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Modeling the Auditory Pathway

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Octopus Cell Model Simplifications. Four dendrites ... Octopus Cell Model ... Levy K.L.; Kipke D.R. A computational model of the cochlear nucleus octopus cell. ... – PowerPoint PPT presentation

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Title: Modeling the Auditory Pathway


1
Modeling the Auditory Pathway
School of Industrial Engineering Department of
Computer Science Purdue University
SERC Showcase, Ball Sate University, November
15-16, 2006 Sponsor National Science Foundation
Research Advisor Aditya Mathur
Graduate Student Alok Bakshi
2
Objective
  • To construct and validate a model of the
    auditory pathway to understand the effect of
    various treatments on children with auditory
    disorders.

3
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.

4
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.

5
Characteristics of our approach
  • Systems, holistic, approach.
  • Detailed versus aggregate models.
  • Explicit modeling of inherent anatomical and
    physiological parallelism.

6
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

7
Brainstem Evoked Auditory 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
8
Auditory Pathway Modeling
9
Hodgkin Huxley Model
m, n and h depend on V
10
Hodgkin Huxley Model (contd.)
http//www.bbraunusa.com/stimuplex/graphics/low_sp
eed_nerve.jpg
11
Auditory Neuron Model
12
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
13
Octopus Cell
Octopus Cell
Receives excitatory input from 60-120 AN fibers
14
Schematic of a typical Octopus Cell
  • Representative Cell
  • Has four dendrites
  • 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
15
Octopus Cell 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

16
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
17
Octopus Cell - Output
  • The output of the model implemented by Levy et.
    al. is compared against our model on the right
    side of the figure for a tone given at CF in
    figure A
  • Same comparison is made in figure B but with a
    tone of different intensity

18
Bushy Cell
AN spikes
Bushy Cell
Time
Bushy Cell spikes
Receives excitatory input from 1-20 AN fibers
Time
Latent period
19
Bushy Cell Model
  • Representative Cell
  • Has no dendrites and axon
  • The soma is equipotential
  • Receives 1-20 AN fibers with different
    characteristic frequency
  • Inhibitory inputs ignored in the model

Soma
20
Bushy Cell Model Characteristics
  • As the number and conductance of inputs is
    varied, the full range of response seen in VCN
    Bushy cell are reproduced
  • For inputs with low frequency(lt 1 kHz), the model
    shows stronger phase locking than AN fibers, thus
    preserving the precise temporal information about
    the acoustic stimuli
  • The model simulates the spherical bushy cell, but
    doesnt reproduce all characteristics of globular
    bushy cell

21
Bushy Cell Model - Output
  • Response of Bushy cell for different number of
    input AN fibers (N), and synaptic conductance (A)
  • Fig. A shows the response of our implemented
    model for N1 and A 9.1, while the output
    obtained by Rothman et. al. is shown in D for
    same parameter.

22
Bushy Cell Model - Output
  • Similarly for N5 and A9.1, our implemented
    models response is shown in B, while response of
    model by Rothman et. al. is shown in E
  • Finally, the fig. C shows response of our model
    for N1, A18.2 and the corresponding response of
    model by Rothman et. al. is shown in fig. F

23
Fusiform Cell
AN discharge rate
Fusiform Cell
Time
Fusiform Cell discharge rate
Receives different inhibitory inputs from DCN
Time
24
Fusiform Cell Model
  • Exhibit buildup and pauser response and nonlinear
    voltage/current relationship
  • The model simulates the soma of fusiform cell
    with three K and two Na voltage dependent ion
    channels
  • The model doesnt take into account the Calcium
    conductance
  • Doesnt model the synaptic input

Electrical model of fusiform cell
25
Fusiform Cell Model Characteristics
  • Predicts the electrophysiological properties of
    the fusiform cell by using basic Hodgkin-Huxley
    equations
  • Simulates the pauser and buildup response by
    virtue of intrinsic membrane properties
  • Synaptic organization of cells in DCN is not
    understood presently, so this model doesnt model
    synapse and take direct current as the input
    instead
  • Doesnt rule out the possibility of inhibitory
    inputs as the reason for pauser and buildup
    response

26
Next Steps
  • Verify the models of Pyramidal and Stellate cell
    in the cochlear nucleus.
  • Identify structural connections of different
    types of cells in the cochlear nucleus.
  • Modify the models if they ignore few inputs for
    the sake of simplification, to account for such
    inputs.
  • Determine the response of the cochlear nucleus as
    a whole with different input waveforms.

27
References
  • Hiroyuki M. Jay T.R. John A.W. Comparison of
    algorithms for the simulation of action
    potentials with stochastic sodium channels.
    Annals of Biomedical Engineering, 30578587,
    2002.
  • Kim D.O. Ghoshal S. Khant S.L. Parham K. A
    computational model with ionic conductances for
    the fusiform cell of the dorsal cochlear nucleus.
    The Journal of the Acoustical Society of America,
    9615011514, 1994.
  • Levy K.L. Kipke D.R. A computational model of
    the cochlear nucleus octopus cell. The Journal of
    the Acoustical Society of America, 102391402,
    1997.
  • Rothman J.S. Young E.D. Manis P.B. Convergence
    of auditory nerve fibers onto bushy cells in the
    ventral cochlear nucleus Implications of a
    computational model. The Journal of
    Neurophysiology, 7025622583, 1993.
  • Zhang X.Heinz M.G.Bruce I.C. Carney L.H. A
    phenomenological model for the responses of
    auditory-nerve fibers 1. nonlinear tuning with
    compression and suppression. The Journal of the
    Acoustical Society of America, 109648670, 2001.

28
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
  • 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
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