1 / 26

synaptic plasticity

DENT/OBHS 131 Neuroscience. synaptic plasticity. 2009. Learning objectives. Understand the properties of long-term potentiation (LTP) that define it as a model of experience-dependent synaptic plasticity

aline-baldwin
Download Presentation

synaptic plasticity

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. DENT/OBHS 131Neuroscience synaptic plasticity 2009

  2. Learning objectives • Understand the properties of long-term potentiation (LTP) that define it as a model of experience-dependent synaptic plasticity • Discuss the characteristics that make NMDA receptors coincident detectors cable of initiating associative information storage (Pavlov’s dog) • Describe the relationship between NMDA receptors, LTP and behavioral memory

  3. learning & memory in taxi drivers • PET study during recall of London route (Maguire et al, 1997)

  4. Papez circuit / loop

  5. place cells / maps • some pyramidal cells in the hippocampus (and other parts of Papez circuit) have preferred spatial orientations & place maps (O’Keefe & Dostrovsky, 1971)

  6. Hebbian learning….in theory • longer term plasticity • Hebbian learning • Hebb (1949) hypothesized that “ if one neuron frequently takes part in exciting another, some growth process or metabolic change takes place in one or both cells and the strength of their connection increases ”

  7. Synapses are plastic • synapses “remember” previous activity • short-term, e.g. post-tetanic potentiation at the nmj control motor neuron motor neuron pre nmj muscle muscle time post

  8. Can synaptic plasticity explain learning? • CS (neutral) - no response • US - UR • After pairing: • CS - CR

  9. Learning Objective #1 • Understand the properties of long-term potentiation (LTP) that define it as a model of experience-dependent synaptic plasticity

  10. Long-term potentiation (LTP) • first demonstration of LTP • high-frequency train • rapid induction • lasts weeks in vivo after before amplitude time (hrs) Bliss & Lomo (1973)

  11. properties of LTP

  12. Learning Objective #2 • Discuss the characteristics that make NMDA receptors coincident detectors cable of initiating associative information storage (Pavlov’s dog)

  13. cellular mechanisms underlying LTP • induction • maintenance

  14. excitatory synaptic transmission • NMDA vs non-NMDA • synaptic transmission AP5 control AP5

  15. LTP depends specifically on NMDA receptor activation • AP5 prevents high frequency-induced LTP (Collingridge et al, 1983)

  16. out +++ Mg+ Mg+ - - - in what is special about NMDA receptors? • voltage-gated channels: voltage • ligand-gated channels: transmitter • NMDA receptors: both + - +

  17. NMDA receptor: a molecular switch • co-incidence detector • requires both presynaptic activity (glutamate) and postsynaptic depolarization (relieve Mg block) • satisfies Hebbian co-incidence rules • explains LTP properties:

  18. how does the NMDA receptorcause a change in synaptic strength?

  19. synaptic transmission is unreliable • increased transmitter release • altered or new receptors • new synapses

  20. hippocampal “integrated circuit” Johnson & Wu (1995)

  21. associative pattern storage from McNaughton & Morris (1987)

  22. Learning Objective #3 • Describe the relationship between NMDA receptors, LTP and behavioral memory

  23. NMDA receptor-dependent learning spatial memory task visual task “Morris” water maze Morris et al (1990)

  24. LTP and learning • saturation of LTP prevents learning a new spatial task • new learning can occur after LTP decay LTP decay Castro et al (1989)

  25. diffuse storage in cortex? • computational theories • e.g., Marr (1970’s) • sensory input to neocortex • stored by association • repetition - association • partial pattern recall

More Related