

evaluation: evidence from neurosurgery

Answer 19

• damage to areas of the brain has been linked to mental disorders
• neurosurgery is a last resort method for treating some mental disorders, targeting specific areas of the brain
• eg. cingulotomy involves isolating a region of called the cingulate gyrus, which has been implicated in OCD
• 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

Question 20

evaluation: evidence from brain scans supports the idea that many everyday brain functions are localised

Answer 20

• 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
• a review of long-term memory studies (buckner and petersen 1996) revealsed that semantic and episodic memories reside in different parts of the prefrontal cortex
• these studies confirmed localised areas for everyday behaviours
• therefore, objective methods for measuring brain activity have provided sound scientific evidence that many brain functions are localised

Question 21

evaluation: challenge to localisation theory from lashley (1950)

Answer 21

• 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 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

Question 22

evaluation: language may not be localised to just broca’s and wernicke’s areas

Answer 22

• 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 technqiues, such as fMRI, mean that neural processes in the brain can be studied with more clarity than every before
• language function seems to be distributed far more holistically in the brain than was first thought
• 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

Question 23

evaluation: case study evidence

Answer 23

• unique cases of neurological gamage support localisation theory, such as the case of phineas gage
• however, there are problems with case studies as 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

Question 24

evaluation: phineas gage (1848)

Answer 24

• a metre-long pole was hurled through his left cheek during an explosion, passing behind his left eye and exiting his skull from the top of his head taking more of his left frontal lobe with it
• the damage to his brain had left a mark on his personality
• he turned from someone who has calm and reserved to someone who was quick-tempered and rude
• the change in temperament following the accident suggested that the frontal lobe may be responsible for regulating mood

Question 25

evaluation: harasty (1997)

Answer 25

• found that women have proportionately larger wernicke and broca’s areas, resulting in women’s greater use of language
• this supports the idea of localisation of function, but suggests invidiual differences
• it suggests that male and female brains operate in a different manner and doesn’t follow the initial theories of the brain as suggested by early research

Question 26

evaluation: bavelier et al. (2011)

Answer 26

• found that when completing silent reading, different parts of the brain were active (eg. occipital or temporal)
• study shows the variability in the patterns of activation across the brain
• this contradicts the notion that specific areas are for specific functions in the brain

Question 27

evaluation: saygin et al. (2003)

Answer 27

• found that some patients displayed symptoms of wernick’es aphasia without any damage to this area
• this raises questions regarding the exact nature of wernicke’s area, and the ability to assign singular functions to brain regions and / or singular regions to complex functions