How to convert this code in vectorize form to be faster?

The code below is correct, but I want to vectorize it (and may convert to GPU) to increase the speed.

How can I convert it to vector form?

    RF = 4;     
    inhibatory = 0;    
    overlap=3;    
    gap = RF-overlap;    

    Image1 = rand(30,22); 
    Image2 = rand(27,19); 
    Image3 = rand(30,22); 

    for u=1:size(Image1,1)
        for v=1:size(Image1,2)
            sum_val=0;
            iLowMax=max(ceil((u-(receptiveFieldSize+inhibatory))/(gap-inhibatory)),1);
            iHighMax=min(floor((u-1)/(gap-inhibatory))+1, UpperLayerSize(1));
            jLowMax=max(ceil((v-(receptiveFieldSize+inhibatory))/(gap-inhibatory)),1);
            jHighMax = min(floor((v-1)/(gap-inhibatory))+1, UpperLayerSize(2));

            sum_sens = sum(sum(Image2(iLowMax:iHighMax,jLowMax:jHighMax)));
            sum_val = sum_sens(:,:) .* Image3(u,v);
            act_output = Image1(u,v);
            result(u,v) = de_activate_Mat(act_output,act_funct) .* sum_val;
        end
    end