Cover legend: Intensity-invariant discrimination seen in spike distances visualized with a spike distance matrix and multidimensional scaling (MDS) for 35 recording sites in songbird field L, an auditory structure. Distance matrices (each identifiable by the diagonal line of zero distance) were generated from computing all of the van Rossum distances between each pair of spike trains from one neuron. Larger distances are represented by brighter colors. Below each distance matrix is a scatter plot of the twodimensional MDS analysis. One bird song is shown as circles and another as triangles, and here bright colors indicate higher-intensity stimuli. The recordings are in reading order of decreasing invariance to intensity. The last 11 recordings are from sites that respond to the songs but show poor discrimination performance at all intensities tested. For more information, see the article by Billimoria et al. in this issue (pages 6304–6308).