Direct visualisation of the PCC.
The relative contribution of each voxel’s colocalisation intensity qi to the correlation coefficient is determined by the individual terms of the summation in the numerator of Eq 3. With x and y axes representing the respective intensities of the two fluorescence channels, we assume a maximum intensity of 255, a mean intensity of 127 and a minimum intensity of 0 for each channel. A) The relative contribution to the PCC is shown for all possible values of qi, with green representing a positive and red representing a negative contribution. B) The colour that would be assigned to each voxel with intensity qi according to the nMDP colourmap [11], calculated using Eq 1. Note that, at the means, there are sudden changes in the colour assigned by nMDP. C) How nMDP labels each colocalisation intensity qi as colocalised or not-colocalised based on its position relative the means. A colocalisation intensity distribution commonly seen for strongly correlated fluorescence channels is shown, with darker shades indicating strong positive correlation and lighter shades indicating weaker positive correlation [3]. The areas marked in red correspond to positively correlated colocalisation that are indicated as negatively correlated when using nMDP.
