Dominance and Laterality

Question 1

Definition: Laterality

Answer 1

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

Question 2

Definition: Dominance

Answer 2

Cerebral hemisphere that is specialized for language, typically left

Question 3

Definition: Crossed Dominance

Answer 3

Condition of right hemispheric dominance for language

Question 4

Definition: Crowding

Answer 4

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

Question 5

Definition: Pathological Left-handedness

Answer 5

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

Question 6

Handedness Measures:

Answer 6

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

Question 7

How is cerebral dominance measured?

Answer 7

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

Question 8

How is IAT used to measure cerebral dominance?

Answer 8

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

Question 9

When would you use IAT to measure cerebral dominance?

Answer 9

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

Question 10

How is fMRI used to measure cerebral dominance?

Answer 10

• 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

Question 11

When would you use fMRI to measure cerebral dominance?

Answer 11

• noninvasive
• used in neurologically healthy individuals

Question 12

Atypical dominance patterns include _______ and _____ hemisphere dominance

Answer 12

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

Question 13

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

Answer 13

left-handed individuals

Question 14

Atypical dominance increases dramatically in individuals with _____ ______ ________.

Answer 14

Atypical dominance increases dramatically in individuals with early brain damage

Question 15

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

Answer 15

Areas of language activation include:

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

Question 16

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

Answer 16

symmetric and right hemisphere dominance patterns relative to healthy normal individuals

Question 17

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

Answer 17

**symmetric and right hemisphere dominance patterns **

Question 18

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

Answer 18

symmetric and right hemisphere dominance patterns

Question 19

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

Answer 19

atypical dominance patterns

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

Question 20

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

Answer 20

age of the individual at the time of injury

Question 21

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

Answer 21

individual typically develops language functions

• typically in the context of a generalize decline intelligence

Question 22

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

Answer 22

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

Question 23

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?

Answer 23

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

Question 24

What causes crossed-dominance?

Answer 24

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

Question 25

**Disorders of Speech (3):**

Answer 25

involve malfunction of the **muscles of speech articulation** 1. **Mutism** 2. **Aphonia** 3. **Aphemia**

Question 26

**Causes of Mutism:**

Answer 26

* ​​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**

Question 27

**Causes of Aphonia:**

Answer 27

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

Question 28

**Causes of Aphemia:**

Answer 28

* **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

Question 29

**Disorders of Language:**

Answer 29

**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”

Question 30

How are disorders of language **localized?**

Answer 30

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

Question 31

How is fluency evaluated?

Answer 31

**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

Question 32

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

Answer 32

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”

Question 33

What is the **Wernicke-Geschwind** model of language organization?

Answer 33

**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**

Question 34

**List the categories of aphasias:**

Answer 34

1. Global aphasia 2. Broca’s aphasia 3. Transcoritcial aphasias * Motor * Sesory * Isolation 4. Conduction aphasia

Question 35

**Global aphasia****:**

Answer 35

occurs when the functions of both **anterior and posterior aspects of the core language zones are impaired** * fluency: **no** * comprehension: **no** * repetition: **no**

Question 36

**Broca’s aphasia:**

Answer 36

**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**

Question 37

**Trancortical Aphasias:**

Answer 37

**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**

Question 38

**Conduction Aphasia:**

Answer 38

**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

Question 39

Aphasias: 1. Fluency 2. Comprhension 3. Repetition

Answer 39