We present an efficient computational method for estimating the mean and va
riance of interspike intervals defined by the timing of spikes in typical o
rbits of one-dimensional neuronal maps. This is equivalent to finding the m
ean and variance of return times of orbits to particular regions of phase s
pace. Rather than computing estimates directly from time series, the system
is modelled as a finite state Markov chain to extract stationary behaviour
in the form of invariant measures and average absorption times. Ergodic-th
eoretic formulae are then applied to produce the estimates without the need
to generate orbits directly. The approach may be applied to both determini
stic and randomly forced systems.