Lateralisation

Question 1

Where can the idea of hemispheric lateralisation be traced from?

Answer 1

• The idea that different hemispheres might have different specialisations can be traced back to Marc Dax, a French Doctor.
• He treated patients who’d lost the ability to speak.
• He observed in every case there was damage in the left hemisphere and no patients had experienced right-hemisphere damage, suggesting language was located in the left hemisphere

Question 2

What does brain lateralisation mean?

Answer 2

Refers to how the two halves of brain aren’t exactly alike. Each hemisphere has functional specialisations.

Question 3

How are the 2 hemispheres connected?

Answer 3

Info received by one hemisphere is sent to the other through connecting bundles of nerve fibres, like the corpus callosum

Question 4

When did the chance to investigate the 2 hemispheres happen?

Answer 4

• When, in treatment of severe epilepsy, surgeons cut the bundle of nerve fibres that formed callosum.
• The aim was to prevent the violent electrical activity that accompanies epileptic seizures crossing from a hemisphere to the other.
• Patients who underwent this surgery are referred to as ‘split-brain’ patients

Question 5

Give evaluation for lateralisation (neural capacity)

Answer 5

• Lateralisation appears to increase neural processing capacity
• By using one hemisphere to engage in a task, the other hemisphere to free to engage in another function. However, little empirical evidence has showed that lateralisation confers any advantage to brain functionality in humans.
• However, Rogers et al found that in domestic chicken, brain lateralisation is associated with enhanced ability to perform 2 tasks simultaneously.
• This provides some evidence that brain lateralisation enhances brain efficiency in cognitive tasks that require the use of both hemispheres

Question 6

Give evaluation for lateralisation (immune system functioning)

Answer 6

• There are disadvantages with hemispheric lateralisation
• e.g. architects and mathematically gifted tend to have better right-hemispheric skills but are more likely to be left-handed and to suffer higher rates of allergies and immune system problems.
• Tonnessen et al found a small, significant relationship between handedness and immune system disorders, suggesting that the same genetic processes that lead to laterlisation may affect the development of immune system
• Morfit and Weekes supported this, finding that left handers were more likely to have immune system disorders in their immediate families than did right-handers

Question 7

Give evaluation for lateralisation (changes with age)

Answer 7

• Lateralisation of function changes with normal ageing
• Lateralised patterns found in younger individuals tend to switch to bilateral patterns in healthy older adults . e.g. Szaflarski et al found language become more lateralised to the left hemisphere with increasing age in children, but after 25, lateralisation decreased with each decade of life
• It’s difficult to know why, but one possibility is that using extra processing resources of the other hemisphere may compensate for age-related declines in function