EN
We wish to understand plasticity mechanisms in a context designed to approximate the stimuli and synaptic input in vivo. While plasticity in the mouse hippocampal slice preparation has been extensively studied, the lack of background activity is a major difference between slice and in-vivo contexts. We approximated steady as well as rhythmic background activity through optically-delivered background stimulus. EPSPs were recorded from CA1 cells while optically stimulating the CA3 region of CA3-cre mice injected with ChannlelRhodopsin2(ChR2)-lox virus. Using optical stimuli makes the STDP and background activity specific to the CA3-CA1 pathway. It further allows us to titrate the number of inputs by scaling spot size and intensity and to present rapidly varying patterned stimuli. We calibrated the optical patterns to deliver background activity to CA1 neurons that approximated in vivo observations. In this talk I will present our results on spike-timing and theta-burst stimuli in the presence of background activity. I will also indicate how the optical stimulus protocol can be adapted to obtain estimates of heterosynaptic plasticity for each of these protocols, across the target cell.