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Aliasing in peripheral vision for flickering gratings under different levels of illumination
1Vision Science Research Group, University of Ulster at Coleraine, School of Biomedical Sciences, Coleraine, Co., Londonderry, N. Ireland, United Kingdom. fa.ennis@ulst.ac.uk
Purpose:
To assess how far retinal illumination can be reduced for sine-wave gratings phase reversing at different temporal frequencies in peripheral vision, while maintaining sampling limited resolution acuity performance, as evidenced by an aliasing zone between detection and resolution.
Methods:
Computer generated sine wave gratings were presented with flicker rates from 0 to 40 Hz under retinal illumination levels of 3.5 to -0.5 log trolands. Resolution and detection thresholds were measured at 30 degrees in the horizontal temporal field using a spatial and temporal 2AFC paradigm respectively.
Results:
At high illumination levels, detection acuity is higher than resolution acuity between 0 and 40 Hz indicating that resolution is sampling limited. As illumination level decreases the aliasing zone becomes narrower, especially at high temporal frequency until it disappears completely at 0.5 log trolands.
Conclusions:
Peripheral resolution acuity ceases to be sampling limited below 1.5 log trolands for low temporal frequency gratings and at higher levels for high temporal frequency gratings. Sampling limited acuity was recorded for high frequency gratings under higher illumination levels which could be mediated by the M cells alone, but this is not the case for the lower levels of illumination.