Untitled

Abstract

Contrast sensitivity (CS) is often used to assess spatial and temporal vision in animals. Conventional behavioral psychophysical techniques are both time and labor intensive, whereas measurement of CS functions by means of the pattern electroretinogram (PERG) is considerably more rapid and efficient. Are the two methods comparable, however? To answer this question, contrast-sensitivity functions were obtained using both the PERG and behavioral psychophysics in the same subjects, which were White Carneaux pigeons. The stimuli, in both methods, were phase-reversing, contrast-modulated sweeps of sinusoidal gratings. The PERG-CS functions were recorded via corneal electrodes and the behavioral data were collected using a modified staircase method that used moderate food deprivation and food reward. The results indicated that the PERG-CS functions had comparable bandwidth and peak spatial frequency to the behavioral CS functions. The PERG-CS functions, however, were lower on average than the behavioral curves by about 54%. The visual acuity of the two methods, as estimated from the high-frequency cutoff of the CS functions, differed by 37%. Both of these values are roughly consistent with the square root of 2 advantage of binocular viewing (behavioral method) over monocular viewing (PERG method). In addition, the peak spatial frequency showed a decrease of 0.125 c/deg with the PERG method and bandwidth was reduced by approximately 0.5 octave. These findings suggest that the PERG is an acceptable alternative to behavioral measurement of CS functions, especially in animal psychophysics, if one takes into account the underestimation of CS by the PERG method and the small changes in peak spatial frequency and bandwidth.

Neural correlates of stimulus spatial frequency-dependent contrast detection

“…Psychophysical investigations on human and vertebrate animals have shown that visual contrast sensitivity depends strongly on stimulus spatial frequency (SF) (Bisti and Maffei, 1974; Uhlrich et al, 1981; Hodos et al, 2002; Sowden et al, 2002; Jarvis and Wathes, 2008). Across species, the CSFs have a similar inverted-U shape with a single peak, although the spatial frequency domain varies in different species and the peak of the CSF shifts slightly with stimulus size and luminance (Uhlrich et al, 1981; Jarvis and Wathes, 2008).…”

The pattern ERG in chicks – Stimulus dependence and optic nerve section

“…On the other hand, the OKN response also involves midbrain processing. Hodos et al (2002) found that the contrast sensitivity function derived from pERG recordings in pigeons had a similar bandwidth and peak spatial frequency to that derived from psychophysical testing, but was lower by approximately 54%. The high-frequency cut-off derived from pERG recordings was also lower than that obtained by psychophysical testing, by 37% (Hodos, Ghim, Potocki, Fields & Storm, 2002).…”

“…Hodos et al (2002) found that the contrast sensitivity function derived from pERG recordings in pigeons had a similar bandwidth and peak spatial frequency to that derived from psychophysical testing, but was lower by approximately 54%. The high-frequency cut-off derived from pERG recordings was also lower than that obtained by psychophysical testing, by 37% (Hodos, Ghim, Potocki, Fields & Storm, 2002). In another study involving chickens, the pERG was used to measure and subsequently correct for refractive errors; peak pERG amplitudes were obtained with +6 to +10 D trial lenses interposed, corresponding to refractive errors of +3 to +7 D after accounting for the working distance (Kruse, Schwahn, Gekeler, Weiss & Schaeffel, 1999).…”

The determination of dark adaptation time using electroretinography in conscious Miniature Schnauzer dogs

“…The ERG is a reliable diagnostic procedure for the early detection of affected dogs before the ophthalmoscopical abnormality becomes apparent [39]. The ERG is also used to diagnose inherited and nutritional photoreceptor degenerations in cats [22,36] as well as retinal disorders in a number of other species, uncluding chickens [5,34], pigeons [9], rabbits [11,33,35], sheep [12], and monkeys [4,8]. …”

“…Even though most animals need to be under general anesthesia to properly measure ERG, various sedatives and anesthetics have been documented to affect ERG responses [10,15,16,27,38]. It is also important to be aware of species variation as to the suitable types and dose levels of anesthetics [9,13,33,34,36]. …”