Emergence of phase invariance.

<p>The two top rows correspond to the most phase invariant SFA units, the bottom row to a unit whose response is phase dependent. Phase dependence of the linear and the quadratic term as well as their sum is depicted in the first column. The second column shows the two ends of the eigenvalue spectrum of <b>H</b>. Eigenvalues are sorted from highest to lowest, then their absolute values are plotted. Columns three and five show the eigenvectors that belong to the four largest, respectively smallest, eigenvalues, plotted as images. Columns four and six show the corresponding Fourier amplitude spectra. The last column shows the linear component of the quadratic form plotted as an image.</p>