May 2011
Volume 52, Issue 6
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Letters to the Editor  |   May 2011
Frequency-Doubling Technology and Parasol Cells
Author Affiliations & Notes
  • Ted Maddess
    ARC Centre of Excellence in Vision Science, Centre for Visual Sciences, Research School of Biology, Australian National University, Canberra, Australia.
Investigative Ophthalmology & Visual Science May 2011, Vol.52, 3759. doi:10.1167/iovs.11-7405
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      Ted Maddess; Frequency-Doubling Technology and Parasol Cells. Invest. Ophthalmol. Vis. Sci. 2011;52(6):3759. doi: 10.1167/iovs.11-7405.

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Swanson et al. 1 have reported an excellent study of the responses of macaque retinal ganglion cells (RGCs) to Goldmann size III stimuli and contrast-modulated grating stimuli. They estimated the contrast gain of the initial rising phase of the contrast response function of the cells. From the physiology shown, the extracellular recorded RGCs are parasol and midget RGCs and are referred to in terms of their lateral geniculate nucleus (LGN) targets as M- and P-cells, respectively. The ratios of the gains for the two RGC types indicated that size III stimuli have higher relative gain for M-cells than the grating stimuli. Given that the gratings are described as displaying the frequency-doubling (FD) illusion, this may be taken to mean that the stimuli of the FDT perimeter do not preferentially stimulate a pathway that is useful for glaucoma diagnosis. 
The original idea of FD stimuli was that they might stimulate nonlinear Y-cells. 2 Such cells had been reported from extracellular recordings of the M-layers of the primate LGN and so were dubbed My-cells. No anatomic substrate was known. The concept was that if humans were like all other mammals, Y-like cells should be larger and less densely overlapping than their X-like (parasol cell) partners. Cell losses could be more easily detected if the lower densities meant few of these Y-cells saw each point in visual space. 23 Recently, anatomic substrates for primate Y-cells have been reported: the smooth monostratified cells. 4,5 These cells match the proposed requirements for cell density but otherwise receive the same inputs as the smaller, denser parasol cells and are anatomically similar to cat α-cells, the original Y-cells. Thus, whether parasol cells prefer size III stimuli to gratings may say nothing about FDT perimetry. Parasol cells projecting to the superior colliculus have also been reported to have Y-like responses. 6 Swanson et al. 1 do not cite these recent papers on primate Y-cells. 
Another caveat is that the grating stimuli used would probably not display the FD illusion. A recent examination of the probability of humans reporting FD at 8 parts of the visual field indicates that subjects would have only a 50% chance of reporting an FD percept for the grating stimuli used. 7 That study also indicated two possible independent sources of the FD illusion at every point in the visual field. So perhaps FD has multiple causes, some of which are useful for visual field assessment. By contrast, small size II stimuli may promote test–retest variability. 8  
Footnotes
 Supported by Australian Research Council (ARC) Grant CEO 561903.
Footnotes
 Disclosure: T. Maddess, P
References
Swanson WH Sun H Lee BB Cao D . Responses of primate retinal ganglion cells to perimetric stimuli. Invest Ophthalmol Vis Sci. 2011;52:764–771. [CrossRef] [PubMed]
Maddess T Henry GH . Nonlinear visual responses and visual deficits in ocular hypertensive and glaucoma subjects. Clin Vis Sci. 1992;7:371–383.
Maddess T Hemmi JM James AC . Evidence for spatial aliasing effects in the Y-like cells of the magnocellular visual pathway. Vision Res. 1998;38:1843–1859. [CrossRef] [PubMed]
Crook JD Peterson BB Packer OS . The smooth monostratified ganglion cell: evidence for spatial diversity in the Y-cell pathway to the lateral geniculate nucleus and superior colliculus in the macaque monkey. J Neurosci. 2008;28:12654–12671. [CrossRef] [PubMed]
Petrusca D Grivich MI Sher A . Identification and characterization of a Y-like primate retinal ganglion cell type. J Neurosci. 2007;27:11019–11027. [CrossRef] [PubMed]
Crook JD Peterson BB Packer OS Robinson FR Troy JB Dacey DM . Y-cell receptive field and collicular projection of parasol ganglion cells in macaque monkey retina. J Neurosci. 2008;28:11277–11291. [CrossRef] [PubMed]
Rosli Y Maddess T Bedford SM . Low spatial frequency channels and the spatial frequency doubling illusion. Invest Ophthalmol Vis Sci. 2009;50:1956–1963. [CrossRef] [PubMed]
Maddess T . The influence of sampling errors on test–retest variability in perimetry. Invest Ophthalmol Vis Sci. 2011;52:1014–1022. [CrossRef] [PubMed]
Copyright © Association for Research in Vision and Ophthalmology
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