Orientation Code Research Articles

Incidental vs. deliberate coding of object orientation across eye movements

Incidental vs. deliberate coding of object orientation across eye movements

Human Body Measurement by Robust Stereo-Matching

We have developed a digital photogrammetry system, which enables us to make all-around 3D measurement using the object pictures obtained through the integrated works of digital cameras, projectors and our specific PC software. The system consists of units, each of which is again consists of two synchronized digital cameras and projectors with PC program.The measuring process is now simplified by making all the operations of orientation and measurement analysis automatic; and this, with a single push of a button. Automation of orientation was realized by creating a calibration box covered by color-coded targets, which enables us to make exterior orientation parameters of the cameras automatically.For stereo-matching, in order to minimize the mismatching, we invented Coarse-to Fine Strategy Method by integrating OCM (Orientation Code Matching) or robust matching with LSM (Least Square Matching). Therefore, improving the accuracy of the initial values of OCM, using LSM for fine measurement and making the involved operations automatic, we enhanced the quality of surface measurement and succeeded to shorten the measuring time considerably.In this paper we are presenting the report on our system of human body measurement and its processing method of stereo-matching, as well as on the result of comparing assessment of each matching method.

Spike latency code for orientation discrimination and estimation by primary visual cortical cells

Event Abstract Back to Event Spike latency code for orientation discrimination and estimation by primary visual cortical cells Oren Shriki1*, Adam Kohn2 and Maoz Shamir1 1 Ben-Gurion University, Israel 2 Albert Einstein College of Medicine, United States Accumulating evidence from behavioral experiments and imaging studies shows we are able to discriminate between different visual objects at a remarkable speed. The high computation speed yields a strong constraint on any possible answer to the question: how is information from one brain region communicated to another? Conventional neural coding research has ignored the temporal structure of the neural response and focused, in many cases, on the neural mean response over long timescales that are often beyond the relevant behavioral timescale. It has been suggested that the temporal structure of the neural initial response and in particular response latency are used by the central nervous system for fast communication of information between different brain regions. However, the accuracy of such a scheme has not been analyzed rigorously. Here we addressed this question in the framework of orientation coding by primary visual (V1) cortical cells of the monkey. To this end, simultaneous recordings of multiple V1 neurons over many repetitions per each orientation were performed. The spike data from these recordings were used to investigate the utility of first spike latency for encoding information about the orientation of visual stimuli. Cells in V1 are known to code for the orientation of a grating stimulus by their rate of firing. Typically, V1 cells show a maximum firing rate in response to a ’preferred orientation’. We find that many cells in the monkey V1 also show tuning of their first spike time latency to the orientation of the stimulus. Most cells have the shortest latency at the preferred orientation of their rate tuning curve. Moreover, by transforming the latency tuning curve to units of rate we find that the two tuning curves have a very similar tuning width. Using various statistical measures, we quantified the performance of a highly nonlinear readout mechanism, which estimates stimulus orientation by the preferred orientation of the cell with the shortest first spike latency, the temporal-Winner-Take-All (tWTA). In the context of a two-alternative forced-choice paradigm, we find that the tWTA discrimination accuracy is comparable to that of a conventional rate-code readout, which takes into account the total number of spikes fired by the cell in response to the visual stimulus. The accuracy of the tWTA readout can be further increased by considering a generalized n-tWTA readout, which estimates the orientation as the preferred orientation of the cell which fired the first n spikes. We find that the stimulus orientation can be estimated by n-tWTA with a relatively small bias for n>=2. The study demonstrates that a readout based on spike latency, or the first few spikes fired, may significantly improve response speed at a small cost to the accuracy of the decision. Conference: Computational and Systems Neuroscience 2010, Salt Lake City, UT, United States, 25 Feb - 2 Mar, 2010. Presentation Type: Poster Presentation Topic: Poster session I Citation: Shriki O, Kohn A and Shamir M (2010). Spike latency code for orientation discrimination and estimation by primary visual cortical cells. Front. Neurosci. Conference Abstract: Computational and Systems Neuroscience 2010. doi: 10.3389/conf.fnins.2010.03.00107 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 21 Feb 2010; Published Online: 21 Feb 2010. * Correspondence: Oren Shriki, Ben-Gurion University, Beer-Sheva, Israel, oren70@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Oren Shriki Adam Kohn Maoz Shamir Google Oren Shriki Adam Kohn Maoz Shamir Google Scholar Oren Shriki Adam Kohn Maoz Shamir PubMed Oren Shriki Adam Kohn Maoz Shamir Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Population coding under normalization

A common computation in visual cortex is the divisive normalization of responses by a pooled signal of the activity of cells within its neighborhood. From a geometrical point of view, normalization constraints the population response to high-contrast stimuli to lie on the surface of a high-dimensional sphere. Here we study the implications this constraint imposes on the representation of a circular variable, such as the orientation of a visual stimulus. New results are derived for the infinite dimensional case of a homogeneous populations of neurons with identical tuning curves but different orientation preferences. An important finding is that the ability of the population to discriminate between any two orientations depends exclusively on the Fourier amplitude spectrum of the orientation tuning curve. We also study the problem of encoding by a finite set of neurons. A central result is that, under normalization, optimal encoding can be achieved by a finite number of neurons with heterogeneous tuning curves. In other words, increasing the number of neurons in the population does not always allow for an improved population code. These results are used to estimate the number of neurons involved in the coding of orientation at one position in the visual field. If the cortex were to code orientation optimally, we find that a small number (∼4) of neurons should suffice.

A unified distance measurement for orientation coding in palmprint verification

Orientation coding based palmprint verification methods, such as competitive code, palmprint orientation code and robust line orientation code, are state-of-the-art verification algorithms with fast matching speeds. Orientation code makes use of two types of distance measure, SUM_XOR (angular distance) and OR_XOR (Hamming distance), yet little is known about the similarities and differences between these two distance measures. In this paper, we propose a unified distance measure, of which both SUM_XOR and OR_XOR can be regarded as special cases, and provide some principles for determining the parameters of the unified distance. Experimental results show that, using the same feature extraction and coding methods, the unified distance measure gets lower equal error rates than the original distance measures.

Chiang Kai-shek's reading: an inquiry based on Chiang's diary, 1920s–1940s

At different times of his life, Chiang Kai-shek entertained three different images of himself: saint, hero and revolutionary guru. The orientation of his reading roughly corresponded with these roles: to be a saint, he emphasized moral learning and self-improvement; to be a hero, he stressed military strategy and politics; and to be the guru for a revolution, he had an enduring interest in the histories of revolutions in other nations. He seldom took an interest in books about knowledge, leisure or entertainment, which had little connection with these three roles. Chiang was closer to a traditional Chinese intellectual than to his predecessor Dr. Sun Yat-sen in his knowledge structure, value orientation and behaviour codes. Although Mao Zedong was as devoted to old Chinese books as Chiang, Mao preferred history and classical literature while Chiang preferred Confucian classics. Mao read old books from a historical materialist point of view, whereas Chiang synthesized “Three Principles of the People” (Sanmin zhuyi) with Confucian doctrines.

Projected disparity, not horizontal disparity, predicts stereo depth of 1-D patterns

Binocular disparities have a straightforward geometric relation to object depth, but the computation that humans use to turn disparity signals into depth percepts is neither straightforward nor well understood. One seemingly solid result, which came out of Wheatstone’s work in the 1830s, is that the sign and magnitude of horizontal disparity predict the perceived depth of an object: ‘positive’ horizontal disparities yield the perception of ‘far’ depth, ‘negative’ horizontal disparities yield the perception of ‘near’ depth, and variations in the magnitude of horizontal disparity monotonically increase or decrease the perceived extent of depth. Here we show that this classic link between horizontal disparity and the perception of ‘near’ versus ‘far’ breaks down when the stimuli are one-dimensional. For these stimuli, horizontal is not a privileged disparity direction. Instead of relying on horizontal disparities to determine their depth relative to that of two-dimensional stimuli, the visual system uses a disparity calculation that is non-veridical yet well suited to deal with the joint coding of disparity and orientation.

Robust Focusing using Orientation Code Matching

This paper proposes a novel scheme for image focusing by introducing a new focus measure based on self-matching methods. A unique pencil-shaped profile is identified by comparing the similarity between all patterns extracted around the same position in each scene. Based on this profile, a new criterion function called Complementary Pencil Volume (hereafter CPV) is defined to evaluate focused or defocused scenes based on similarity rate of self-matching, which visually represents the volume of a pencil-shaped profile. Among matching methods, Orientation Code Matching (hereafter OCM) is recommended due to its invariance with regards to illumination and contrasts. Several experiments using a telecentric lens are implemented to demonstrate the efficiency of proposed measures. Outstandingly, comparing Orientation Code Matching-based (hereafter OCM-based) focus measure with conventional focus measures shows that OCM-based focus measure is robust against changes of illuminations and contrast. Using this method, depth is measured by comparing the focused and defocused region in the scenes both under high and low illumination conditions.

Palmprint verification using binary orientation co-occurrence vector

The development of accurate and robust palmprint verification algorithms is a critical issue in automatic palmprint authentication systems. Among various palmprint verification approaches, the orientation based coding methods, such as competitive code (CompCode), palmprint orientation code (POC) and robust line orientation code (RLOC), are state-of-the-art ones. They extract and code the locally dominant orientation as features and could match the input palmprint in real-time and with high accuracy. However, using only one dominant orientation to represent a local region may lose some valuable information because there are cross lines in the palmprint. In this paper, we propose a novel feature extraction algorithm, namely binary orientation co-occurrence vector (BOCV), to represent multiple orientations for a local region. The BOCV can better describe the local orientation features and it is more robust to image rotation. Our experimental results on the public palmprint database show that the proposed BOCV outperforms the CompCode, POC and RLOC by reducing the equal error rate (EER) significantly.

A precise form of divisive suppression supports population coding in the primary visual cortex

The responses of neurons in the primary visual cortex (V1) to an optimally-oriented grating are suppressed when a non-optimal grating is superimposed. Although cross-orientation suppression is thought to reflect mechanisms that maintain a distributed code for orientation, the impact of superimposed gratings upon V1 populations is unknown. Using intrinsic signal optical imaging, we find that patterns of tree shrew V1 activity evoked by superimposed equal-contrast gratings were predicted by the mean of patterns evoked by individual component gratings. This prediction held across contrasts, for summed sinusoidal gratings or non-summing square-wave gratings, and was reflected in single-unit extracellular recordings. Intracellular recordings revealed consistent levels of suppression throughout the evolution of subthreshold responses. These results indicate that divisive suppression powerfully governs population responses to multiple orientations. Moreover, the specific form of suppression we observe appears to support independent population codes for stimulus orientation and strength, and calls for a reassessment of mechanisms that underlie cross-orientation suppression.

Attention Alters Visual Plasticity during Exposure-Based Learning

It is generally believed that attention enhances the processing of sensory information during perception and learning. Here we report that, contrary to common belief, attention limits the degree of plasticity induced by repeated exposure to image features. Specifically, daily exposure to oriented stimuli that are not linked to a specific task causes an orientation-specific improvement in perceptual performance along the "exposed" axes. This effect is modulated by attention: human subjects showed a larger improvement in orientation discrimination when attention is directed toward the location where stimuli are presented. However, the capacity to perform discriminations away from the exposed orientation is enhanced when the exposure stimuli are unattended. Importantly, the improvement in orientation discrimination at the unattended location leads to a robust enhancement in the discrimination of complex stimuli, such as natural texture images, with orientation components along the exposed axes, whereas the improvement in orientation discrimination at the attended location exhibits only weak transfer to complex stimuli. These results indicate that sensory adaptation by passive stimulus exposure should be viewed as a form of perceptual learning that is complementary to practice-based learning in that it reduces constraints on generalization.

Reproducibility – a new approach to estimating significance of orientation and direction coding

Reproducibility – a new approach to estimating significance of orientation and direction coding

Robust Color Orientation Code Matching with Weighting for Fluctuation in Illumination Spectrum

Robust Color Orientation Code Matching with Weighting for Fluctuation in Illumination Spectrum

Robust Focusing using Orientation Code Matching

This paper proposes a novel scheme for image focusing by introducing a new focus measure based on self-matching methods. A unique pencil-shaped profile is identified by comparing the similarity between all patterns extracted around the same position in each scene. Based on this profile, a new criterion function called Complementary Pencil Volume (CPV) is defined to evaluate focus or defocus scenes based on similarity rate of self-matching, which visually represents the volume of a pencil-shape profile. Among matching methods, Orientation Code Matching (OCM) is recommended due to its invariant with regards to illuminations and contrasts. Several experiments using a Telecentric lens are implemented to demonstrate the efficiency of proposed measures. Outstandingly, comparing conventional focus measures, shows that the proposed method, focus measure based on OCM is robust against changes of brightness or illumination. Using this method, pan-focused images are composed and depth informations are represented by comparing the focus and defocus region in the scenes both under low and high illumination conditions.

The effect of action goal hierarchy on the coding of object orientation in imitation tasks: Evidence from patients with parietal lobe damage

In order to explore parietal patients' difficulties in the processing of orientation information, we asked parietal patients (N = 8) and healthy and brain-damaged controls to imitate multicomponent actions where object orientation was one component. In Experiment 1 orientation was not the most relevant aspect of the action to be imitated, and the parietal group showed significant difficulties in processing object orientation. However, in Experiment 2, where orientation was placed at the top end of the goal hierarchy, the parietal group were able to process stimulus orientation sufficiently to place it within the goal hierarchy of the action and to reproduce it accurately. We conclude that patients with parietal lesions might be able to include object orientation in a goal hierarchy, but if their processing of orientation information is impaired they might be disproportionately prone to errors when object orientation is lower in the goal hierarchy and so not prioritized for processing resources.

Path Integration Using a Model of e-Vector Orientation Coding in the Insect Brain: Reply to Vickerstaff and Di Paolo

In their response to our article (Haferlach, Wessnitzer, Mangan, & Webb, 2007), Vickerstaff and Di Paolo correctly note that the response function of input units used to evolve our network was the same cos(ha – hp) as that used by Vickerstaff and Di Paolo (2005), and resembles the POL neuron arrangement in insects (Labhart & Meyer, 2002) only in the use of three instead of two such units. However it is important to note that our evolved network structure—which maintains a population encoding of the home vector over a set of memory neurons that integrate the input coming from the direction cells—is in fact generalizable to a wide range of direction cell response functions. To demonstrate this point, we here show the results of integrating this network with a very recent model of e-Vector orientation coding in the central complex of the insect brain (Sakura, Lambrinos, & Labhart, 2008)

Different Dynamics of Performance and Brain Activation in the Time Course of Perceptual Learning

Perceptual learning is regarded as a manifestation of experience-dependent plasticity in the sensory systems, yet the underlying neural mechanisms remain unclear. We measured the dynamics of performance on a visual task and brain activation in the human primary visual cortex (V1) across the time course of perceptual learning. Within the first few weeks of training, brain activation in a V1 subregion corresponding to the trained visual field quadrant and task performance both increased. However, while performance levels then saturated and were maintained at a constant level, brain activation in the corresponding areas decreased to the level observed before training. These findings indicate that there are distinct temporal phases in the time course of perceptual learning, related to differential dynamics of BOLD activity in visual cortex.

Palmprint verification based on robust line orientation code

In this paper, we propose a novel robust line orientation code for palmprint verification, whose performance is improved by using three strategies. Firstly, a modified finite Radon transform (MFRAT) is proposed, which can extract the orientation feature of palmprint more accurately and solve the problem of sub-sampling better. Secondly, we construct an enlarged training set to solve the problem of large rotations caused by imperfect preprocessing. Finally, a matching algorithm based on pixel-to-area comparison has been designed, which has better fault tolerant ability. The experimental results of verification on Hong Kong Polytechnic University Palmprint Database show that the proposed approach has higher recognition rate and faster processing speed.

Standing Waves and Traveling Waves Distinguish Two Circuits in Visual Cortex

The visual cortex represents stimuli through the activity of neuronal populations. We measured the evolution of this activity in space and time by imaging voltage-sensitive dyes in cat area V1. Contrast-reversing stimuli elicit responses that oscillate at twice the stimulus frequency, indicating that signals originate mostly in complex cells. These responses stand clear of the noise, whose amplitude decreases as 1/frequency, and yield high-resolution maps of orientation preference and retinotopy. We first show how these maps are combined to yield the responses to focal, oriented stimuli. We then study the evolution of the oscillating activity in space and time. In the orientation domain, it is a standing wave. In the spatial domain, it is a traveling wave propagating at 0.2-0.5 m/s. These different dynamics indicate a fundamental distinction in the circuits underlying selectivity for position and orientation, two key stimulus attributes.

Feature-Based Attention Modulates Orientation-Selective Responses in Human Visual Cortex

How does feature-based attention modulate neural responses? We used adaptation to quantify the effect of feature-based attention on orientation-selective responses in human visual cortex. Observers were adapted to two superimposed oblique gratings while attending to one grating only. We measured the magnitude of attention-induced orientation-selective adaptation both psychophysically, by the behavioral tilt aftereffect, and physiologically, using fMRI response adaptation. We found evidence for orientation-selective attentional modulation of neuronal responses-a lower fMRI response for the attended than the unattended orientation-in multiple visual areas, and a significant correlation between the magnitude of the tilt aftereffect and that of fMRI response adaptation in V1, the earliest site of orientation coding. These results show that feature-based attention can selectively increase the response of neuronal subpopulations that prefer the attended feature, even when the attended and unattended features are coded in the same visual areas and share the same retinotopic location.