2. AUDITORY CORTEX 1 SEPT 11, 2015 – DAY 8 Brain & Language LING 4110-4890-5110-7960 NSCI 4110-4891-6110 Fall 2015

3. Course organization http://www.tulane.edu/~howard/BrLg/ Fun with https://www.facebook.com/BrLg15/https://www.facebook.com/BrLg15/ I am still working on grading. Do the "test test". > Use Blackboard for P2? 9/11/15Brain & Language - Harry Howard - Tulane University 2

4. AUDITORY TRANSDUCTION review 9/11/15Brain & Language - Harry Howard - Tulane University 3

5. Hair cells along the basilar membrane 9/11/15Brain & Language - Harry Howard - Tulane University 4

6. Outer hair cells They can contract, and therefore act as motor units that amplify the movement of the basilar membrane in response to a stimulus. Think of a swing: if a person sitting on a swing (basilar membrane) pumps his legs (OHC), the amplitude of the swing motion is increased in response to a push (sound stimulus) 9/11/15Brain & Language - Harry Howard - Tulane University 5

7. Philosophy of perception Direct or naïve realism: we perceive reality directly. Indirect or representative realism: we can only perceive a representation of reality (mediated through the limitations of the senses). Constructivism: we construct a representation of reality through sensory data and experience. 9/11/15Brain & Language - Harry Howard - Tulane University 6

8. AUDITORY CORTEX 1 9/11/15Brain & Language - Harry Howard - Tulane University 7

9. The central auditory pathway Note that the subcortical pathway is rather complex. 9/11/15Brain & Language - Harry Howard - Tulane University 8

10. Another version 9/11/15Brain & Language - Harry Howard - Tulane University 9

11. A1, A2, A3 A1 = core A2 = belt A3 = parabelt 9/11/15Brain & Language - Harry Howard - Tulane University 10

12. A1 Tonotopic mapping of organ of Corti (in the cochlea) to area A1 9/11/15Brain & Language - Harry Howard - Tulane University 11

13. Temporal lobe 9/11/15Brain & Language - Harry Howard - Tulane University 12

14. 9/11/15Brain & Language - Harry Howard - Tulane University 13 Hickok & Poeppel (2004)’s model superimposed on the brain

15. Old vs. new 9/11/15Brain & Language - Harry Howard - Tulane University 14

16. The speech mode hypothesis (SMH) Speed of speech vs. non-speech perception The articulators move at the rate of 8-10 phones per second = 3-4 syllables per second = 2-3 words per second. Early researchers tried to build a machine for reading to the blind [the auditory cipher] which converted each letter to a different non- speech sound and found that no one could understand it at greater than 2-3 sounds per second, which is about a quarter of the rate at which speech is understood. What to do about this inconsistency? 9/11/15Brain & Language - Harry Howard - Tulane University 15

17. Speech is different! How so? Speech perception is different from other forms of auditory perception because its targets are linked to a specialized system for their production … … which we might engage when we listen to speech. Motor theory of speech perception Speech mode hypothesis 9/11/15Brain & Language - Harry Howard - Tulane University 16

18. Can you turn your speech mode off? What is this?It is this. 9/11/15Brain & Language - Harry Howard - Tulane University 17

19. Weak vs. strong versions of SMH What does such a distinction mean? The weak speech mode hypothesis When we listen to speech, we engage our knowledge of language. The strong speech mode hypothesis When we listen to speech, we engage perceptual mechanisms specialized for speech. More recent: knowledge of speech production can be engaged for 'hard' tasks; for other, 'easier' tasks, it may not be necessary. 9/11/15Brain & Language - Harry Howard - Tulane University 18

20. The result 9/11/15Brain & Language - Harry Howard - Tulane University 19

21. Dichotic listening Tendencies of right-ear advantage by speech sound No advantage Weak right-ear advantage Strong right-ear advantage vowels liquids (l,r), glides (j,w), fricatives stops the acoustic cues for vowels do not depend on context the acoustic cues for consonants depend on context [see p. 116] > special machinery? 9/11/15Brain & Language - Harry Howard - Tulane University 20

22. Intermission: Voice onset time (VOT) 9/11/15Brain & Language - Harry Howard - Tulane University 21 [b] [p] [p ʰ ]

23. Categorical perception 9/11/15Brain & Language - Harry Howard - Tulane University 22 Chinchillas do this too! The Clinton-Kennedy continuum

24. Category boundary shifts Thus the phonetic feature detectors must compensate for the context –– because they know how speech is produced? 9/11/15Brain & Language - Harry Howard - Tulane University 23 But Japanese quail do this too. The shift in VOT is from ‘bin’ to ‘pin’:

25. NEXT TIME P2 on Blackboard Reading "Schnupp13-AuditoryCoding.pdf" on Blackboard - go back & talk about auditory brainstem 9/11/15Brain & Language - Harry Howard - Tulane University 24