Figure 3.   Two examples of classical receptive fields determined by spike triggered (combined for ON and OFF responses) averages of the spatial location of flashed bars.  A circle was then fit to the 50% response rate of the Gaussian curve that fit the CRF.  The region inside this circle (solid line) represents approximately 75% of the action potentials generated in response to flashed bars.  The dashed line represents 3X the CRF.  Moves were presented either as 1X, 3X or as an annulus (3X minus 1X).