What Have we Learned about Memory from Rodents in Mazes? Loren - - PowerPoint PPT Presentation

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What Have we Learned about Memory from Rodents in Mazes? Loren - - PowerPoint PPT Presentation

Nov 07, 2022 149 likes •324 views

What Have we Learned about Memory from Rodents in Mazes? Loren Frank Howard Hughes Medical Institute Kavli Institute for Fundamental Neuroscience Department of Physiology University of California, San Francisco Why Build a Model of the World?

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What Have we Learned about Memory from Rodents in Mazes?

Loren Frank

Howard Hughes Medical Institute Kavli Institute for Fundamental Neuroscience Department of Physiology University of California, San Francisco

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Why Build a Model of the World?

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Conclusions

  • The same systems represent current experience and past / future

experience.

  • Representations can cycle between present and future.
  • Memories engage links between specific and general knowledge.
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Hippocampal (CA1) Neural Activity

Cell number

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Awake Replay of Remote Experiences During Sharp-Wave Ripple Events

Karlsson and Frank, Nature Neuroscience (2009)

1 2 3 … … 8 14 15 16 E1 Place Fields Sharp-Wave Ripple E1 “Replay”

Decoding

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Representations of Possible Future Paths

Decoded Trajectory Actual Location and Trajectory

Karlsson and Frank, Nature Neuroscience (2009)

Sharp-Wave Ripple

Is this a memory? Or a plan?

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Alternating Representations of Future Possibilities

Clusterless decoding method: Deng et. al. Neural Computation (2015) ”Theta sequences”: Skaggs et. al. (1996) Work from Colgin, Foster and Redish labs.

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Conclusions

  • The same systems represent current experience and past / future

experience.

  • Representations can cycle between present and future.
  • Memories engage links between specific and general knowledge.
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Hippocampal and Prefrontal (PFC) Contributions to Memory

  • The hippocampus is critical for storing memories

for specific events.

  • For these memories to be useful, the specifics

need to be linked to general knowledge structures (”schema”).

– The PFC is known to be important for learning and using schema.

  • How these links manifest in neural activity remains

unknown.

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Specific and Reliable Representations in Hippocampus

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Heterogeneous Representations in PFC

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Heterogeneous Representations in PFC

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Contrasting Representations in Hippocampus and PFC

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Preferential Reactivation of PFC Cells with High Reliability and Similarity

Reactivated during MAP SWRs Not reactivated during MAP SWRs

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Preferential Reactivation of PFC Cells with High Reliability and Similarity

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Many-to-One Mapping from MAP to PFC Cells

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Conclusions

  • The same systems represent current experience and past / future

experience.

  • Representations can cycle between present and future.
  • Memories engage links between specific and general knowledge.