Memory systems

1. Memory systems Off-line processing, consolidation, and interference

3. Instructions and motor learning • Green and Flowers (1991) • Wulf (1997) • Verdolini-Marston & Belota (2003) • Boyd & Winstein (2004)

4. Purpose • “Complex” skill learning (i.e. real learning) • Occurs in context of both explicit and implicit processes • Trying to understand the interactivity of the two systems in learning

5. Two views of interaction • Independent • Explicit memory arises from “witnessing” implicit learning and does not assist it • The different systems emerged from different origins • Integrated • Explicit memory is a necessary part of acquiring implicit memory • Explicit memories are transformed into implicit

6. Method • Provide explicit instruction, learn implicit task • Integrated – explicit should help • Independent – should have either no effect or hinder learning • Serial interception sequence learning • http://reberlab.psych.northwestern.edu/SISL/v0.2.0/SISL.html • Like a continuous version of the classic sequence learning task • Guitar hero! • 12 item repeating sequence

7. Task • “catch” the balls using the appropriate keys

8. Method • 2 groups – • Explicit: • memorize the sequence • Watch the balls drop without hitting keys • Print out of sequence visible as they watch • Self-paced • Implicit – none of the above • All: • 24 random cues for familiarization • 6 X 480 learning trial blocks (384 sequenced, 96 novel) • 540 trial test block • 3 different sequences – I from practice • 5 reps per sequence (60 trials) • Used to show performance diffs due to learning

9. Method • Following practice: • Explicit recognition test • 5 different sequences have two reps each • Rated confidence that sequence was the one practiced • Explicit recall task • Try to produce sequence using keys without balls being seen

10. Results • No group differences in performance or learning

11. Results • Differences in explicit recall… Only statistical difference – explicit group could produce the sequence better than the implicit group

12. Conclusions • Independent, multiple memory systems ideas are better supported • This provides direct evidence against the integrated, single system argument • Implicit learning here is not aided by explicit knowledge • …but it’s not hurt either (unlike earlier studies) • Task specific issues? • Is this learning coordination?

14. Historically… • H.M. • Squire & others (e.g. Cohen and Squire 1980) • Declarative and procedural memory systems are independent • Alzheimer’s: declarative impaired, procedural not • Huntington’s: procedural impaired, declarative not • fMRI scanning: procedural & declarative “work” lights up different neural circuitry

15. New evidence… • Willingham (1997) • Activity within medial temporal lobe and striatum associated • Brown and Robertson (2007a and b) • Learning word list after motor skill impairs motor skill • Learning motor skill after word list impairs word learning

16. Interference paradigm • Consolidation and reconsolidation… • Susceptibility to interference, and time:

17. Lines of evidence… • A shared resource? • Medial temporal lobes active during both declarative and procedural processing. • Coupling causing shift from independence? • Damage to frontal lobe prevents interference • Wakefulness vs. sleep – dorsolateral prefrontal cortex invoked when awake but not when asleep • Seems to be that frontal lobe makes MTL and Striatum interfere

18. Interference possibilities & findings

19. Role of dorsolateral prefrontal cortex…

20. Function of interference… • When learning motor skill first… • Interference prevented by stimulating motor cortex • Neither memory impaired or enhanced when interference prevented • Interference independent of memory processing • Stimulated areas (DLPFC, M1) seem to be producing the interference…why?

21. Function of interference… • Why? • New memories are unstable at time of learning • Retrieved memories are unstable when recalled • Maybe instability of both makes for better reorganization of the paired memories? • DLPFC or M1 may • Exert executive control over memory • Select memories susceptible to interference

22. Brain state & processes • Areas of brain interfere when awake, but not when asleep • When awake, memories are organized interactively • When asleep they are organized independently • Learning… • Independent acquisition but interactive after learning? • Aging • DLPFC function alters with age. Youth – mature – old.

23. Manipulating interference • Altered sequence of learning to avoid interference? • Maybe, but what’s the function of the interference? • Maybe it leads to greater memory integration?

24. Memory stability • New memories become resistant to interference over a few hours. • Circuits effecting this change depend on type of practice… • Single block – M1 • Multiple blocks – DLPFC • “Offline” processes stabilize learning.

25. Offline learning • Can be enhanced by • Sleep (motor learning 20-30%) • Praise • Cues at encoding • Learning & consolidation (offline learning) rely on similar brain areas and chemical processes • Circuitry in bird song similar when actually singing and when dreaming.

26. Retrieval and stability • Retrieved memories can be interfered with • But only when new information is to be paired with retrieved information • Possible link with need to integrate new with old memory