scholarly journals Normalization by orientation anisotropy in human V1-V3

2021 ◽  
Author(s):  
Zeming Fang ◽  
Catherine Olsson ◽  
Wei Ji Ma ◽  
Jonathan Winawer
Keyword(s):  
Classical Model ◽  
Local Population ◽  
Extrastriate Cortex ◽  
Linear Filters ◽  
Complex Cells ◽  
Energy Models ◽  
Spatial Frequencies ◽  
High Anisotropy ◽  
Orientation Anisotropy ◽  
Band Pass

An influential account of neuronal responses in primary visual cortex is the normalized energy model. This model is often implemented as a two-stage computation. The first stage is the extraction of contrast energy, whereby a complex cell computes the squared and summed outputs of a pair of linear filters in quadrature phase. The second stage is normalization, in which a local population of complex cells mutually inhibit one another. Because the population includes cells tuned to a range of orientations and spatial frequencies, the result is that the responses are effectively normalized by the local stimulus contrast. Here, using evidence from human functional MRI, we show that the classical model fails to account for the relative responses to two classes of stimuli: straight, parallel, band-passed contours (gratings), and curved, band-passed contours (snakes). The snakes elicit fMRI responses that are about twice as large as the gratings, yet traditional energy models, including normalized energy models, predict responses that are about the same. Here, we propose a computational model, in which responses are normalized not by the sum of the contrast energy, but by the orientation anisotropy, computed as the variance in contrast energy across orientation channels. We first show that this model accounts for differential responses to these two classes of stimuli. We then show that the model successfully generalizes to other band-pass textures, both in V1 and in extrastriate cortex (V2 and V3). We speculate that high anisotropy in the orientation responses leads to larger outputs in downstream areas, which in turn normalizes responses in these later visual areas, as well as in V1 via feedback.

Oblique Effect: A Neural Basis in the Visual Cortex

2003 ◽  
Vol 90 (1) ◽  
pp. 204-217 ◽  
Author(s):  
Baowang Li ◽  
Matthew R. Peterson ◽  
Ralph D. Freeman
Keyword(s):  
Striate Cortex ◽  
Oblique Effect ◽  
Orientation Tuning ◽  
Neural Basis ◽  
Linear Filters ◽  
Simple Cells ◽  
Tuning Curves ◽  
Complex Cells ◽  
Behavioral Studies ◽  
Spatial Frequencies

The details of oriented visual stimuli are better resolved when they are horizontal or vertical rather than oblique. This “oblique effect” has been confirmed in numerous behavioral studies in humans and to some extent in animals. However, investigations of its neural basis have produced mixed and inconclusive results, presumably due in part to limited sample sizes. We have used a database to analyze a population of 4,418 cells in the cat's striate cortex to determine possible differences as a function of orientation. We find that both the numbers of cells and the widths of orientation tuning vary as a function of preferred orientation. Specifically, more cells prefer horizontal and vertical orientations compared with oblique angles. The largest population of cells is activated by orientations close to horizontal. In addition, orientation tuning widths are most narrow for cells preferring horizontal orientations. These findings are most prominent for simple cells tuned to high spatial frequencies. Complex cells and simple cells tuned to low spatial frequencies do not exhibit these anisotropies. For a subset of simple cells from our population ( n = 104), we examined the relative contributions of linear and nonlinear mechanisms in shaping orientation tuning curves. We find that linear contributions alone do not account for the narrower tuning widths at horizontal orientations. By modeling simple cells as linear filters followed by static expansive nonlinearities, our analysis indicates that horizontally tuned cells have a greater nonlinear component than those tuned to other orientations. This suggests that intracortical mechanisms play a major role in shaping the oblique effect.

A neural and computational model for the chromatic control of accommodation

1990 ◽  
Vol 5 (6) ◽  
pp. 547-555 ◽  
Author(s):  
D. I. Flitcroft
Keyword(s):  
Image Quality ◽  
Computational Model ◽  
Cortical Neurons ◽  
Chromatic Aberration ◽  
Refractive State ◽  
Spatial Frequencies ◽  
Proposed Model ◽  
Band Pass ◽  
Chromatic Cues ◽  
Chromatic Processing

AbstractAccommodation is more accurate with polychromatic stimuli than with narrowband or monochromatic stimuli. The aim of this paper is to develop a computational model for how the visual system uses the extra information in polychromatic stimuli to increase the accuracy of accommodation responses. The proposed model is developed within the context of both trichromacy and also the organization of spatial and chromatic processing within the visual cortex.The refractive error present in the retinal image can be estimated by comparing image quality with and without small additional changes in refractive state. In polychromatic light, the chromatic aberration of the eye results in differences in ocular refractive power for light of different wavelengths. As a result, the refractive state of the eye can be estimated by comparing image quality in the three types of cone photoreceptor. The ability of cortical neurons to perform such comparisons on image quality with a crude form of spatial-frequency analysis is examined theoretically. It is found that spatially band-pass chromatically opponent neurons (that may correspond to double opponent neurons) can perform such calculations and that chromatic cues to accommodation are extracted most effectively by neurons responding to spatial frequencies of between 2 and 8 cycles/deg.

scholarly journals Modular preprocessing pipelines can reintroduce artifacts into fMRI data

2018 ◽  
Author(s):  
Martin A. Lindquist ◽  
Stephan Geuter ◽  
Tor D. Wager ◽  
Brian S. Caffo
Keyword(s):  
Fmri Data ◽  
Linear Filter ◽  
Linear Filtering ◽  
Linear Filters ◽  
Data Set ◽  
Temporal Filtering ◽  
Global Signal ◽  
In Series ◽  
Band Pass ◽  
Fmri Analysis

AbstractThe preprocessing pipelines typically used in both task and restingstate fMRI (rs-fMRI) analysis are modular in nature: They are composed of a number of separate filtering/regression steps, including removal of head motion covariates and band-pass filtering, performed sequentially and in a flexible order. In this paper we illustrate the shortcomings of this approach, as we show how later preprocessing steps can reintroduce artifacts previously removed from the data in prior preprocessing steps. We show that each regression step is a geometric projection of data onto a subspace, and that performing a sequence of projections can move the data into subspaces no longer orthogonal to those previously removed, reintroducing signal related to nuisance covariates. Thus, linear filtering operations are not commutative, and the order in which the preprocessing steps are performed is critical. These issues can arise in practice when any combination of standard preprocessing steps—including motion regression, scrubbing, component-based correction, global signal regression, and temporal filtering—are performed sequentially. In this work we focus primarily on rs-fMRI. We illustrate the problem both theoretically and empirically through application to a test-retest rs-fMRI data set, and suggest remedies. These include (a) combining all steps into a single linear filter, or (b) sequential orthogonalization of covariates/linear filters performed in series.

scholarly journals Are Spatial Chromatic Contrast Sensitivity Band-pass or Lowpass Functions?

2020 ◽  
Vol 2020 (28) ◽  
pp. 125-129
Author(s):  
Qiang Xu ◽  
Stephen Westland ◽  
Marcel Lucassen ◽  
Dragan Sekulovski ◽  
Sophie Wuerger ◽  
...  
Keyword(s):  
Contrast Sensitivity ◽  
Threshold Method ◽  
Colour Difference ◽  
Chromatic Contrast ◽  
Experimental Conditions ◽  
Colour Centres ◽  
Spatial Frequencies ◽  
Wide Range ◽  
Band Pass ◽  
Chromatic Contrast Sensitivity

The goal of this research is to generate high quality chromatic Contrast Sensitivity Function (CSF) over a wide range of spatial frequencies from 0.06 to 3.84 cycles per degree (cpd) surrounding 5 CIE proposed colour centres (white, red, yellow, green and blue) to study colour difference. At each centre, 6 colour directions at each of 7 frequencies were sampled, from 0.06 to 3.84 cycles per degree (cpd) corresponding to the number of cycles: from 2.3 to 144.4 respectively. A threshold method based on forced-choice stair-case was adopted to investigate the just noticeable (threshold) colour difference. The results revealed that the chromatic CSF under the present experimental conditions having many lower spatial frequencies covering five colour centres to be band pass, whereas previous results indicated it was low pass. However, this could be caused by the present experimental conditions such as fixed-size stimuli and constant luminance. The new chromatic CSF for R-G and Y-B channels were also developed.

Internal Spatial Organization of Receptive Fields of Complex Cells in the Early Visual Cortex

2007 ◽  
Vol 98 (3) ◽  
pp. 1194-1212 ◽  
Author(s):  
Kota S. Sasaki ◽  
Izumi Ohzawa
Keyword(s):  
Visual Cortex ◽  
Minimal Model ◽  
Spatial Organization ◽  
Receptive Fields ◽  
Simple Cell ◽  
Complex Cell ◽  
Linear Filters ◽  
Simple Cells ◽  
Complex Cells ◽  
Early Visual Cortex

The receptive fields of complex cells in the early visual cortex are economically modeled by combining outputs of a quadrature pair of linear filters. For actual complex cells, such a minimal model may be insufficient because many more simple cells are thought to make up a complex cell receptive field. To examine the minimalist model physiologically, we analyzed spatial relationships between the internal structure (subunits) and the overall receptive fields of individual complex cells by a two-stimulus interaction technique. The receptive fields of complex cells are more circular and only slightly larger than their subunits in size. In addition, complex cell subunits occupy spatial extents similar to those of simple cell receptive fields. Therefore in these respects, the minimalist schema is a fair approximation to actual complex cells. However, there are violations against the minimal model. Simple cell receptive fields have significantly fewer subregions than complex cell subunits and, in general, simple cell receptive fields are elongated more horizontally than vertically. This bias is absent in complex cell subunits and receptive fields. Thus simple cells cannot be equated to individual complex cell subunits and spatial pooling of simple cells may occur anisotropically to constitute a complex cell subunit. Moreover, when linear filters for complex cell subunits are examined separately for bright and dark responses, there are significant imbalances and position displacements between them. This suggests that actual complex cell receptive fields are constructed by a richer combination of linear filters than proposed by the minimalist model.

RESOLVING POWER OF THREE ANTENNA PATTERNS DERIVED FROM THE SAME APERTURE

1959 ◽  
Vol 37 (11) ◽  
pp. 1216-1229 ◽  
Author(s):  
E. Covington ◽  
Gladys A. Harvey
Keyword(s):  
Phase Shift ◽  
Rectangular Band ◽  
Cutoff Frequency ◽  
Angular Spectrum ◽  
Point Sources ◽  
Antenna Pattern ◽  
Resolving Power ◽  
Spatial Frequencies ◽  
Band Pass ◽  
Zero Phase

Three antenna patterns are derived from the same linear aperture and may be described in terms of an angular spectrum of spatial frequencies ranging from zero to a common cutoff frequency. The band passes according to the shape of the spectrum are rectangular, triangular, and cosinusoidal for the three patterns, and give resolving powers respectively of 1.33, 1.00, and 1.05, in terms of the cutoff period. The rectangular band pass gives rise to the optimum antenna pattern and allows the Fourier components of a source from zero to cutoff frequency to be received with equal intensity and zero phase shift. Scanning curves of two equally intense point sources and a uniformly bright line are investigated.

The physics of visual perception

1980 ◽  
Vol 290 (1038) ◽  
pp. 5-9 ◽  
Keyword(s):  
Visual Perception ◽  
Spatial Frequency ◽  
Visual System ◽  
Contrast Threshold ◽  
High Contrast ◽  
Spatial Frequencies ◽  
Band Pass ◽  
High Contrast Grating ◽  
Orientational Tuning

By measuring the contrast threshold for gratings of different waveform and spatial frequency, Campbell & Robson suggested in 1968 that there may be ‘channels’ tuned to different spatial frequencies. By using the technique of adapting to a high contrast grating, it was possible to measure the band-pass characteristics of these channels. Similar techniques were used to establish the orientational tuning of the channels. Reasons are put forward why it is advantageous to organize the visual system in this manner.

Low-level processing deficits underlying poor contrast sensitivity for moving plaids in anisometropic amblyopia

2012 ◽  
Vol 29 (6) ◽  
pp. 315-323 ◽  
Author(s):  
YONG TANG ◽  
LINYI CHEN ◽  
ZHONGJIAN LIU ◽  
CAIYUAN LIU ◽  
YIFENG ZHOU
Keyword(s):  
Contrast Sensitivity ◽  
Significant Loss ◽  
Extrastriate Cortex ◽  
Motion Processing ◽  
Motion Direction ◽  
Temporal Area ◽  
Anisometropic Amblyopia ◽  
Low Level ◽  
Spatial Frequencies ◽  
Processing Deficits

AbstractMany studies using random dot kinematograms have indicated a global motion processing deficit originated from extrastriate cortex, specifically middle temporal area (MT) and media superior temporal area (MST), in patients with amblyopia. However, the nature of this deficit remains unclear. To explore whether the ability of motion integration is impaired in amblyopia, contrast sensitivity for moving plaids and their corresponding component gratings were measured over a range of stimulus durations and spatial and temporal frequencies in 10 control subjects and 13 anisometropic amblyopes by using a motion direction discrimination task. The results indicated a significant loss of contrast sensitivity for moving plaids as well as for moving gratings at intermediate and high spatial frequencies in amblyopic eyes (AEs). Additionally, we found that the loss of contrast sensitivity for moving plaids was statistically equivalent to that for moving component gratings in AEs, that is, the former could be almost completely accounted for by the latter. These results suggest that the integration of motion information conveyed by component gratings of moving plaids may be intact in anisometropic amblyopia, and that the apparent deficits in contrast sensitivity for moving plaids in anisometropic amblyopia can be almost completely attributed to those for gratings, that is, low-level processing deficits.

Temporal-frequency selectivity in monkey visual cortex

1996 ◽  
Vol 13 (3) ◽  
pp. 477-492 ◽  
Author(s):  
M. J. Hawken ◽  
R. M. Shapley ◽  
D. H. Grosof
Keyword(s):  
Frequency Tuning ◽  
Temporal Frequency ◽  
Higher Order ◽  
Primary Input ◽  
Simple Cells ◽  
Complex Cells ◽  
Lateral Geniculate ◽  
Low Pass ◽  
Band Pass ◽  
Visual Delay

AbstractWe investigated the dynamics of neurons in the striate cortex (V1) and the lateral geniculate nucleus (LGN) to study the transformation in temporal-frequency tuning between the LGN and V1. Furthermore, we compared the temporal-frequency tuning of simple with that of complex cells and direction-selective cells with nondirection-selective cells, in order to determine whether there are significant differences in temporal-frequency tuning among distinct functional classes of cells within V1. In addition, we compared the cells in the primary input layers of V1 (4a, 4cα, and 4cβ) with cells in the layers that are predominantly second and higher order (2, 3, 4b, 5, and 6). We measured temporal-frequency responses to drifting sinusoidal gratings. For LGN neurons and simple cells, we used the amplitude and phase of the fundamental response. For complex cells, the elevation of impulse rate (F0) to a drifting grating was the response measure. There is significant low-pass filtering between the LGN and the input layers of V1 accompanied by a small, 3-ms increase in visual delay. There is further low-pass filtering between V1 input layers and the second- and higher-order neurons in V1. This results in an average decrease in high cutoff temporal-frequency between the LGN and V1 output layers of about 20 Hz and an increase in average visual latency of about 12–14 ms. One of the most salient results is the increased diversity of the dynamic properties seen in V1 when compared to the cells of the lateral geniculate, possibly reflecting specialization of function among cells in V1. Simple and complex cells had distributions of temporal-frequency tuning properties that were similar to each other. Direction-selective and nondirection-selective cells had similar preferred and high cutoff temporal frequencies, but direction-selective cells were almost exclusively band-pass while nondirection-selective cells distributed equally between band-pass and low-pass categories. Integration time, a measure of visual delay, was about 10 ms longer for V1 than LGN. In V1 there was a relatively broad distribution of integration times from 40–80 ms for simple cells and 60–100 ms for complex cells while in the LGN the distribution was narrower.

scholarly journals Neurons in cat V1 show significant clustering by degree of tuning

2015 ◽  
Vol 113 (7) ◽  
pp. 2555-2581 ◽  
Author(s):  
Avi J. Ziskind ◽  
Al A. Emondi ◽  
Andrei V. Kurgansky ◽  
Sergei P. Rebrik ◽  
Kenneth D. Miller
Keyword(s):  
Spatial Frequency ◽  
Frequency Tuning ◽  
Direction Selectivity ◽  
Preferred Orientation ◽  
Orientation Tuning ◽  
Complex Cells ◽  
Spatial Frequency Tuning ◽  
Spatial Frequencies ◽  
Tuning Width ◽  
Simple And Complex Cells

Neighboring neurons in cat primary visual cortex (V1) have similar preferred orientation, direction, and spatial frequency. How diverse is their degree of tuning for these properties? To address this, we used single-tetrode recordings to simultaneously isolate multiple cells at single recording sites and record their responses to flashed and drifting gratings of multiple orientations, spatial frequencies, and, for drifting gratings, directions. Orientation tuning width, spatial frequency tuning width, and direction selectivity index (DSI) all showed significant clustering: pairs of neurons recorded at a single site were significantly more similar in each of these properties than pairs of neurons from different recording sites. The strength of the clustering was generally modest. The percent decrease in the median difference between pairs from the same site, relative to pairs from different sites, was as follows: for different measures of orientation tuning width, 29–35% (drifting gratings) or 15–25% (flashed gratings); for DSI, 24%; and for spatial frequency tuning width measured in octaves, 8% (drifting gratings). The clusterings of all of these measures were much weaker than for preferred orientation (68% decrease) but comparable to that seen for preferred spatial frequency in response to drifting gratings (26%). For the above properties, little difference in clustering was seen between simple and complex cells. In studies of spatial frequency tuning to flashed gratings, strong clustering was seen among simple-cell pairs for tuning width (70% decrease) and preferred frequency (71% decrease), whereas no clustering was seen for simple-complex or complex-complex cell pairs.

Sign in / Sign up

Export Citation Format

Share Document