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Learning associations while retaining specificity: Competing demands on network plasticity rules.

Learning associations while retaining specificity: Competing demands on network plasticity rules. Paul Miller, Brandeis University with Mark Bourjaily (Neuroscience Program). Talk Synopsis Introduction to task and plasticity mechanisms Associativity and specificity without persistence

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Learning associations while retaining specificity: Competing demands on network plasticity rules.

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  1. Learning associations while retaining specificity: Competing demands on network plasticity rules. Paul Miller, Brandeis University with Mark Bourjaily (Neuroscience Program) Talk Synopsis • Introduction to task and plasticity mechanisms • Associativity and specificity without persistence • Formation of sequential working memory

  2. Introduction: paired associates McCain has won the election

  3. Introduction: paired associates Obama has won the election

  4. Introduction: paired associates McCain has lost the election

  5. Introduction: paired associates Obama has lost the election

  6. Introduction: paired associates The Associative Inference Task (phases 1,2) Associative inference task phases 1-2. Bunsey and Eichenbaum 1996 Nature 379 25-257

  7. Introduction: stimulus-response pools

  8. Introduction: stimulus-response pools

  9. Introduction: stimulus-response pools

  10. Introduction: stimulus-response pools Pair-responsive pools form via correlations of stimuli? Biased choice arises from reward-based plasticity?

  11. Questions to address How can all these connections form? Can they be stable once they have formed? What biological plasticity rules help/don’t help? Does initial network “architecture” matter much?

  12. Plasticity mechanisms: STDP

  13. Long-term potentiation of inhibition, LTPi I to E connection increases with I-spike, veto by E-spike Maffei et al, Nature 2006

  14. 2) Associativity and specificity without persistence a) Structured inputs E-cells, random sparse connections I-cells, all-to-all

  15. 2) Associativity and specificity without persistence Protocol, 2 secs of separate inputs A : B : A+B

  16. 2) Associativity and specificity without persistence Initial responses Initial responses of selected cells in each pool

  17. 2) Associativity and specificity without persistence Cell responses after 200 trials: enhanced selectivity

  18. Pre synaptic pool Pre synaptic pool Post synaptic pool Post synaptic pool A B AB

  19. STDP alone destroys AB specificity (200 trials with homeostasis)

  20. Inputs are all-to-all, randomized, no structure. AB selectivity arises with inhibitory plasticity alone

  21. Summary of Part 2 (no persistence) STDP tends to over-associate LTPi enhances specificity of neural activity Inhibitory plasticity in an unstructured network can lead to specific stimulus-pair responses

  22. Part 3 (formation of sequential working memory) E-to-E plasticity certainly needed for persistence (cf GQ Bi’s work) Best results with small-world connectivity: Mostly local E-E connections < 1% all-to-all E-E connections STDP can generate “bumps” of memory activity.

  23. 3) Formation of sequential working memory Bump and ring attractor schematic

  24. 3) Formation of sequential working memory Bump and ring attractor schematic

  25. 3) Formation of sequential working memory Bump and ring attractor schematic

  26. 3) Formation of sequential working memory Bump and ring attractor schematic

  27. 3) Formation of sequential working memory Bump and ring attractor schematic

  28. 3) Formation of sequential working memory Bump and ring attractor schematic

  29. 3) Formation of sequential working memory Bump and ring attractor schematic

  30. 3) Formation of sequential working memory: Initial network response to X then Y I-cells Y X B A cue 1 cue 2 Time (sec)

  31. 3) Formation of sequential working memory: Evolved network response to X then Y Icells Y X B A cue 1 cue 2

  32. 3) Formation of sequential working memory: Evolved network response to A then Y Icells Y X B A cue 1 cue 2

  33. 3) Formation of sequential working memory: Evolved network response to A then B Icells Y X B A cue 1 cue 2

  34. 3) Formation of sequential working memory: Evolved network response to X then B cue 1 cue 2 Icells Y X B A

  35. Stimulus-pair-dependent activity profiles (average firing rates between 1.5-2s after 2nd cue) A-Y A-B X-B X-Y

  36. Some cells most responsive to X-B …

  37. Some cells most responsive to X-B … … only a few most responsive to A-B

  38. 3) Formation of sequential working memory: What about order of stimuli? Obama beats McCain

  39. 3) Formation of sequential working memory: What about order of stimuli? McCain beats Obama

  40. 3) Formation of sequential working memory: What about order of stimuli? M. Warden and E.K. Miller, Cereb Cortex 2007

  41. M. Warden & E.K. Miller, Cereb Cortex 2007

  42. 3) Formation of sequential working memory: What about order of stimuli?

  43. 3) Formation of sequential working memory: What about order of stimuli?

  44. 3) Formation of sequential working memory: What about order of stimuli?

  45. 3) Formation of sequential working memory: What about order of stimuli?

  46. 3) Formation of sequential working memory: What about order of stimuli?

  47. 3) Formation of sequential working memory: What about order of stimuli?

  48. 3) Formation of sequential working memory: What about order of stimuli?

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