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PubMed2001

Behavioural assessment of visual acuity in bumblebees (Bombus impatiens).

The present study used previously developed techniques to measure resolution acuity in bumblebees (Bombus impatiens). Bees were required to discriminate between horizontal and vertical gratings in a Y-maze apparatus. The gratings had a mean luminance of 9 cd m(-)(2) and a Michelson contrast of 84 %. For different bees, either the horizontal or vertical grating was rewarded. Rewarded gratings were associated with a sucrose and water solution (30 % sucrose by volume) and unrewarded gratings with plain water. Acuity estimates were established at several different viewing distances over several sessions using a method of constant stimuli. Visual acuity functions were generated from the performance data, and acuity thresholds were interpolated at a performance level of 65 % correct. When corrected for viewing distance, best angular acuity obtained for horizontal and vertical gratings was 0.35 and 0.36 cycles degree(-)(1), respectively. These results are compared with those of the honeybee and discussed in the context of the bumblebee's foraging behaviour.

Animals↗
PubMed1985

Visual acuity of neurones in the cat lateral suprasylvian cortex.

The spatial acuity was measured for cells of the posteromedial lateral suprasylvian area (PMLS) of the cat. Acuities were found to be 2 cycles/degree (15 mins arc) at best, and 1 cycle/degree (30 mins arc) on average. Both best acuity and average acuity remained constant with receptive field eccentricity within 20 degrees of the area centralis, and then fell gradually with eccentricity. Acuity was good, given receptive field size, and was not correlated with receptive field size. Comparisons are drawn with other visual structures.

Animals↗
PubMed2000

Experience-dependent plasticity of visual acuity in rats.

Rats have become a popular model for investigating the mechanisms underlying ocular dominance plasticity; however, no quantitative assessment of the effects of visual deprivation on behavioural acuity has been reported in this species. We measured the spatial acuity of monocularly and binocularly deprived rats with a visual discrimination task. The average spatial acuity of normal rats and rats deprived of vision after postnatal day 40 was approximately 1 cycle/degree. Monocular deprivation up to postnatal day 40 resulted in a 30% decrease in acuity and there was no recovery after 8 months. Identical binocular deprivation produced a comparable but significantly smaller reduction in acuity. The deleterious effects of monocular and binocular deprivation on visual acuity indicate that the development of cortical receptive field properties related to spatial tuning are affected by both monocular and binocular deprivation. The similarities in the effects of visual deprivation on visual acuity between rats and other mammals confirm that rats are a good model system for studying the cellular and molecular mechanisms underlying experience-dependent visual plasticity.

Age Factors↗
PubMed2002

Variation in visual acuity within pigmented, and between pigmented and albino rat strains.

Many researchers assume that laboratory rats have poor vision, and accordingly, that they need not consider differences in the visual function of rats as a consequence of strain or experience. Currently, it is not specifically known whether rat domestication has negatively affected the visual function of laboratory rat strains, what the effects of strain albinism are on rat visual function, or whether there are strain differences in the visual function of laboratory rats that are independent of pigmentation. In order to address these questions, we measured psychophysically the vertical grating acuity of three pigmented (Dark Agouti, Fisher-Norway, Long-Evans) and three albino (Fisher-344, Sprague-Dawley, Wistar) strains of laboratory rats, and compared their acuity with that of wild rats. The grating thresholds of Dark Agouti, Long-Evans and wild strains clustered around 1.0 cycle/degree (c/d) and did not significantly differ from one another. Fisher-Norway rats, however, had a significantly higher threshold of 1.5 c/d. The grating thresholds of Fisher-344, Sprague-Dawley, and Wistar strains, which were clustered around 0.5 c/d, were significantly lower than those of the pigmented strains. These data demonstrate that there is significant strain variability in the visual function of laboratory rats. Domestication of Long-Evans and Dark Agouti strains does not appear to have compromised visual acuity, but in the case of Fisher-Norway rats, selective breeding may have enhanced their acuity. Strain selection associated with albinism, however, appears to have consistently impaired visual acuity. Therefore, a consideration of strain differences in visual function should accompany the selection of a rat model for behavioral tasks that involve vision, or when comparing visuo-behavioral measurements across rat strains.

Albinism↗