Language and the Brain Understanding how language is

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

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

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

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

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

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

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

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

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

Split-brain patients & language key in left hand L R Brain

Split-brain patients & language key in right hand L R Brain

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

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

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

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

Broca’s Aphasia and Syntactic Disorder Broca’s aphasics tend to omit inflectional morphemes (-ing, -ed, -en, -s)—necessary for syntax n Broca’s aphasics can’t determine grammaticality in following sentences: n – – 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 n a. The mouse was chased by the cat. n b. The cat was chased by the mouse n Broca’s aphasiacs tend to interpret (a) correctly, but they tend to give (b) the same interpretation as (a) n Our understanding of (a) and (b) is driven by syntax; a Broca’s aphasiac’s understanding is driven by semantics.

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

(Akmajian et al. 2001: p. 544) Sample speech: Wernicke’s aphasia Examiner: n Aphasic: n Examiner: Do you like it here in Kansas City? Yes, I am. I’d like to have you tell me something about your problem. n 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. . . n

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