Coincidence detection of synaptic inputs is facilitated at the distal dendrites after long-term potentiation induction

Two major aspects of dendritic integration, coincidence detection and temporal integration, depend critically on the spatial and temporal properties of the dendritic summation of synaptic inputs. Neuronal activity capable of inducing synaptic long-term potentiation (LTP) leads to increased linearity of the spatial summation of synchronous EPSPs. Whether such activity can also modulate the temporal summation of EPSPs is unknown. In the present study, we examined the linearity of the summation of EPSPs spaced by different time intervals in hippocampal CA1 pyramidal neurons, before and after LTP induction. We found that LTP induction resulted in an increased linearity of summation of the potentiated input with another synchronous or asynchronous input, with a striking dendritic location specific selectivity for the timing of the summed inputs. At distal dendrites, LTP induction led to an increased linearity of summation only for EPSPs arriving within 5 ms, thus favoring the summation of coincident inputs. In contrast, LTP induction at proximal dendrites increased the linearity of summation for EPSPs arriving within a time window of > 20 ms. Furthermore, for synaptic inputs at the distal dendrite, enhanced spiking output after LTP induction was observed only for coincidently summed EPSPs, suggesting facilitated coincidence detection. In contrast, for proximal inputs, enhanced spiking output after LTP induction occurred for EPSPs arriving within a broader time window of similar to 20 ms, favoring temporal integration. Such dendritic location-dependent differential modulation of coincidence detection and temporal integration by neuronal activity represents a form of activity-dependent and domain-specific plasticity in the function of dendritic information processing.