A study on nonlinearity of the visual system in response to the flickering stimuli in the low temporal frequency domain.

The first steps of processing in the visual system of the blowfly are well suited for studying the relationship between the properties of the environment and the function of visual processing (eg Srinivasan et al, 1982 Proceedings of the Royal Society, London B216 427; van Hateren, 1992 Journal of Comparative Physiology A171 157). Although the early visual system appears to be linear to some extent, there are also reports on functionally significant nonlinearities (Laughlin, 1981 Zeitschrift für Naturforschung36c 910). Recent theories using information theory for understanding the early visual system perform reasonably well, but not quite as well as the real visual system when confronted with natural stimuli [eg van Hateren, 1992 Nature (London)360 68]. The main problem seems to be that they lack a component that adapts with the right time course to changes in stimulus statistics (eg the local average light intensity). In order to study this problem of adaptation with a relatively simple, yet realistic, stimulus I recorded time series of natural intensities, and played them back via a high-brightness LED to the visual system of the blowfly ( Calliphora vicina). The power spectra of the intensity measurements and photoreceptor responses behave approximately as 1/ f, with f the temporal frequency, whilst those of second-order neurons (LMCs) are almost flat. The probability distributions of the responses of LMCs are almost gaussian and largely independent of the input contrast, unlike the distributions of photoreceptor responses and intensity measurements. These results suggest that LMCs are in effect executing a form of contrast normalisation in the time domain.

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Organization of simple cell responses in the three-dimensional (3-D) frequency domain

Visual Neuroscience ◽

10.1017/s0952523800001644 ◽

1994 ◽

Vol 11 (2) ◽

pp. 295-306 ◽

Cited By ~ 28

Author(s):

J. McLean ◽

L. A. Palmer

Keyword(s):

Spatial Frequency ◽

Frequency Domain ◽

Spectral Response ◽

Temporal Frequency ◽

Three Dimensional ◽

Direction Selectivity ◽

Two Dimensions ◽

Three Dimensions ◽

Simple Cells ◽

Amplitude Spectra

AbstractThe amplitude spectra of simple cells in areas 17 and 18 were estimated in two and three dimensions (2–D and 3–D) using drifting sinusoidal gratings. In 2–D, responses were sampled with 16 x 16 resolution in spatial and temporal frequency at the optimal orientation. In 3–D, responses were sampled with 12 x 12 x 10 resolution in spatial frequency, orientation, and temporal frequency. For 45/50 cells studied, the spatial attributes of the receptive fields (RFs) were independent of temporal frequency except for a scale factor. The five exceptions to this general finding could be described as follows: For four area 17 cells, responses in the null direction increased with temporal frequency, reducing direction selectivity. For one area 18 cell, the optimal spatial frequency increased with temporal frequency and vice versa. The 2–D discrete Fourier transform was applied to all of the estimated amplitude spectra assuming zero spatial and temporal phase. These transforms were compared with the results of first-order reverse correlations as described in the previous paper (McLean et al., 1994). Direction selective cells exhibited excitatory subregions that were obliquely oriented in space-time in both the raw correlation data and inverse transforms of the spectral data. The slopes of the subregions found in these two measures were highly correlated. Direction indices obtained from space and frequency domain measures were comparable. We demonstrate that the spectral response profiles of most simple cells are aligned with the coordinate axes in frequency domain. That is, they may be considered one-quadrant separable, suggesting that these cells are not velocity tuned per se, but are tuned for spatiotemporal frequency. The spectral bandwidth establishes the range of velocities to which these cells will respond. These findings are consistent with the one-quadrant separability constraint of linear quadrature models. We conclude that most simple cells perform as roughly linear filters in two dimensions of space and time.

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A Frequency Accurate Temporal Derivative Finite Difference Approximation

Journal of Computational Acoustics ◽

10.1142/s0218396x97000216 ◽

1997 ◽

Vol 05 (04) ◽

pp. 371-382 ◽

Cited By ~ 3

Author(s):

Peter A. Orlin ◽

A. Louise Perkins ◽

George Heburn

Keyword(s):

Finite Difference ◽

Spatial Frequency ◽

Frequency Domain ◽

Temporal Frequency ◽

Finite Difference Approximation ◽

Difference Approximation ◽

Linear Matrix ◽

Matrix Formulation ◽

Temporal Derivative ◽

Spatial Frequency Domain

A method is presented for designing temporal derivative finite difference approximations that achieve specified accuracy in the frequency domain. A general average value approximation with undetermined coefficients is fitted in the spatial frequency domain to attain the desired properties of the approximation. A set of constraints to insure that the approximation convergences as the grid spacing approaches zero and satisfies the Lax Equivalence Theorem are imposed on the fitted coefficients. The specification of the underlying partial differential equation is required in order to replace the temporal frequency domain dependence of the approximation with an explicit spatial frequency domain relation based on the dispersion relation of the PDE. A practical design of the approximations is pursued using an heuristic zero placement method which results in a linear matrix formulation.

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Gaze stabilisation behaviour is anisotropic across visual field locations in zebrafish

10.1101/754408 ◽

2019 ◽

Cited By ~ 4

Author(s):

Florian A. Dehmelt ◽

Rebecca Meier ◽

Julian Hinz ◽

Takeshi Yoshimatsu ◽

Clara A. Simacek ◽

...

Keyword(s):

Visual Field ◽

Visual System ◽

Temporal Frequency ◽

Visual Fields ◽

Visual Space ◽

Relevant Information ◽

Stimulus Size ◽

Motion Vision ◽

Optokinetic Response ◽

Retinal Photoreceptor

AbstractMany animals have large visual fields, and sensory circuits may sample those regions of visual space most relevant to behaviours such as gaze stabilisation and hunting. Despite this, relatively small displays are often used in vision neuroscience. To sample stimulus locations across most of the visual field, we built a spherical stimulus arena with 14,848 independently controllable LEDs, measured the optokinetic response gain of immobilised zebrafish larvae, and related behaviour to previously published retinal photoreceptor densities. We measured tuning to steradian stimulus size and spatial frequency, and show it to be independent of visual field position. However, zebrafish react most strongly and consistently to lateral, nearly equatorial stimuli, consistent with previously reported higher spatial densities in the central retina of red, green and blue photoreceptors. Upside-down experiments suggest further extra-retinal processing. Our results demonstrate that motion vision circuits in zebrafish are anisotropic, and preferentially monitor areas with putative behavioural relevance.Author summaryThe visual system of larval zebrafish mirrors many features present in the visual system of other vertebrates, including its ability to mediate optomotor and optokinetic behaviour. Although the presence of such behaviours and some of the underlying neural correlates have been firmly established, previous experiments did not consider the large visual field of zebrafish, which covers more than 160° for each eye. Given that different parts of the visual field likely carry unequal amount of behaviourally relevant information for the animal, this raises the question whether optic flow is integrated across the entire visual field or just parts of it, and how this shapes behaviour such as the optokinetic response. We constructed a spherical LED arena to present visual stimuli almost anywhere across their visual field, while tracking horizontal eye movements. By displaying moving gratings on this LED arena, we demonstrate that the optokinetic response, one of the most prominent visually induced behaviours of zebrafish, indeed strongly depends on stimulus location and stimulus size, as well as on other parameters such as the spatial and temporal frequency of the gratings. This location dependence is consistent with areas of high retinal photoreceptor densities, though evidence suggests further extraretinal processing.

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Human visual and auditory characteristics in the temporal frequency domain

Artificial Life and Robotics ◽

10.1007/bf02480858 ◽

2000 ◽

Vol 4 (2) ◽

pp. 62-67

Author(s):

Jing-Long Wu ◽

Osamu Nobuki

Keyword(s):

Frequency Domain ◽

Temporal Frequency

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Analogue models of motion perception

Philosophical Transactions of the Royal Society of London Series B Biological Sciences ◽

10.1098/rstb.1980.0086 ◽

1980 ◽

Vol 290 (1038) ◽

pp. 117-135 ◽

Cited By ~ 55

Keyword(s):

Visual System ◽

Frequency Domain ◽

Motion Perception ◽

Apparent Motion ◽

Spatial Interpolation ◽

Spatial Location ◽

Moving Object ◽

Low Frequencies ◽

Analogue Models ◽

Spatial Locations

An object moving in discrete spatial jumps is difficult to distinguish from a continuously moving object, provided the time between jumps is not too great. The extent of this perceived continuity may be measured by probing the perceived spatial location at times between the target jumps, by either a vernier alignment or a stereoscopic technique. As the time between jumps increases the accuracy of spatial interpolation falls, until finally the object is seen only at its actual spatial locations. These results can be analysed in the frequency domain by treating the signal for apparent motion as the analogue of a periodic waveform containing relatively low frequencies (the continuous motion) and higher frequencies giving rise to the discreteness of the motion. If such an input has the higher frequencies progressively removed by physical filtering, it is perceived as increasingly continuous. The fact that such filtering is not necessary for perceived continuity when the discrete jumps occur at rates greater than about 30 Hz suggests that frequencies greater than that limit are removed by the visual system itself.

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