Movement-sensitive neurones in the toad's retina

Ewert, Jörg-Peter; Hock, Franz J.

doi:10.1007/bf00233373

Cited by 96 publications

(47 citation statements)

References 6 publications

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“…Most cells were of the class 2 or class 3 types described by Ewert & Hock (1972) in the retina of the common European toad (Bufo bufo). These cell classes respond both at 'on' and 'off' to relatively small spots of light (diameter < 0-5 mm).…”

Section: Ganglion Cell Classesmentioning

confidence: 99%

Ganglion cell performance at absolute threshold in toad retina: effects of dark events in rods.

Copenhagen

Donner

Reuter

1987

The Journal of Physiology

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SUMMARY1. The performance of ganglion cells in detecting flashes of light near the absolute threshold was studied in an isolated eye-cup preparation of toad retina. Retinal ganglion cells, through which all visual information from the rods must flow to the brain, are in a key position for evaluating the still unproven hypothesis that the absolute light sensitivity is limited by rod noise (Barlow, 1956).2. The dark-adapted threshold intensity for these cells, which were selected on the basis of their high sensitivity, averaged 0-029 Rh* flash-' (range 0-008-0{062), where Rh* signifies one photoisomerization per rod. On average, 46 photoisomerizations were needed per receptive field per flash to evoke a threshold response (range 16-84).3. In the threshold region, frequency of responses versus mean flash intensity was determined. Threshold performance could be described by theoretical frequency of response curves, allowing intrinsic noise to be estimated in terms of an equivalent rate of photoisomerization-like (dark) events. In two completely characterized cells the rate of dark events corresponded to 0-03 and 0-06 Rh* s-1, where Rh* signifies one dark event per rod.4. Threshold elevations produced by dim backgrounds were studied. The results of these experiments are consistent with a dark event rate equivalent to 0-046

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Section: Ganglion Cell Classesmentioning

confidence: 99%

Ganglion cell performance at absolute threshold in toad retina: effects of dark events in rods.

Copenhagen

Donner

Reuter

1987

The Journal of Physiology

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“…Bufo bufo L., kept under standard laboratory conditions [Ewert and Hock, 1972). All experiments were performed in the main 'hunting season' lor this species and locality, i.e.…”

Section: Methodsmentioning

confidence: 99%

“…I lAa) is not remark ably changed if a black stimulus (Si, S;>, W or A) traverses the ERF against a homogeneous white or black/white-textured stationary background (u = 0.12 or 0.46°). Secondly, the stimulus-response proper ties of these neurons [Ewert and Hock, 1972;Ewert and von Wietersheim, 1974a] are not basically influ enced by a stationary black/white-textured back ground as far as investigated for u = 0.12 or 0.46°. In most neuronal classes, the discriminatory acuity was slightly decreased [except for one T5(2) neuron, cf.…”

Section: Stationary Textured Backgroundmentioning

confidence: 99%

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Influence of Stationary and Moving Textured Backgrounds on the Response of Visual Neurons in Toads <i>(Bufo bufo </i>L.)

Tsai¹,

Ewert²

1988

Brain Behav Evol

Self Cite

141

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Previous studies have shown that configurational prey recognition in common toads is performed by feature-analyzing functional units consisting of assemblies of connected neurons such as retinal (classes R2, R3), tectal [classes T5(1), T5(2), T5(3)], and pretectal (class TH3) cells. In the present paper, effects of textured backgrounds on the response of these neurons to a configurational moving stimulus have been tested quantitatively. (1) In all investigated neurons, neither the overall activation nor the respective stimulus-response relationships were significantly influenced by a stationary black/white-textured background as far as black stimulus objects are concerned. (2) The neuronal activity in response to a moving object (signal) could be inhibited (masked) if a black/white-textured background (noise) was moving simultaneously at the same speed. The strength (I) of this 'surround inhibition' (signal masking by the background) was different in the various classes of neurons, i.e. strongest for T5(2) and weakest for R3: I_T5(2) I_T5(1) I_T5(3) > I_R2 > I_TH3 I_R3. These inhibitory effects were not correlated with the size of the neuronal excitatory receptive field (ERF), since T4 neurons (ERF = 180°) in this context displayed response properties similar to T5(2) neurons (ERF < 30°). (3) It is suggested that the signal (prey)-masking effect of a moving textured background is brought about by pretecto (TH3)-tectal [T5(1), T5(2)] inhibitory connectivity which allows toads: (a) to select prey from nonprey; (b) to discriminate between prey and a textured background, and (c) to determine the origin of moving retinal images caused either by object movement or by self-induced motion.

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“…The points of intersection of the 45°l ines and the horizontal straight lines for each set of data (shown by gray dashed arrows) show the critical durations. (Ewert, 1970;Ewert and Hock, 1972). The specializations associated with "feature extraction" properties are also attended by differences in basic temporal transfer characteristics.…”

Section: The Diversity Of Retinal Ganglion Cellsmentioning

confidence: 99%

Rod Phototransduction Determines the Trade-Off of Temporal Integration and Speed of Vision in Dark-Adapted Toads

Haldin

Nymark²,

Aho³

et al. 2009

J. Neurosci.

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Human vision is ϳ10 times less sensitive than toad vision on a cool night. Here, we investigate (1) how far differences in the capacity for temporal integration underlie such differences in sensitivity and (2) whether the response kinetics of the rod photoreceptors can explain temporal integration at the behavioral level. The toad was studied as a model that allows experimentation at different body temperatures. Sensitivity, integration time, and temporal accuracy of vision were measured psychophysically by recording snapping at worm dummies moving at different velocities. Rod photoresponses were studied by ERG recording across the isolated retina. In both types of experiments, the general timescale of vision was varied by using two temperatures, 15 and 25°C. Behavioral integration times were 4.3 s at 15°C and 0.9 s at 25°C, and rod integration times were 4.2-4.3 s at 15°C and 1.0 -1.3 s at 25°C. Maximal behavioral sensitivity was fivefold lower at 25°C than at 15°C, which can be accounted for by inability of the "warm" toads to integrate light over longer times than the rods. However, the long integration time at 15°C, allowing high sensitivity, degraded the accuracy of snapping toward quickly moving worms. We conclude that temporal integration explains a considerable part of all variation in absolute visual sensitivity. The strong correlation between rods and behavior suggests that the integration time of dark-adapted vision is set by rod phototransduction at the input to the visual system. This implies that there is an inexorable trade-off between temporal integration and resolution.

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Movement-sensitive neurones in the toad's retina

Cited by 96 publications

References 6 publications

Ganglion cell performance at absolute threshold in toad retina: effects of dark events in rods.

Ganglion cell performance at absolute threshold in toad retina: effects of dark events in rods.

Influence of Stationary and Moving Textured Backgrounds on the Response of Visual Neurons in Toads <i>(Bufo bufo </i>L.)

Rod Phototransduction Determines the Trade-Off of Temporal Integration and Speed of Vision in Dark-Adapted Toads

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