(a) Tonotopic organization of a tilted (30° from D-V axis) coronal slice of A1, over four consecutive days. A mask has been applied to focus on the tonotopic area. Scale bar: 1 mm. (b) PCA analysis over the averaged response for each frequency and all the voxels highlighted in (a), for the single slice designed by an arrowhead. Plotted here as plain lines are the mean hemodynamic response (starting from the center at sound onset, and increasing in all five directions), superimposed on the density of the peak responses at the single trial levels (N = 75 trials per frequency). Each frequency is designed by its color, and the intensity of the colored shading shows the density of trials displaying a response at this location. We can clearly see a separation of the different frequencies on a single-trial basis (reflected in the decoding analysis). (c) Decoding accuracy as a function of depth (slow speed vessels only). Left: different depth for the specific slice. Right: decoding accuracy peaks again around −400 µm, thus confirming that this effect could be observable on a single-slice basis. (d) Similar analysis as in (b), but this time the PCA is computed over the mean responses averaged over trials and daily sessions. The density map shows here the density of the peak responses at a single session level, averaged over all trials. The fact that densities are quite centered around the mean response suggests that all sessions have similar patterns of activity, and that tonotopic organization is relatively stable. (e) Decoding analysis as a function of depth, over days. Upper panel: mean decoding accuracy for all sessions (all blood vessel speeds). Heatmap shows the dependence of decoding accuracy on cortical depth. Stars show the peak of accuracy for each day, which is summed up in the right histogram showing the distribution of peak accuracy position. It clearly peaks around −300/400 µm, thus confirming our results over multiple recordings in the same slice. The blue arrowhead indicates the position of the slice shown in (c). Far right: mean decoding accuracy as a function of depth, averaged over days. The heterogeneity in decoding accuracy can be due to many parameters, such as small sample size and real biological variations.