Learning and Plasticity

Transcript

1. The Human Brain in the Animal Kingdom (HEB 1339) | lecture 15
   Learning and Plasticity
   Suhas Vijayakumar
   postdoc | evolutionary neuroscience lab
   @neuroacademic
   @neuroacademic a
   Learning and Plasticity | April 01, 2020
   suhas_vijayakumar@harvard.edu
   

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2. part I: introduction
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3. @neuroacademic a
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   < discuss >
   Learning and Plasticity
   

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4. @neuroacademic a
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   Definitions
   Experience
   Memory
   (LTP - LTD)
   Development
   Aging
   Adaptation
   Problem solving
   Lesion
   

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5. @neuroacademic a
   Learning and Plasticity | April 01, 2020
   Definitions
   ¯\_(ツ)_/¯
   learning plasticity
   acquiring new experience changes the brain
   

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6. Learning and Plasticity
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7. Learning and Plasticity
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   the one about
   how acquiring new information
   changes the brain
   

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8. Learning is how you acquire new information
   about the world, and memory is how you store
   that information over time
   Eric R. Kandel
   “
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9. Learning
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   ‣ preferential strengthening
   ‣ non-associative
   permanent change to repeated stimulus
   habituation and sensitization
   ‣ associative
   stimulus => behavior
   classical conditioning
   operant conditioning
   

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10. Learning Plasticity
    ‣ produce more neurons
    ‣ produce more glial cells
    ‣ capillary growth (increase O2
    )
    ‣ synaptic connections
    @neuroacademic a
    Learning and Plasticity | April 01, 2020
    ‣ preferential strengthening
    ‣ non-associative
    permanent change to repeated stimulus
    habituation and sensitization
    ‣ associative
    stimulus => behavior
    classical conditioning
    operant conditioning
    

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11. Learning
    ‣ preferential strengthening
    ‣ non-associative
    permanent change to repeated stimulus
    habituation and sensitization
    ‣ associative
    stimulus => behavior
    classical conditioning
    operant conditioning
    Plasticity
    ‣ produce more neurons
    ‣ produce more glial cells
    ‣ capillary growth (increase O2
    )
    ‣ synaptic connections
    @neuroacademic a
    Learning and Plasticity | April 01, 2020
    change across generations
    “adaptation”
    Krubitzer & Dooley 2013
    Front in Hum NeuroSci [link]
    

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12. Learning
    ‣ preferential strengthening
    ‣ non-associative
    permanent change to repeated stimulus
    habituation and sensitization
    ‣ associative
    stimulus => behavior
    classical conditioning
    operant conditioning
    Plasticity
    ‣ produce more neurons
    ‣ produce more glial cells
    ‣ capillary growth (increase O2
    )
    ‣ synaptic connections
    @neuroacademic a
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13. Recap
    Learning: how we process and acquire incoming new information
    Plasticity: changes to the nervous system
    (usually within one’s lifetime)
    Both can be studied at multiple levels
    Both have highly specific and specialized mechanisms
    (outside the scope of this talk)
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    Any learning will likely result in some plasticity
    

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14. part II: absence of input and plasticity
    case of the visual system
    nervous system has evolved to expect certain kinds of inputs
    but can certainly be repurposed
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15. ‣ auditory localization task
    Evidence for reorganization in humans
    Weeks et al., 2000
    JNeuroSci [link]
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16. ‣ auditory localization task
    ‣ reading Braille
    Evidence for reorganization in humans
    Sadato et al., 1996
    Nature letters [link]
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17. ‣ auditory localization task
    ‣ reading Braille
    ‣ auditory discrimination task
    ‣ faster in processing language . . .
    Evidence for reorganization in humans
    *Not limited to visual cortex.
    There are reorganizations of the auditory cortex of deaf individuals.
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18. Visual cortex organization
    ‣ Hubel & Wiesel
    https://www.youtube.com/watch?v=8VdFf3egwfg
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19. Extent of reorganization
    ‣ Hubel & Wiesel, LGN
    Hubel & Wiesel, 1970
    J Physiol [link]
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    right eye closed (d23 - d26) right eye closed (d23 - d29)
    

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20. Extent of reorganization
    ‣ Hubel & Wiesel, recordings from left visual cortex
    right eye closed (d23 - d26)
    normal development right eye closed (d23 - d29)
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    Hubel & Wiesel, 1970
    J Physiol [link]
    

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21. Cnops et al., 2008
    Cerebral Cortex [link]
    Extent of reorganization
    ‣ at layer-level
    ‣ protein expression
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22. back to system-level plasticity
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23. Extent of reorganization in short-tailed opossums (Monodelphis domestica)
    ‣ n = 6
    ‣ enucleated
    ‣ postnatal day 4
    area X: auditory + somatosensory
    Kahn & Krubitzer, 2002
    PNAS [link]
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24. Recap
    Parts of the brain have evolved to expect certain kinds of inputs
    In absence of such typical input, cortical function is often altered
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25. part III: learning and plasticity
    nervous system has evolved to expect certain kinds of inputs
    but can certainly be repurposed
    by training
    @neuroacademic a
    Learning and Plasticity | April 01, 2020
    

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26. @neuroacademic a
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    Extent of reorganization
    ‣ auditory localization task
    ‣ reading Braille
    ‣ auditory discrimination task
    ‣ faster in processing language . . .
    *natural adaptations.
    What about active training?
    

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27. @neuroacademic a
    Learning and Plasticity | April 01, 2020
    echolocation
    Plasticity through active adaptation
    ‣ EB, early blind - 13 months
    ‣ LB, late blind - 14 years
    ‣ fMRI *
    Thaler et al., 2011
    PlosOne [link]
    

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28. @neuroacademic a
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    echolocation
    Plasticity through active adaptation
    Thaler et al., 2011
    PlosOne [link]
    ‣ echo > silence
    blind visual cortex
    control auditory cortex
    

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29. echolocation
    Plasticity through active adaptation
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    Thaler et al., 2011
    PlosOne [link]
    ‣ echo > silence
    blind visual cortex
    control auditory cortex
    ‣ more than normal hearing
    blind visual cortex
    control none
    

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30. @neuroacademic a
    Learning and Plasticity | April 01, 2020
    echolocation
    Plasticity through active adaptation
    Thaler et al., 2011
    PlosOne [link]
    ‣ echo > silence
    blind visual cortex
    control auditory cortex
    ‣ more than normal hearing
    blind visual cortex
    control none
    ‣ lateralization
    blind contralateral preference for EB
    control auditory
    

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31. Extent of reorganization due to phantom limb
    ‣ V S Ramachandran
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    Side note: TED talk “3 clues to understanding your brain”
    https://www.youtube.com/watch?v=Rl2LwnaUA-k
    

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32. ‣ V S Ramachandran
    Ramachandran & Rogers-Ramachandran, 2000
    ArchNeurol [link]
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    Extent of reorganization due to phantom limb
    face hand upper arm
    right hemi left hemi
    

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33. @neuroacademic a
    Learning and Plasticity | April 01, 2020
    Okay, but shouldn’t this be in part II?
    

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34. ‣ V S Ramachandran
    Ramachandran & Rogers-Ramachandran, 2000
    ArchNeurol [link]
    @neuroacademic a
    Learning and Plasticity | April 01, 2020
    Extent of reorganization due to phantom limb
    plasticity through training
    

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35. @neuroacademic a
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    Hand grafts!
    Plasticity through active adaptation
    

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36. @neuroacademic a
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    Hand grafts!
    Plasticity through active adaptation
    Giraux et al., 2001
    NatNeuro [link]
    

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37. part III: learning and plasticity
    nervous system has evolved to expect certain kinds of inputs
    but can certainly be repurposed
    by training
    @neuroacademic a
    Learning and Plasticity | April 01, 2020
    

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38. @neuroacademic a
    Learning and Plasticity | April 01, 2020
    String instrument players
    Plasticity through active training
    Elbert et al., 1995
    Science [link]
    

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39. @neuroacademic a
    Learning and Plasticity | April 01, 2020
    The taxi driver study
    Plasticity through active training
    Maguire et al., 2000
    PNAS [link]
    ‣ Hippocampus
    ‣ “the knowledge”
    ‣ VBM
    (voxel-based morphometry)
    

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40. @neuroacademic a
    Learning and Plasticity | April 01, 2020
    The taxi driver study
    Plasticity through active training
    Maguire et al., 2000
    PNAS [link]
    ‣ Hippocampus
    ‣ “the knowledge”
    ‣ VBM
    (voxel-based morphometry)
    

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41. @neuroacademic a
    Learning and Plasticity | April 01, 2020
    The juggling study
    Plasticity through active training
    Scholz et al., 2000
    NatNeuro [link]
    supplementary material
    ‣ Juggling training
    juggling patterns (ranks)
    0: 2-ball pattern
    1: 1 cycle of 3-ball cascade
    2: 2 cycles
    3: 3 cycles
    4: 60 s 3-ball cascade.
    

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42. @neuroacademic a
    Learning and Plasticity | April 01, 2020
    The juggling study
    Plasticity through active training
    Scholz et al., 2000
    NatNeuro [link]
    ‣ Juggling training
    ‣ White matter changes
    (FA:= fractional anisotropy)
    ‣ Grey matter changes
    (VBM)
    

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43. @neuroacademic a
    Learning and Plasticity | April 01, 2020
    The toolmaking study
    Plasticity through active training
    Hecht et al., 2015
    BSAF [link]
    ‣ Paleolithic stone tool
    

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44. @neuroacademic a
    Learning and Plasticity | April 01, 2020
    The toolmaking study
    Plasticity through active training
    ‣ Paleolithic stone tool
    ‣ White matter changes
    (FA:= fractional anisotropy)
    Hecht et al., 2015
    BSAF [link]
    

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45. @neuroacademic a
    Learning and Plasticity | April 01, 2020
    The toolmaking study
    Plasticity through active training
    ‣ Paleolithic stone tool
    ‣ White matter changes
    (FA:= fractional anisotropy)
    ‣ Tractography
    Hecht et al., 2015
    BSAF [link]
    

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46. Recap
    Cortical function is changed due to various reasons!
    (echolocation, lost effector, regained effector, skill training…)
    Both grey matter and white matter changes have been observed
    Changes seem to be related to the intensity of training
    @neuroacademic a
    Learning and Plasticity | April 01, 2020
    

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47. part IV: can we “enhance” function?
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48. @neuroacademic a
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    The tDCS study
    Enhancing function, transient plasticity
    ‣ transcranial direct current stimulation
    Wikimedia
    

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49. @neuroacademic a
    Learning and Plasticity | April 01, 2020
    The tDCS study
    Enhancing function, transient plasticity
    ‣ transcranial direct current stimulation
    ‣ effect lasted ~30 minutes
    

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50. @neuroacademic a
    Learning and Plasticity | April 01, 2020
    Okay, but what does it do?!
    ¯\_(ツ)_/¯
    

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51. @neuroacademic a
    Learning and Plasticity | April 01, 2020
    Thank you!
    @neuroacademic
    suhas_vijayakumar@harvard.edu
    

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