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Language

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Language

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  1. Language

  2. Using Language • What is language for?

  3. Using Language • What is language for? • Rapid, efficient communication • To accomplish this goal, what needs to happen in the brain?

  4. Understanding Linguistic Input • To accomplish this goal, what needs to happen in the brain? • Encode input (speech, writing, other?) • Make neural representation(s) • transform the input (e.g. written word to internal sound) • This probably involves many intermediate steps • Associate input with meaning – access the lexicon • Lexicon – a mental representation of the meaning of words • Mental dictionary is a poor but useful analogy

  5. Written Input • Some terms: • Orthography – visual form of a word • Non-trivial problem! Like all objects, words can have many different instances of the same item • bird bird bird bird bird bird

  6. Written Input • Visual Word Form Area (WFA) is specialized for representing written words • Words are not just pictures • Specialization may be related to the need to “overcome” mirror-invariance • E.g. b, p, d are all different letters but Are all the same object !! Dehaene (2009)

  7. Spoken Input • Phonology – how the word sounds; acoustic • Words are comprised of acoustic speech units called phonemes

  8. Spoken Input • Phonology – how the word sounds; acoustic • Phonemes are not invariant – different acoustic inputs are “mapped” onto the same phoneme

  9. Spoken Input • The Segmentation Problem: • The stream of acoustic input is not physically segmented into discrete phonemes, words, phrases, etc. • Silent gaps don’t always indicate (aren’t perceived as) interruptions in speech

  10. Spoken Input • The Segmentation Problem: • The stream of acoustic input is not physically segmented into discrete phonemes, words, phrases, etc. • Continuous speech stream is sometimes perceived as having gaps

  11. Spoken Input • The Segmentation Problem: • How do we solve the segmentation problem? Overlay additional information: • Prosody • Inflection, syllabic stress, pauses

  12. Spoken Input • The Segmentation Problem: • How do we solve the segmentation problem? Overlay additional information: • Vision • Read lips! • Demonstrated by the McGurk effect

  13. Functional Anatomy of Spoken Input • Note that the low-level auditory pathway is not specialized for speech sounds • Both speech and non-speech sounds activate primary auditory cortex (bilateral Heschl’sGyrus) on the top of the superior temporal gyrus

  14. Functional Anatomy of Spoken Input • Which parts of the auditory pathway are specialized for speech? • Binder et al. (2000) • fMRI • Presented several kinds of stimuli: • white noise • pure tones • non-words • reversed words • real words These have non-word-like acoustical properties These have word-like acoustical properties but no lexical associations word-like acoustical properties and lexical associations

  15. Functional Anatomy of Spoken Input • Relative to “baseline” scanner noise • Widespread auditory cortex activation (bilaterally) for all stimuli • Why isn’t this surprising?

  16. Functional Anatomy of Spoken Input • Statistical contrasts reveal specialization for speech-like sounds • superior temporal gyrus • Somewhat more prominent on left side

  17. Functional Anatomy of Spoken Input • Further highly sensitive contrasts to identify specialization for words relative to other speech-like sounds revealed only a few small clusters of voxels • Brodmann areas • Area 39 • 20, 21 and 37 • 46 and 10