Transcript Slide 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 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 Broca’s Aphasia • Bouillaud (1825): large series of speech loss with frontal lesions • Marc Dax (1836): LH damage, right hemiplegia, & aphasia linked Paul Broca (1824-1880) • Paul Broca (1861) convincing evidence of speech laterality; Tan “Nous parlons avez l’hemispheregauche” Broca’s aphasia 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 Wernicke’s aphasia 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 Carl Wernicke (1874) reports that temporal lobe lesion disturbs comprehension. Developed connectionism model of language and predicated conduction aphasia Wernicke-Geschwind Model (1965) Auditory cortex Visual cortex Angular gyrus Wernicke’s area Wernicke’s area translates verbal information into thought, and vice versa Broca’s area translates verbal information into vocal, and vice versa (i.e., articulation) Pathway between areas: arcuate fasciculus Broca’s area Motor cortex Aphasias • Wernicke’s – Fluent speech – Poor comprehension – Poor repetition – Poor naming • Posterior superior temporal lobe lesion (first temporal gyrus) Conduction – Fluent speech – Good comprehension – Poor repetition – Poor naming • Global – Non-fluent speech – Poor comprehension – Poor repetition – Poor naming Lesion in arcuate fasciculus or its connections in inferior parietal lobule • Lesion involves frontal, temporal and parietal lobes, Including Broca’s and Wernicke’s area • Broca’s – Non-fluent speech – Good comprehension – Poor repetition – Poor naming • Posterior inferior frontal lesion • • Aphasias • Anomia – Fluent speech – Good comprehension – Good repetition – Poor naming • Transcortical Motor – Non-fluent speech – Good comprehension – Good repetition – Poor naming • Temporal or temporo-parietal lesion • Lesion involves frontal lobe but spares Broca’s area • Transcortical Sensory – Fluent speech – Poor comprehension – Good repetition – Poor naming • Lesion in posterior temporoparietooccipital junction while sparing Wernicke’s area • • Mixed Transcortical – Non-fluent speech – Poor comprehension – Good repetition – Poor naming Anterior and posterior association cortex lesions while sparing perisylvian language region Anomia and categorical label storage in temporal lobe Lateralization from Functional Neuroimaging Individual Differences in Language localization • Wilder Penfield, 1930s: Electrical stimulation leading to language disruption, others produce episodic memories Language of Split Brain Patients 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 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 Spreading Activation butter gate bread castle path cheese Spreading Activation Collins & Loftus (1975) rejected the notion of a strict hierarchical structure Errors can revealed type of dysfunction Deep Dyslexia