1. 1 Modeling the Auditory Pathway Research Advisor: Aditya Mathur School of Industrial Engineering Department of Computer Science Purdue University Graduate Student: Alok Bakshi SERC Showcase, Motorola Labs, Schaumburg, IL, June 7-8, 2006 Sponsor: National Science Foundation

2. 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. 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. 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. 5 Characteristics of our approach Systems, holistic, approach. Detailed versus aggregate models. Explicit modeling of inherent anatomical and physiological parallelism.

6. 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. 7 Brainstem Auditory Evoked Potential http://www.iurc.montp.inserm.fr/cric/audition/english/audiometry/ex_ptw/e_pea2_ok.gif http://www.iurc.montp.inserm.fr/cric/audition/english/audiometry/ex_ptw/voies_potentiel.jpg Normal children Language impaired children

8. 8 Modeling the Auditory Pathway Auditory Nerve fiber model by Zhang et. al. Octopus Cell model by Levy et. al. Models of other cells being implemented

9. 9 Model of the Auditory Neuron (Zhang et al., 2001) (Heinz et al., 2001) (Bruce et al., 2003)

10. 10 Cochlear Nucleus Consist of 13 types of cells Single cell responses differ based on # of excitatory/inhibitory inputs Input waveform pattern Onset response Buildup response Input tone

11. 11 Octopus Cell Receives excitatory input from 60-120 AN fibers AN discharge rate Time Octopus Cell discharge rate Time Latent period

12. 12 Schematic of a typical Octopus Cell http://www.ship.edu/~cgboeree/neuron.gif 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’

13. 13 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

14. 14 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 SomaDendrite

15. 15 K + ion channel http://personal.tmlp.com/Jimr57/textbook/chapter3/images/pro5.gif Outside I ext IKIK I Na ILIL gKgK g Na gLgL VKVK V Na VLVL C Inside ( At potential V ) m, n and h depend on V Hodgkin Huxley Model

16. 16 Hodgkin Huxley Model (contd.) http:// www.bbraunusa.com/stimuplex/graphics/low_speed_nerve.jpg

17. 17 Next Step Implement model of Octopus Cell and connect it with AN fiber’s 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?

18. 18 References Drawing/image/animation from "Promenade around the cochlea" 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