Introduction to Neuropsychology Language Example Exam Questions 1.How have neuropsychological investigations informed our current understanding about the neural underpinnings of language? n 2.What differences exist between the behavioural deficits resulting from damage to anterior and posterior language structures? n 3.How have investigations into conduction aphasia informed us about the layout of language in the brain? n Basic Anatomy BA_Image.gif Lobes_Image.gif Not an anatomy course Basic Anatomy Arteries 4.jpg Arteries 5.jpg Arteries 3.jpg Stroke: Ischemic (clot) vs. Hemorrhage (rupture) Basic Anatomy 1 - MCA.GIF 2 - pMCA.GIF Arteries 3.jpg Language Lecture Outline 1.Expressive (Broca’s) Aphasia 2.Receptive (Wernicke’s) Aphasia 3.Conduction Aphasia 4.Disconnection Syndromes Lateralisation of Language n70-95% demonstrate a left-sided lateralisation n~95% of right-handers n~70% of left-handers n~20% of left-handers have right-sided lateralisation n~20% of left-handers have language distributed across both hemispheres nBut what about categories of language? n n“Wada” (neuropsychological) test nIntra-arterial amobarbital procedure nCandidates for surgical resections of epileptic foci nAnaesthetise each hemisphere to confirm hemispheric dominance for language nCannot localise speech or other primary language functions Lateralisation of Language Expressive Aphasia Prototypical Patient nLeborgne (“Tan”) n nSingle syllable speech (“tan tan”) at 21yrs nNo initial motor behaviour impairment (oral movements unimpaired) nEventually right-sided hemipariasis nComprehension unimpaired nResponded to numbers nLesion to left posterior inferior frontal gyrus n (Broca, 1861; http://psychclassics.yorku.ca/Broca/perte-e.htm) Broca's Brain.GIF Expressive Aphasia Typical Symptomatology... n nImpairment of verbal expression (spoken and written), with (relatively) unimpaired comprehension n nSpeech limited to stereotyped expressions/expletives nShort, effortful agrammatical sentences with many hesitations nNouns and verbs persevered, but omissions of modifiers or propositions ne.g. “Me go” vs “I am going” nWords beginning with phonemes produced at the front of the mouth (“p”, “b”, “m”) easier than others (“s”, “t”) ne.g. “Peech gone, no palk” (Geschwind, 1970; Ogden, 2005) Expressive Aphasia ...Typical Symptomatology... n nCopying better than spontaneous writing or diction nImpaired prosody (melody) nOral apraxia nImpaired performance of learned motor skills (e.g. tongue poking) on command nContralateral hemipariasis of arm n (Geschwind, 1970; Ogden, 2005) Expressive Aphasia ...Typical Symptomatology... Motor homunculus.GIF (Penfield & Rasmussen, 1950; see Schott, 1993) Expressive Aphasia ...Typical Symptomatology Receptive Aphasia Typical Symptomatology... n nImpairment of verbal comprehension (spoken and written), with (relatively) unimpaired fluent expression n nSpoken and written language is fluent and grammatically correct, but nonsensical nContain paraphasias (phonetic – “dell” for “bell”; semantic – “ding ding” for “bell”) and neologisms (non-existent) nRepetition impaired (Geschwind, 1970; Ogden, 2005) Receptive Aphasia ...Typical Symptomatology... n nNo limb weakness nFrequent visual field defect nContralateral upper quadrant or entire visual field (homonymous hemianopia) n (Geschwind, 1970; Ogden, 2005) Receptive Aphasia ...Typical Symptomatology Double Dissociations nSingle Dissociation nDamage to brain structure A causes a deficit in behaviour A but not in behaviour B nSuggest that behaviours A and B are independent of one another and associated with the brain structure(s) nBut resource artefact nDouble Dissociation nDamage to brain structure A causes a deficit in behaviour A but not in behaviour B, and damage to brain structure B causes a deficit in behaviour B but not in behaviour A nBehaviours A and B are independent of one another and associated with independent brain structures n n (Chater & Ganis, 1991) Global Aphasia n“Speech is non-fluent, and comprehension, repetition, and naming are severely impaired. The patient cannot read or write. Most patients have a right hemiplegia.” (Ogden, 2005) Wernicke’s Theory The Arcuate Fasciculus (Catani & Mesulam, 2008) n“…the first frontal gyrus, which has motor function, acts as center for motor imagery; the first temporal gyrus, which is sensory in nature, may be regarded as the centre of acoustic images; the fibrae propriae, converging into the insular cortex, form the mediating arc reflex… aphasia may be caused by any disruption of this pathway.” (Wernicke, 1874) 1.GIF Wernicke’s Theory The Arcuate Fasciculus Wernicke's aphasia.GIF (Geschwind, 1965; 1970) Wernicke’s Theory The Arcuate Fasciculus Wernicke's aphasia.GIF (Geschwind, 1965; 1970) Wernicke’s Theory The Arcuate Fasciculus Wernicke's aphasia.GIF (Geschwind, 1965; 1970) Wernicke’s Theory The Arcuate Fasciculus Wernicke's aphasia.GIF (Geschwind, 1965; 1970) Wernicke’s Theory The Arcuate Fasciculus Wernicke's aphasia.GIF (Geschwind, 1965; 1970) Conduction Aphasia Typical Sympomatology... nImpairment of repetition, with (relatively) unimpaired fluent expression and verbal comprehension n nRepetition severely impaired nSpoken language is fluent and grammatically correct nContains many phonemic paraphasias nComprehension is unimpaired nWriting is impaired nSpelling errors; syntax errors; word omission nReading aloud is impaired; Silent reading for comprehension unimpaired n Conduction Aphasia ...Typical Sympomatology... n nLittle or no hemiplegia nBut can be accompanied by minor motor or visual-field deficits contralateral to lesion nApraxia on verbal command and imitation n n n“Aphasia of the insula region” (Wernicke, 1874) n (Geschwind, 1965; 1970) Conduction Aphasia ...Typical Sympomatology Superior Longitudinal Fasciculus Superior Longitudinal Fasciculus (I; money).GIF Superior Longitudinal Fasciculus (II; money).GIF Superior Longitudinal Fasciculus (III; money).GIF (Petrides & Pandya, 1984; see Mariën & Abutalebi, 2008) Superior Longitudinal Fasciculus Arcuate fasciculus.GIF n“…lesions of association cortex, if extensive enough, act to disconnect primary receptive or motor areas from other regions of the cortex in the same or in the opposite hemisphere.. Thus a ‘disconnexion lesion’ will be a large lesion either of association cortex or of the white matter leading from this association cortex…” n nStressed “…the importance of the angular gyrus in acting as a region involved in cross-modal associations... A name passes through Wernicke’s area, then via the angular gyrus arouses associations in the other parts of the brain…” Geschwind’s Theory Inferior Parietal Lobule (Geschwind, 1965; Catani & Muselam, 2008) Geschwind’s Theory Echolalia nImpairment of spontaneous speech, with (relatively) unimpaired repetition and verbal comprehension nIntact production (Broca’s area) and comprehension (Wernicke’s area), and intact connection between them (arcuate fasciculus) n (Geschwind, 1965) Geschwind’s Theory Inferior Parietal Lobule 1.GIF (Fridriksson et al., 2010) 1.GIF New Arcuate Fasciculus.GIF (Catani et al., 2005) New Arcuate Fasciculus (2).GIF Geschwind’s Theory Inferior Parietal Lobule Discussion nAdvantages 1.Animals models can’t be used to investigate language 2.Clear double dissociations permit strong inferences and models nLimitations 1.Lesions often effect diffuse brain structures 2.The lesion approach ignores subtle facets of language n Limitations 1.GIF (Glasser & Rilling, 2008) The End