Visual acuity in larval zebrafish: behavior and histology

Abstract

BackgroundVisual acuity, the ability of the visual system to distinguish two separate objects at a given angular distance, is influenced by the optical and neuronal properties of the visual system. Although many factors may contribute, the ultimate limit is photoreceptor spacing. In general, at least one unstimulated photoreceptor flanked by two stimulated ones is needed to perceive two objects as separate. This critical interval is also referred to as the Nyquist frequency and is according to the Shannon sampling theorem the highest spatial frequency where a pattern can be faithfully transmitted. We measured visual acuity in a behavioral experiment and compared the data to the physical limit given by photoreceptor spacing in zebrafish larvae.ResultsWe determined visual acuity by using the optokinetic response (OKR), reflexive eye movements in response to whole field movements of the visual scene. By altering the spatial frequency we determined the visual acuity at approximately 0.16 cycles/degree (cpd) (minimum separable angle = 3.1°). On histological sections we measured the retinal magnification factor and the distance between double cones, that are thought to mediate motion perception. These measurements set the physical limit at 0.24 cpd (2.1°).ConclusionThe maximal spatial information as limited by photoreceptor spacing can not be fully utilized in a motion dependent visual behavior, arguing that the larval zebrafish visual system has not matured enough to optimally translate visual information into behavior. Nevertheless behavioral acuity is remarkable close to its maximal value, given the immature state of young zebrafish larvae.

The Optokinetic Response as a Quantitative Measure of Visual Acuity in Zebrafish

“…We found that the adult zebrafish acuity is about 70% of what would be predicted given their photoreceptor spacing. 23 Contrast that with optimal human performance ~20/12, which is about 80% of the predicted 20/10, and OKR technique for measuring visual capability in adult zebrafish is impressive 24,25 .…”

Comparative neurophysiology of spatial luminance contrast sensitivity.

“…Rinner et al (2005) found a band-pass CSF that peaked at 0.07-0.08 cpd, with visual acuity of 0.2-0.4 cpd. Haug et al (2010) found visual acuity of 0.16 cpd. Also using fish optokinetic nystagmus, Mueller and Neuhauss (2010) studied eye velocity as a function of stimulus contrast and spatial frequency in adult zebrafish and medaka.…”

“…The visual response of fish to contrast as a function of spatial frequency has been investigated in several species, some of which are laboratory animals that have been studied for numerous reasons: bluegill sunfish (Lepomis macrochirus), zebrafish (Danio rerio), medaka or Japanese killifish (Oryzias latipes), and goldfish (Carassius auratus; Bilotta & Powers, 1991;Haug, Biehlmaier, Mueller, & Neuhauss, 2010;Northmore & Dvorak, 1979;Northmore, Oh, & Celenza, 2007;Rinner, Rick, & Neuhauss, 2005; Figure 2D). Northmore and Dvorak (1979) and Bilotta and Powers (1991) used Pavlovian conditioning to suppress respiration upon the presentation of a sinusoidal grating.…”

“…They found that the CSF had a band-pass shape, peaked at 0.3-0.4 cpd, and had a cut-off frequency of 5-7 cpd. Rinner et al (2005) and Haug et al (2010) used the optokinetic nystagmus response to estimate the contrast sensitivity of larval zebrafish. These studies immobilized zebrafish larvae and then stimulated the larvae with gratings projected onto a cylindrical screen.…”

Comparison of functional and anatomical estimations of visual acuity in two species of coral reef fish

“…Because the visual system of fish has evolved in response to a range of social and environmental pressures (Dobberfuhl et al, 2005), the visual capabilities of different species are highly variable (Lythgoe, 1979;Endler, 1990Endler, , 1993, and can be described using a range of measures including (but not limited to) acuity, temporal resolution and absolute visual sensitivity. Visual acuity, or spatial resolution, is a measure of the minimum separable angle that can be resolved by the eye (Neave, 1984) and is one of the most common measures to assess the visual capability of an animal (Reymond, 1985;Harman et al, 1986;Collin and Pettigrew, 1989;Aho, 1997;Haug et al, 2010). Knowledge of visual acuity of an animal allows us to evaluate the level of detail an animal can see in a visual scene, which is important if we wish to understand various aspects of their visual behaviour independently of the human visually guided behaviour perception.…”