1. Language Disorders October 12, 2005

2. Types of Disorders Aphasia: acquired disorder of language due to brain damage Dysarthria: disorder of motor apparatus of speech Developmental language disturbances Associated disorders –Alexia –Apraxia –Agraphia

3. Major Historical Landmarks Broca (1861): Leborgne: loss of speech fluency with good comprehension Wernicke (1874): Patient with fluent speech but poor comprehension Lichtheim (1885): classic description of aphasic syndromes

4. C M A Lichtheim’s Model

5. Arcuate fasciculus

6. SyndromeSymptomDeficitLesion Broca’s Aphasia  speech production; sparse, halting speech, missing function words, bound morphemes Impaired speech planning and production Posterior aspects of 3 rd frontal convolution Wernicke’s Aphasia  Auditory comprehension, fluent speech, paraphasia, poor repetion and naming Impaired representation of sound structure of words Posterior half of the first temporal gyrus Pure motor speech disorder Disturbance of articulation, apraxia of speech, dysarthria, aphemia Disturbance of articulationOutflow from motor cortex Pure Word Deafness Disturbance of spoken word comprehension, repetition also impaired Failure to access spoken words Input tracks from auditory cortex to Wernicke’s area Transcortical Motor Aphasia Disturbed spontaneous speech similar to BA; relatively preserved repetition, comprehension Disconnection between conceptual word/sentence representations and motor speech production Deep white matter tracks connecting BA to parietal lobe Transcortical Sensory Aphasia Disturbance in single word comprehension with relatively intact repetition Disturbed activation of word meanings despite normal recognition of auditorily presented words White matter tracks connecting parietal and temporal lobe Conduction Aphasia Disturbance of repetition and spontaneous speech, phonemic paraphasia Disconnetion between sound patterns and speech production mechanisms Arcuate fasciculus; connection between BA and WA Lichtheim’s (1885) Aphasic Syndromes

7. Additional Aphasia Syndromes SyndromeSymptomDeficitLesion Anomic Aphasia  single-word production, marked for common nouns; repetition and comprehension intact Impaired storage or access to lexical entries Inferior parietal lobe or connections within perisylvian language areas Global Aphasia  Performance in all language functions Disruption of all/most language components Multiple perisylvian language components Isolation of the language zone  Spontaneous speech, comprehension, some preservation of repetition; echolalia common Disconnection between concepts and both representations of word sounds and speech production Cortex outside perisylvian association cortex

8. Broca’s Aphasia Telegraphic, effortful speech Agrammatism Some degree of comprehension deficit Writing and reading deficits Repetition abnormal – drops function words Buccofacial apraxia, right hemiparesis

9. Wernicke’s Aphasia Fluent, nonsensical speech Impaired comprehension Grammar better preserved than in BA Reading impairment often present May be aware or unaware of deficit Finger agnosia, acalculia, alexia without agraphia

10. Conduction Aphasia Fluent language Naming and repetition impaired May be able to correct speech off-line Hesitations and word-finding pauses May have good reading skills

11. Global Aphasia Deficits in repetition, naming, fluency and comprehension Gradations of severity exist May communicate prosodically Involve (typically) large lesions Outcome poorest; anomic

12. Transcortical Aphasias Transcortical Motor Good repetition Impairment in producing spontaneous speech Good comprehension Poor naming Transcortical Sensory Good repetition Fluent speech Impaired comprehension Poor naming Semantic associations poor

15. Associated Deficits Alexia without Agraphia –Impairment in reading with spared writing Apraxia –Loss of skilled movement not due to weakness or paralysis

18. Fundamental Lessons Language processors are localized Different language symptoms can be due to an underlying deficit in a single language processor Language processors are regionally associated with different parts of the brain in proximity to sensory or motor functions

19. What Language Disorders Reveal about Underlying Processes Pure Word Deafness: selective processing of speech sounds implies a specific speech- relevant phonological processor Transcortical Sensory Aphasia: repetition is spared relative to comprehension; selective loss of word meaning; some cases suggest disproportionate loss of one or more categories

20. What Language Disorders Reveal about Underlying Processes Aphasic errors in word production: reveal complex nature of lexical access –Phonological vs. semantic errors: independent vs. interactive relationship? –Grammatical class: nouns vs. verbs (category specificity) Broca’s aphasia: syntax comprehension and production –Central syntactic deficit; loss of grammatic knowledge –Problems in “closed-class” vocabulary (preposition, tense markers) –Limited capacity account –Mapping account (inability to map from parsing to thematic roles)

21. Aphasia and the Semantic System Meaning stored separately from form Models of representation in semantics –Feature-based models (see categorization) –Nondecompositional meaning Modality-specific semantic deficits: optic aphasia as an example

22. Two Models of Semantic Organization One Semantic SystemMultiple Semantic Systems