Does the retina respond slower in the center?

Yes.  The center of the eye has a high concentration of "cones" (color
receptors), which are relatively slow.  As you get into the peripheral
areas, the concentration of "rods" (B&W receptors) goes up.  These are
faster and more sensitive to absolute light levels.  This is also why you
can see dim stars/commets/etc better when you're not looking directly at
them.

BillW