The Auditory Pathway

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The Auditory Pathway

• Slides from Neuroscience module lecture

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Left Auditory cortex
Right Auditory cortex
Medial geniculate nucleus
Cochlea
Inferior colliculus
Auditory nerve fiber
Superior Olivary nucleus
Ipsilateral Cochlear nucleus
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http//www.kumc.edu/SAH/OTEd/OCTH455/LectureNotes/
auditory.html
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The cochlear nucleus is a switchboard of sorts,
distributing auditory information to several
different areas in the auditory pathway. It also
does a substantial amount of processing of both
time and frequency information.
http//serous.med.buffalo.edu/hearing/cochlear_nuc
lei.html
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• The Cochlear Nuclei are typically divided into
  three regions
• Anterior Ventral Cochlear Nucleus (AVCN)
• Posterior Ventral Cochlear Nucleus (PVCN)
• Dorsal Cochlear Nucleus (DCN).
• The auditory pathway diverges into multiple
  parallel tracts as it leaves the cochlear
  nucleus. While the auditory nerve connects
  almost exclusively to the ipsilateral cochlear
  nucleus, the cochlear nucleus divides its output
  bilaterally into several different ascending
  tracts.
• The three divisions are each associated with a
  specific pathway.
• The entryway to the "Binaural Pathway" is the
  AVCN. Through the binaural pathway, the AVCN
  provides direct and indirect input to the
  Superior Olivary Complex (SOC). This pathway is
  likely to be involved in spatial localization and
  other tasks requiring convergence of information
  from both ears.
• The PVCN is the starting point of the
  "Intermediate Brainstem Pathway." The
  functionality of this pathway is poorly
  understood. However it is known to connect to
  Periolivary Nuclei (PON), ascend up the Lateral
  Lemniscus (LL) where it connects to nuclei of the
  LL and Inferior Colliculus (IC).
• "The Monaural Contralateral Pathway" begins at
  the DCN. As its name suggests this pathway
  caries information from only the contralateral
  ear (right ear for a neuron left of midline).
  This pathway is unique in that it carries a
  substantial amount of descending input.

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Localisation in 3 dimensions

• Azimuth (left/right)
• (Arab. as-sumut, i.e. as al the sumut, pl of
  samt way)
• Binaural cues ITD and ILD
• Median-plane (front, up, back, down)
• Pinna-induced spectral cues
• Head movements
• Distance
• Absolute level, excess IID (inverse-square law),
  spectral balance, reverberation

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Interaural time-difference - ITD
t R
t L
ITD t R - t L
Maximum c 0.6 ms
www.biols.susx.ac.uk/home/ Chris_Darwin/Perception
/Lectures/3.ppt
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Note how short the conduction distances are from
cochlear nerve (dark purple/red), via cochlear
nucleus (green) to the superior olivary complex
(red). This presumably helps preserve precise
timing information, important for binaural hearing
http//serous.med.buffalo.edu/hearing/cochlear_nuc
lei.html
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Interaural Level Difference (ILD)
From David McAlpine
Processed in Lateral Superior Olive
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Figure 2 Diagrammatic representation of human
cerebral cortical surface, showing relative
locations of primary auditory cortex ( Brodmann
areas 41, 42) and assocation auditory cortex
(Brodmann areas 22, 52 ).
http//www.wfubmc.edu/neurology/rosenberg/audio1.h
tml
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The presentation of pulsed sine tones is a simple
mode to produce activation in the Heschl's gyrus
and the planum temporale. A typical BOLD response
upon acoustic stimulation (1000 Hz sine tone,
pulse at 5 Hz) acquired with an fMRI technique is
shown left. (Neuroimag Clin N Am 2001 1 275)
http//www.unibas.ch/dmr/mr_physik/research/fMRI/a
uditory/main.htm
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trachea
http//ispl.korea.ac.kr/wikim/research/speech.htm
l
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http//ispl.korea.ac.kr/wikim/research/speech.htm
l
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Spectrogram and time-domain presentation of
Finnish word kaksi (two). http//www.acoustics.hut
.fi/slemmett/dippa/chap3.html
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Damage to Broca's Area (Broca's aphasia) Prevents
a person from producing speech. Person can
understand language words are not properly
formed speech is slow and slurred.
Damage to Wernicke's Area (Wernicke's
aphasia) Loss of the ability to understand
language. Person can speak clearly, but the words
that are put together make no sense. This way of
speaking has been called "word salad" because it
appears that the words are all mixed up like the
vegetables in a salad.
http//www.furman.edu/7Eeinstein/general/neurodem
o/lang.htm