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

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)

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

23. 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

24. 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.

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 Bump and ring attractor schematic

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

32. 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)

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

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

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

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

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

38. Some cells most responsive to X-B …

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

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

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

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

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

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?

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

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