Modeling the Auditory Pathway

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Modeling the Auditory Pathway
School of Industrial Engineering Department of
Computer Science Purdue University
SERC Showcase, Motorola Labs, Schaumburg, IL,
June 7-8, 2006 Sponsor National Science
Foundation
Research Advisor Aditya Mathur
Graduate Student Alok Bakshi
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Objective

• To construct and validate a model of the
  auditory pathway to understand the effect of
  various treatments on children with auditory
  disorders.

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Background and Problem

• Children with some forms of auditory disorders
  are unable to discriminate rapid acoustic changes
  in speech.
• It has been observed that auditory training
  improves the ability to discriminate and identify
  an unfamiliar sound.
• Computational model desired to reproduce this
  observation.
• A validated model would assist in assessing the
  impact of disorders in the auditory pathway on
  brainstem potential. This would be useful for
  diagnosis. This appears related to fault
  diagnosis and tolerance in software systems. It
  might have an impact on the design of redundant
  software systems.

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Methodology

• Study physiology of the auditory system.
• Simulate the auditory pathway by constructing new
  models, or using existing models, of individual
  components along the auditory pathway.
• Validate the model against experimental results
  pertaining to the auditory system.
• Mimic experimental results of auditory processing
  tasks in children with disabilities and gain
  insight into the causes of malfunction.
• Experiment with the validated model to assess the
  effects of treatments on children with
  auditory/learning disabilities.

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Characteristics of our approach

• Systems, holistic, approach.
• Detailed versus aggregate models.
• Explicit modeling of inherent anatomical and
  physiological parallelism.

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Progress

• Synaptic model is implemented for connection
  between two neurons
• Following (existing) models incorporated for the
  simulation of the Auditory pathway
• Phenomenological model for the response of
  Auditory nerve fibers
• Computational model of the Cochlear Nucleus
  Octopus Cell

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Brainstem Auditory Evoked Potential
Normal children
Language impaired children
http//www.iurc.montp.inserm.fr/cric/audition/engl
ish/audiometry/ex_ptw/voies_potentiel.jpg
http//www.iurc.montp.inserm.fr/cric/audition/engl
ish/audiometry/ex_ptw/e_pea2_ok.gif
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Modeling the Auditory Pathway
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Model of the Auditory Neuron
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Cochlear Nucleus

• Consist of 13 types of cells
• Single cell responses differ based on
• of excitatory/inhibitory inputs
• Input waveform pattern

Input tone
Onset response
Buildup response
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Octopus Cell
Octopus Cell
Receives excitatory input from 60-120 AN fibers
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Schematic of a typical Octopus Cell

• Representative Cell
• Receives 60 AN fibers with 1.4 - 4 kHz CF
• Majority of input from high SA fibers, medium SA
  fibers denoted by superscript m

http//www.ship.edu/cgboeree/neuron.gif
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Model Simplifications

• Four dendrites replaced by a single cylinder
• Active axon lumped into soma
• Synaptic transmission delay taken as constant 0.5
  ms
• Compartmental model employed with
• 15 equal length dendritic compartments
• 2 equal length somatic compartments

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Octopus Cell Model
2 somatic compartments and 15 dendritic
compartments modeled by the same circuit with
different parameters Different number of
dendritic compartments depending on number of
synapses with AN fibers
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Hodgkin Huxley Model
m, n and h depend on V
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Hodgkin Huxley Model (contd.)
http//www.bbraunusa.com/stimuplex/graphics/low_sp
eed_nerve.jpg
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Next Step

• Implement model of Octopus Cell and connect it
  with AN fibers model
• Implement models of all cells of Cochlear Nucleus
  and connect them through synapse models
• Find out the response of Cochlear Nucleus as a
  whole with different input waveform signals.
• Relation to SE?

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References

• Drawing/image/animation from "Promenade around
  the cochlea" ltwww.cochlea.orggt EDU website by R.
  Pujol et al., INSERM and University Montpellier
• Gunter E. and Raymond R. , The central Auditory
  System 1997
• Kraus N. et. al, 1996 Auditory Neurophysiologic
  Responses and Discrimination Deficits in Children
  with Learning Problems. Science Vol. 273. no.
  5277, pp. 971 973
• Levy et. al. 1997 A computational model of the
  cochlear nucleus octopus cell, Acoustical
  Society of America S0001-4966(97)00807-2
• Purves et al, Neuroscience 3rd edition
• P. O. James, An introduction to physiology of
  hearing 2nd edition
• Tremblay K., 1997 Central auditory system
  plasticity generalization to novel stimuli
  following listening training. J Acoust Soc Am.
  102(6)3762-73