Memory systems Off-line processing, consolidation, and interference

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

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

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

Method Provide explicit instruction, learn implicit task – Integrated – explicit should help – Independent – should have either no effect or hinder learning Serial interception sequence learning – Like a continuous version of the classic sequence learning task – Guitar hero! 12 item repeating sequence

Task “catch” the balls using the appropriate keys

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

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

Results No group differences in performance or learning

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

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?

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

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

Interference paradigm Consolidation and reconsolidation… – Susceptibility to interference, and time:

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

Interference possibilities & findings

Role of dorsolateral prefrontal cortex…

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?

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

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.

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?

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.

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.

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