| This thesis reports three studies on plasticity at the hippocampal CA3-CA1 synapse. First, using recordings from large populations of synapses, we explore the idea that bidirectional synaptic learning rules can be dissected into separate components describing LTP and LTD. By using inhibitors of kinases and phosphatases, and by saturating LTP and LTD, we characterize the activity dependencies of LTP and LTD in isolation. We show that a simple model with two states of strength can reproduce a common learning rule as well as generate a form of metaplasticity that explains several results from the literature. Second, using recordings from one or very few synapses in the same preparation, we show that LTP and LTD are initiated by switch-like, all-or-none transitions between extremes of strength. These rapidly saturating transitions are sufficient to explain the timecourse of plasticity across populations of synapses. Finally, we analyzed changes in success rate and potency at synapses during bidirectional plasticity, and find that both parameters change in a temporally coordinated manner. |
