Cellular Neuroscience

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Auditory Neuroscience 1 Spatial Hearing
Systems Biology Doctoral Training
Program Physiology course Prof. Jan
Schnupp jan.schnupp_at_dpag.ox.ac.uk HowYourBrainWor
ks.net
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Hearing an impossible task!
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http//auditoryneuroscience.com/foxInSnow
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Interaural Time Difference (ITD) Cues

• ITDs are powerful cues to sound source direction,
  but they are ambiguous (cones of confusion)

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Front-Back Ambiguity and Phase Ambiguity
http//auditoryneuroscience.com/ear/bm_motion_2
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Interaural Level Cues (ILDs)
ILD at 700 Hz
ILD at 11000 Hz

• Unlike ITDs, ILDs are highly frequency dependent.
  At higher sound frequencies ILDs tend to become
  larger, more complex, and hence potentially more
  informative.

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Spectral (Monaural) Cues
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Adapting to Changes in Spectral Cues

• Hofman et al. made human volunteers localize
  sounds in the dark, then introduced plastic molds
  to change the shape of the concha. This disrupted
  spectral cues and led to poor localization,
  particularly in elevation.
• Over a prolonged period of wearing the molds, (up
  to 3 weeks) localization accuracy improved.

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EI neuron
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Phase locking improves in the cochlear nucleus
Sphericalbushycell
Endbulbof Held
Auditory nervefiber
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EE neuron
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The Jeffress model mapping ITDs in the brain?
http//auditoryneuroscience.com/topics/jeffress-mo
del-animation
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ITD tuning varies with sound frequency no map?
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The Auditory Pathway
CN, cochlear nuclei SOC, superior olivary
complex NLL, nuclei of the lateral lemniscus
IC, inferior colliculus MGB, medial geniculate
body.
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Lesion Studies Suggest Important Role for A1
Jenkins Merzenich, J. Neurophysiol, 1984
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Binaural Frequency-Time Receptive Field
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Linear Prediction of Responses
FTRF w matrix
Inputi vector
r(t) i1(t-?1)? w1(?1) i1(t-?2)? w1(?2) ...
i2(t-?1)? w2(?1) i2(t-?2)? w2(?2) ...
i3(t-?1)? w3(?1) i2(t-?2)? w3(?2) ...
Frequency kHz
Latency
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Predicting Space from Spectrum
Left and Right Ear Frequency-Time Response Fields
a
Virtual Acoustic Space Stimuli
d
Frequency kHz
Elev deg
e
b
c
f
Schnupp et al Nature 2001
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Higher Order Cortical Areas

• In the macaque, primary auditory cortex(A1) is
  surrounded by rostral (R), lateral (L),
  caudo-medial (CM) and medial belt areas.
• L can be further subdivided into anterior, medial
  and caudal subfields (AL, ML, CL)

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Are there What and Where Streams in Auditory
Cortex?
AnterolateralBelt

• Some reports suggest that anterior cortical belt
  areas may more selective for sound identity and
  less for sound source location, while caudal belt
  areas are more location specific.
• It has been hypothesized that these may be the
  starting positions for a ventral what stream
  heading for inferotemporal cortex and a dorsal
  where stream which heads for postero-parietal
  cortex.

CaudolateralBelt
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A Panoramic Code for Auditory Space?

• Middlebrooks et al.found neural spike patterns
  to vary systematically with sound source
  direction in a number cortical areas of the cat
  (AES, A1, A2, PAF).
• Artificial neural networks can be trained to
  estimate sound source azimuth from the neural
  spike pattern.
• Spike trains in PAF carry more spatial
  information than other areas, but in principle
  spatial information is available in all auditory
  cortical areas tested so far.

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Artificial Vowel Sounds

• Bizley et al J Neurosci 2009 292064

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Responses to Artificial Vowels in Space

• Bizley et al J Neurosci 2009 292064

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Azimuth, Pitch and Timbre Sensitivity in Ferret
Auditory Cortex

• Bizley et al J Neurosci 2009 292064