Cortical Localization of Speech

1
Cortical Localization of Speech

• Lecture 26

2
Aphasias

• Speech Disturbances
• comprehension
• production
• cerebrovascular damage
• Location of lesion ---gt type of deficit
• Anomia
• deficit in comprehension of nouns
• common vs proper

3
Wernicke-Gescwind Model

• Serial model
• too simple
• parallel processing involved
• Left hemisphere
• temporal
• frontal

4
Brocas Area Production
Arcuate Fasciculus
Angular gyrus
B
A
V1
A1
W
Left Hemisphere
Wernickes area comprehension
5
Hearing vs. Reading

• Production of speech
• 2 pathways

6
Repeating a spoken word
B
7
Reading a word aloud
B
A
8
Lateralization

• Wada test
• sodium amytal
• determines hemisphere dominance
• Language ---gt Left hemispehere
• Right-handed - 95
• Left-handed - 70
• Females less lateralization
• unilateral lesion ---gt less aphasia

9
Anatomical Asymmetries

• Left hemisphere
• Herschels gyrus - A1
• 2 small on right
• 1 large on left
• Planum temporale
• larger on left

10
Classification of Aphasias

• Various classification schemes
• variability in diagnosis
• lesions not consistent
• 3 main tests
• spontaneous speech
• listening for comprehension
• repeating

11
Brocas Aphasia

• Expressive or motor aphasia
• Lesion in left frontal lobe
• Motor programs
• Fluency deficits
• Slow, laborious speech
• great difficulty with function words
• Comprehension OK
• Aware of deficits
• Impaired repetition

12
Brocas Aphasia

• Comprehension OK, but...
• Problems w/ passive voice
• The ball was hit by the boy.
• active voice better
• The boy hit the ball.
• Difficult to read
• To be or not to be.
• Can read
• Two bee oar knot two bee.

13
Evidence Brocas Area

• Support
• Brocas are ---gt motor programs
• required for muscle contractions
• Against
• remove Brocas only ---gt few deficits
• Strokes damage not limited to Brocas
• other cortical/subcortical areas involved
• e.g. caudate

14
Wernickes Aphasia

• Receptive or sensory aphasia
• Deficits
• comprehension
• generation and of meaningful speech
• fluency OK
• Word salad
• Impaired repetition
• Unaware of deficits
• Memories of words

15
Wernickes Aphasia

• Damage to Wernickes Area
• temporary deficits
• swelling produces deficits
• Permanent deficits
• damage to underlying white matter
• fiber systems

16
Conduction Aphasia

• Damage to arcuate fasciculus
• good comprehension, fluent speech,
• poor repetition
• say auto
• repeat car

17
Other Aphasias

• Transcortical motor
• lesion anterior to Brocas area
• similar deficits except repetition OK
• Transcortical sensory
• lesion junction of temporal, parietal, occipital
  lobes
• similar to Wernickes, but repetition OK
• Anomic
• lesion inferior temporal lobe
• inability to name things

18
Pure Word Deafness

• I can hear you talking, but I dont know what
  you are saying.
• Disconnection b/n A1 Wernickes area