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PSYCHOBIOLOGY > 6 - HEMISPHERIC SPECIALISATION > Flashcards

6 - HEMISPHERIC SPECIALISATION Flashcards

1
Q

what is functional asymmetry?

A
  • different functional specialisation of the cerebral hemispheres
  • some tasks better done by a certain hemisphere
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2
Q

empirical evidence for hemispheric specialisation

wada test

A
  • invasive procedure in humans to prep for brain surgery
  • inject an anaesthetic into left or right internal carotid artery (to ‘knock it out)
  • assess each hemispheres language and memory function with behavioural tests
  • result = most people > language function almost exclusively in the left hemisphere
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3
Q

what type of analysis is the left hemisphere

A

temporal analysis

  • analysing the time stream
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4
Q

what type of analysis is the right hemisphere

A

spatial analysis

  • manipulation of spatial objects
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5
Q

what frequency/pitch is the left hemisphere

A

high frequencies

  • high pitch
  • temporal change (how many in a second)
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6
Q

what frequency/pitch is the right hemisphere

A
  • low frequency / pitch

- frequency determines pitch

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7
Q

hemispheric detail ability

A

left = local details

right = global form

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8
Q

what language features does the left hemisphere specialise in

A

discrete language features

  • consonants, words, grammar
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9
Q

what language features does the right hemisphere specialise in

A

prosodic language features

  • vowels, voice melody (how a sentence goes up at the end)
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10
Q

which hemisphere specialises in fine motor control?

A

left

why most people are right handed

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11
Q

what words describe the left hemisphere?

A

analytical

sequential

propositional

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12
Q

what words describe the right hemisphere

A

synthetic

holistic

gestalt (whole)

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13
Q

what would spatial frequency be represented as?

A

bars

high = thin and close together

low = thick and further a part

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14
Q

empirical evidence for hemispheric specialisation

split brain surgery

A
  • cutting the corpus callosum disconnects the hemispheres
  • for untreatable epilepsy - as seizure usually only happens in one hemisphere
  • causes patients to not be able to name objects presented in the left visual field, but can name if presented in the right
  • cannot name objects (without looking) by touching them with the left hand and can by touching with the right
  • cannot perform action with left hand after a verbal instruction
  • cannot retrieve an object only shown in the left hemifield with right hand
  • the motor functions of the hands cross over subcortically
  • cutting corpus callosum doesn’t affect cross over of motor functions of hands (so right VF can move right hand as right hand motor area is in the LH)
  • just can’t move opposite hand to VF / hemifield
  • motor areas of the left hemisphere control movement of the right hand
  • because language centre in left hemisphere!!
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15
Q

which hemisphere controls the right hand

A

left hemisphere controls the right hand (motor cortex)

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16
Q

which hemisphere controls the left hand?

A

right hemisphere controls the left hand (motor cortex)

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17
Q

hemifields and hand movement

A

left hemifield = CAN move LEFT hand

left hemifield = CANT move RIGHT hand

right hemifield = CANT move left hand

right hemifield = CAN move right hand

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18
Q

information:

verbal centre = left hemisphere

  • cannot move left hand when given verbal instruction
  • cannot cross CC to RH for left motor control
A

-

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19
Q

what does ipsilateral mean?

A

same side

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20
Q

what does contralateral mean

A

different side

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21
Q

question:

after split brain surgery, patients typically cannot follow instruction (verbal) to perform certain movement with their left hand

later on they regain (most of) their ability, what does this suggest?

(2 things)

A

1 the left hemisphere might restructure itself as to gain ipsilateral control over the left hand

2 right hemisphere might acquire SOME language skills (usually very limited - hard to retrain brain as adult)

  • also, patient unable to learn new complex bamanual coordination tasks (eg playing the piano)
  • one hand wouldn’t know what the other is doing
22
Q

empirical evidence - electrical stimulation

experimentally induced only in animals

A

conducted during brain surgery (patient awake to react to different tasks - brain has no pain receptors)

stimulating particular areas interferes with particular tasks

  • eg if interferes with ability to speak - shows which areas to stay away from (area is different in different people = slight variations)
23
Q

empirical evidence - lesion studies

experimentally induced only in animals

A

removal (partial or total) of one hemisphere

behavioural tests to assess remaining function

24
Q

empirical evidence - patient studies (lesion studies)

A

lesion studies due to accidents or strokes etc

behavioural tests

brain imaging methods

25
Q

what is a hemifield

A

half of the retina

26
Q

what does wernwickes area do

A

understanding language

27
Q

what does the broca’s area do

A

produce speech

28
Q

information:

things in RVF processes in LH

things in LVF processes in RH

A

-

29
Q

information:

objects in RVF - seen by LEFT half of each eye and vice versa

  • right half or left/right eye ganglion cells of axons of the retina travel to brain > to optic chiasm > from right half of left eye cross into RH
    > left side of right eye crosses into the LH
A

-

30
Q

what is the right word advantage?

A

in lexical decision tasks

RVF responds quicker as it’s already in LH - shorter path

LVF must travel across CC from RH to LH

(all flipped if Broca’s area in RH - rare!)

31
Q

dichotic listening / right ear advantage

A

shadowing task

  • present diff sounds in both ears at same time - patient says one
  • auditory processing crosses hemispheres via brainstem auditory regions
  • should be quicker hearing in right ear as doesn’t have to cross to auditory processing (auditory cortex in left ear and language processing)
  • hear something in left ear and it’s processed in the RH and sent back to the LH for language
  • hear something in right ear, and it’s processed in LH and also LH for language
32
Q

behavioural studies

A

women often show less behavioural asymmetry than me

  • especially at the end of the menstrual cycle (high level of female sex hormones - estradiol and progesterone) (could be due to something else)
  • high estrogen levels = over threshold
    = impairs mental rotation scores (men and women)
  • beginning of cycle = similar asymmetry as men (lower estrogen)
  • female sex hormones affect language laterilsation of language functions - measures through asymmetry scores

MENTAL ROTATION CANNOT INFORM US ABOUT LATERILISATION (as only speculation that they’re linked)

33
Q

brain imaging studies

A

women ‘use’ both hemispheres in tasks where men ‘use’ mainly one hemisphere

‘use’ = to show particularly high correlated activity
- whole brain activity typically fluctuates in activity

34
Q

clinical evidence

A

after a stroke, women recover language skills quicker than men

35
Q

hypothesis:

women’s brains are less functionally laterilised

A
  • more language functions in RH than men
  • language processing of RVF words in LH, but language processing of LVF (at least partially) in RH
  • after a stroke, women can use remaining language functions in undamaged hemisphere to ‘bootstrap’ speech
  • RH less specialised for visuospatial task
  • men out perform women in mental rotation tasks etc

possible reasons

  • more equal development of both hemispheres in women embryonic development?
  • better interconnection of both hemispheres?
36
Q

galaburda-geschwind model

background

A

‘grand theory’ integrating handedness, sex hormones, cerebral lateralisation, cognitive skills and deficits and disorders of the immune system

  • propose in early 1980s
37
Q

galaburda-geschwind model

hypotheses

A
  • prenatal testosterone slows development of left hemisphere
  • newborns brains differ due to prenatal testosterone levels (depends on sex)
  • high level (mostly boys)=asymmetrical hemisphere
    LH less mature
    RH more mature
  • low levels (mostly girls) = symmetrical hemispheres
    both equally mature
38
Q

galaburda-geschwind model

evaluation

A

sex hormones influence brain development (at least in other animals)

but cognitive functions might no better as strongly localised (makes it difficult to evaluate-hard to know where cognitions are actually based)

39
Q

galaburda-geschwind model

navon figure

A

a big letter made of smaller letters

say which you see first

men = see big one first
women = see the little ones first
40
Q

what can the galaburda-geschwind model account for?

A
  • the larger number of male-left handedness
  • if RH is overdeveloped - the chances of RH taking over fine motor control are increased so higher chance of being left handed
  • superior visuo-spatial skills in men (eg mental rotation)
  • but might be a fluke
  • faster language acquisition in girls
  • as LH would be underdeveloped in men
  • but evidence isn’t overly strong
41
Q

what can the galaburda-geschwind model not (directly) account for?

A
  • superior visuo-spatial skills in women (spatial memory)
  • some special relationship between eg visuo-spatial giftedness and reduced lateralisation
  • eg chess = visuospatial
  • top chess players have reduced lateralisation
  • would predict that they have more developed RH
  • normal chess players engage RH more than LH
42
Q

question:

over the last 50 years, sex differences in cognitive tasks seem to have steadily declined due to

1 - increased levels of chemicals in the environment that interfere with normal sex hormone production (some pesticides gave an endocrine disruption that causes higher estrogen levels in men and women)
2 increased number of female experimenters
3 changes in societal expectations regarding male and female behaviour

A

-

43
Q

statement:

only a FEW people have language centres in the RH

of the few, most are left handers

but not all lefhanders have it in the RH

A

-

44
Q

statement:

we are able to measure RT with millisecond accuracy 50 years ago

hasn’t developed or needed to since then

A

-

45
Q

question:

if the hypothesis is correct that mens brains are more strongly functionally lateralised than women’s brain, then:

A
  • women should have a better chance than men to regain functions lost after damage to one hemisphere
  • identifying a word presented to the right hemisphere should be more difficult (compared to identifying a word presented to the left hemisphere) for men than for women
  • men should show a stronger right ear advantage than women
46
Q

statement:

there is no gender difference in vocabulary size

A

-

47
Q

** if a statement said men/women are more likely… and then a statement then it’s okay to put it if friederike said it wasn’t true - as it’s an assumption**

A

-

48
Q

** in a question, if it’s asking between left and right temporal/spatial analysis - first focus on whether it was high or low frequencies**

high = left
low = right

regardless of whether it’s temporal or spatial

A

-

49
Q

statement:

neither hemisphere processes shapes, colour, touch or sound exclusively

A

-

50
Q

lexical decision task

A
  • if it’s a word you press a key
  • if it’s not then you don’t
  • see a word in either LVF or RVF and use corresponding hand
  • participants had to hit the right key with the right hand. And because the left hemisphere controls the right hand, its the left motor cortex that has to be activated

PSYCHOBIOLOGY (29 decks)

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