Intro to musical processing Day 10

1. Intro to musical processing Day 10 Music Cognition MUSC 495.02, NSCI 466, NSCI 710.03 Harry Howard Barbara Jazwinski Tulane University

2. Course administration • Spend provost's money Music Cognition - Jazwinski & Howard - Tulane University

3. Goals for today • Introduce a cognitive model of musical processing in general terms • Refer to a neurological model of musical processing • Incorporate one of Sacks’ musical disorders (cochlear amusia) • Do a better job of explaining how the cochlea works Music Cognition - Jazwinski & Howard - Tulane University

4. Musical processing

5. Reasons for recent advances in the understanding of musical disorders • Background. 30 years ago … • the functional organization of the brain could only be studied by implanting electrodes in the common 'animal models': rats, cats, and monkeys, which are not known for their musical (or linguistic) abilities • detailed anatomical information about lesion patients was only available in the rare cases where there was accompanying pathological data. • The understanding of the normal functional organization of the brain has increased enormously from new, non-invasive imaging techniques: • haemodynamic (PET and functional MRI) and • electrophysiological (EEG and MEG) • The understanding of the normal structural organization of the brain has increased enormously from the same techniques. • Lesions can now be defined precisely using structural MRI, allowing us to visualize which parts of the normal cortical network have been damaged. • Tools for evaluating different aspects of musical disorders have been refined, so that reports of musical disorders have progressed from historical anecdotes to systematic accounts. • These instruments are the musical equivalents of the better-known aphasia batteries. Music Cognition - Jazwinski & Howard - Tulane University

6. Models for new results • What would a cognitive model of musical processing look like? • What would a neural model of musical processing look like? Music Cognition - Jazwinski & Howard - Tulane University

7. Ingredients of music cognition mostly receptive, mostly from Levitin Music Cognition - Jazwinski & Howard - Tulane University

8. Cognitive model of musical processing Music Cognition - Jazwinski & Howard - Tulane University

9. Brain substrates for musical listening disorders across (lesion) studies Music Cognition - Jazwinski & Howard - Tulane University

10. Early music processing Music, like any sound, is processed in the ascending auditory pathway to the auditory cortex.

11. The ascending auditory pathway, again That processing includes active analysis of the spectro-temporal structure of the stimulus rather than the simple passive relay of information. Music Cognition - Jazwinski & Howard - Tulane University

12. Auditory transduction: the cochlea • The cochlea is filled with a watery liquid, which moves in response to vibrations coming from the middle ear via the oval window. • As the fluid moves, thousands of "hair cells" are set in motion, and convert that motion to electrical signals that are communicated via neurotransmitters to many thousands of nerve cells. • These primary auditory neurons transform the signals into electrical impulses known as action potentials, which travel along the auditory nerve to structures in the brainstem for further processing. Music Cognition - Jazwinski & Howard - Tulane University

13. Cross section of the cochlea • The basilar membrane within the cochlea is a stiff structural element that separates two liquid-filled tubes that run along the coil of the cochlea. • The tubes transduce the movement of air that causes the tympanic membrane and the ossicles to vibrate into movement of liquid and the basilar membrane. • This movement is conveyed to the organ of Corti, composed of hair cells attached to the basilar membrane and their stereocilia embedded in the tectorial membrane. • The movement of the basilar membrane compared to the tectorial membrane causes the sterocilia to bend. • They then depolarise and send impulses to the brain via the cochlear nerve. Music Cognition - Jazwinski & Howard - Tulane University

14. Frequency dispersion • The basilar membrane is a pseudo-resonant structure that, like the strings on an instrument, varies in width and stiffness, which causes sound input of a certain frequency to vibrate some locations of the membrane more than others and thus ‘maps’ the frequency domain that humans can hear. • High frequencies lead to maximum vibrations at the basal end of the cochlear coil (narrow, stiff membrane) • Low frequencies lead to maximum vibrations at the apical end of the cochlear coil (wide, more compliant membrane). Music Cognition - Jazwinski & Howard - Tulane University

15. The cochlea & basilar membrane Music Cognition - Jazwinski & Howard - Tulane University

16. Primary auditory cortex (PAC or A1) tonotopic map Music Cognition - Jazwinski & Howard - Tulane University

17. Observation • Both the cochlea and the PAC are organized as a tonotopic map. • The layout of the ascending auditory pathway suggests that it is one-way (ascending). • What would happen if it were a two-way street? Music Cognition - Jazwinski & Howard - Tulane University

18. What is amusia? • Amusia refers to a number of disorders which are indicated by the inability to recognize musical tones or rhythms or to reproduce them. • It can be congenital (present at birth) or be acquired later in life (as from brain damage). • The term "amusia" is composed of "a-" + "-musia" which means the lack of music. Music Cognition - Jazwinski & Howard - Tulane University

19. Pitch imperfect: cochlear amusia • Who is the protagonist? • Jacob L., a distinguished composer in his late 60s • What were his symptoms? • “I hadn’t been playing or composing much for a month, and then I suddenly noticed the upper register of the piano I was playing [at a friend’s house] was grossly out of tune.” • These notes were sharpened by a quarter of a tone or so for the first octave and a semitone or so for the next octave up, more so in left ear than right. • He was already being treated for a hearing loss also in the upper ranges (2000 Hz ~ 3 octaves above middle C) • The E-natural 10 notes above middle C were flattened by almost a quarter tone. Music Cognition - Jazwinski & Howard - Tulane University

20. Accommodations • “Contextual correction” • a single instrument sounded out of tune, but an orchestral context ‘corrected’ it • He would work out a high passage on the keyboard below the distorted range and then notate the music in the correct range • Conclusion • he knew how music should sound; • it was only his perception that was distorted. Music Cognition - Jazwinski & Howard - Tulane University

21. Analysis • How did the disorder progress? • Eventually, Jacob got better. • Why? • There are massive connections (the olivocochlear bundles) from the PAC to the cochlea and outer hair cells. • The outer hair cells tune tshe inner hair cells. • Conclusion? • A two-way street, giving the PAC the ability to tune the cochlea, for instance, to attend to a tiny but significant sound in the environment. Music Cognition - Jazwinski & Howard - Tulane University

22. Pitch Pitch is thought to be a fundamental component of music in every known human culture.

23. Primary auditory cortex (PAC or A1) tonotopic map Music Cognition - Jazwinski & Howard - Tulane University

24. Regions and connections of primate and human prefrontal and auditory cortex Music Cognition - Jazwinski & Howard - Tulane University

25. Schematic diagram of the primate auditory cortex • The core is made up of the primary auditory cortex (AI), the rostral field (R), and the rostrotemporal (RT) area. • These three fields have a tonotopic organization as shown by the lower-case letters h (high frequency) and l (low frequency). Music Cognition - Jazwinski & Howard - Tulane University

26. Pitch • It is a percept, rather than a physical attribute of the sound stimulus. • The exact relationship between the stimulus attributes and the percept is still debated. • Studies reveal activity in secondary cortex in lateral Heschl’s gyrus rather than primary cortex > possible ‘pitch centre’ where there is encoding of the percept as opposed to the stimulus properties. Music Cognition - Jazwinski & Howard - Tulane University

27. Pitch in music • It is used to construct: • melodies (patterns of pitch over time), • chords (the simultaneous presentation of more than one pitch) and • harmonies (the simultaneous presentation of more than one melody). Music Cognition - Jazwinski & Howard - Tulane University

28. Pitch experiments • In passive listening experiments, bilateral brain activation occurs in the anterior and posterior superior-temporal lobes with a degree of right lateralization (see Fig. 2), without any difference between random-pitch sequences and tonal melodies. • In experiments where subjects were required to follow a melody and compare the pitch at different points, additional activation was demonstrated in the right frontal operculum. Music Cognition - Jazwinski & Howard - Tulane University

29. Pitch processing in superior-temporal cortex (Fig. 2) Music Cognition - Jazwinski & Howard - Tulane University

30. Next Monday Expand the model Add more of Sacks’ disorders §1-2 of Levitin