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The visual system V Neuronal codes in the visual system

The visual system V Neuronal codes in the visual system. What‘s the code?. time. Firing rate. Spike timing Synchrony Timing patterns. The codes – firing rate. ’Firing rates are the only code that ALWAYS works’. The codes – firing rate. We start with the question

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The visual system V Neuronal codes in the visual system

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  1. The visual system VNeuronal codes in the visual system

  2. What‘s the code? time Firing rate • Spike timing • Synchrony • Timing patterns

  3. The codes – firing rate ’Firing rates are the only code that ALWAYS works’

  4. The codes – firing rate We start with the question Does the brain use rate or precise timing? We turn that into: How noisy are networks? Latham & London (submitted)

  5. The codes – firing rate Identical input on every trial t=0 Latham & London (submitted)

  6. one extra spike on trial 2 Identical input on every trial small noise large noise t=0 Latham & London (submitted)

  7. The codes – firing rate We start with the question Does the brain use rate or precise timing? We turn that into: How noisy are networks? And finally: How many extra postsynaptic spikes are caused by one extra presynaptic spike? Latham & London (submitted)

  8. Experimental details: • in vivowhole cell recordings • layer 5 pyramidal cells of rat barrel cortex • urethane anesthetic • with and without whisker stimulation • current injection rather than PSPs Latham & London (submitted)

  9. V θ 100 ms Latham & London (submitted)

  10. extra spike V θ 100 ms Latham & London (submitted)

  11. V θ 100 ms small effect Latham & London (submitted)

  12. V θ 100 ms small effect Latham & London (submitted)

  13. V θ 100 ms big effect!!! Latham & London (submitted)

  14. number of extra spikes caused by just one extra spike = p1× number of connections per neuron ≈p1× 1000 ≈ 0.025× 1000 = 25 Latham & London (submitted)

  15. one extra spike on trial 2 Identical input on every trial small noise large noise t=0 Latham & London (submitted)

  16. Manipulation of firing rates influences visual perception Salzman et al., (1992)

  17. Manipulation of firing rates influences visual perception Salzman et al., (1992)

  18. The codes – synchrony ’Perception is about association. Synchrony is too.’

  19. The codes – synchrony

  20. The codes – synchrony

  21. The codes – synchrony

  22. Center-surround interactions Biederlack et al. (2006)

  23. Center-surround interactions Biederlack et al. (2006)

  24. The escape of the bullfrog Ishikane et al. (2005)

  25. The escape of the bullfrog Ishikane et al. (2005)

  26. The codes – precise timing ’If it works, precise timing has incredible coding capacity’

  27. The codes – precise timing Thorpe & Fabre-Thorpe (2001) 20 ms per stage! 1 spike per neuron! 40-50 ms 30-50 ms 20-40 ms 50-70 ms 70-90 ms 80-100 ms

  28. What can one spike tell us?

  29. What can one spike tell us?

  30. Theories on spike timing in the cortex Van Rullen & Thorpe (2001)

  31. Fast OFF cell Biphasic OFF cell Time[ms] Time[ms] Onset latencies in vision Gollisch & Meister (2008)

  32. Onset latencies in vision Gollisch & Meister (2008)

  33. From external to internal timing

  34. 0.2 mm Experimental setup • Anaesthesia • Primary visual cortex • Grating stimuli • 16 channels per recording probe • Multi- and single unit activity

  35. Raw data Neuron # Time [ms]

  36. Raw data Neuron # Time [ms]

  37. Raw data Neuron # Time [ms]

  38. Raw data Neuron # Time [ms]

  39. Preferred firing sequences Preferred relative firing time [ms]

  40. Stimulus-dependent changes Relative firing time [ms]

  41. Stability 7 hours Relative firing time [ms]

  42. Firing sequences and firing rates Firing rate Firing time rtotal = 0.28 r2total = 0.08

  43. Firing sequences and firing rates Relative firing time [ms] # of action potentials Time [sec] Time [sec] rtotal = 0.01 r2total = 0.00

  44. Neuronal coding in the real world – what is a response?

  45. Responses are multi-dimensional Basole et al. (2003)

  46. Information from ‘non-responsive‘ areas Haxby et al. (2001)

  47. Natural vision is dynamic Things move. The body moves. Your eyes move. Everything moves. Vision is made to be a dynamic process.

  48. ´Lab´ activation Mainen & Sejnowski (1995)

  49. ´Natural´ activation Mainen & Sejnowski (1995)

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