Hemispheric lateralisation and split- brain research

Question 1

what is hemispheric laterisation?

Answer 1

• two halves of the brain are functionally different
• mental processes and behaviours are mainly controlled by one hemisphere e.g. language

Question 2

what is split- brain research?

Answer 2

• studies in the 60’s which involve people with epilepsy
• they had surgical separation of the hemispheres of their brains to reduce severity of epilepsy
• seperating the corpus collosum
• able to test lateral functions of the brain in isolation

Question 3

what is localisation?

Answer 3

• some functions are governed by very specific areas in the brain

Question 4

what is lateralisation?

Answer 4

• there are two sides
• hemispheric lateralisation
• some functions appear in both hemispheres e.g. vision
• left and right visual area in the left and right occitipal lobe

Question 5

How is language lateralised?

Answer 5

• Brocas area is in the left frontal lobe
• Wernickes area is in the left temporal lobe
• RH can only produce rudimentary words/ phrases but contributes to emotional context
• LH is analyser while RH is synthesiser

Question 6

Which functions are not lateralised?

Answer 6

• vision
• motor
• somotasensory appear in both hemispheres

Question 7

how is the motor area contralaterally wired?

Answer 7

• RH controls movement on the left side of the body
• LH controls movement on the right side of the body

Question 8

How is the visual areas contralaterally and ipsilaterally wired?

Answer 8

• it is opposite and same sided
• each eye recieves light from the left and right visual field (LVF) (RVF)
• LVF of both eyes is connected to the RH
• RVF of both eyes is connected to the LH
• visual areas compare the slightly different perspective from each eye

Question 9

Hemispheric laterlisation Evaluation strength: Lateralisation is connected to the brain

Answer 9

• Fink et al. used PET scans to see which areas where active during a visual processing task
• those with connected brains who were asked to describe global elements, regions of the RH where more active
• when asked to focus on finer detail the LH dominated
• during visual processing hemispheric lateralisation is a feature of both the split brain and connected brain

Question 10

Hemispheric lateralisation Evaluation Limitation: One brain

Answer 10

• different functions of the LH and RH but research says peopledont have a dominant side that creates a diff personality
• Neilson looked @ brain scans of over 1000 people
  -used different hemispheres for different tasks but no dominant side
• no right or left brained people

Question 11

Sperry’s split brain research: procedure

Answer 11

• 11 people with a split brain
• imagine projected onto LVF (processed by LH) and the same or diff imagine projected onto RVF (processed by LH)
• ‘normal’= corpus collosum would share the info across creating a full image
• split brain= info cant be shared to the other hemisphere

Question 12

Sperry’s split brain research: findings (1)

Answer 12

• picture showed to RVF= could describe what was seen
• picture showed to LVF= nothing there
• in connected, messages from RH shared to language centres in LH

Question 13

Sperry’s split brain research: findings (2)

Answer 13

• couldnt give verbal description of object shown to LVF (RH)
• they could select the matching object that was out of sight using their left hand (RH)
• if a pinup picture was shown to the LVF there was an emotional reaction but they reported seeing nothing or just a flash

Question 14

Sperry’s split brain research: conclusion

Answer 14

• show how certain functions are lateralised
• support that the LH is verbal and the RH is ‘silent’ but emotional

Question 15

Split brain research evaluation: strength research support

Answer 15

• Gazzaniga showed split brain patients perform better than connected at certain tasks
• faster at identifying odd one out
• in normal brain LH’s better cognitive strategies are watered down by inferior RH
• left and right brain are distinct

Question 16

Split brain research evaluation: limitation generalisation issues

Answer 16

• causal relationships are hard to establish
• behaviour of sperry’s group was compared to a neurotypical control group
• none of the pp in control group had epilepsy= confounding variable
• difference in results may be due to epilepsy not split brain