The spatial frequency gap between the two curves grows increasingly larger as the target is moved further into the periphery and there can be an order of magnitude difference in cutoff spatial frequencies for these two psychophysical tasks.

When we first published these results a decade ago, they were controversial and difficult for others to accept for a couple of reasons. First, a detection cutoff of 30 cyc/deg in the periphery is outrageously high, and the more skeptical members of the community suspected the results might be due to some sort of artifact in the stimulus. The results also seemed to be at odds with the commonly accepted notion that visual receptive fields of retinal bipolar cells and ganglion cells were much too large in the periphery to permit the detection of such fine fringes. Indeed, cutoff frequency for detecting fringes is so high that psychophysical performance appears to be supported by receptive fields no larger than single cones photoreceptors, which are about 2 arc minutes in diameter in the mid-peripheral retina.

At that time there was little anatomical or physiological evidence to suggest that bipoar cells or ganglion cells in the mid periphery might have receptive field centers served by a single cone. Subsequently our anatomical colleagues have shown that individual midget bipolar cells and midget ganglion cells may indeed have receptive fields the size of single cones in the parafovea, and perhaps even into the mid-periphery.

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WWWaveTM 1996
World Wide Web automated virtual environment TM 1996
Kevin Haggerty, Indiana University.