Frequency histograms showing the timing of spikes relative to surface ridges (278 ms temporal period).

<p>The stimulus event time was recovered via ad-hoc observation of the spike data. Three key stages of run 2 are shown: 1) Top panel: the 30 s adaptation period; 2) middle panel: the first five top-ups; and 3) bottom panel: the last five top-ups. Shades give the rank order of the spikes after the onset of a given ridge.