Language
description
Transcript of Language
Language
Using Language
• What is language for?
Using Language
• What is language for?– Rapid, efficient communication
• To accomplish this goal, what needs to happen in the brain?
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
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
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
Dehaene (2009)Are all the same object !!
Spoken Input– Phonology – how the word sounds; acoustic
• Words are comprised of acoustic speech units called phonemes
Spoken Input– Phonology – how the word sounds; acoustic
• Phonemes are not invariant – different acoustic inputs are “mapped” onto the same phoneme
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
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
Spoken Input
• The Segmentation Problem:– How do we solve the segmentation problem? Overlay
additional information:• Prosody
– Inflection, syllabic stress, pauses
Spoken Input
• The Segmentation Problem:– How do we solve the segmentation problem? Overlay
additional information:• Vision
– Read lips!– Demonstrated by the McGurk effect
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’s Gyrus) on the top of the superior temporal gyrus
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
Functional Anatomy of Spoken Input
• Relative to “baseline” scanner noise– Widespread auditory cortex
activation (bilaterally) for all stimuli
– Why isn’t this surprising?
Functional Anatomy of Spoken Input
• Statistical contrasts reveal specialization for speech-like sounds– superior temporal gyrus– Somewhat more prominent on left side
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