SPLIT BRAIN RESEARCH
Two hemispheres in the brain; left and right both have separate functions.
Left hemisphere; deals with language functions.
Broca’s area deals with speed production (Tan could only say ‘Tan’)
Wernicke’s area deals with language comprehension.
Right hemisphere; deals with visual motor activity.
—————
It is contralateral which means the right side of the brain deals with left body
movement whilst the left side of the brain deals with right body movement.
Sperry et al wanted to know more about hemispheres and therefore used a
process called split brain research. Sperry (1968) used a group of individuals
who had their corpus callosum and other tissues severed. They used epileptic
patients as they had already had their corpus callosum cut to reduce brain
storms. Four tasks were completed by split brain patients including describing,
tactile, drawing and composite.
11 split brain patients, all right handed
- Describing task; patients sat in front of screen, words were flashed up. Words
flashed in the right visual field were processed by the left hemisphere. As it
was in the left hemisphere they could speak the word. Words in the left vis-
ual field were unable to be spoken as there was no language production in
the right hemisphere. We can conclude that the language centres are in the
left hemisphere.
- Drawing tasks; word flashed up in the right visual field were processed by the
left hemisphere. As there is no visual motor activity in the left hemisphere
participants were unable to draw. Can conclude that the right hemisphere
controls visual motor activity.
- Composite tasks; word is flashed up in left visual field. You cannot say the
word but can draw it. Word is flashed up in the right visual field, can say the
word but cannot draw it.
EVALUATION
+ Specialised standardised methodology and procedure. For instance,
Sperry was able to vary aspects of the basic procedure and ensure that only
one hemisphere was receiving the information. Consequently, Sperry created
a very useful and well controlled procedure which could be replicated. There-
fore, the research could be completed at a later stage to check for reliability.
- Much of the research is flawed as split-brain research is very rarely carried
out now. Such studies often include very little participants, Sperry’s had 11
participants, all of which had varying degrees of epilepsy. Consequently,
some psychologists have argued that Sperry’s research is really a collection
of case studies that take an idiographic approach. Therefore, any conclusions
drawn are representative of those individuals who had a physical disorder.
This is problematic as such results cannot be generalised to the wider popu-
lation, thus, lacking population validity.
,- Language may not be restricted to the left hemisphere. Turk et al discovered
patient (JW) had suffered damage to the left hemisphere but developed the
capacity to speak in the right hemisphere, eventually leading to the ability to
speak about the information presented to either side of the brain. This sug-
gests that lateralisation is not fixed and the brain can adapt to damaged ar-
eas.
Localisation of function in the brain and hemispheric lateral-
isation
A holistic approach - Suggests all parts of the brain were involved in the processing of
all thoughts and actions.
Localisation - Psychologists argued that different parts of the brain were involved in
performing different tasks and actions.
Hemisphere - The brain is divided into two halves called hemispheres.
Lateralisation - Some of our physical and psychological functions are controlled or
dominated by a particular hemisphere.
Contralateral control - The opposite side of the brain controls the opposite side of the
body.
Frontal lobe; at the front of the brain. Controls thinking, planning, movement and
production of speech. Areas within include the motor area (movement) and Broca’s
area (production of speech).
Temporal lobe; site behind the temples. Controls hearing, memory, emotion and
comprehension of speech. Areas within include auditory area (hearing) and Wernicke’s
area (comprehension of speech).
Parietal lobe; top of the head. Controls processes such as sensation, touch, heat and
pressure. Includes somatosensory.
Occipital lobe; back of the head. Controls vision and each eye sends information to
the visual field. Includes visual area.
Cerebellum; just above the spinal cord, 10% of the brain. The brain neuron's control
movement, attention and language.
EVALUATION
- Fails to take into account individual differences. Herasty (1997) found that women
have proportionally larger Broca’s and Wernicke’s areas then men, which can per-
haps explain the greater ease of language use amongst women. This suggests a
level of beta bias in the theory: the differences between men and women are ig-
nored and the size of the areas observed are not considered. Therefore we are un-
able to generalise research examining localisation to males and females equally as
the different brain structures suggest that different considerations are required.
- Criticising research. Lashley proposed the equipotentiality theory which suggests
that basic motor and sensory functions are localised, but that higher mental func-
tions are not. He claimed that intact areas of the cortex could take responsibility for
specific cognitive functions following brain injury. Critics such as Lashley argue the
theory is biologically reductionist as it reduces complex human behaviour to one
specific brain region. This therefore casts doubt on theories such as localisation sug-
gesting that functions are not localised to one region as other regions can take over
following brain injury.
+Wealth of case studies on patients with damage to Broca’s (e.g. Tan) and Wernicke’s
area that have demonstrated their functions. For example, Broca’s aphasia is an im-
paired ability to produce language; in most cases, this is caused by brain damage in
Broca’s area. Wernicke’s aphasia is an impairment of language perception, demon-
, strating the important role played by the brain region in language comprehension.
Case studies provide evidence to support elements of language production and com-
prehension are localised within the Broca’s and Wernicke’s area.
+ Supporting research. Peterson et al (1998) used brain scans to show activity in
Wernicke’s area during a listening task and in Broca’s area during a reading task,
suggesting these areas of the brain have different functions. Also, a study of long-
term memory (Tulving et al) revealed semantic and episodic memories are located in
different parts of the brain. There now exists a number of sophisticated and objective
methods for measuring activity in the brain, providing sound scientific evidence of lo-
calisation of function.
PLASTICITY AND FUNCTIONAL RECOVERY OF THE BRAIN AFTER
TRAUMA
Two types of plasticity; plasticity (general) and functional recovery (specific
form of plasticity).
Plasticity is the brains tendency to change and adapt as a result of experience
or new learning; can also be referred to as neuroplasticity or cortical remap-
ping.
The peak amount of synaptic connections is approximately 15,000 at the age
of 2-3 years old. As we age, rarely used connections are deleted and frequently
used connections are strengthened in a process called synaptic pruning.
Maguire et al (2000) studied the brain of London taxi drivers using an MRI and
found significantly more grey matter in the posterior hippocampus than in the
matched control group. This part of the brain is associated with spatial and
navigational skills.
Functional recovery occurs following physical injury or other forms of trauma
such as infection or the experience of a stroke. There are three ways in which
functional recovery can occur; 1. Axon sprouting - new nerve endings grow and
connect with undamaged areas. 2. Reformation of blood vessels. 3. Recruit-
ment of homologous (similar) areas on the opposite hemisphere to do specific
tasks.
Factors affecting functional recovery; cognitive reserve refers to the person’s
educational attainment influencing how well the brain adapts after injury.
Schneider found the more time spent in education meant a greater chance of
recovery; 40% of patients who had a disability free recovery spent 16 years in
education whilst 10% of patients who had a disability free recovery spent 12
years in education.
Age is also a factor considered (Jodi Miller).
EVALUATION
+ Research to support Maguire’s research. For example Draganski et al im-
aged the brains of medical students 3 months before and after their final
exam. Learning induced changes were seen to have occurred in the posterior
hippocampus as a result of this exam. This supports both structural plasticity
and Maguire’s research as it suggests the brain has a tendency to change
and adapt as a result of new learning.
Two hemispheres in the brain; left and right both have separate functions.
Left hemisphere; deals with language functions.
Broca’s area deals with speed production (Tan could only say ‘Tan’)
Wernicke’s area deals with language comprehension.
Right hemisphere; deals with visual motor activity.
—————
It is contralateral which means the right side of the brain deals with left body
movement whilst the left side of the brain deals with right body movement.
Sperry et al wanted to know more about hemispheres and therefore used a
process called split brain research. Sperry (1968) used a group of individuals
who had their corpus callosum and other tissues severed. They used epileptic
patients as they had already had their corpus callosum cut to reduce brain
storms. Four tasks were completed by split brain patients including describing,
tactile, drawing and composite.
11 split brain patients, all right handed
- Describing task; patients sat in front of screen, words were flashed up. Words
flashed in the right visual field were processed by the left hemisphere. As it
was in the left hemisphere they could speak the word. Words in the left vis-
ual field were unable to be spoken as there was no language production in
the right hemisphere. We can conclude that the language centres are in the
left hemisphere.
- Drawing tasks; word flashed up in the right visual field were processed by the
left hemisphere. As there is no visual motor activity in the left hemisphere
participants were unable to draw. Can conclude that the right hemisphere
controls visual motor activity.
- Composite tasks; word is flashed up in left visual field. You cannot say the
word but can draw it. Word is flashed up in the right visual field, can say the
word but cannot draw it.
EVALUATION
+ Specialised standardised methodology and procedure. For instance,
Sperry was able to vary aspects of the basic procedure and ensure that only
one hemisphere was receiving the information. Consequently, Sperry created
a very useful and well controlled procedure which could be replicated. There-
fore, the research could be completed at a later stage to check for reliability.
- Much of the research is flawed as split-brain research is very rarely carried
out now. Such studies often include very little participants, Sperry’s had 11
participants, all of which had varying degrees of epilepsy. Consequently,
some psychologists have argued that Sperry’s research is really a collection
of case studies that take an idiographic approach. Therefore, any conclusions
drawn are representative of those individuals who had a physical disorder.
This is problematic as such results cannot be generalised to the wider popu-
lation, thus, lacking population validity.
,- Language may not be restricted to the left hemisphere. Turk et al discovered
patient (JW) had suffered damage to the left hemisphere but developed the
capacity to speak in the right hemisphere, eventually leading to the ability to
speak about the information presented to either side of the brain. This sug-
gests that lateralisation is not fixed and the brain can adapt to damaged ar-
eas.
Localisation of function in the brain and hemispheric lateral-
isation
A holistic approach - Suggests all parts of the brain were involved in the processing of
all thoughts and actions.
Localisation - Psychologists argued that different parts of the brain were involved in
performing different tasks and actions.
Hemisphere - The brain is divided into two halves called hemispheres.
Lateralisation - Some of our physical and psychological functions are controlled or
dominated by a particular hemisphere.
Contralateral control - The opposite side of the brain controls the opposite side of the
body.
Frontal lobe; at the front of the brain. Controls thinking, planning, movement and
production of speech. Areas within include the motor area (movement) and Broca’s
area (production of speech).
Temporal lobe; site behind the temples. Controls hearing, memory, emotion and
comprehension of speech. Areas within include auditory area (hearing) and Wernicke’s
area (comprehension of speech).
Parietal lobe; top of the head. Controls processes such as sensation, touch, heat and
pressure. Includes somatosensory.
Occipital lobe; back of the head. Controls vision and each eye sends information to
the visual field. Includes visual area.
Cerebellum; just above the spinal cord, 10% of the brain. The brain neuron's control
movement, attention and language.
EVALUATION
- Fails to take into account individual differences. Herasty (1997) found that women
have proportionally larger Broca’s and Wernicke’s areas then men, which can per-
haps explain the greater ease of language use amongst women. This suggests a
level of beta bias in the theory: the differences between men and women are ig-
nored and the size of the areas observed are not considered. Therefore we are un-
able to generalise research examining localisation to males and females equally as
the different brain structures suggest that different considerations are required.
- Criticising research. Lashley proposed the equipotentiality theory which suggests
that basic motor and sensory functions are localised, but that higher mental func-
tions are not. He claimed that intact areas of the cortex could take responsibility for
specific cognitive functions following brain injury. Critics such as Lashley argue the
theory is biologically reductionist as it reduces complex human behaviour to one
specific brain region. This therefore casts doubt on theories such as localisation sug-
gesting that functions are not localised to one region as other regions can take over
following brain injury.
+Wealth of case studies on patients with damage to Broca’s (e.g. Tan) and Wernicke’s
area that have demonstrated their functions. For example, Broca’s aphasia is an im-
paired ability to produce language; in most cases, this is caused by brain damage in
Broca’s area. Wernicke’s aphasia is an impairment of language perception, demon-
, strating the important role played by the brain region in language comprehension.
Case studies provide evidence to support elements of language production and com-
prehension are localised within the Broca’s and Wernicke’s area.
+ Supporting research. Peterson et al (1998) used brain scans to show activity in
Wernicke’s area during a listening task and in Broca’s area during a reading task,
suggesting these areas of the brain have different functions. Also, a study of long-
term memory (Tulving et al) revealed semantic and episodic memories are located in
different parts of the brain. There now exists a number of sophisticated and objective
methods for measuring activity in the brain, providing sound scientific evidence of lo-
calisation of function.
PLASTICITY AND FUNCTIONAL RECOVERY OF THE BRAIN AFTER
TRAUMA
Two types of plasticity; plasticity (general) and functional recovery (specific
form of plasticity).
Plasticity is the brains tendency to change and adapt as a result of experience
or new learning; can also be referred to as neuroplasticity or cortical remap-
ping.
The peak amount of synaptic connections is approximately 15,000 at the age
of 2-3 years old. As we age, rarely used connections are deleted and frequently
used connections are strengthened in a process called synaptic pruning.
Maguire et al (2000) studied the brain of London taxi drivers using an MRI and
found significantly more grey matter in the posterior hippocampus than in the
matched control group. This part of the brain is associated with spatial and
navigational skills.
Functional recovery occurs following physical injury or other forms of trauma
such as infection or the experience of a stroke. There are three ways in which
functional recovery can occur; 1. Axon sprouting - new nerve endings grow and
connect with undamaged areas. 2. Reformation of blood vessels. 3. Recruit-
ment of homologous (similar) areas on the opposite hemisphere to do specific
tasks.
Factors affecting functional recovery; cognitive reserve refers to the person’s
educational attainment influencing how well the brain adapts after injury.
Schneider found the more time spent in education meant a greater chance of
recovery; 40% of patients who had a disability free recovery spent 16 years in
education whilst 10% of patients who had a disability free recovery spent 12
years in education.
Age is also a factor considered (Jodi Miller).
EVALUATION
+ Research to support Maguire’s research. For example Draganski et al im-
aged the brains of medical students 3 months before and after their final
exam. Learning induced changes were seen to have occurred in the posterior
hippocampus as a result of this exam. This supports both structural plasticity
and Maguire’s research as it suggests the brain has a tendency to change
and adapt as a result of new learning.
