Language and the Brain Understanding how language is represented and processed in the brain

Psycholinguisics The study of acquisition, storage, comprehension and production of language Neurolinguistics: branch of psycholinguistics dealing with language and the brain

Cerebral cortex Cerebral cortex: A one-quarter-inch thick membrane covering the brain –consciousness, thinking, learning, emotions, language –Constitutes the difference between humans and other animals Corpus callosum: bundle of nerve fibers that connects the brain’s right and left hemispheres

LATERALIZATION RIGHT HEMISPHERE holistic reasoning music processing processing of non- linguistic sounds visual, spatial processing LEFT HEMISPHERE analytic reasoning temporal ordering arithmetic language processing Each hemisphere specializes in diff. cognitive functions (referred to as lateralization)

Lateralization (Cont’d) Most right-handers left-hemisphere dominance for language Left-handers generally less lateralized for language Evidence of Lateralization: Language damage far more likely following left-hemisphere damage (70% vs. 1%) Dichotic listening test Split-brain patients

Dichotic listening test Two different stimuli are presented simultaneously through earphones to the left and right ears The listeners are asked to say what they hear three two Which one do you think is more accurately reported?

Contralateralization The connection between the brain and the body are almost completely contralateral L sensory information R sensory information three two

The right ear advantage (REA) three two L L ear R ear R nonlinguistic sound processing language processing Listeners can identify linguistic stimuli more accurately when presented to their right ear. two

The left ear advantage Ha ha ha Zzzz L L ear R ear R Listeners can identify nonlinguistic stimuli more accurately when presented to their left ear. Riiing! nonlinguistic sound processing language processing

Split brain experiments The hemispheres of the brain are connected by the corpus callosum Corpus callosum severed to prevent severe seizures In these experiments, patients are blindfolded and an object (let’s say a key) is placed in their right or left hand

Split-brain patients & language Brain RL key in left hand

Split-brain patients & language Brain RL key in right hand

Split Brain Experiments KEY IN RIGHT HAND –Patient can name object KEY IN LEFT HAND –Patient unable to name object

Broca’s area FRONT BACK Angular gyrus Language centers Speech production Syntactic info Language comprehension Lexicon Integrates visual & auditory info Crucial for reading Wernicke’s area

Language Disorders A damage to one of these areas will affect the ability to produce/perceive language –Aphasia: –Broca’s Aphasia –Wernicke’s Aphasia

Broca’s area Involved in speech production –motor programming for articulation Involved in morphosyntactic analysis –Inflection –Structural complexity Add grammatical refinements to content words selected in Wernicke’s area.

Sample speech: Broca’s aphasia Examiner:Tell me, what did you do before you retired? Aphasic:Uh, uh, uh, pub, par, partender, no. Examiner:Carpenter? Aphasic:(Nodding to signal yes) Carpenter, tuh, tuh, twenty year. (Akmajian et al. 2001: p. 543)

Broca’s Aphasia and Syntactic Disorder Broca’s aphasics tend to omit inflectional morphemes (-ing, -ed, -en, -s)—necessary for syntax Broca’s aphasics can’t determine grammaticality in following sentences: –The boy ate it up. –* The boy ate up it. –* Boy ate it up. –The boy ate up the cake.

Broca’s Aphasia and Syntactic Disorder a. The mouse was chased by the cat. b. The cat was chased by the mouse Broca’s aphasiacs tend to interpret (a) correctly, but they tend to give (b) the same interpretation as (a) Our understanding of (a) and (b) is driven by syntax; a Broca’s aphasiac’s understanding is driven by semantics.

Wernicke’s area Essential to language comprehension Involved in selection/evaluation of content words (contained in lexicon)

Sample speech: Wernicke’s aphasia Examiner:Do you like it here in Kansas City? Aphasic:Yes, I am. Examiner:I’d like to have you tell me something about your problem. Aphasic:Yes, I, ugh, can’t hill all of my way. I can’t talk all of the things I do, and part of the part I can go alright, but I can’t tell from the other people. I usually most of my things. I know what can I talk and know what they are, but I can’t always come back even though I know they should be in, and I know should something eely I should know what I’m doing... (Akmajian et al. 2001: p. 544)

Wernicke’s aphasia Fluent, but their speech doesn’t make any sense.