POSTSYNAPTIC COMPLEX SPIKE BURSTING ENABLES THE INDUCTION OF LTP BY THETA-FREQUENCY SYNAPTIC STIMULATION

Long-term potentiation (LTP), a persistent enhancement of synaptic tra nsmission that may be involved in some forms of learning and memory, i s induced at excitatory synapses in the CA1 region of the hippocampus by coincident presynaptic and postsynaptic activity. Although action p otentials back-propagating into dendrites of hippocampal pyramidal cel ls provide sufficient postsynaptic activity to induce LTP under some i n vitro conditions, it is not known whether LTP can be induced by patt erns of postsynaptic action potential firing that occur in these cells in vivo. Here we report that a characteristic in vivo pattern of acti on potential generation in CA1 pyramidal cells known as the complex sp ike burst enables the induction of LTP during theta frequency synaptic stimulation in the CA1 region of hippocampal slices maintained in vit ro. Our results suggest that complex spike bursting may have an import ant role in synaptic processes involved in learning and memory formati on, perhaps by producing a highly sensitive postsynaptic state during which even low frequencies of presynaptic activity can induce LTP.