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Brain Dysfunction > Lecture 3 - Cerebral Asymmetry > Flashcards

Lecture 3 - Cerebral Asymmetry Flashcards

1
Q

What’s the name of the process that implies that certain brain functions are dominated by one hemisphere ?

A

Lateralisation

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2
Q

What’s the definition of laterality ?

A

The idea that 2 cerebral hemispheres have separate functions

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3
Q

What are the anatomical differences between the 2 hemispheres ?

A
  • R : larger/heavier, L : relatively more gray matter (more dense)
  • Temporal lobes asymmetry
  • Thalamus asymmetry : L>R
  • Slope lateral fissure : R>L
  • Frontal operculum differently organized
  • Different distribution of neurotransmitters
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4
Q

What’s the difference between Neuroneal asymmetry & Genetic asymmetry ?

A
  • Neuronal asymmetry : distinct patterns of dendritic branching
  • Genetic asymmetry : epigenetic changes differentially affect the 2 hemispheres
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5
Q

Using Brain Stimulation on neurological patients, what is equally frequent when stimulating both hemispheres ?

A
  • Localized movements
  • Sensory experiences
  • Light flashes
  • Buzzing sounds
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6
Q

Using Brain Stimulation on neurological patients, what is equally frequent when stimulating L-hemisphere ?

A
  • Speech acceleration
  • Speech disruption
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7
Q

Using Brain Stimulation on neurological patients, what is equally frequent when stimulating R-hemisphere ?

A
  • Report of visual/auditory memories/experiences
  • Deja-vu
  • Emotional responses
  • Disruption of judgment of line orientation, facial expressions, short-term memory for faces
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8
Q

What’s “double disscociation” ?

A

When 2 areas of the Neocortex are functionally dissociated by 2 tests
= each test (measuring a specific function) is affected by a lesion in one zone but not in the other

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9
Q

What can be disturbed if the L temporal lobe is damaged ?

A
  • Language
  • Speech
  • Writing
  • Reading
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10
Q

What can be disturbed if the R temporal lobe is damaged ?

A
  • Spatial tasks
  • Non-verbal memory
  • Singing/music/tonal patterns
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11
Q

What’s a commissurotomy ?

A

Dissection of Corpus Callosum

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12
Q

What’s a “split-brain” patient ?

A

A patient who had a commissurotomy

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13
Q

What happens if the Corpus Callosum is severed ?

A
  • Each hemisphere functions independently
  • No access to the other’s sensations, thoughts & actions
  • Unaffected sensory & motor systems and their bodily receptors & effectors
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14
Q

What’s the WADA test ?

A

Anesthesia of one brain side with Carotid Sodium Amobarbital injection

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15
Q

What does the WADA test enable us to do ?

A

Study one hemisphere separately in functional absence of the anesthetized one

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16
Q

What happens if the L carotid area is briefly anesthetized ?

A
  • Cannot speak
  • Cannot move the R arm
  • Cannot see on R visual field
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17
Q

Which hemisphere is most commonly dominant for language ?

A

L hemisphere for :
- 95% of R-handed
- 70% of L-handed

18
Q

What’s the difference between a monaural presentation and a dichotic presentation ?

A
  • Monaural : earing a sound only from one ear (goes to both hemispheres)
  • Dichotic : earing a different sound in both ears (goes to contralateral hemisphere, ipsilateral pathway suppressed)
19
Q

Is the auditory system completely crossed ?

A

No : ipsilateral & contralateral pathway from each ear, but crossed connections conduct more rapidly

20
Q

What is each hemisphere dominant for in visual processing ?

A
  • L-hemisphere : letters & words
  • R-hemisphere : complex patterns & faces
21
Q

What is each hemisphere dominant for in auditory processing ?

A
  • L-hemisphere : verbal sounds & temporal structure of sounds (e.g. Morse code)
  • R-hemisphere : non-verbal, emotional & musical sounds
22
Q

What is each hemisphere dominant for in somatosensory processing ?

A

L-hemisphere (R hand) : objects & spatial patterns (e.g. Braille)
- R-hemisphere (L hand) : letters & temporal patterns (e.g. dynamic Braille)

23
Q

Give 3 examples of behavioural measures

A
  • Visual half field stimulation
  • Dichotic listening tests
  • Somatosensory tests
24
Q

What are the limits of behavioural measures ?

A
  • Indirect measures of lateralization
  • Laterality measures often don’t correlate
  • Effects of attention & behavioural strategies
25
Q

What is each hand dominant for ?

A
  • R hand (L-hemisphere) : verbal motor tasks
  • L hand (R-hemisphere) : spatial motor tasks
26
Q

What’s the difference between the 2 lateralization models ?

A
  • Unilateral specialization model : each hemisphere has its own functions & methods, performs these independently
  • Interaction models : both hemispheres capable of performing all cognitive functions, but are somewhat specialized
27
Q

What can lead to variations in cerebral asymmetry ?

A

Individual differences :
- Handedness
- Sex
- Environment

28
Q

In what type of persons are anatomical asymmetries more pronounced ?

A

R-handed persons

29
Q

What are some sex differences in brain function ?

A
  • Males (more asymmetry) : more intrahemispheric connections
  • Females : more interhemispheric connections
30
Q

Give an example of brain difference related to sexual orientation

A

Hypothalamus & hypothalamic connections differ in homosexual men (fMRI)

31
Q

What are the different explanations of sex differences in cerebral asymmetry ?

A
  • Hormonal effects
  • Environment
  • Maturation rate
  • Cognitive mode
32
Q

What hormones affect brain functions ?

A
  • Testosterone (male)
  • Estradiol (female)
33
Q

Give 3 examples of environmental effects that could influence cerebral organization

A
  • Different languages
  • Sensory deprivation (deaf, blind)
  • Environmental deprivation (orphans, SES)
34
Q

How does the Inhibition Model explain hemispheric specialization ?

A

Each hemisphere has the capacity to perform certain functions, but the dominant hemisphere inhibits similar functions in the non-dominant one

35
Q

What are the different theories regarding hand preference ?

A
  • Environmental theories
  • Anatomical theories
  • Hormonal theories
  • Genetic theories
36
Q

What differences in brain structure favored female brains ?

A
  • Larger language areas
  • Larger medial paralimbic areas
  • Larger lateral frontal areas
  • Greater relative amount of grey matter
  • More densely packed neurons in temporal lobe
  • More gyri
  • Thicker cortex
37
Q

What differences in brain structure favored male brains ?

A
  • Larger medial frontal areas
  • Larger cingulate areas
  • Larger amygdala & hypothalamus
  • Larger overall white matter volume
  • Larger cerebral ventricles
  • More neurons overall
  • Larger brain
38
Q

To what is sex differences in brain structure related to ?

A

Differences in the distribution of estrogen and androgen (e.g. testosterone) receptors during development

39
Q

What does the fluctuation of estrogen affect during the menstrual cycle ?

A
  • Catecholamine : epinephrine & dopamine
  • Stimulation of dopamine receptors
40
Q

How does estrogen affects neuronal structure ?

A

Affects the number of dendritic spines on hippocampal neurons

Brain Dysfunction (13 decks)

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