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Hemispheric Specialisation
Contribution of studies to the investigation of
cognitive processes of the brain and
implications for the understanding of
consciousness including:
studies of aphasia (Broca’s and Wernicke’s)
Spatial Neglect caused by stroke or brain injury
Split-brain studies including work of Roger Sperry &
Michael Gazzaniga
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Hemispheric Specialisation/hemispheric
dominance or hemispheric lateralisation.
Two hemispheres appear replicas in size,
shape and certain functions. Some functions
are ‘contralateralised’.
The somatosensory cortex of Right parietal
lobe receives information from Left side of
body. The primary motor cortex in Right
parietal lobe controls movement of Left side
of body
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Evidence about HS from people with brain
damage.
Damage to Left Hemisphere result in
language-related difficulties.
Damage to Right Hemisphere – difficulties
with visual and spatial tasks
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Verbal Functions: word recognition – reading,
writing, speaking, understanding speech.
Analytical Functions: sequential, step-bystep task completion, logical reasoning,
interpreting and solving maths problem,
critically evaluating, developing an argument,
time management
Receives and processes sensations from R
side of body
Controls voluntary movement of R side of
body
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Non-verbal Functions: spatial and visual
thinking e.g.
doing a jigsaw puzzle,
reading a map,
visualising objects in space,
Recognising faces, patterns, tunes
Music appreciation
Creative thinking, daydreaming
Sensations from L side of body and motor
control of L side of body
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Aphasia – refers to a language disorder
apparent in speech (comprehension or
production), writing or reading produced by
injury to brain areas specialised for these
functions.
Broca’s Aphasia & Wernicke’s Aphasia
Most common cause – stroke.
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Damage to area in Left frontal lobe (next to
motor cortex).
speech is non-fluent with pauses between words,
short sentences mainly verbs & nouns.
Words may be mispronounced.
Partial/complete loss of memory for finding
correct word
Can be confused if change order of words in
sentence. E.g. I broke the vase to The vase was
broken by me.
Aware of their difficulties. Deaf people with
Broca’s aphasia have difficulty producing sign
language.
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Damage to Left Hemisphere – Temporal Lobe
Can produce fluent speech but generally
nonsensical
Difficulty understanding speech & written
language
Impaired ability to recall words.
Some can ‘sing’ sentences and make sense
(RH- musical)
Generally not aware of their difficulties.
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An attentional disorder in which individuals
fail to notice anything either on their left or
right (not as common) side. Failure of
attention and not a disorder due to
impairment of memory, the visual system or
other sensory systems.
Most common in stroke/accident victims –
extensive damage to rear of parietal lobe of
Right Hemisphere
Side of world opposite to (contralateral)
damaged hemisphere tends to be neglected.
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Involves surgically cutting the corpus
callosum hence disconnecting one
hemisphere from the other.
Originally conducted to treat epilepsy
1950s Roger Sperry – study with cats’ visual
system
Each eye normally sends visual information to
both hemispheres via the optic nerve and
optic chiasm. Cutting this means that visual
information to left eye is sent only to left
hemisphere etc. (Textbook pg. 224)
Nelson Psychology VCE Units 3 & 4: Teacher Resource CD
9780170185219
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Gazzaniga – designed series of experiments
to test split-brain patients.
Check YouTube – Gazzaniga and split-brain
experiments
Nelson Psychology VCE Units 3 & 4: Teacher Resource CD
9780170185219
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If information flashed on Left Visual Field –
goes to Right Hemisphere. Individual cannot
SAY what they have seen but can draw it with
Left hand. (the right hemisphere is
nonverbal). The visual information sent to the
right hemisphere cannot cross back to left
hemisphere because corpus callosum is cut,
then unable to say what they saw.
If information from Right Visual Field goes to
Left Hemisphere individual can say what
object is.
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Pretend to be a Split-brain patient. The
experiment, the patient, the recorder
Patient closes their eyes. Experimenter places
an item in the patient’s right hand. Can the
patient identify the item by name? Why?
Experimenter places a different item in the
patient’s left hand. Can the slit-brain patient
name the object? Why?
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Experimenter writes the name of an item on a
piece of paper and flashes this to Left Visual
Field of the patient. From an array of different
items, can the patient select the right item?
Why?
Experimenter now flashes name of an item in
the Right Visual Field. Can the patient now
select the correct item from an display of
items? Why?
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Is she likely to say that she saw an object?
Give reason.
Is she able to verbally identify the object?
Give reason
Is she able to identify the object with her left
hand by touch (selecting the item from
behind the screen)? Reasons
Is she able to identify the object with her
right hand by touch (selecting the item from
behind the screen)? reasons
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Is she likely to say that she saw an object?
Give reasons
Is she able to verbally identify the object?
Give reasons
Is she able to identify the object with her left
hand by touch (selecting the item from
behind the screen)? Give reasons
Is she able to identify the object with her
right hand by touch (selecting the item from
behind the screen)? Give reasons