19
for Vc=-104/-94 mV.
For most recordings, equation 2.2 was sufficient to estimate the variance in the current
[4,53,66].
1 n
σ2W = ΛFTT∑⅛W--rW)2
(2.2)
where ⅛(∕) is the trace and the mean, ʃ(t) is defined by:
An isochrone is defined as a cross section of the ensemble of traces with respect to one
point in time:
{ix(τ) : 1 ≤ x ≤ N}
where τ is a particular time of interest that defines the isochrone.
However, for the whole cell NSFA estimates and some cell attached NSFA estimates, a
method that could account for the time dependent ’’rundown” in the current traces in the
ensemble was necessary [4]. Rundown is noticeable when the amplitude of HCN activation
current or cell capacitance drifts over time, and successive traces in the ensemble are then
no longer stationary with respect to their isochrone. This change could be due to a washout
of cell cytoplasm, a change in membrane capacitance, or deactivation of some HCN chan-
nels over time. To minimize the effect of rundown, we calculated the variance from the
differences between the traces, as in equation 2.3 [4, 66].