L3 Neuropsychology

• Aphasia


  Loss of language generally, particularly refers to impairments of speech production
• Exclusions for aphasia


  • Language disturbances that have congenital causes
  • Purely auditory deficits
  • Purely articulatory deficits
  • Confusional or psychotic states
• 25-40% of stroke survivors develop aphasia
• Roughly 1,000,000 persons in the USA have aphasia, with roughly 100,000 new cases per year
• Broca's Aphasia


  Severely non-fluent speech, reduced grammatical complexity, poor articulation, poor melodic line, poor speech volume
• Wernicke's Aphasia


  Severe auditory comprehension deficits, rapid (fluent) but often meaningless speech, phonemic errors, semantic errors, neologisms
• Cookie Theft - Fluent Speech

  • "Well this is… mother is away here working her work out here to get her better, but when she's looking, the two boys looking in the other part. One their small tile into her time here. She's working another time because she's getting to. So two boys work together and one is sneakin' around here, making his work an' his further his time he had."
• Broca's Aphasia

  • Caused by dorsolateral frontal lesions, focused on dominant hemisphere, region for motor speech representations
• Wernicke's Aphasia

  • Caused by superior temporal lesions, region for "sound images", impairment to acoustic-phonological analysis of spoken words
• Wernicke suggested a third aphasic type due to disconnection between Broca's and Wernicke's regions (the arcuate fasciculus)
• Contemporary clinical classifications of aphasia

  • Broca's & Wernicke's Aphasia
  • Conduction Aphasia
  • Anomia
  • Global Aphasia
  • Transcortical Motor Aphasia
  • Transcortical Sensory Aphasia
• Transcortical Motor Aphasia

  • Block to spontaneous speech, repetition and comprehension good, damage to dorsolateral frontal extending to deep frontal white matter
• Transcortical Sensory Aphasia

  • Fluent/empty speech, repetition good, comprehension poor, naming also poor, reading & writing often impaired, damage to middle & inferior temporal gyri
• Aetiology of aphasia cases include strokes, trauma, and tumours
• Transcortical Aphasia Syndromes


  Characterized by intact repetition but deficits involving the mappings between the forms and meanings of utterances
• Transcortical Motor Aphasia

  • Affects speech production (mapping meaning onto form)
• Transcortical Sensory Aphasia


  • Affects speech comprehension (mapping form onto meaning)
• Limitations of aphasia classification systems include: criteria are quite general, impairments are matters of degree, syndromes depend on specific symptoms being present, deficits-lesion correlations are sometimes violated, syndromes are not necessarily stable over time
• Cognitive neuropsychology emphasises case differences rather than syndrome classification, aphasic cases can often differ in important theoretical ways
• Anomia


  Effectively like being caught in a permanent state of 'tip of the tongue'
• Anomia is a disorder of object naming
• Anomia


  • Utilisation of confrontational naming tasks, cognitive variables can be manipulated, errors differentially classified (semantic, circumlocution, phonological, neologisms)
• Modular models of anomia

  Provide simple outline of underlying cognitive processes, impairments implicate damage to particular parts of model, predicted outcomes of patient impairments from model, individual components can be selectively impaired
• Causes of naming impairment

  • Visual processing (object agnosia)
  • Semantic/conceptual processing (what an object is)
  • Phonological output processing (speech sounds access)
• Damage can implicate central impairments or access impairments in anomia
• Semantic dementia patients tend to retain most typical items, while stroke patients make many 'associative' errors and other types
• Dysphasia


  Disorders of repetition
• Repetition routes


  • Lexical route (auditory input-semantics-phonological output lexicon)
  • Sub-lexical route (spoken word decomposed and converted to speech output)
• Neuroanatomy of speech input-output routes

  • Auditory "input" regions - bilateral superior temporal gyrus

  Dorsal "sound-to-articulation" route - projects from STG to boundary between parietal/temporal regions

  Ventral "sound-to-meaning" route - projects from STG to posterior inferior temporal lobe
• Receptive aphasic syndromes


  • Damage to STG = pure word deafness

  Damage to "dorsal" projections = conduction aphasia

  Damage to "ventral" projections = transcortical sensory aphasia

  Damage to BOTH ventral/dorsal input mappings = Wernicke's aphasia
• Wernicke's aphasia involves a dual deficit in acoustic-phonological analysis and semantic impairment
• Three hypotheses have been proposed to account for the comprehension impairment in Wernicke's aphasia:
• Hypotheses for Wernicke's aphasia comprehension impairment

  • (1) a disruption to acoustic and/or phonological analysis
  • (2) a semantic impairment
  • (3) a combined phonological-semantic impairment (the dual process hypothesis)
• The WA group were impaired on both nonverbal and verbal comprehension assessments consistent with a generalised semantic impairment and similar to semantic aphasic cases.
• Wernicke's comprehension impairment


  a dual deficits in acoustic-phonological analysis (associated with pSTG) and semantic cognition (associated with pMTG and angular gyrus) - reflecting deregulated semantic control (executive control mechanisms – e.g., inhibition, retrieval, selection) – that interact with semantic representations
• Dejerine (1892) described a patient with a very specific reading impairment where he could read and recognise numbers with ease, but had a severe impairment of reading words.
• Disorders of reading and writing

  • Acquired Alexia/Dyslexia (Disorder of reading)
  • Acquired Agraphia/Dysgraphia (Disorder of writing/spelling)
• Marshall & Newcombe (1973) first conducted detailed neuropsychological study of acquired dyslexia/dysgraphia and discovered that patients with such disorders could be further subdivided in important theoretical ways.
• Classifications of disorders of reading and writing

  • Developmental
  • Acquired
  • Peripheral
  • Central
  • Phonological Dyslexia/Dysgraphia
  • Deep Dyslexia/Dysgraphia
  • Surface Dyslexia/Dysgraphia
• Peripheral dyslexia


  Such cases are due to "low level" visual processing problem or other general impairment (i.e., visual attention) such that reading is impaired (but its not a reading specific problem)