Language and the brain- lessons from aphasia

Question 1

BROCAS (non fluent ) APHASIA symptoms (stroke patient)

Answer 1

• Slow, laboured speech output
• Anomia (no names) – difficulties finding words
• Paraphasic errors – “plashing … flashing … pashing … Running …” (splashing?) – [Phonemic paraphasia]
• Telegraphic speech (no or few function words)
• In extreme cases, only a small number of syllables, words or phrases (e.g., Broca’s patient “Tan” )
• Difficulty mostly with production rather than comprehension
• Agrammatism

Question 2

Agrammatism

Answer 2

• Indicated by absence of function words in telegraphic speech
• Cannot use syntax to disambiguate
• Cannot work out which animal died from a sentence vv
  i. The lion killed the leopard
  ii. The leopard was killed by the lion

Question 3

WERNICKES APHASIA `(symptoms of a stroke patient)

Answer 3

a) Problems understanding spoken or written language
b) Communication cut off
c) Fluent but meaningless speech
d) Phonemic paraphasia
e) Semantic paraphasia
b. Substituting words related in meaning (e.g., dog for cat)
i. This happens in deep dyslexia as well
f) Difficulty connecting to meaning

Question 4

WERNICKE-GESCHWIND MODEL - repeating spoken words

Answer 4

The classic Wernicke-Geschwind model for the neural circuit that might be involved in speaking aloud a word that’s just been heard. The auditory cortex processes the sound structure and Wernicke’s area is involved in accessing meaning. Activation then travels to Broca’s area through a bundle of axons called the arcuate fasciculus. Broca’s area accesses the speech representation of the word and instructs the motor cortex to execute action.

Question 5

WERNICKE-GESCHWIND MODEL - Repeating spoken words

Answer 5

The scenario here is similar except that the word is processed by the visual cortex and information is transmitted to the angular gyrus. Here, according to this model, the visual code of the written word is converted into a phonological code, not unlike in the case of the spoken word. This phonological representation is interpreted in the Wernicke’s area and then the rest of the pathway is the same.

Question 6

wernicke-geschwind Model Success: Conduction aphasia

Answer 6

•	Wernicke’s area is intact
	 -Comprehension is OK
•	Broca’s area is intact
         - Speech production is OK
•	Arcuate fasciculus damaged
	 -problem with repeating heard words

Question 7

wernicke-geschwind Model limitations:

Answer 7

• Always get mixture of production and comprehension problems
• Function recovery after stroke - other cortical areas can functionally substitute
• Surgical removal of cortical tissue produces less disruption than stroke
• Stroke damages sub-cortical tissue in
thalamus and basal ganglia
• Broca’s area damage is often accompanied by insula damage

Question 8

BRAIN STIMULATION

Answer 8

The patient is brought out of anaesthesia once the skull has been opened and the surgical area prepared. When the brain tissue is electrically stimulated, the patient can report the corresponding experiences. There are no pain receptors in the central nervous system, so the electrical stimulation not objectionable. By meticulously mapping brain areas in this way, a functional map was created and related to what was known from brain damage data.
In a modern version of this procedure an electrode grid is placed on the brain to greatly increase the efficiency of the procedure.