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January 17, 2018 | Author: Anonymous | Category: Science, Health Science, Neurology
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NSF Science of Learning Lila Davachi Dept Psychology and Neural Science New York University

Introduction We’ve known the hippocampus and MTL are critical for new memories to become consolidated Decades of work to understand how the hippocampus (in particular) supports memory

Divergence in the field - Rodent physiologists mostly studying spatial learning - Psychologists studying word-list learning - They could not be more different Recent convergence (worth exploring further!) - Reactivation mechanism for memory consolidation - Sequences critical! Related accomplishments - Reactivation facilitates building complex knowledge structures through ‘integrative learning’

Objectives •

1. Reactivation •

Mechanism for consolidation during awake rest



More general mechanism for integrative learning

2. Active Learning

Objectives •

1. Reactivation •

Mechanism for consolidation during awake rest



More general mechanism for integrative learning

2. Active Learning

Systems consolidation of memory Systems consolidation is a process of trace reorganization proposed to shift the memory representation from a hippocampal-dependent to a hippocampal-independent representation. Hypothesized to be achieved through both online and offline hippocampal-cortical interactions that occur after the initial learning. Specifically, ‘replay’ of the pattern of activity linked with the initial experience has been hypothesized to be at least one mechanism supporting memory consolidation

Background Hippocampal neural ‘replay’ has been shown in the rodent both during sleep (Pavlides & Winson, 1989; Wilson & McNaughton, 1994) and during awake rest (Foster & Wilson, 2006; Diba & Buzsaki, 2007).

Critically, recent work has shown that selective suppression of hippocampal replay during offline periods can impair spatial memory (Girardeau et al, 2009; Ego-Stengel & Wilson, 2010)

Hippocampal Replay

When does reactivation occur? Consciousness

Experience

Off-line

time

Retrieval

When does reactivation occur? Retrieval

Consciousness

Experience

Off-line

time

Off-line? Sleep Awake rest? Brain region resting?

Awake rest and memory consolidation Baseline Rest

ObjectFace Task 21 mins

8.4 mins

Post-Task Rest 8.4 mins

r = .37

(Tambini, Ketz and Davachi ,2010, Neuron

Awake rest and memory consolidation Baseline Rest

ObjectFace Task 21 mins

8.4 mins

r r==.37 .37

Post-Task Rest 8.4 mins

r = .60

(Tambini, Ketz and Davachi ,2010, Neuron

Resting Hippocampal-LO correlations

Assoc hits > misses

(Tambini, Ketz and Davachi ,2010, Neuron

Change in correlations predict later memory for the preceding representations

(Tambini, Ketz and Davachi, 2010, Neuron)

Patterns of replay? Sleep before task

Sleep after task

Sutherland and McNaughton, CONB 2000

• Reactivation of patterns of activity across cells is specific

Post-Task Rest

Baseline Rest

Encoding Task

Summary •

Reactivation is seen during immediate post-encoding rest periods



Initial evidence that this can be seen at the level of single voxels in their patterns of activation with other voxels



The magnitude of reactivation is related to later memory



How long a rest period needed?



What counts as rest?

Objectives •

1. Reactivation •

Mechanism for consolidation during awake rest



More general mechanism for integrative learning

2. Active Learning

Integration during learning: mediated by reactivation

(Zeithamova et al, 2012, Neuron)

Integration during learning: mediated by reactivation

(Zeithamova et al, 2012, Neuron)

Summary •

Reactivation during new encoding can enhance memory updating/integration



Using multivariate methods, can measure the reactivation of categorical representations. This methodological innovation opens many doors to understanding how and when reactivation occurs and when is it beneficial/detrimental?



How could this be leveraged to enhance conceptual learning?



How much can be reactivated at once?



How effect reactivation? Single cue? Context?

Reactivation different functions? •

Reactivation during sleep/awake rest/online tasks?



Possibilities: •

Reactivation during sleep: integrating into existing knowledge?



Awake rest: good for strenghthening?



On line tasks: good for updating?

Objectives •

1. Reactivation •

Mechanism for consolidation during awake rest



More general mechanism for integrative learning

2. Active Learning

Active Learning •







Hypothesis testing? Using what we know we don’t know to select information? Recent work suggests that just the act of selecting, itself, may enhance encoding Action systems in the brain rely on dopamine, for e.g. to reinforce appropriate behaviors Is it possible then when learning in an active manner, the brain brings on another system that may not be technically ‘needed’ but that has the consequence of enhancing learning?

Active Learning

Active Learner

‘Yolked’ Learner Voss et al, 2011, Nature Neuroscience

Active Learning

Memory is enhanced!

Active Learning •





Different levels of ‘active’ Possibility that simply pressing a button can leverage another system (dopamine) and enhance long-term retention of representations Think iPAD!

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