I have two heatmaps of a 3D model of the brain, with the color of each pixel being an intensity of the response to a stimuli, and I want to get a metric of how "alike" those to heatmaps are, what can I use? In this picture you can see an example (2D projection) of a heatmap I want to analyze

[![Here's an example of a heatmap][1]][1]


  [1]: https://i.sstatic.net/ZhIgi.png