10 Language

1. 10 Language Psychology 355

2. Introduction Language • System by which sounds, symbols, and gestures used for communication • Process • Language comes into brain through visual and auditory systems • Motor system: Produces speech, writing • Processing between sensory and motor systems Psychology 355

3. Specialized Language Areas Aphasia • Partial/complete loss of language abilities following brain damage • Latin Lingua: Thought the tongue controlled language • 1770: Johann Gesner: aphasia is a form of brain damage disconnecting ideas from words • 1825: Jean-Baptist Bouillard: speech is controlled by frontal lobes • 1861: Paul Brocca: Cortical area in left frontal lobe Psychology 355

4. Specialized Language Areas • Wada procedure: Anesthetize single hemisphere (sodium amytal in left carotid artery) • Left Hemisphere dominance • Broca’s areaPaul Broca in 1864: Region of dominant left frontal lobe: Articulate speech, speech production • Wernicke’s area Karl Wernicke in 1874: Superior surface of temporal lobe between auditory cortex and angular gyrus: Lesions disrupt normal speech but more so comprehension Psychology 355

5. Specialized Language Areas Broca’s Aphasia (motor, nonfluent aphasia) • Difficulty speaking, but understand spoken/heard language • Paraphasic errors • Pause to search for words, repeat “overlearned” things, difficulty repeating words Psychology 355

6. Specialized Language Areas Wernicke’s aphasia • Speech fluent, comprehension poor • Strange mixture of clarity and gibberish • undisturbed by sound of own or other’s speech • Correct sounds, incorrect sequence • Incorrect word similar to correct word • Comprehension difficult to assess • Playing music, writing similar Psychology 355

7. Specialized Language Areas • Broca’s area • Wernicke’s area • Arcuate Fasciculus • Angular gyrus Wernicke-Geschwind Model Psychology 355

8. Specialized Language Areas • Broca’s area • Wernicke’s area • Arcuate Fasciculus • Angular gyrus Psychology 355

9. Specialized Language Areas Conduction Aphasia • Lesion of fibers composing arcuate fasciculus • Comparison with Broca’s aphasia, Wernicke’s aphasia: Comprehension good, speech fluent • Difficulty repeating words • Symptoms: Repetition substitutes/omits words, paraphasic errors, cannot repeat function, nonsense words, polysyllabic words Psychology 355

10. Specialized Language Areas Aphasia in Bilinguals and the Deaf • Aphasia in bilinguals- Language affected depends on: Order, fluency, use of language • Sign language aphasias analagous to speech aphasias  but can be produced by lesions in slightly different locations • Verbal and sign language recovered together in one case indicating overlapping regions used for both • Evidence suggests some universality to language processing in the brain Psychology 355

11. Asymmetrical Language Processing Split-Brain Studies • Roger Sperry (1950s) • Split-brain procedure • Sever axons making up the corpus callosum • No major deficits • With proper experiments, animals behaved as if they had 2 brains ? Psychology 355

12. Asymmetrical Language Processing Split-Brain Humans Psychology 355

13. Asymmetrical Language Processing Left Hemisphere Language Dominance • Right visual field, repeated easily • Left visual field, difficulty verbalizing • Image only in left visual field, object in left hand, unable to describe • Split-brain: Unable to describe anything to left of visual fixation point Psychology 355

14. Asymmetrical Language Processing Language Functions of the Right Hemisphere • Functions of right hemisphere: Read and understand numbers, letters, and short words (nonverbal response) • Baynes, Gazzaniga, and colleagues: Case of patient with right hemisphere able to write, but not speak • Right hemisphere: Drawing, 3-D puzzles, sound nuances • Prosidy Psychology 355

15. Asymmetrical Language Processing Anatomical Asymmetry and Language • Left lateral (Sylvian) fissure longer and less steep than right • Geschwind and Levitsky: Left planum temporal larger than right in 65% cases • Functional human asymmetry: More than 90% humans right-handed • Animals: Equal numbers of right-handers and left-handers, or no dominance Psychology 355

16. Language: Brain Stimulation and Brain Imaging • Old methods: Correlate language deficits with postmortem analysis of brain damage • Recent techniques • Electrical brain stimulation • Functional Imaging Psychology 355

17. Brain Stimulation • Motor cortex: Immediate speech arrest • Broca’s area: Speech stopped after strong stimulation, • speech hesitation from weak stimulation • Posterior parietal lobe near Sylvian fissure and temporal lobe: Word confusion and speech arrest • Small parts of cortex: naming, reading, repeating facial movements Psychology 355

18. Brain Stimulation N, naming difficulty with intact speech (anomia); A, arrested speech; G, grammatical errors; J, jargon (fluent speech with frequent errors); R, failure to read; M, facial movement errors. Psychology 355

19. Brain Imaging fMRI:Record during language tasks • Activated brain areas consistent with temporal and parietal language areas • More activity than expected in nondominant hemisphere Generate words fromacategory Silently repeat a heard sentence Listen to a story Psychology 355

20. Brain Imaging PET: Compare Sensory responses to words vs. Speech production Psychology 355

21. Language Acquisition • Mechanism in infants • Syllable emphasis • Motherese • Adults talk to infants; Speech slower, exaggerated, vowel sounds clearly articulated • Complexity: Foreign language • Dehaene-Lambertz: 3 month infant, brain response to spoken words similar to adults Psychology 355

22. Concluding Remarks • Language processing • Person repeats word read • Initial activity in visual cortex, then activity in motor cortex corresponding to muscles that move vocal apparatus • Multiple brain areas critical for language • Language skills: Naming, articulation, grammar usage, comprehension • Further brain imaging studies will reveal more about language systems organization Psychology 355

23. End of Presentation Psychology 355