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 COMPREHENSION Auditory Single words Phrases Commands (Token Test) Syntax Visual (Reading - alexia) 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)

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 (1824-1880)

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 Broca’s Fluent speech Non-fluent speech Poor comprehension Poor repetition Poor naming Posterior superior temporal lobe lesion (first temporal gyrus) Global Non-fluent speech 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 Conduction Fluent speech Lesion in arcuate fasciculus or its connections in inferior parietal lobule

Aphasias Anomia Fluent speech Good comprehension Good repetition Poor naming Temporal or temporo-parietal lesion Mixed Transcortical Non-fluent speech Poor comprehension 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 Lesion in posterior temporo-parietooccipital junction while sparing Wernicke’s area

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 cheese path

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

Errors can revealed type of dysfunction

Deep Dyslexia