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Extension of Superior Colliculus Based Models of Multisensory Integration to the Cortex

Extension of Superior Colliculus Based Models of Multisensory Integration to the Cortex. Michael Hadley Advisor: Dr. Elaine Reynolds Readers: Dr. Chun Wai Liew , Dr. Jeffrey Pfaffmann , Dr. Luis Schettino. Outline. Background SOM MMA Model My Extensions Conclusion.

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Extension of Superior Colliculus Based Models of Multisensory Integration to the Cortex

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  1. Extension of Superior Colliculus Based Models of Multisensory Integration to the Cortex Michael Hadley Advisor: Dr. Elaine Reynolds • Readers:Dr. Chun WaiLiew, Dr. Jeffrey Pfaffmann, Dr. Luis Schettino

  2. Outline • Background • SOM • MMA Model • My Extensions • Conclusion

  3. The Multisensory World • Windows to the world • Information is information • Implication for learning, sensory loss, sensory substitution http://media.photobucket.com/image/the%20senses/Kassiah/WotD/senses.jpg http://www.medical-look.com/systems_images/Sensory_organs.gif

  4. Literature Superior Colliculus (SC) Cerebral Cortex

  5. Chemical Explanation Behavioral Effects Multisensory Depression Multiple Receptive Fields Inhibition Time Dynamics Multisensory Enhancement Sigmoidal Activation Inverse Effectiveness System Level Explanation Developmental Explanation Ascending and Descending Connections More than Three Senses Different Thresholds

  6. Modeling • Ursino, Cuppini, Magosso, Serino and Pellegrino (2009) • Anastasio and Patton (2003) • Martin, Meredith and Ahmad (2003)

  7. Outline • Background • SOM • MMA Model • My Extensions • Conclusion

  8. Self-Organizing Maps • Topographical • Trained • Vector Form A = ( 1,0,0,0,0 ) B = ( 2,0,0,0,0 ) 3 = ( 3,3,6,2,3 )

  9. SOMs: How they Work A1 A2 A3 A4 A5 B 2 0 0 0 0

  10. Outline • Background • SOM • MMA Model • My Extensions • Conclusion

  11. Martin, Meredith and Ahmad Eyes Ears Skin

  12. MMA Design Inputs ( 0, 0, 0 ) ( 0, 0, 1 ) ( 0, 1, 0 ) ( 1, 0, 0 ) ( 0, 1, 1 ) ( 1, 0, 1 ) ( 1, 1, 0 ) ( 1, 1, 1 ) 1 3 Eyes Skin 2 Ears

  13. Experiments On MMA • Parameters: • Size • Inputs • Active and Noisy Levels • Probability Functions • Conclusions: • Sensitive integration • Signal-to-noise ratio balance

  14. Outline • Background • SOM • MMA Model • My Extensions • Conclusion

  15. My Work

  16. My Extensions • More Complex Senses • Inhibition • Overlapping RFs

  17. Complex Senses Original Model My Extensions

  18. 2 x 2 Within-Sense Enhancement

  19. 4 x 4

  20. Conclusions • Works for small cases • Larger cases are a problem • Both cases still have a problem

  21. Inhibition

  22. Conclusions • Rudimentary • Signal to noise ratio

  23. Overlapping Receptive Fields

  24. Overlapping Receptive Fields xPos yPos Bimodal MSE No Overlapping RFs Overlapping RFs

  25. Results • SOMs only handle 1 relation Eyes Skin Ears 1 1 3 3 2 2 1 3 Eyes 1 1 3 3 Skin 2 2 2 Ears

  26. MMA is Not Extendable • Within-modality integration • Requires inhibition • SOM can only handle 1 relation

  27. Outline • Background • SOM • MMA Model • My Extensions • Conclusion

  28. Theoretical Model Unisensory Layer 1 Multisensory Layer Unisensory Layer 2

  29. Areas in the multisensory layer are SOMs

  30. Why? • Increases explanatory power • Foundation

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