Calculation of transfer impedance (Zc) was done as previously described (Jaffe et al, 1999). The following formula was used to compute average Zc,
Where Vsoma is the peak voltage at the soma, Isyn is peak current at the location of the synapse, Dsyn is synaptic density per μm-1 and (dseg x π x Lseg) is the segment cylinder surface μm-1. To generate synaptic current, we attached a bi-exponential conductance-based synapse model to the spine head with rise time τ1 of 0.2 ms, a decay of τ2 of 3 ms, a peak conductance density of 0.291 nS and a reversal potential of 0 mV to approximate the experimentally determined current amplitude and time course corresponding to unitary EPSP amplitude in the soma in the range of 0.2 - 0.8 mV (Popovic et al, 2015). Average density of excitatory synapse (D, synapse μm-2) was adjusted to 1 synapse 1 synapse μm-2, to match the data from high-resolution confocal microscopy measurement (human, 0.8 ± 0.2 spine μm-1, n = 5; rodent (rat), 0.8 ± 0.1 spine μm-1, n = 5).