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Psychology 475: Human Neuropsychology > Chapter 11: Asymmetry > Flashcards

Chapter 11: Asymmetry Flashcards

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1
Q

What is Laterality?

A

the idea that the two cerebral hemispheres have separate functions
- laterality is not absolute but it is relevant meaning that both hemispheres are involved

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2
Q

There cerebral site is just as important as the what?

A
  • cerebral side

- hemisphere/ side of the brain

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3
Q

Do animals exhibit laterality?

A
  • yes a range of them do

- birds, rats, cats, monkeys

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4
Q

Do we act as though there is a single mind ?

A
  • yes

- there is 2 hemispheres that specialize in different things but they act through one processor or mind

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5
Q

What are the anatomical asymmetry differences between the two hemispheres

A

Left
- producing and understanding language
- controlling movement on the right side of the body
- gyri and sulci mature more rapidly
- there is 1 heschl’s gyri (auditory cortex)
- there is a larger planum temporale/ wernickes
Right
- perceiving and synthesizing non-verbal information
- music, facial expression
- control movements on left side of body
- auditory cortex larger
- there is 2 heschls gyri (auditory cortex)

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6
Q

What are the 8 major anatomical asymmetry differences between the two hemispheres

A
  1. RH larger and heavier but LH contains more gray matter (neurons) relative to white matter (connections)
  2. LH larger planum temporale which provide anatomical basis for observed RH specialization in music and LH or language
  3. LH thalamus is dominant for language function and slightly larger in LH
  4. slope of lateral fissure less steep on LH, so the temporoparietal cortex appears larger in RH
  5. frontal operculum/ brocas is 1/3 larger surface on RH, but under surface larger in LH
  6. distribution of various NT
  7. RH extends more anteriorly and LH more posteriorly
  8. asymmetry patterns
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7
Q

What are the neuronal differences between the hemispheres

A
  • the LH language areas have more dendritic branches which means more ability to enhance or suppress graded potentials
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8
Q

What are the 5 ways to study asymmetry in patients?

A
  1. brain stimulation
  2. double dissociation
  3. split-brain and commissurotomy patients
  4. Cartoid sodium amobardital injection
    5.
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9
Q

What is Brain stimulation

A
  • Wilder Penfields study
  • this used on patients with epilepsy whose seizures were not controlled with medication
  • this is done in conscious patients laying on right side with left side of brain exposed, EEG helps to identify source of seizures
  • stimulate brain areas then observe patients behaviour/ responses
  • the stimulation of the LH can block the ability to speak (ex telling a memory) , does not happen for the RH
  • LH stimulation can accelerate speech production
  • the RH stimulation can produce interpretive and experiential responses such as their interpretation of surroundings, such as deja vu or fear
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10
Q

What is Double Dissociaton

A
  • two neocortical areas are functionally dissociated by 2 behavioural tests
  • LH lesions in Rhanded patients produce language deficits that are not produced with RH lesions
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11
Q

Patients with a left temporal lobectomy shows what deficits

A

-deficits in memory and verbal IQ (specifically verbal recall)
(double dissociation studies)

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12
Q

Patients with a right temporal lobectomy showed what results?

A
  • deficits in non-verbal recall, performance IQ, copy recall, memory quotient
  • these scores continued to decrease over time
    (double dissociation studies)
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13
Q

What are split-brain and Commissurotomy Patients

A
  • epileptic seizures may begin in a restricted region of one hemisphere and progressively spread through the fibers of the corpus callosum to the homologous location in other hemisphere
  • when medication failed, commissurotomy was the surgical procedure of disconnecting the two hemispheres
  • william Van Wagnen 1940
  • 200 million nerve fibers cut
  • showed that hemispheres can function independently
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14
Q

Input from the left visual field goes where?

A
  • visual input from the left visual field gets transferred from the left visual field to the right visual cortex via the corpus callosum
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15
Q

What happens when the LH of a split brain patient has access to information?

A
  • it can initiate speech and hence communicate about information
  • showed the RH was good at recognition abilities but poor at speech initiation because RH lacks access to the speech abilities in the RH
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16
Q

What happens when a split brain patient is shown an object in each visual field and asked to say what they see?

A
  • when the LH (which can speak) sees the object in the Right visual fields the patient will respond correctly “ verbally answers I see blank object)
  • but when the RH ( which cannot speak) sees the object in the Left visual field the patient replies with they see nothing
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17
Q

What is “ The Interpreter”

A
  • when a split brain patient is presented with 2 pictures, 1 in each hemisphere and asked to select a third image that matches, each hand will choose differently
  • when asked to explain their choice the patient will describe the image selected by the right hand, suggesting the only the LH is engaged in the interpretation of the situation
  • RH specialized with facial recognition
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18
Q

How do split brain patients respond to the Chimeric Figures test

A
  • a split brain patient will always choose the face presented in the left visual field (RH) suggesting specialization in facial recognition in patients
  • when the patient sees a mismatched face they do not notice the difference because they are only seeing what is in that visual field
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19
Q

What is the Chimeric-Figures Test

A
  • 4 faces made into 2 mismatched faces
  • used to test facial recognition specialization
  • LH vocal naming of visual object
  • RH visual recognition
20
Q

What percent of right handed people have specialized speech in their RH

A

2%

21
Q

What percentage of L handed gave speech in the LH?

A

70%

22
Q

What percentage of R handers have speech in the LH

A

98%

23
Q

What is the Cartoid Sodium Amobarbital Injection

A
  • this is the WADA test
  • language usually located in the LH but in small percent of people (most left handed) showed RH controlling language
  • To avoid brain damage to speech zones in patients about to undergo brain surgery, surgeon inject sodium amobarbital into the cartoid artery which determines which hemisphere is involved in speech
  • this drug anesthetizes the hemisphere
  • L cartoid artery injection anesthetizes the L hemisphere and vice versa
  • Patients are aphasic after (dont remember)
24
Q

What happens with a Cartoid Sodium Amobarbital injection to the left cartoid artery

A
  • patient cannot speak, move R arm, no RVF

- RH nondominant but aware for speech so they cannot report on the experience later

25
Q

What happens with a Cartoid Sodium Amobarbital injection to the right cartoid artery

A
  • sensory and motor disturbances but no speech disturbances

- UNLESS they are RH dominant for speech

26
Q

What are tachistoscopic Studies?

A
  • special instrument called tachistoscope, visual information can be presented to each visual field independently
  • fixate on a marked center point and image is flashed in one VF for 50 milliseconds (only long enough to allow one item processed in VF)
  • this is for asymmetry studies in healthy brains
  • found that words presented verbally to LH processed more efficiently then RH
  • Faces are processed in RH or LVF
27
Q

How can you study asymmetry in the auditory system

A
  • kimuras dichotic listening model (Ba-Ga)
  • auditory system is not as completely crossed as the visual system because both H receive projections from each ear
  • information presented to either ear reaches both H by both ipsilateral and contralateral pathways
  • the contralateral pathway has more numerous and rapidly conducting connections?
28
Q

What is Monaural Presentation

A
  • kimuras dichotic listening model
  • “Ba” presented to only L ear will travel to both sides of brain and vice versa with “ga”
  • there is no ear preference for vowels or rhythm in monaural presentation
29
Q

What is Dichotic Presentation

A
  • kimura
  • info to both ears goes to both H
  • information that enters the L ear will go to the RH more quickly than the left and vice versa
  • RH specialization for music, melody, environmental sounds, emotional sounds, tones
  • LH words and syllables
  • ipsilateral pathway gets suppressed
30
Q

Damage to corpus callosum does what to our auditory system

A
  • if corpus callosum is cut, the patient will only report hearing ‘ga’ or information entering the R ear because the information in L ear cannot cross the corpus callosum
31
Q

Asymmetry in the Primary Sensorimotor cortex

A
  • somatosensory pathways and motor pathways are almost wholly crossed
  • each limb is severed primarily by the cerebral hemisphere on the opposite side
  • bind fold patient and they will perform a variety of tasks
32
Q

Which hand do blind children read more fluently with?

A
  • the left hand

- rh superior in pattern and spatial recognition

33
Q

Asymmetry in the motor system

A
  • almost completely asymmetrical
  • the right side of the mouth opens more widely and faster for both verbal and non verbal which suggests left hemisphere specialization in selecting, programming and producing verbal and nonverbal oral movements
  • the onset of facial expression is also quicker on the left side of the face
34
Q

what can left hemisphere lesions produce

A

apraxia- severe deficits in making or copying voluntary movement sequences

35
Q

How to study/ asses motor asymmetries

A
  1. direct observation

2. interference tasks

36
Q

What is an interference task

A
  • multitasking
  • performing two complex tasks at the same time is difficult
    ex, playing piano and humming
  • as we become more proficient at motor tasks we are less prone to interference effects
37
Q

Region blood flow and asymmetry

A
  • LH speaking (many activations shown in LH)
  • RH speaking (mouth and auditory cortex in RH active but less than LH)
  • LH listening (sensations activates blood flow in auditory cortex only
38
Q

How does lateralization in the brain work, what are the two theories

A
  • specialization theories: propose unique functions for each hemisphere
  • interaction theories: propose cooperation between hemispheres
39
Q

Can both hemispheres perform all functions?

A
  • yes to some extent but dont
40
Q

What hemisphere does morse code operators display advantage in?

A
  • Left Hemisphere, it is a temporal sequence
41
Q

What does the Left hemisphere specialize in

A
  • language
  • bias toward self interaction
  • brocas area aka language
42
Q

What ate the two distinct forms of functional lateralization in the human brain?

A
  • integration : hemispheres could have extensive functional connections with each other
  • Segregation: or they could more extensively interact unilaterally
43
Q

What are the three interaction models

A
  1. The two hemispheres function simultaneously but work on different aspects of processing
  2. Although the two hemispheres have the capacity to perform a given function they inhibit or suppress each other activity
  3. Either the two hemispheres receive information preferentially and thus perform different analysis simultaneously or some mechanism enables each hemisphere to pay attention to specific types of information thus leading to different hemispheric analyses
44
Q

Anxiety related behaviours are associated with what part of the hippocampus

A
  • anterior
45
Q

memory and spatial navigation are associated with what part of the hippocampus?

A
  • posterior

Psychology 475: Human Neuropsychology (8 decks)

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