Visual inspection of traces reveals the difficulty of the problem.

<p>First column: templates of spiking neurons. Second to fourth columns: responses of one (<b>A</b>) or two (<b>B</b>) cells to electrical stimulation at increasing stimulation amplitudes as recorded in the stimulating electrode (first rows) or a neighboring, non-stimulating electrode (third rows). If the stimulation artifact is known (gray traces) it can be subtracted from raw traces to produce a baseline (second and fourth rows) amenable for template matching: traces with spike(s) (colored) match, on each electrode, either a translation of a template (<b>A</b> and <b>B</b>) or the sum of different translations of two or more templates (<b>B</b>). As reflected by the activation curves (fifth column) for strong enough stimuli spiking occurs with probability close to one, consistent with the absence of black traces in the rightmost columns.