Speech/Language & Cerebral Dominance Flashcards
What percentage of people (without histories of epilepsy or brain injury) are right-handed?
How many demonstrate right hemispheric dominance?
How do these change following early brain damage? Why?
90%, decreases to about 80% with brain damage.
About 5% (more common among the left-handed), increases to around 20% with brain damage*.
Presumably, these changes occur due to destruction of the centers that originally controlled these processes.
*These numbers are across both groups and are approximate; focus on their relative magnitudes and the directions of their changes.
How is handedness measured?
How is cerebral dominance measured?
Inventories (questionnaires); seeing which hand one writes with.
fMRI, previously intracarotid amobarbital testing (Wada test)
What factors influence the level of laterality of cerebral dominance?
Age: Lateralization increases during puberty, then decreases.
Gender: Males MAY more lateralized than females.
What is a better predictor of cerebral dominance than handedness?
Below what age will (focal) brain damage not affect long-term language development? What other deficits are seen then?
Interestingly, family history of left-handedness may be more strongly predictive.
Below age 5. Prior to age 1, there will be generalized cognitive deficit. Between 1 and 5, there will be visual-spatial deficit (crowding).
Describe the four discussed speech disorders.
How are they different from language disorders?
Mutism: Absence of speech (may be intellectual, from anxiety, frontal lobe injury…)
Aphonia: Physical inability to vocalize (disruption of innervation)
Aphemia: Impaired articulation (can produce sounds)
Dysarthria: Impaired speech (eg slurring)
Speech disorders are malfunctions of the muscles of speech. Aphasias involve impairment of higher linguistic functions.
What factors are considered in evaluating language disorders (aphasias)?
How can you assess these criteria?
Fluency (words per utterance, grammar, prosody), Auditory comprehension, and repetition of speech.
Presenting a visual scene and asking the patient about it can facilitate assessment of these.
What are paraphrasias? In what conditions are they seen?
Why might emotional speech be preserved?
Substitutions of words for others (instead of “chair”: table or hair). Seen in Wernicke’s, Transcortical Sensory, and Conduction aphasias.
Apparently, this is handled by other brain regions.
Around what structure are most of the speech-related centers located? Name some of these areas.
What is the band of white matter that connects Broca’s and Wernicke’s areas?
The sylvian fissure. Consider Broca’s & Wernicke’s areas (articulation and storage/recognition), the temporal lobe (semantics), frontal lobe (language retrieval/initiation), and parietal (object recognition).
The arcuate fasciculus. IMPORTANT: A patient with sensory cortex loss can still repeat words back because of this connection.
Global Aphasia
What does it result from?
How are fluency, language comprehension, and repetition affected?
Global Aphasia
Results from lesion of both anterior and posterior speech regions.
All three are affected.
Isolation Aphasia
What does it result from?
How are fluency, language comprehension, and repetition affected?
Isolation Aphasia
Lesions of both motor and sensory regions, leaving core speech zones (Wernicke’s and Broca’s) intact.
Fluency lost, comprehension lost, but repetition okay.
Broca’s Aphasia
What does it result from?
How are fluency, language comprehension, and repetition affected?
Broca’s Aphasia
Lesion of Broca’s area on the dominant side (loss of motor component).
Fluency is lost (can’t initiate), comprehension OK, repetition lost.
Transcortical Motor Aphasia
What does it result from?
How are fluency, language comprehension, and repetition affected?
Transcortical Motor Aphasia
Lesion of the premotor region or SMA. Patient can’t initiate speech.
Fluency lost, comprehension & repetition OK.
Wernicke’s Aphasia
What does it result from?
How are fluency, language comprehension, and repetition affected?
Wernicke’s Aphasia
Lesion of Wernicke’s area on the dominant side. Patient can speak, but only produces gibberish.
Fluency OK, comprehension & repetition lost.
Transcortical Sensory Aphasia
What does it result from?
How are fluency, language comprehension, and repetition affected?
Transcortical Sensory Aphasia
Lesions of the angular gyrus or posterior/inferior temporal lobule.
Fluency and repetition OK, comprehension lost.
Conduction Aphasia
What does it result from?
How are fluency, language comprehension, and repetition affected?
Conduction Aphasia
Damage to the arcuate fasciculus.
Fluency and comprehension OK, but repetition lost.
