Spatial and temporal properties of human rod vision in the achromat.

Abstract

SUMMARY1. The spatial and temporal properties of rod vision were measured for stimuli at and above the detection threshold in an achromat whose spectral sensitivity, dark adaptation, spatial and temporal thresholds and Stiles-Crawford effect suggest the presence of only a normally functioning rod system. The properties of rod and cone vision were compared at illuminances where their respective sensitivities were optimum.2. The threshold spatial sensitivity of the rod mechanism under optimum illumination (180 scotopic trolands) exhibits bandpass properties with a peak sensitivity of around 80 at 0 5 cycles/deg and a spatial acuity of 6-7 cycles/deg. The threshold temporal sensitivity also exhibits bandpass properties under these conditions with a peak sensitivity of around 80 at 5 Hz and a temporal acuity of 30 Hz. For stimuli of low spatial frequency (< 0 3 cycles/deg) and low temporal frequency, the threshold sensitivities of rod-and cone-mediated vision are identical.3. Rod-and cone-mediated vision display comparable spatial and temporal discrimination for targets ofequal suprathreshold contrast over the low to mid spatial and temporal range that they share. Rod-mediated discriminations fall below those of cone vision above 1 cycle/deg for spatial judgements and above 15 Hz for temporal judgements.4. The number of discriminable steps in spatial frequency and temporal frequency at threshold is similar for rod and cone vision over the spatio-temporal frequency range that they share. Over this range rod-and cone-mediated vision can discriminate four steps in spatial frequency and one step in temporal frequency.5. These results suggest that rod vision shows comparable spatio-temporal discrimination performance to cone vision and that it is subserved by at least five spatial and two temporal labelled detectors. The response of the highest spatial frequency filter subserving rod vision extends from 0 5 to 6 cycles/deg.

Spatial vision of the achromat: spatial frequency and orientation‐specific adaptation.

“…For scotopic luminance levels, contrast sensitivity of the achromat is similar to that of the trichromat, but as luminance is increased to photopic levels, the spatial acuity of the achromat rapidly deteriorates, whereas that of the trichromat increases to a value of 50-60 cycles/deg (Hess & Nordby, 1986a). A further study of the achromat's ability to discriminate spatial and temporal frequencies at threshold revealed that five discriminable steps in spatial frequency and one step in temporal frequency could be made by the achromat, and as such is comparable to the rod-based vision of the trichromat (Hess & Nordby, 1986b). These results and several other findings obtained in this subject are consistent with the notion that achromat vision reflects normal rod-based vision, and that the achromat's spatial performance can be completely accounted for by the coarse spatial organization of rod input to the retinal ganglion cells.…”

Speed, Spatial, and Temporal Tuning of Rod and Cone Vision in Mouse

“…At lower (scotopic) levels, sensitivity decreases for high spatial frequencies, and contrast sensitivity functions (CSFs) have a low-pass profile (humans, van Nes et al, 1967;cats, Pasternak and Merigan, 1981). The intensity-dependent changes in contrast sensitivity reflect the transition from rod to cone vision (Hess and Nordby, 1986).…”

Is the DeVries-Rose to Weber Transition Empirically Possible with Sine-Wave Gratings?

“…The source of the relationship between sensitivity to sinewave gratings and retinal illuminance seems to require a new theoretical justification. Hess and Nordby (1986b) and Figure 6 in Hess and Nordby (1986a) were digitally scanned at a resolution of 600 dots per inch and the digital versions of these figures were used to extract the coordinates of the data points plotted on them. The empirical data in Figure 1 of Hess and Nordby (1986b) were described by the function CSF(x) = 188 x 0.82 exp [-0.25 …”

“…These curves represent fits to data from Figure 1 of Hess and Nordby (1986b) and Figure 6 of Hess and Nordby (1986a), which come from the same normal subject. The empirical CSF was obtained at a reportedly optimal illuminance of 2000 scotopic td (optimal in that sensitivity did not increase significantly at higher illuminance levels) and the empirical acuity limit was obtained by determining the highest frequency that could be resolved at a 100% contrast at each illuminance.…”

“…The thick line on the base of the plot indicates the implied relationship between visual acuity (defined as the highest-frequency grating that can be resolved at a 100% contrast) and illuminance. (b) Sensitivity surface constrained to satisfy the empirical acuity versus illuminance (AVI) curve shown as a thick line on the base of the plot (from Figure 1 of Hess & Nordby, 1986b), the empirical ceiling CSF shown as a thick line on the surface at an illuminance of 2000 scotopic td (from Figure 6 of Hess & Nordby, 1986a), and the requirement that, at all frequencies, SVI curves increase with a slope of 0.5 until they reach the ceiling CSF. Note that these three constraints cannot be met simultaneously, as the ceiling CSF can only be reached at frequencies below 1 c/deg.…”