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Aphasia “Impairment of central language abilities in the speech modality following brain damage.“ In contrast to: peripheral speech problems (dysarthria)

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Presentation on theme: "Aphasia “Impairment of central language abilities in the speech modality following brain damage.“ In contrast to: peripheral speech problems (dysarthria)"— Presentation transcript:

1 Aphasia “Impairment of central language abilities in the speech modality following brain damage.“ In contrast to: peripheral speech problems (dysarthria) non-linguistic cognitive impairments impairments of writing and reading loss of language due to psychotic states, congenital or developmental structural abnormalities problems of language acquisition

2 Language Impairments PRODUCTION Spontaneous Speech Fluent versus nonfluent Unintended or “off” words (paraphasias) Word finding difficulties (anomia) Poor articulation Prosody (aprosodia) Repetition Single words Phrases Writing (agraphia) COMPREHENSION Auditory Single words Phrases Commands (Token Test) Syntax Visual (Reading - alexia) Single words Phrases

3 Broca’s Aphasia Bouillaud (1825): large series of speech loss with frontal lesions Marc Dax (1836): LH damage, right hemiplegia, & aphasia linked Paul Broca (1861) convincing evidence of speech laterality; Tan “Nous parlons avez l’hemispheregauche” Paul Broca ( )

4 Damage to Broca’s area results in: slow labored speech little grammatical fluency omission of function words omission of inflections word finding difficulty comprehension may be impaired Broca’s aphasia

5 Damage to Wernicke’s area results in: Loss of meaningful messages But fluent and grammatical paraphasias or inappropriate words neologisms - invented words language comprehension difficulty, especially with complex sentences Wernicke’s aphasia

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7 Carl Wernicke (1874) reports that temporal lobe lesion disturbs comprehension. Developed connectionism model of language and predicated conduction aphasia

8 Wernicke’s area translates verbal information into thought, and vice versa Broca’s area translates verbal information into vocal, and vice versa (i.e., a rticulation) Pathway between areas: arcuate fasciculus Wernicke-Geschwind Model (1965) Auditory cortex Visual cortex Angular gyrus Wernicke’s area Broca’s area Motor cortex

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10 Aphasias Broca’s –Non-fluent speech –Good comprehension –Poor repetition –Poor naming Posterior inferior frontal lesion Conduction –Fluent speech –Good comprehension –Poor repetition –Poor naming Lesion in arcuate fasciculus or its connections in inferior parietal lobule Wernicke’s –Fluent speech –Poor comprehension –Poor repetition –Poor naming Posterior superior temporal lobe lesion (first temporal gyrus) Global –Non-fluent speech –Poor comprehension –Poor repetition –Poor naming Lesion involves frontal, temporal and parietal lobes, Including Broca’s and Wernicke’s area

11 Aphasias Anomia –Fluent speech –Good comprehension –Good repetition –Poor naming Temporal or temporo-parietal lesion Mixed Transcortical –Non-fluent speech –Poor comprehension –Good repetition –Poor naming Anterior and posterior association cortex lesions while sparing perisylvian language region Transcortical Motor –Non-fluent speech –Good comprehension –Good repetition –Poor naming Lesion involves frontal lobe but spares Broca’s area Transcortical Sensory –Fluent speech –Poor comprehension –Good repetition –Poor naming Lesion in posterior temporo- parietooccipital junction while sparing Wernicke’s area

12 Anomia and categorical label storage in temporal lobe

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14 Lateralization from Functional Neuroimaging

15 Individual Differences in Language localization Wilder Penfield, 1930s: Electrical stimulation leading to language disruption, others produce episodic memories

16 Language of Split Brain Patients

17 Chronic Callosal Disconnection Syndromes –Social ordinariness –Lack of interhemispheric transfer (undetectable by normal means) –Inappropriate politeness –Alexithymia – inability to discuss emotions –Self-focus Joe Bogen performed 1st series of surgeries

18 Mystery of Right Hemisphere Language Focal damage in left hemisphere produces aphasias (Broca, Wernicke, etc), but removal of entire left hemisphere allows right hemisphere verbal functioning –Why? Roger Sperry, Nobel Laureate, 1981

19 Spreading Activation bread butter cheese castle gate path

20 Spreading Activation Collins & Loftus (1975) rejected the notion of a strict hierarchical structure

21 Errors can revealed type of dysfunction

22 Deep Dyslexia

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