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Behavioural And Cogntive Neuroscience > Week 5: Lateralisation & language > Flashcards

Week 5: Lateralisation & language Flashcards

1
Q

Why does contralateral control mean?

A

The left side of the brain controls the right side of the body and vice versa

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2
Q

How do the hemispheres communicate?

A

Through a large band of fibres known as the corpus callosum - white matter

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3
Q

Do we have a dominant hemisphere?

A

Yes e.g. right handed people are left dominant

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4
Q

What anatomical direction refers to the top of the brain?

A

DORSAL (superior)

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5
Q

Which anatomical direction is rostral?

A

FRONT (anterior)

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6
Q

What anatomical direction is caudal?

A

BACK (posterior)

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7
Q

Which anatomical direction refers to the bottom of the brain?

A

VENTRAL (inferior)

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8
Q

Looking at the spinal cord, what are the anatomical directions?

A

Dorsal refers to the back of the neck

Opposite to this (front?) is ventral

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9
Q

What is a frontal plane?

A

Brain is cut through the middle, leaving just the front regions

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10
Q

What is a horizontal plane?

A

Brain is cut horizontally, separating the frontal/parietal lobes from the temporal/occipital lobes

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11
Q

What is a Sagittarius plane?

A

Essentially cutting apart the hemispheres

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12
Q

What do asymmetries in the brain allow insight into?

A

Potential differences in function

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13
Q

What are some of the asymmetries seen in the brain?

A

Right hemisphere: enlargement of the anterior portion

Left hemisphere: Enlargement of wernickes area and parts of the thalamus - neurons in LH tend to have longer dendrites

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14
Q

What is white matter?

A

Axons or connections

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15
Q

Grey matter?

A

Where cell bodies are located

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16
Q

Explain regional differences in the corpus callosom

A

3 different parts:
Genu - at the front near the prefrontal cortex (anterior side)
Body
Splenium - at the back near the occipital lobes (posterior)

All connect different regions of the brain

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17
Q

What are ipsilateral connections?

A

Connections that stay within the same hemisphere - don’t cross the corpus callosom

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18
Q

What are homotopic connections?

A

Connections that cross over the CC to the same region of the opposite hemisphere

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19
Q

What are heterotopic connections?

A

Connections that cross over the CC to a different region on opposite hemisphere

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20
Q

Where do collosal connections start and finish?

A

The same layer of the neocortex that they start in e.g. start in layer 1, end in layer 1 (6 layers)

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21
Q

What is functional homotophy

A

Functional connectivity synchrony between brain areas in the different hemispheres

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22
Q

Explain empirical studies looking at synchrony across the CC

A

If you look at firing rates when watching light bars move across the visual field

When have two seperate light bars - one moving up, one moving down, the firing rate is not synchronised

When have just one bar, moving in same direction across both, brain regions are firing in synchrony - shows efficiency of CC
However, this condition doesn’t produce same affects if CC is severed - don’t get synchrony anymore

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23
Q

What are the 4 other commissures (not including CC)? and what do they make possible?

A

Anterior
Habenular
Posterior
Hippocampal

Means if CC is severed completely, there can still be some information crossing the hemispheres

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24
Q

What does the anterior commissure do?

A
  • Plays a role in olfactory pathway
  • Pain sensation
  • Connects temporal regions

This information can still cross without CC

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25
Q

What does the posterior commissure do?

A
  • Plays a role in pupillary light reflexes
  • Right next to pineal gland
  • May play a role in hormone system
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26
Q

Which commissure is right next to the posterior commissure?

A

The habenular commissure.

- Hormonal role

27
Q

Hippocampal commissure?

A

Called the commissure of fornix

Connects the 2 halves of the hippocampus

28
Q

Explain the Myers and Sperry experiment

A
  • They wanted to restrict visual information to strictly 1 hemisphere in cats - cut CC, cut, optic chiasm and blindfolded one eye
  • Control groups: cats with only either their CC or OC severed and blindfolded, learned the discrimination task at a normal rate - retaining this perfectly when blindfold was switched. When you only cut 1 of these 2 things, the animal behaves like normal
  • Cats with both regions severed, learned the task when had one eye blindfolded, however when changed eyes, they had to completely relearn the task - all learning information remained on the same hemisphere
29
Q

What conclusions were drawn from the Myers and Sperry experiment?

A

The cat forebrain has the ability to act as two seperate forebrains, each capable of independent learning and of storing its own memories

30
Q

Why would we ever cut the CC in humans seeing as it is important?

A

Performed on patients with life threatening cases of epilepsy - remarkably effective in controlling seizures

Few obvious side effects though

Temporal lobe epilepsy - seizures start in TL and spread across whole brain

31
Q

What information is still transferred if the genu of the CC is spared?

A

Transfer of higher order semantic info is spared

32
Q

If there was damage from the splenium of the CC forward?

A

Tactile information is disrupted, but tactile information still gets across because the splenium is what is connecting the occipital cortex

33
Q

What happens if there is damage to the posterior portion of the the CC (including Splenium)?

A

Disruptions to transfers of visual, tactile, and auditory information

34
Q

What areas of the brain are involved in vision sensation?

A 
Eyes
Optic nerve 
Optic chiasm 
Lateral Geniculate nucleus (relay station in thalamus for visual info)
Primary visual cortex
35
Q

Explain a split brain patient scenario

A

Word ‘knight’ presented on the left visual field - once in right hemisphere, info crosses over to the left hemisphere and able to recite the word (normal brain)

Partial split in back back of CC - spare genu can get semantic meaning cross over. Can work out semantically and logically that the word presented is Knights - created images based on semantic properties that cross over

Complete split - say they didn’t see anything because the right side of the brain sees the stimulus bit the speech centre didn’t see anything

36
Q

Explain the spoon-apple task of lateralisation

A

Spoon presented in the left visual field so goes to the right hemisphere

Apple is presented in the right visual field so goes to left hemisphere

When asked what you see - will say apple as this information is on the same side as speech centres (LH)

When asked to pick the item up with your left hand that is controlled by the right hemisphere, you will pick up the spoon as this is the information that is available for this motion

37
Q

Face recognition disparities: what is the left hemisphere better at?

A

Better at recognising the self

38
Q

Face recognition disparities: what is the right hemisphere better at?

A

Better at recognising familiar others

39
Q

What is the right hemisphere specialised for?

A

Visuospatial processing

- mental rotation, spatial matching, mirror image task, block design performance (better with left hand - right hem)

40
Q

What happens when the block task is attempted by both hands?

A

Seem to compete almost as if independent systems

41
Q

How do we test language lateralisation?

A

Sodium amytal test
Dichotic listening task
Brain imaging

42
Q

What is the sodium amytal test?

A

Done prior to brain surgery so that the surgeon knowns where speech originates to take care not to damage these areas

  • Anesthetises the ipsilateral hemisphere by injecting a small amount of sodium amytal into the carotid artery on one side fo the neck, allowing the abilities of the contralateral hemisphere to be assessed
  • When injection is on the side of the dominant speech hemisphere, the patient is totally mute for 1-2 minutes
43
Q

What is a dichotic listening task?

A

Each ear presented with different words/phrases/numbers

The side that does better on this task is dominant

44
Q

What is a limitation of using a dichotic listening task to determine hemispheric dominance?

A

The right hemisphere is better for melodies

Left hemisphere is better for letters

45
Q

What is the hemispheric anatomy of language?

A

Language areas are typically left lateralised and are areas surrounding the sylvian fissure

There are some right hemisphere roles in language - anything to do with visualisation (rhythm, metaphors)

46
Q

Which area is thought responsible for language production?

A

Broca’s area

47
Q

Which area is thought responsible for language comprehension?

A

Wernicke’s area

48
Q

What is anomia?

A

Difficulty finding words

49
Q

What is dysarthria?

A

Difficulty using muscles controlled in speech

50
Q

What is apraxia?

A

Impairment of motor planning and programming or speech articulation

51
Q

What is aphasia?

A

Deficits in language comprehension or production

52
Q

What is broca’s aphasia? And what problems may arrise from it?

A

Cannot produce speech

  • trouble with spontaneous speaking
  • trouble with repeating (dysarthria)
  • listening for comprehension in certain situations (even though it is a production area - shows how areas are connected)
53
Q

Wernicke’s aphasia is caused by….

A

Damages to connections from Broca’s area - even if wernickes area is still intact
(Angular gyrus, arcuate fasciculus)

54
Q

Do people use one side of the brain more than other?

A

No. You use both sides of the brain equally no matter how creative or maths orientated you are

55
Q

Is lateralisation only present in humans?

A

No it is present in many species, not exclusive to humans - maybe even invertebrates

56
Q

Split brain animals?

A

Split brain monkeys show similar hemispheric interactions to humans in visual perception tasks

57
Q

What are the theories of hemispheric lateralisation?

A

Motor theory
Linguistic theory
Analytic-synthetic

58
Q

What does the motor theory propose?

A

Posits that the LH is specialised for fine motor movement (claims speech is an example of this movement specialisation, moving mouth and tongue to speak)

59
Q

What evidence supports the motor theory?

A

Lesions to LH disrupt facial movements then RH lesions, even when not related to speech

The degree of disruption of non-verbal facial movements is positively correlated with the degree of aphasia

60
Q

What is a limitation to the motor theory?

A

Does not suggest why motor function became lateralised in the first place

61
Q

What does the linguistic theory say?

A

The primary function of the left hemisphere is language

62
Q

What evidence is there for the linguistic theory?

A

Deaf people who communicate via sign language lose the ability to do so if they suffer damage to the left hemisphere - even if hold the ability to make the movements required to do so

63
Q

What is the analytic-synthetic theory?

A

Suggests 2 fundamentally different modes of thinking - analytic and synthetic and the neural circuitry for each is fundamentally different.

As a result - the 2 are presumed to have segregated during evolution with analytic (logical, sequential, analytic) mode in the left and synthetic (makes immediate, overall synthetic judgements) in the right

64
Q

What is a limitation to the analytic-synthetic theory?

A

It is really hard to test empirically

Behavioural And Cogntive Neuroscience (9 decks)

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