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