(A) Scatterplots of spike amplitudes on two of the four recording channels (ch1, ch4) from a tetrode different from the one shown in the main Figure 4, but also implanted in an animal with epilepsy. Each colored cluster corresponds to spikes from one cell. In this projection (peaks from ch1, peaks from ch4), the cluster denoted by dark blue was clearly distinct from the noise and far from other clusters (cells), therefore boundaries were drawn around the cluster to define it. The gray dots within these boundaries were excluded by boundaries set in a different projection. All boundary definitions were assigned manually, i.e. we did not employ automated spike sorting. Note, the relationship of spike clusters to other cells and the noise did not change for a cluster over the recording session. (B) For each cluster shown in (A), the waveforms recorded on each tetrode channel (1 – 4) are shown for each behavioral period, with average waveforms superimposed in white. Dotted lines are drawn to mark the height of the average waveform at its largest in Rest 1, and extended so that a by-eye comparison can be made across the behavioral periods. Although different firing rates can be observed during different behavioral periods, the relationship of the spike amplitude across channels remains constant. This consistency is an indicator of a stable tetrode position in relation to the cell layer. (C) L-Ratio was the same for clusters recorded in control (n = 203; median, IQR, 0.0023, 0.0009–0.0076) and in epileptic animals (n = 795; median, IQR, 0.0025, 0.0009 -. 0073) (p = 0.54, Wilcoxon Rank Sum Test, z-value = −0.6). (D) Isolation distance was large in control and epileptic animals (98.7% of clusters had isolation distance > 10 cm). In epileptic animals, the isolation distance (n = 795; median, IQR, 48.6, 32.6–78.3) was larger than in controls (n = 203; median, IQR, 24.7, 17.1–43.3) (p = 5.1 * 10−29, Wilcoxon Rank Sum Test, z-value = −11.2). (E) for each cell, the channel that recorded the largest waveform in the first session (e.g., channel 4 for cluster one shown in (B)) was selected, and the average waveform is plotted for Rest one versus Rest 2. Note that all cells lie close to the identity line, confirming that waveforms were stable across the entire recording. (F) Changes in waveform amplitude from the first to the second rest session were the same for cells recorded in control (n = 35; median, IQR, 0.7–1.6 – 9.1) and epileptic animals (n = 177; median, IQR, 1.8,–4.1 – 10.8)(not significant, Wilcoxon Rank Sum Test, p = 0.57, z-value = −0.57). The results in (C) – (F) indicate that cluster quality does not differ significantly between control and epileptic animals, and when there is a significant difference it is toward higher cluster quality in epileptic animals.