Neurolinguistics

Neurolinguistics

1. Broca was the first person to suggest that speech is lateralised in the left hemisphere

2. Broca's Aphasia

   • Posterior frontal lesion
   • Disturbance of speech planning and production
   • Results in agrammatic impoverished speech
   • Speech is slow, laborious, nonfluent

3. Wernicke's Aphasia

   • Posterior temporal lesion
   • Disturbance of word sound patterns
   • Results in poor auditory comprehension, but copious, fluent speech
   • Speech is non-laboured, but lacks content

4. Right Hemisphere Language

   • Patients with LH damage are often still capable of producing nonpropositional speech (counting from 1 to 10, singing happy birthday), automatic context-bound utterances e.g., nursery rhymes, counting, swearing
     • These forms of expressive language do NOT involve the generation of new ideas or processing of such ideas into novel situations
   • Language deficits associated with damage to the RH are subtler than those following LH damage, thus were less likely to capture clinician's attention
     • At least 50% of RH damage patients exhibit a verbal communication deficit
     • Language impairments following RH lesion are most likely following right middle cerebral artery infarct, such occlusions tend to produce lesions that do not respect anatomic boundaries, depending on where the blockage occurs, will affect how bad the stroke is
     • Speech of patients with RH damage has been described as: Excessive, rambling, inappropriate, off colour, confabulatory, irrelevant, literal, sometimes bizarre
     • Tompkins examined the ability to revise interpretations in RHD and normal adults, participants heard 2 sentences: the first was ambiguous and the second resolved the ambiguity in favour of the less likely interpretation
       • Participants judged whether a target word fit the overall meaning of the sentence, RHD often can't go back and revise a sentence, once they've made an initial interpretation, they can't go back and revise it
     • Nonliteral Language Processing
       • Pragmatics involves the context-appropriate social use of language
       • Myers reported that RHD patients missed nuances and subtleties: they ignored context and could not fill in what was no present in the words
       • Foldi et al. asked RHD participants to interpret both direct and indirect speech, they found that patients interpreted indirect speech literally, without taking contextual information into account
       • RHD patients have difficulties interpreting nonliteral language such as: interpreting indirect requests, selecting punchlines for joke, recognising irony or sarcasm, interpreting idioms/metaphors
       • RHD patients perform poorly on semantic judgment tasks involving metaphoric or emotional meanings, but perform just as well as LHD patients for semantic judgments involving literal or affectively neutral meanings
     • Contextual Cues
       • RHD patients often miss body language and facial expression cues that we use to figure out true intention and emotional state of the people we interact with
       • May also have a 'flat affect' and monotonous speech, this doesn't necessarily reflect a depressed mood but is a specific prosodic deficit
         • Prosody is the "melody of language", it encompasses alterations in pitch, stress and rhythm that allow us to communicate meaning and emotion
           • Pell reported that patients with RHD are less proficient in conveying emphasis to listeners as such patients exploit fewer than normal cues to communicate their emphasis in their utterances
           • RHD often suffer from APROSODIA: speak with a flattened emotional tone, even when describing personal experiences likely to elicit strong emotion, they also have difficult interpreting the emotional tone in speech produced by others
           • Aprosodic patients do not lose the knowledge of how emotional representations are vocally encoded; they have difficulty in 'fine-tuning' the acoustic properties of their emotional utterances

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