PSY 3061 1st Edition Lecture 18Outline of Last Lecture I. Parkinson’sII. Huntington’sIII. Learning and memoryIV. HMOutline of Current Lecture V. Memory formation in hippocampusVI. Long term potentiationVII. Long term results of LTPCurrent LectureI. Memory formation in hippocampusa. One proposed mechanism of how learning occurs is called long-term potentiation (LTP)b. When certain synapses are used repeatedly, and produce action potentials in the post-synaptic neuron, the connection between pre and post-synaptic neurons may become strongerc. Study on hippocampus cells of rats demonstrating how repeated stimulation (cells firing together) begets long term changes (cells “wiring” together)d. Keep in mind, this is a multiple-unit extracellular recording we are listening to the post-synaptic potentialof many neuronsII. Long term potentiationa. With low-frequency (rare) electrical pulses, the “population spike” (EPSP of many neurons) has a baseline levelb. Record multi-unit extracellular potentialc. With long bursts of high-frequency electrical stimulation, the post-synaptic neuron fires repeatedlyd. Induction: the process of “training” two neurons to fire together via LTPe. The result: many action potentials in the post synaptic neuron f. Stimulate the same pathway with the same low-frequency pulses as in step 1, the post synaptic response has increased g. LTP can last for minutes to weeks post-synapticpotentials with each stimulationh. Two ionotropic glutamatergic receptorsi. AMPA- ligand gated channelii. NMDA- voltage and ligand gated channel (polarized/hyperpolarized) conditions, a magnesium blocks calcium influxi. LTP creates a surplus of intracellular calcium ions that caninduce changes in protein expressionj. LTP can induce protein synthesis that generates new dendritic spines, to enhance connections between presynaptic axons and postsynaptic dendritesIII. Long term results of LTPa. LTP can induce long-term changes in the structure (more receptor proteins) and functional (enhanced vesicle release) relationship between two neuronsb. Memory and LTP occur on similar time scalesc. Blocking NMDA receptors impairs memory formationd. Training animals to do something increases LTP in their
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