BBSQ4900 Research and independent study: Language Disorders in Adults

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BBSQ4900 Research and independent study
Language Disorders in Adults

• Topic 3 Brocas aphasia 1

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Etiologies

• Stroke hemorrhagic / embolic
• Middle cerebral artery is the primary blood
  supply for most of the language areas
• small, focal lesion to Brocas area ? dyspraxia /
  dysarthria
• Mohr et al 1978 Dronkers et al 1992, 1994
• Persistent Brocas aphasia is usually associated
  with deep subcortical lesions, encompassing
  cortex in BA 44 PLUS
• Frontal operculum
• Insula
• Subcortical white matter

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Frontal operculum
Brocas area
Insula
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Characteristics of Brocas aphasia

• Spoken language
• Short phrase length
• Telegraphic speech primarily content words
• Speech may be very effortful prosody is often
  abnormal
• Articulatory difficulties are common (apraxia /
  dysarthria)
• Poor repetition
• Disrupted naming ability
• A range of impairments in reading and writing
• Receptive language
• Relatively good for single words and short
  sentences
• Impairments in comprehension of grammatically
  complex sentences
• Often very good insight into deficits

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(No Transcript)
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Agrammatism

• Deficits in production and comprehension of
  sentences
• Problems occur at the level of sentence structure
  so the word level is often (comparatively)
  spared
• Agrammatism has been identified in other clinical
  populations, but has been studied most
  extensively in Brocas aphasics
• Symptoms of agrammatic production
• Reduced variety of grammatical form
• May stick to sentences with canonical word order
• Impairments are more severe in embedded
  constructions than in main clauses
• Omission of function words and inflections
• Tense is harder than agreement
• Omission of main verbs
• Slow rate of speech

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Agrammatic comprehension

• Sentence-picture matching tasks
• Non-reversible sentences are easier to interpret
  than reversible ones
• Canonical sentences subject-verb-object are
  easier to interpret than non-canonical ones
• Passive vs active
• Object relative vs subject relative
• Less complex phrase structure makes a sentence
  easier to understand

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The mother is calling her child who has light hair
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The woman who is fat is kissing her husband
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Syntactic trees
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Understanding agrammatism a phonological
disorder?

• Perhaps function words cause comprehension
  problems because they are de-stressed and
  difficult to perceive
• But some content words are de-stressed, and some
  functional morphemes do carry stress
• And its not the case that function words have no
  content e.g. tense, gender
• No real evidence that agrammatic aphasia carries
  with it a perceptual deficit and perceptual
  training did not have noticeably good effects on
  agrammatic comprehension
• Compares with the earlier economy of effort
  hypothesis

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Understanding agrammatism a central syntactic
deficit?

• Caramazza and Zurif 1976 agrammatics do have a
  comprehension deficit, and it parallels their
  production disabilities
• The test case Semantically reversible sentences
• Theta-roles assignment of interpretive roles to
  syntactic objects
• subject verb object
  Grammatical roles
• John kissed Mary
• Theta roles
• Non-canonical word order ? reliance on
  grammatical structure
• object verb subject
• John was kissed by Mary
• central disruption of the syntactic parsing
  component of the language system Berndt
  Caramazza 1980

Agent
Patient
Agent??
Patient??
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Understanding agrammatism a mapping deficit?

• Problems with the central syntactic deficit
  account
• agrammatics do have some ability to interpret
  complex utterances - in particular, they are
  quite good at grammaticality judgement
• Some agrammatics are modality-specifically
  impaired note assumptions of central deficit
  hypothesis
• Some fluent aphasics show comprehension deficits
  similar to those found in Brocas aphasics
• Perhaps the deficit is not central to syntax, but
  involves the transfer from syntactic structure to
  semantic structure of a sentence a mapping
  deficit (Saffran et al 1980)

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Understanding agrammatism the trace deletion
hypothesis

• We have seen that things move around in sentences
• And we have seen that interpreting sentences does
  not just mean knowing where the subject and the
  object are it means knowing what theta roles to
  assign, too
• In the normal language system, movement leaves
  traces behind
• Theta roles can be assigned to traces, and then
  transmitted to the moved item
• Grodzinsky (1990) asked what if traces get
  deleted from the syntactic representation?
• Maybe this is what happens in agrammatism
• The trace deletion hypothesis

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Trace Deletion Hypothesis

• Assigning a theta role to the girl should be no
  problem no trace involved in that
• P by assigns a theta role of Agent so the
  girl Agent
• But, if traces are deleted, then the boy has no
  theta role
• So follow your instincts USUALLY, the first
  noun in a sentence is the Agent
• So the boy is probably an Agent
• Now, the agrammatic thinks
• the boy Agent AND
• the girl Agent
• What to do? Guess at the right interpretation of
  this sentence
• Grodzinsky found that agrammatics were correct at
  interpretation of passives around 50 of the time
  so they are indeed guessing

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Tree-pruning

• A simple version originally proposed by Ouhalla
  (1993) to account for comprehension deficits
• Adapted by Grodzinsky and others to account for
  production problems in agrammatism
• The syntactic tree of a typical sentence is large
  and complex, with a great deal of functional
  architecture (some of which we know about, but
  some of which remains mysterious)
• People who have an agrammatic deficit may be
  unable to access higher parts of the tree (
  the syntactic structure)
• This can account for some cross-linguistic
  variation in patterns of agrammatism
• In any case, it makes sense that we should not be
  using the higher parts of the tree, so far as
  possible, when working with agrammatic patients
  so we dont use functional categories where
  possible, use less syntactic movement where
  possible
• Can educate communicative partners this way too
  show how a wh question involves a great deal of
  syntactic complexity a yes-no question is
  relatively simpler passives, relative clauses
  and locatives may overload the system very easily
• simplest of all is an active, nonreversible
  statement

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Questions