Figure 4

Behavior of the three variables accounting for the predictive value of FLEYE statistical model. Values of the three statistical model variables obtained in healthy (WT) and degenerated (gmr > SCA1) fly eye samples (n = 35/genotype). (A) LOGNNVAR variable operates over the whole ROI (grid-cell independent). The nearest neighbor distances are expected to be more similar to each other in a WT eye than in a degenerated one, which has lost regularity and hence distances display a higher variance. (B) The variable DISTM for a grid cell (a representative pair is enlarged and shown in gray in the grid) is calculated as the mean difference between the centroid (the center point of the cell, marked as the intersection of dashed lines) and the maxima center of mass (the brightness-weighted average of the x and y coordinates of all pixels in the image or selection, marked with asterisks). A WT eye is expected to have a more regular distribution of maxima in a cell than a degenerated one, thus resulting in a mass center value closer to the centroid (lower difference output). (C) The variable DISTSKEW for a grid cell represents an asymmetry measure of the distance between the centroid and mass center (third spatial moment). As low values of DIST are more frequent in WT, a right-tailed distribution is expected, resulting in a positive skew value.