vis.revcorr.gauss3fit

  ERROR: this function is not working
  GAUSSSPOTFIT - Fit a 2d gaussian to data

   [MU,C,AMP,FIT_RESPONSES] = vlt.fit.gaussspotfit(X, Y, T, RESPONSE, ON)

   Fits a 3d gaussian PDF to responses to circle stimulation at different positions.

   INPUTS:
     X, Y, and T specify the mesh grid of the responses.
     RESPONSE is an size(X,1) x size(Y,2) x size(T,3) matrix of responses
     ON is a boolean that indicates response on or response off is going to
     be calculated.
   OUTPUTS:
     MU - The mean of the best-fit gaussian PDF, in X and Y
     C  - The covariance matrix of the best-fit gaussian PDF
     AMP - The amplitude of the response for each circle size.
     FIT_RESPONSES - the fit responses