T
 Duration of epoch  Chosen by experimenter 
N(T)  Number of spikes from the output neuron in epoch, T
 Measured experimentally 
〈N(T)〉  Mean spike count from the output neuron; also read as the expectation of the spike count  Measured experimentally using repetitions of identical stimuli 
Var[N(T)]  Variance of spike count from the output neuron  Measured experimentally using repetitions of identical stimuli 
n
_{i}(T)  Number of spikes from the i
^{th} input neuron in epoch, T
 Unknown; we assume that input and output spike counts are the same, on average: 〈N(T)〉 = 〈n
_{i}(T)〉 
λ  Intended spike rate of the output neuron; result of the neural computation  Theoretical quantity; assumed to be constant over the epoch, so 〈N(T)〉 = 〈λT〉; this assumption can be relaxed, however; then,

C
_{VISI}
 Coefficient of variation of ISI distribution, which characterizes a renewal process: ς_{ISI}/μ_{ISI}
 Theoretical quantity; can only be measured when λ is constant; for the renewal processes considered here C
_{VISI} is the same for all possible values of λ 
 Average correlation coefficient between pairs of input neurons  Estimated experimentally from pairwise recording, using repetitions of identical stimuli 