Long-Term Plasticity of Glutamatergic Synaptic Transmission in the Cerebral Cortex

Experience modifies synapses in the brain. It is widely hypothesized that these changes are critically involved in fine-tuning sensory and motor systems, as well as in cognitive processes such as learning and memory. A major goal in neurobiology is to understand the cellular and biochemical mechanisms underlying synaptic modi. cations and to relate these to systems-level functions of the brain. In this chapter we discuss some of the processes that establish long-term, activity-dependent synaptic modi. cations in the hippocampus in vitro. Longlasting modi. cations in synaptic transmission-that is, "plasticity"-can be produced experimentally by the appropriate amounts of presynaptic and postsynaptic activities at many glutamatergic synapses in the central nervous system. The best-characterized forms of activity-dependent synaptic plasticity in the cortex are long-term potentiation (LTP) and long-term depression (LTD). In this chapter we discuss the experimental methodology, induction parameters, and expression mechanisms that result in LTP and LTD in vitro. The chapter ends with a brief discussion of how LTP and LTD might relate to experience-dependent plasticity in vivo.