Audition Day 8

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AuditionDay 8

• Music Cognition
• MUSC 495.02, NSCI 466, NSCI 710.03
• Harry Howard
• Barbara Jazwinski
• Tulane University

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Course administration

• Spend provost's money

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Macrostructure of the brain

• The parts of the brain that you can see with the
  naked eye

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Questions

• What are the axes of the brain?
• What are the lobes of the brain and what do they
  do?
• What are the main connections between parts of
  the brain?
• What are the three ways of referring to areas of
  the brain?

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Macrostructure overview

• Three axes of the brain
• Vertical
• Horizontal
• Longitudinal
• Lateral
• Connections
• Naming conventions
• Gyrii sulcii
• Brodmanns areas
• Stereotaxic (Talairach) coordinates

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Vertical axis ventral/dorsal

• Orientation of picture
• Which way is forward?
• to the left cerebellum at back
• Which hemisphere do we see?
• medial side of right left is cut away gt sagittal
  view
• Vertical axis
• Dorsal is up, like dorsal fin (dorsal comes from
  Latin word for back)
• Ventral is down (ventral comes from Latin word
  for belly)
• Cortical vs. subcortical division
• Cerebrum vs. cerebellum
• Cerebral cortex (neocortex) vs. cerebellar cortex

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Longitudinal axis anterior/posterior

• Lobes
• Sylvian fissure
• Perisylvian area

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Longitudinal axis, functions
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Lateral axis left/right
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Lateral axis

• General
• Which way is anterior?
• Motor and sensory organs are crossed
• Ipsilateral, contralateral
• LH
• Language
• Math
• Logic
• RH
• Spatial abilities
• Face recognition
• Visual imagery
• Music

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Connections

• Corpus callosum

• Arcuate fasciculus

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Naming conventions

• How to refer to specific areas of the brain

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Gyrii

• AnG - angular gyrus
• FP - frontal pole
• IFG - inferior frontal gyrus
• IOG - inferior occipital gyrus
• ITG - inferior temporal gyrus
• LOG - lateral occipital gyrus
• MFG - middle frontal gyrus
• MTG - middle temporal gyrus
• OG - orbital gyrus
• oper - pars opercularis (IFG)
• orb - pars orbitalis (IFG)
• tri - pars triangularis (IFG)
• poCG - postcentral gyrus
• preCG - precentral gyrus
• SFG - superior frontal gyrus
• SOG - superior occipital gyrus
• SPL - superior parietal lobe
• STG - superior temporal gyrus
• SmG - supramarginal gyrus

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Sulcii

• cs - central sulcus (Rolandic)
• hr - horizontal ramus
• ifs - inferior frontal sulcus
• ios - inferior occipital sulcus
• ips - intraparietal sulcus
• syl - lateral fissure (Sylvian)
• los - lateral occipital sulcus
• ls - lunate sulcus
• pof - parieto-occipital fissure
• pocs - postcentral sulcus
• precs - precentral sulcus
• sfs - superior frontal sulcus
• tos - transoccipital sulcus
• vr - vertical ramus

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Brodmanns areas
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Brodmanns areas, functions
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Frequency
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Sound creation

• Sound creation is created in most instruments,
  including the voice, by turbulent oscillation
  between phases in which air is compressed and
  phases in which it is rarefied.
• The following figure depicts such a transition,
  in which increasing darkness symbolizes
  increasing compression of the airflow.
• The heavy line represents the pressure of airflow
  as a single quantity between a minimum and a
  maximum.
• as air is compressed, its pressure rises
• as air is rarefied, its pressure falls.
• A single cycle of compression and rarefication is
  defined by the distance between two peaks, marked
  by dotted white lines.

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Graph of turbulent oscillation (of vocal air)
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Frequency

• This cycling of airflow has a certain frequency
• the frequency of a phenomenon refers to the
  number of units that occur during some fixed
  extent of measurement.
• The basic unit of frequency, the hertz (Hz), is
  defined as one cycle per second.

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Two sine functions with different frequencies

• A simple illustration can be found in the next
  diagram. It consists of the graphs of two sine
  functions.
• The one marked with os, like beads on a
  necklace, completes an entire cycle in 0.628 s,
  which gives it a frequency of 1.59 Hz.
• The other wave, marked with xs so that it looks
  like barbed wire, completes two cycles in this
  period. Thus, its frequency is twice as much,
  3.18 Hz.

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Graph of two sine functions with different
frequencies
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Fundamental frequency

• The pitch of an instrument corresponds to the
  lowest frequency of oscillation, called
  fundamental frequency or F0.
• Fundamental frequency gender
• the fundamental frequency of a mans voice
  averages 125 Hz,
• the fundamental frequency of a womans voice
  averages 200 Hz
• This 60 increase in the pitch of a womans voice
  can be accounted for entirely by the fact that a
  mans vocal folds are on average 60 longer than
  a womans.

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The fundamental higher frequencies

• This brief introduction to frequency leads one to
  believe that an instrument vibrates at a single
  frequency, that of its fundamental frequency,
  much as the schematic string on the left side of
  the next diagram is shown vibrating at its
  fundamental frequency.

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Higher frequencies

• However, this is but a idealization for the sake
  of simplification of a rather complex subject.
• In reality, instruments vibrate at a variety of
  frequencies that are multiples of the
  fundamental.
• The diagram depicts how this is possible a
  string can vibrate at a frequency higher than its
  fundamental because smaller lengths of the string
  complete a cycle in a shorter period of time.
• In the particular case of the central diagram,
  each half of the string completes a cycle in half
  the time.

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Superposition of frequencies

• This figure displays the outcome of superimposing
  both frequencies on the string and the waveform.
• The result is that a pulse of vibration created
  by the vocal folds projects an abundance of
  different frequencies in whole-number multiples
  of the fundamental.
• If we could hear just this pulse, it would sound,
  as Loritz (199993) says, more like a quick,
  dull thud than a ringing bell.

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Audition
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Overview of the auditory pathway
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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.

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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.

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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).

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The cochlea basilar membrane
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More recent auditory pathway- note complexity
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Schematic auditory pathway
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Auditory regions of the brain
A lateral view of the cerebral cortex that
highlights the prominent neural regions for
auditory perception. The temporal lobe is shaded
and the numbers refer to the Brodmann areas of
primary auditory cortex (area 41) and secondary
auditory cortex (areas 22 and 42). The right
hemisphere contains homologous regions.
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Auditory cortex
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Primary auditory cortex (A1)
tonotopic map
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Absolute vs. relative pitch

• Thus A1 represents absolute pitch
• We do not know how relative pitch is represented

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Timbre

• Different parts of a musical instrument vibrate
• with different onsets (attack)
• See Levitins discussion of Schaeffers
  perceptual experiments on onset (attack), pp.
  53-4.
• at different frequencies (steady state)
• for different durations (flux or decay)

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The timbre of the human voice
Supralaryngeal
Laryngeal
Respiratory
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Back to our regularly scheduled program
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Ingredients of music cognition mostly receptive,
mostly from Levitin
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Next Monday

• Go over other musical perceptual attributes
• 1-2 of Levitin