localisation and lateralisation

Question 1

what does Localisation of function refer to

Answer 1

the theory that different parts of the brain are solely responsible for certain tasks or abilities.

Question 2

Broca’s area

Answer 2

Responsible for producing speech. Believed to only exist in the left hemisphere.

Question 3

Motor cortex

Answer 3

Responsible for generating voluntary movement. Different parts of the cortex control different body parts.

Question 4

Somatosensory cortex

Answer 4

Responsible for receiving sensations. Senses touch, pain, pressure and temperature.

Question 5

Visual cortex

Answer 5

Registers visual information, sent from the retina. This is where we see.

Question 6

Wernicke’s area

Answer 6

Responsible for understanding language. Also believed to only exist in the left hemisphere.

Question 7

Auditory cortex

Answer 7

Registers audio information, which travels from the inner ear. Sounds are recognised here.

Question 8

is function localised - yes arguments

Answer 8

• Case studies – Wernicke’s aphasia (inability to understand language) and Broca’s aphasia (inability to produce fluent speech) patients have specific lesions to these specific brain regions. Patient HM – had his hippocampus removed and lost a specific ability (was unable to learn new explicit LTMs)
• Evidence from brain scans – researchers consistently find that specific brain regions are active during specific tasks, using fMRI scans.

Question 9

is function localised - not quite arguments

Answer 9

• Functional recovery – some brain-damaged patients are able to regain a brain function, even if the damaged area never recovers. Other parts of the brain may take on the function, suggesting localisation of function is not as clear as believed.
• Reductionist - More about communication than localisation – although one area might be more responsible for a particular function, if the communication between that area and another is cut this could lead to just as many issues.
• Equipotentiality – All parts of the brain are equally active in overall mental functioning. Simple functions, such as somatosensory functions, may be localised to a specific area. However, more complex functions (like consciousness and decision-making) require the communication across different regions to produce.

Question 10

what is split brain research

Answer 10

Some people have ‘split-brain’ surgery to treat epilepsy. This involves the surgeon cutting their corpus callosum (the bundle of nerves that connect the two hemispheres) and therefore stopping the two hemispheres of their brain from communicating.

Question 11

what did sperry do

Answer 11

gathered 11 split-brain patients to test this.
• They were shown words on either the left and/or right side of a
screen and asked to say what they saw.
• Sperry found that they were able to say the words that appeared
to the right of the screen (and therefore their left hemisphere),
but not the left of the screen (right hemisphere)
• Sperry concluded that language must exist solely in the left
Sperry, 1968
A later study by Gazzaniga (2005) found that facial recognition exists only in the right hemisphere. Images of faces made up of objects were seen as a face by the right hemisphere, but as objects by the left hemisphere.
hemisphere

Question 12

is brain function lateralised - yes arguments

Answer 12

• Sperry’s study – shows cause and effect – performance on the tasks can be compared with participant whose corpus callosum is intact. Variables are controlled, e.g. images presented to only one hemisphere.
• Supported by evolutionary theory – lateralisation may have survival benefits, as it could help with multitasking (e.g. foraging for food whilst remaining alert to predators)

Question 13

is function lateralised - not quite arguments

Answer 13

• Evidence of language potential in the right hemisphere (Patient JW) – JW was a split-brain patient who initially could only read words on the right side of the screen (as usual). However, over time he was able to read words from the left side too. This suggests his right hemisphere has the potential for language.
• Evidence that children’s brains are not lateralised (e.g. hemispherectomy patients) – children under 5 with severe brain disorders can have an entire hemisphere removed and still live functional lives. Even if the left hemisphere is removed, they can retain language function. Suggests lateralisation comes later in life, and that both hemispheres have potential for all functions.