a typical retinal ganglion cell. [**(B)**]{} Responses of $N=160$ neurons to a $19.2\,{\rm s}$ naturalistic movie clip; dots indicate the times of action potentials from each neuron. In subsequent analyses these events are discretized into binary (spike/silence) variables in time slices of $\Delta\tau = 20\,{\rm ms}$. [**(C)**]{} 1000 most common binary patterns of activity across $N=160$ neurons, in order of their frequency. [**(D)**]{} Number of occurrences of each pattern, with labels for the total number of spikes in each pattern. \[fig1\]](fig1){width="\linewidth"}

An experimental example
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The vertebrate retina offers a unique system in which the activity of most of the neurons comprising a local circuit can be monitored simultaneously using multi–electrode array recordings. As described more fully in Ref [@tkacik+al_14a], we stimulated salamander retina with naturalistic grayscale movies of fish swimming in a tank (Fig \[fig1\]A), while recording from 100–200 retinal ganglion cells (RGCs), the output cells of the retina that in an intact animal project to the central brain; additional experiments used artificial stimulus ensembles, as described in Appendix \[methods\]. Sorting the raw data [@marre+al_12], we could reliably identify single spikes from 160 neurons whose activity passed our quality checks and was stable for the whole $\sim$2 hour duration 