Localisation of function in the brain
Scientists used to believe that the brain worked in a more holistic way, where all parts of the
brain were involved in the processing of thought and action
Broca + Wernicke argued for localisation of function (also referred to as cortical specialisation)
which was the idea that different parts of the brain were responsible for different tasks
- if a certain part of the brain becomes damaged then that function will no longer be able
to be carried out
Hemispheres;
- cerebrum divided into two symmetrical halves
- some physical/physiological functions are dominated by specific halves (aka
lateralisation)
- left side of the body controlled by right hemisphere + vice versa
Motor centre;
- back of the frontal lobe + controls movement
- damage may result in the loss of fine movements
Somatosensory centre;
- separated from the motor area by a ‘valley’ called the central sulcus
- where sensory information from the skin is processed eg. heat, pressure
- more receptors = more sensitivity (half of all receptors are in our face and hands)
Visual centre;
- in the occipital lobe at the back of the brain
- right visual field ---> left visual cortex + vice versa
- eg. if there was damage to the left hemisphere, the right visual field in both eyes could be
affected (can lead to blindness in rvf)
Auditory centre;
- temporal lobe + processes speech based information
- damage may lead to hearing loss/deafness
Language centres in the brain;
- language is usually restricted to the left hemisphere
- Broca’s area ---> responsible for speech production (patient Tan, aphasia)
- Wernicke’s area ---> responsible for language comprehension (nonsense speech
produced if Wernicke’s aphasia is developed
Evaluation;
- evidence from neurosurgery; damage to areas of the brain have been linked to mental
illnesses (cingulate gyrus linked to OCD, improvement shown after a cingulotomy)
- evidence from brain scans; Peterson, 1988, brain scans to show Wernicke’s area to be
active during a listening task + Broca’s active during a reading task)
- case study as evidence; Phineas Gage supports the concept of localisation
- challenging research; Lashley, 1950, experimented on rats by cutting out parts of their
brain and found that when learning a route in a maze, no area was proven to be more
important than another
, Hemispheric lateralisation and split-brain research
Lateralisation; two hemispheres function differently and certain mental processes are
controlled by one hemisphere rather than the other, eg. language dominated by the left
hemisphere
Left and right hemispheres;
- language dominated by the LH but the RH can only produce simple words and provides
emotional context so LH = analyser and RH = synthesiser
- motor area; brain is cross-wired (contralateral wiring) meaning that LH controls right
side and RH controls the left side
- vision is both contralateral and ipsilateral (opposite and same sided) left visual field of
both eyes is connected to the RH and vice versa which enables different perspectives and
aids depth perception (similar arrangement for auditory)
Evaluation;
- hemispheres process information differently; Fink used PET scans during a visual task
---> found that when looking at a larger perspective (eg.a forest), the RH was more active
but when told to look at finer details, the LH was more active
- research suggests that people do not have a dominant side of the brain so the idea of the
LH as the analyser + RH as the synthesiser may be wrong ---> Nielson, 2013 analysed
over 1000 brain scans and found no dominant side
Split brain research was conducted by Sperry et al (1968) involving the removal of the corpus
callosum in an attempt to relieve epilepsy in patients
Procedure;
- 11 participants who had undertaken split-brain surgery
- in normal brains information would have been shared between the hemispheres
- in split brains the image wouldn’t have been able to be conveyed between hemispheres
FINDINGS;
- when an image was shown to the RVF the participant was able to see it
- but when an image was shown to the LVF they claimed that there was nothing there
- this is because messages are relayed to the language centres in the LH so the split brain
participants were unable to give the images a verbal label
- they could select a matching image using their left hand
- if an image was shown to the LVF there would be an emotional reaction (eg. a giggle) but
the participants would report that they saw nothing or just a flash
To conclude; this demonstrates how certain functions are lateralized + supports the idea that
the LH is verbal and the RH is silent but provides emotional context
Evaluation;
- research support; Gazzinga, 1989, found that split brain participants performed better
than connected brain participants in some tasks (eg. picking the odd one out)
- lack of generalisability; none of the control group had epilepsy so any differences may
be due to epilepsy rather than a split or connected brain
- good ethics; the removal of the corpus callosum in the participants was not for the
purpose of the study, meaning any harm was not deliberate
Scientists used to believe that the brain worked in a more holistic way, where all parts of the
brain were involved in the processing of thought and action
Broca + Wernicke argued for localisation of function (also referred to as cortical specialisation)
which was the idea that different parts of the brain were responsible for different tasks
- if a certain part of the brain becomes damaged then that function will no longer be able
to be carried out
Hemispheres;
- cerebrum divided into two symmetrical halves
- some physical/physiological functions are dominated by specific halves (aka
lateralisation)
- left side of the body controlled by right hemisphere + vice versa
Motor centre;
- back of the frontal lobe + controls movement
- damage may result in the loss of fine movements
Somatosensory centre;
- separated from the motor area by a ‘valley’ called the central sulcus
- where sensory information from the skin is processed eg. heat, pressure
- more receptors = more sensitivity (half of all receptors are in our face and hands)
Visual centre;
- in the occipital lobe at the back of the brain
- right visual field ---> left visual cortex + vice versa
- eg. if there was damage to the left hemisphere, the right visual field in both eyes could be
affected (can lead to blindness in rvf)
Auditory centre;
- temporal lobe + processes speech based information
- damage may lead to hearing loss/deafness
Language centres in the brain;
- language is usually restricted to the left hemisphere
- Broca’s area ---> responsible for speech production (patient Tan, aphasia)
- Wernicke’s area ---> responsible for language comprehension (nonsense speech
produced if Wernicke’s aphasia is developed
Evaluation;
- evidence from neurosurgery; damage to areas of the brain have been linked to mental
illnesses (cingulate gyrus linked to OCD, improvement shown after a cingulotomy)
- evidence from brain scans; Peterson, 1988, brain scans to show Wernicke’s area to be
active during a listening task + Broca’s active during a reading task)
- case study as evidence; Phineas Gage supports the concept of localisation
- challenging research; Lashley, 1950, experimented on rats by cutting out parts of their
brain and found that when learning a route in a maze, no area was proven to be more
important than another
, Hemispheric lateralisation and split-brain research
Lateralisation; two hemispheres function differently and certain mental processes are
controlled by one hemisphere rather than the other, eg. language dominated by the left
hemisphere
Left and right hemispheres;
- language dominated by the LH but the RH can only produce simple words and provides
emotional context so LH = analyser and RH = synthesiser
- motor area; brain is cross-wired (contralateral wiring) meaning that LH controls right
side and RH controls the left side
- vision is both contralateral and ipsilateral (opposite and same sided) left visual field of
both eyes is connected to the RH and vice versa which enables different perspectives and
aids depth perception (similar arrangement for auditory)
Evaluation;
- hemispheres process information differently; Fink used PET scans during a visual task
---> found that when looking at a larger perspective (eg.a forest), the RH was more active
but when told to look at finer details, the LH was more active
- research suggests that people do not have a dominant side of the brain so the idea of the
LH as the analyser + RH as the synthesiser may be wrong ---> Nielson, 2013 analysed
over 1000 brain scans and found no dominant side
Split brain research was conducted by Sperry et al (1968) involving the removal of the corpus
callosum in an attempt to relieve epilepsy in patients
Procedure;
- 11 participants who had undertaken split-brain surgery
- in normal brains information would have been shared between the hemispheres
- in split brains the image wouldn’t have been able to be conveyed between hemispheres
FINDINGS;
- when an image was shown to the RVF the participant was able to see it
- but when an image was shown to the LVF they claimed that there was nothing there
- this is because messages are relayed to the language centres in the LH so the split brain
participants were unable to give the images a verbal label
- they could select a matching image using their left hand
- if an image was shown to the LVF there would be an emotional reaction (eg. a giggle) but
the participants would report that they saw nothing or just a flash
To conclude; this demonstrates how certain functions are lateralized + supports the idea that
the LH is verbal and the RH is silent but provides emotional context
Evaluation;
- research support; Gazzinga, 1989, found that split brain participants performed better
than connected brain participants in some tasks (eg. picking the odd one out)
- lack of generalisability; none of the control group had epilepsy so any differences may
be due to epilepsy rather than a split or connected brain
- good ethics; the removal of the corpus callosum in the participants was not for the
purpose of the study, meaning any harm was not deliberate
