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!