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Language and the Brain (I) Chapter 12 (pp. 360-371) Dr. Morten H. Christiansen 1 Previous Class: Genes and Language Cognitive deficit manifesting itself as a • SLI: developmental language disorder • FOXP2 = language gene? • Common allelic variation in FOXP2 is associated with • individual differences in language and sequential learning Same genetic basis for individual differences in both sequential learning and language all children bring the same genetic biases to bear • Do on language acquisition? • Common allelic variation in ASPM may lead to differences in phonological biases relevant for learning tone languages Language and the Brain: Aphasia (I) • Aphasia: A disturbance or loss of language function as a result of brain damage. • Stroke, traumatic head injury, or infection. • Anomia: Access to word forms impaired while access to semantic concepts is intact. • Damage to angular gyrus. 3 Language and the Brain: Aphasia (II) Aphasia: Labored, ungrammatical speech with • Broca’s severe word access problems. to posterior portion of lower frontal lobe: • Damage Broca’s area. Aphasia: Fluent, grammatical but often • Wernicke’s meaningless speech with severe comprehension problems. to posterior half of temporal area: Wernicke’s • Damage area. 4 Language and the Brain: Aphasia (III) • Conduction Aphasia: Inability to repeat speech. • Damage to arcuate fasciculus. • Global Aphasia: All language skills absent but thought processes are intact. • Damage to all language areas. 5 Language Areas in the Brain Arcuate Fasciculus Angular Gyrus 6 The Classical Lichtheim-Geschwind Model of Language Localization in the Brain • Wernicke’s Area: Representation of sound. • Broca’s Area: Planning and organization of speech. • Parietal Lobe (Angular Gyrus): Representation of concepts. • Problem: Patterns of symptoms may be a product of brain damage and patient’s attempts to compensate. 7 Neuroimaging Techniques I • Neuroimaging techniques are noninvasive. • The brain can be studied without surgery. • Structural Techniques • Computerized Tomography (CT) • Computer-enhancement of multiple X-ray scans ! 3D image of the brain. • Magnetic Resonance Imaging (MRI): • Exposes the brain to powerful magnetic fields, and records voltage reactions (“resonance”) when the fields are turned off. 8 Neuroimaging Techniques II • Functional Techniques: Time-Course of Processing • Event-Related Potentials (ERPs): Using EEG technology to record brain waves temporarily linked to the processing of stimuli. • N400 (400 msec late negative shift) ! semantic incongruity. Neuroimaging Techniques III • Functional Techniques: Localization of Processing • Positron Emission Tomography (PET): • • Subjects injected with a glucose solution + radioactive isotope. • Scanner detects amount of radioactivity (" glucose consumption) in different brain areas while subjects are processing stimuli. Glucose = brain fuel ! high brain activation " high glucose consumption. 10 Neuroimaging Techniques IV • Functional Techniques: Localization of Processing (cont.) • Functional Magnetic Resonance Imaging (fMRI): • Records MRI scans while subjects process stimuli (fine resolution). • Changes in blood flow within the brain can be detected " changes in brain activation. • BOLD (Blood-Oxygen-Level-Dependent) fMRI measures differences in oxygenated blood. 11 Next Class The Organization of Language Processes in the Brain Chapter 12 (pp. 371-386) • Is there localization of lexical processing? • Is there localization of syntactic processing? • Is there localization of integrative processing?