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Flashcards in Dominance and Laterality Deck (39)
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1
Q

Definition: Laterality

A

Cerebral hemisphere that is specialized for a group or class of cognitive operations

2
Q

Definition: Dominance

A

Cerebral hemisphere that is specialized for language, typically left

3
Q

Definition: Crossed Dominance

A

Condition of right hemispheric dominance for language

4
Q

Definition: Crowding

A

Refers to condition that occurs after early left hemisphere damage where development of language shifts to the right hemisphere at the expense of development of cognitive capacities typically associated with right hemisphere

5
Q

Definition: Pathological Left-handedness

A

Condition of left-handedness that has occurred because of early injury to left hemisphere that cause a shift in natural handedness pattern

6
Q

Handedness Measures:

A
  1. Inventories:
    • Inventories sample a range of activities
      • e.g. hand used in throwing, cutting, eating
    • then establish a quantitative index of handedness
  2. Handwriting:
    • Single most telling (and common) questions used to establish handedness
      • “What hand do you use to write?”
  3. Result:
    • 90% R handed, 10% L handed
7
Q

How is cerebral dominance measured?

A
  1. Intracarotid Amobarbital Test (IAT)
  2. functional neuroimaging (fMRI)
8
Q

How is IAT used to measure cerebral dominance?

A

Wada test:

  1. catheter is routed into the internal carotid artery
  2. barbiturate is injected into the left or right side, anesthetizing the greater part of the hemisphere
  3. patient is given tests of language
    • measures how well the unanaesthetized hemisphere can perform the tests
9
Q

When would you use IAT to measure cerebral dominance?

A
  • invasive test that is only used in individuals who have abnormalities in brain function
  • may not generalize well to neurologically healthy populations
10
Q

How is fMRI used to measure cerebral dominance?

A
  • based on changes in the ratio of oxyhemoglobin to deoxyhemoglobin
    • cognitive activity is correlated with a change in this ratio
  • used to identify those brain regions activated by a given cognitive task
11
Q

When would you use fMRI to measure cerebral dominance?

A
  • noninvasive
  • used in neurologically healthy individuals
12
Q

Atypical dominance patterns include _______ and _____ hemisphere dominance

A

Atypical dominance patterns include “bilateral” and “right” hemisphere dominance

13
Q

Is atypical dominance patterns more common in left-handed relative or right-handed individuals?

A

left-handed individuals

14
Q

Atypical dominance increases dramatically in individuals with _____ ______ ________.

A

Atypical dominance increases dramatically in individuals with early brain damage

15
Q

When conducting a fMRI study, what areas of the brain are “activated” for language?

A

Areas of language activation include:

  1. left frontal, temporal and parietal regions
  2. right cerebellum
16
Q

Patients with epilepsy are more likely to show what type of dominance?

A

symmetric and right hemisphere dominance patterns relative to healthy normal individuals

17
Q

What type of dominace pattern is likely to be seen in a healthy left hander?

A

**symmetric and right hemisphere dominance patterns **

18
Q

What type of dominace pattern is likely to be seen in a patient with late onset of brain damage?

A

symmetric and right hemisphere dominance patterns

19
Q

If a patient has early onset of brain damage, what type of dominace profile will they most likely express?

A

atypical dominance patterns

  • both crossed-dominance and symmetric dominance
  • often associated with pathological left-handedness
20
Q

What determines precisely how well an individual develops language functions after injury to the left hemisphere?

A

age of the individual at the time of injury

21
Q

How will language develop if a left hemisphere injury occurs very early in life (prior to one year of age)?

A

individual typically develops language functions

  • typically in the context of a generalize decline intelligence
22
Q

How will language develop if a left hemisphere injury occurs between ages 1 and 5?

A

language functions still typically develop

  • however, often this occurs at the expense of development of non-linguistic skills
    • Ex: visual-spatial skills
  • Theory:
    • language development occurs in regions of brain that otherwise would have been devoted to the development on non-linguistic skills“crowds” the non-linguistic skills out of development
23
Q

How will language develop if a left hemisphere injury occurs after the age of 5?

What have we learned from studying these types of injuries?

A

specific abnormalities of language skills that are apparent ⇒ brain plasticity diminishes with age

24
Q

What causes crossed-dominance?

A

crossed-dominance

  • Injury to the core or central speech zones
    • may cause a complete shift in language function to the **right hemisphere **
  • Selective injury to anterior or posterior speech zones often cause a shift of the functions associated that that zone only
25
Q

Disorders of Speech (3):

A

involve malfunction of the muscles of speech articulation

  1. Mutism
  2. Aphonia
  3. Aphemia
26
Q

Causes of Mutism:

A
  • ​​psychogenic or neurological
  • neurological mutism typically occurs in the context of a syndrome known as akinetic mutism
  • Akinetic mutism:
    • Failure to initiate action
    • Extensive bifrontal brain disease or bilateral lesions in the supplementary motor area
27
Q

Causes of Aphonia:

A

injury to the peripheral nervous system that enervates the muscles of the vocal chords, preventing sound production

28
Q

Causes of Aphemia:

A
  • individual can produce vocal sounds (e.g., grunts, groans, song-like features), but is not able to generate speech
  • disconnection syndrome
    • whitematter lesion beneath Broca’s area that severs the final output pathway for speech production
29
Q

Disorders of Language:

A

Aphasias

  • involve impairment in one or more dimensions of linguistic functions
  • all aphasias can be classified by the integrity of speech
    • “fluency”
      • most useful dimension
    • “comprehension”
    • “repetition”
30
Q

How are disorders of language localized?

A

localize brain dysfunction to anterior or posterior regions:

  1. non-fluent aphasias ⇒ dysfunction in anterior brain regions
  2. fluent aphasias ⇒ dysfunction in posterior brain regions
31
Q

How is fluency evaluated?

A

3 dimensions:

  1. **Phrase length: **max number of words per utterance
  2. Degree of apparent effort in production of speech
  3. **Prosody: **preservation of melodic elements of speech
32
Q

What are the typical charactersitics of nonfluent speech? How is fluency of speech evaluated?

A

Nonfluent speech:

  1. typically contains fewer than 3 words in most utterances
  2. laborious in production
  3. monotonic in delivery

Evaluating fluency of speech:

  1. ask the patient open-ended questions
  2. ask the patient to describe complex pictures
    • “Cookie Theft Card”
33
Q

What is the Wernicke-Geschwind model of language organization?

A

core language zones are those that surround the Sylvian fissure:

  1. posterior superior temporal gyrus (Wernicke’s area)
    • ​​critical for speech comprehension
  2. ​posterior and inferior frontal lobe (Broca’s area)
    • ​​critical for speech production
  3. ​whitematter fibers that connects these two zones (arcuate fasciculus)
    • critical to repetition speech
34
Q

List the categories of aphasias:

A
  1. Global aphasia
  2. Broca’s aphasia
  3. Transcoritcial aphasias
    • Motor
    • Sesory
    • Isolation
  4. Conduction aphasia
35
Q

Global aphasia:

A

occurs when the functions of both anterior and posterior aspects of the core language zones are impaired

  • fluency: no
  • comprehension: no
  • repetition: no
36
Q

Broca’s aphasia:

A

Nonfluent aphasia that has rather profound impairment in speech articulation. Repetition speech is impaired because of the articulation difficulties:

  • fluency: no
  • comprehension: yes
  • repetition: no
37
Q

Trancortical Aphasias:

A

Repetition speech is preserved:

  1. Transcortical motor aphasia:
    • lesions to the premotor region or SMA
    • fluency: no
    • comprehension: yes
  2. Transcortical sensory aphasia:
    • fluent aphasia
    • language comprehension deficits at the word level
    • lesions of the angular gyrus or posterior and inferior temporal lobe
  3. Isolation aphasia:
    • lesions of both transcortical motor and sensory aphasia are present
      • isolates the core speech zones
    • i.e. no fluency and no comprehension of language
38
Q

Conduction Aphasia:

A

fluent aphasia

  • profound impairment in repetition speech
  • preserved comprehension
  • repetition speech deficit is thought due to impairment in auditory storage buffer or the transmission pathway (arcuate fasciculus) between speech sound recognition and articulation centers
39
Q

Aphasias:

  1. Fluency
  2. Comprhension
  3. Repetition
A