Neural Mechanisms of Learning Memory Lesson 24 Neural
- Slides: 21
Neural Mechanisms of Learning & Memory Lesson 24
Neural Mechanism of Memory Short-term Memory l Change in neural activity l Reverberatory Circuits n Long-Term Memory l structural change in brain l Hebb Synapse l simultaneous activity in pre- & postsynaptic neurons ~ n
Neural Plasticity Nervous System is malleable l learning occurs l Structural changes at synapses n Changes in synaptic efficiency l Long-term potentiation (LTP) l Long-term depression (LTD) n Studied in hippocampus l and other places ~ n
Inducing LTP Stimulating electrode Presynaptic Neuron Record Postynaptic Neuron
Postsynaptic Potential Single elec. stimulation + -70 mv - 100 Hz. burst Single stim.
LTP Duration In humans: years n Experimentally-induced LTP l Strong, high frequency stimulation l 100 Hz n Intact animals l seconds - months n HC slice l 40 hrs ~ n
LTP: Molecular Mechanisms Presynaptic & Postsynaptic changes n HC: Glutamate l excitatory n 2 postsynaptic receptor subtypes l AMPA-R Na+ l NMDA-R Ca++ n Glu NT for both ~ n
NMDA Receptor N-methyl-D-aspartate l chemically-gated l voltage-gated n Activation requires l Membrane depolarization and l Glu bound to receptor~ n
Single Action Potential Glu AMPA-R l Na+ influx l depolarization n Glu NMDA-R l does not open l Mg++ blocks channel l no Ca++ into postsynaptic cell n Followed by more APs ~ n
Activation of NMDA-R Postsynaptic membrane depolarized l Mg++ dislodged l Glu binding opens channel n Ca++ influx post-synaptic changes l strengthens synapse ~ n
Ca++ Na+ AMPA G G G Mg NMDA
Ca++ Na+ AMPA G G G Mg NMDA
Na+ AMPA G Mg G Ca++ G NMDA
AMPA Ca++ Mg Na+ G G G NMDA
LTP: Postsynaptic Changes Receptor synthesis n More synapses n Shape of dendritic spines n Nitric Oxide synthesis ~ n
Before LTP Presynaptic Axon Terminal Dendritic Spine
After LTP Presynaptic Axon Terminal less Fodrin Less resistance Dendritic Spine
Nitric Oxide - NO Retrograde messenger l Hi conc. poisonous gas n Hi lipid solubility l storage? n Synthesis on demand l Ca++ NO synthase NO n Increases NT synthesis in presynaptic neuron l more released during AP ~ n
Glu NO G NO NOS Ca++ G G Ca++
Long-term Depression: Hippocampus Decreased synaptic efficiency l Forgetting? n Glutamamte-R l AMPA-R & NMDA-R n Stimulation pattern? l 1 Hz for 10 -15 min l Low Ca++ influx n Decrease # of AMPA-R l Weaker EPSPs ~ n
Hippocampus: LTP vs LTD Same receptors l Different stimulation frequency l Different Ca++ concentrations n LTD can reverse LTP n LTP can reverse LTD n Similar mechanisms in other areas l Not necessarily identical ~ n
- Auto associative memory
- Cuadro comparativo e-learning y b-learning
- Episodic memory vs semantic memory
- Implicit memory vs explicit memory
- Long term memory vs short term memory
- Internal memory and external memory
- Primary memory and secondary memory
- Memory swaping
- Which memory is the actual working memory?
- Virtual memory and cache memory
- Virtual memory in memory hierarchy consists of
- Eidetic memory vs iconic memory
- Shared vs distributed memory
- Least mean square algorithm in neural network
- Adaptive learning neural network
- Few shot learning with graph neural networks
- Terminator 2 neural net processor
- Neural networks and learning machines
- Cellular bases of learning and memory
- Learning and memory consumer behavior
- Wraml age range
- Learning is embedded in memory history and story