Synaptic Modifications in Cultured Hippocampal Neurons: Dependence on Spike Timing, Synaptic Strength, and Postsynaptic Cell Type

Abstract

In cultures of dissociated rat hippocampal neurons, persistent potentiation and depression of glutamatergic synapses were induced by correlated spiking of presynaptic and postsynaptic neurons. The relative timing between the presynaptic and postsynaptic spiking determined the direction and the extent of synaptic changes. Repetitive postsynaptic spiking within a time window of 20 msec after presynaptic activation resulted in long-term potentiation (LTP), whereas postsynaptic spiking within a window of 20 msec before the repetitive presynaptic activation led to long-term depression (LTD). Significant LTP occurred only at synapses with relatively low initial strength, whereas the extent of LTD did not show obvious dependence on the initial synaptic strength. Both LTP and LTD depended on the activation of NMDA receptors and were absent in cases in which the postsynaptic neurons were GABAergic in nature. Blockade of L-type calcium channels with nimodipine abolished the induction of LTD and reduced the extent of LTP. These results underscore the importance of precise spike timing, synaptic strength, and postsynaptic cell type in the activity-induced modification of central synapses and suggest that Hebb's rule may need to incorporate a quantitative consideration of spike timing that reflects the narrow and asymmetric window for the induction of synaptic modification.

Self-organization in the olfactory system: one shot odor recognition in insects

“…The parameters are c 10 = 10 5 , c 01 = 20, c 11 = 5, τ l = 25 ms, τ shift = 10 ms, τ decay = 10 5 ms, and g 0 = 0.125 nS if not stated otherwise. Because of the large value of c 01 the synaptic strength is only depressed if post-synaptic spikes are not paired with presynaptic ones, consistent with experimental observations [36,37,28,30] and biophysical models [1,52].…”

Complexity of calcium signaling in synaptic spines

“…2). This finding is robust and has been found in neurons from the hippocampus using acute, (23) organotypic slices, (31) or dissociated cell culture, (32) and in layers V (33,34) and II/III (35) of the cerebral cortex, as well as in vivo preparations using cat (36,37) and Xenopus (38) visual systems. The temporal window permissive for LTP induction is 10-20 ms (milliseconds) whereas the window in which the presynaptic spike can follow the postsynaptic spike in order to induce LTD ranges from 20 to 100 ms in different preparations.…”

Time scales of memory, learning, and plasticity

“…An influence of the temporal signal order on plasticity was proposed by Gerstner et al (1996) and experimentally confirmed by Markram et al (1997), Magee and Johnston (1997), and Bi and Poo (1998) [although Levy and Steward (1983) had already discovered this phenomenon]. These authors found that for the expression of LTP or LTD not only the activity as such matters but also the timing.…”

“…Neural systems have several different mechanisms (Bi and Poo 1998;Turrigiano et al 1998;Royer and Paré 2003;Zhou et al 2003), which are also used in theoretical studies (Rochester et al 1956;Bienenstock et al 1982;Riedel and Schild 1992;Van Rossum et al 2000) to avoid these runaway dynamics.…”