Cognitive Neuroscience of Language

1. Cognitive Neuroscience of Language

2. Cognitive Neuroscience of Language • Premise 1: Constituent Cognitive Processes • Phonological analysis • Syntactic analysis • Semantic analysis • Premise 2: Areas of the brain involved in language are not exclusively involved with that function • Premise 3: Brain areas involved with language are small and widely distributed & parts of other functional systems

3. Methodolodogy of Cognitive Neuroscience Approach • Wernicke-Geschwind model – analysis of brain-damaged patients • Cog Neuro approach employs a wide array of other techniques • fMRI, PET, • TMS • Functional brain imaging studies have revolutionized study of language • Caveat: Correlation ≠ Causation

4. Functional Brain Imaging and Localization of Language • Bevalier’s fMRI study of reading – sought to establish cortical involvement in reading • Reading sentences versus control periods (strings of consonants) • Areas of activity were tiny and spread out • Active areas varied between subjects and trials • Activity was widespread

5. FIGURE 16.16 The areas in which reading-associated increases in activity were observed in the fMRI study of Bavelier and colleagues (1997). These maps were derived by averaging the scores of all participants, each of whom displayed patchy increases of activity in 5–10% of the indicated areas on any particular trial.

6. Damasio’s PET Study of Naming • Damasio and colleagues (1996) PET study of naming • Images of famous faces, animals, and tools • Activity while judging image orientation subtracted from activity while naming • Left temporal lobe areas activated by naming varied with category • Activity seen well beyond Wernicke’s area

7. PET Study of Naming

9. Cognitive Neuroscience of Dyslexia • Dyslexia – reading difficulties not due to some other deficit (e.g., vision, intelligence) • Developmental dyslexia – apparent when learning to read • Heritability estimate = 50% • More common in boys than girls • Acquired dyslexia • Due to brain damage • Relatively rare

10. Developmental Dyslexia: Causes and Neural Mechanisms • Brain differences identified, but none seems to play a role in the disorder • Multiple types of developmental dyslexia – possibly multiple causes • Various subtle visual, auditory, and motor deficits are commonly seen • Weight of evidence: deficit of phonological processing rather than sensorimotor processing

11. Developmental Dyslexia and Culture • Genetic component – yet the disorder is also influenced by culture • Twice as many English speakers as Italian speakers diagnosed with dyslexia • Sound-symbol correspondence in English is more complex and difficult to learn

12. Cognitive Neuroscience of Deep and Surface Dyslexia • Two procedures for reading aloud • Lexical – using stored information about words • Phonetic – sounding out • Surface dyslexia – lexical procedure lost, can’t recognize words • Deep dyslexia – phonetic procedure lost, can’t sound out unfamiliar words

13. Cognitive Neuroscience of Deep and Surface Dyslexia Continued • Surface dyslexia – loss of visual recognition of words (cannot “look and say”) • Deep (or “phonological”) dyslexia – loss of ability to “sound out” unfamiliar words or “nonwords” • Different error patterns for surface and deep • Surface – e.g. trouble with the pronunciation exceptions “have” or “lose” • Deep: - e.g. “quill” for “quail” or “hen” for “chicken”

14. Cognitive Neuroscience of Deep and Surface Dyslexia Continued • Deep dyslexia – extensive damage to left-hemisphere language areas • How is it that lexical procedure is spared? • May be housed in left language areas that are spared • May be mediated by the right hemisphere • Evidence for both exists