Hemispheric Lateralisation & Localisation of Function Flashcards
hemispheric lateralisation
idea that the two halves of the brain are functionally different and certain mental processes/behaviours controlled by one hemisphere rather than the other
eg our ability to produce and understand language is controlled by the left hemisphere
Investigated by split-brain research
Two hemispheres bridged by corpus callosum: bundle of fibres; communication pathway to exchange info
the brain is contralateral so each hemisphere deals with the opposite side of the body, so if there is damage on one side, it will affect the corresponding side of the body
left hemisphere
Language processing
Stroke on left side of brain -> speech affected
Broca’s area, Wernicke’s area
Small details
right hemisphere
Recognising emotions in others
Research: photo of face split (one side smiling, other neutral) -> emotion displayed on left side recognised (right hemisphere processes left visual field)
Case study: woman had damage to RH -> would get lost, even in familiar situations -> found RH more adept at spatial relationships/info
Holistic information/overall patterns
localisation of function
idea that specific functions (eg language, memory, hearing) have specific locations within the brain
therefore, if a certain area of the brain becomes damaged through illness or injury, the function associated will be affected
draw/label the areas/cortexes of the brain
x
motor centres
Motor cortex: back of frontal lobe just both hemispheres
Sends messages to muscles via brain stem and spinal cord
responsible for generating voluntary motor movements
each hemisphere controls movement in the opposite sides on the body
damage -> loss of control over fine movements
somatosensory cortex
Somatosensory cortex: front of parietal lobe in both hemispheres
somatosensory refers to sensation of the body
Sensory info from skin (eg touch, heat, pressure) is represented
perceived touch, so the amount of neuronal connections needed dictates the amount of somatosensory cortex needed for that area of the body
each cortex receives sensory information from the opposite side of the body each
Visual centres
Occipital lobe in each hemisphere
each eye sends visual information from the left visual field to the right hemisphere and from the right visual field to the left hemisphere
Damage -> blindness in VF of each eye
Area V1: necessary for visual perception, damage -> no vision at all
auditory centres
temporal lobe in each hemisphere
receives info from both ears via two pathways that transmit information about what the sound is and its location
damage -> hearing loss (may be more extensive)
language centres
Left hemisphere = language processing in majority of population
Broca’s area
- left temporal lobe
- responsible for speech production
- Damage -> Broca’s aphasia (speech lacking in fluency, slow, laborious)
Wernicke’s area
- left temporal lobe
- Wernicke found that patients who had damage to the auditory cortex had specific language impairments
- inability to comprehend language, anomia (struggling to find the word they need)
- BUT had fluent speech when they could access the words quickly
- responsible for understanding language/accessing words.
- Damage -> Broca’s aphasia (nonsense words, anomia, low comprehension)
Evaluate: hemispheric lateralisation & localisation of function
- STRENGTHS
P) support from case studies of brain damaged patients
E) Broca: damage to broca’s area -> brocas aphasia (difficulty producing speech) eg. Tan (only word he could say)
E) Wernicke: damage to Wernickes area -> Wernickes aphasia (difficulty understanding language, producing fluent but meaningless speech)
L) specific functions are localised in the brain
E) low population validity: rare cases/small samples
P) support from brain scan research
E) Paterson et al (1988) Wernickes area active during a listening task, Broca’s area active during a reading task
E) Tulving et al (1994) episodic/semantic memories recalled from different sides of prefrontal cortex, procedural memory associated with cerebellum
L) wide range of scientific/empirical evidence to support the idea that different areas of the brain have different functions
E) objective/high internal validity
Evaluate: hemispheric lateralisation & localisation of function
- LIMITATIONS
P) evidence against from animal research
E) Lashley (1950) removed between 10-50% of the cortex in rats that were learning a maze
E) no area was more important than another in terms of their ability to learn the maze
L) learning is too complex to be localised/ requires involvement of the whole brain
E) findings can’t be accurately extrapolated to humans
P) brain functioning is more complex than localisation suggests
E) research suggests the way the brain areas communicate with each other is more important than which specific areas control particular processes
E) Dejerine (1892): patient with damage to visual cortex/Wernickes area: lost ability to read
L) damage to communication between two areas can produce impairments that resemble damage to a different area
E) more research needed
P) evidence against from research into brain activity
E) Lashley: when brain is damaged through illness/injury and a function is compromised, the rest of the brain can reorganise itself to recover the damaged function
E) eg cases of stroke victims recovered lost functions
L) localisation theory is too simplistic; brain is able to be more adaptive and operate in a more holistic way
E) reductionist
