Target Template Research Articles

Object-based target templates guide attention during visual search.

During visual search, attention is believed to be controlled in a strictly feature-based fashion, without any guidance by object-based target representations. To challenge this received view, we measured electrophysiological markers of attentional selection (N2pc component) and working memory (sustained posterior contralateral negativity; SPCN) in search tasks where two possible targets were defined by feature conjunctions (e.g., blue circles and green squares). Critically, some search displays also contained nontargets with two target features (incorrect conjunction objects, e.g., blue squares). Because feature-based guidance cannot distinguish these objects from targets, any selective bias for targets will reflect object-based attentional control. In Experiment 1, where search displays always contained only one object with target-matching features, targets and incorrect conjunction objects elicited identical N2pc and SPCN components, demonstrating that attentional guidance was entirely feature-based. In Experiment 2, where targets and incorrect conjunction objects could appear in the same display, clear evidence for object-based attentional control was found. The target N2pc became larger than the N2pc to incorrect conjunction objects from 250 ms poststimulus, and only targets elicited SPCN components. This demonstrates that after an initial feature-based guidance phase, object-based templates are activated when they are required to distinguish target and nontarget objects. These templates modulate visual processing and control access to working memory, and their activation may coincide with the start of feature integration processes. Results also suggest that while multiple feature templates can be activated concurrently, only a single object-based target template can guide attention at any given time. (PsycINFO Database Record

A novel capacitive sensor based on molecularly imprinted nanoparticles as recognition elements

Molecularly Imprinted Polymers (MIPs) are synthetic receptors capable of selective binding to their target (template) molecules and, hence, are used as recognition elements in assays and sensors as a replacement for relatively unstable enzymes and antibodies. Herein, we describe a manufacturing-friendly protocol for integration of MIP nanoparticles (nanoMIPs) with a (label-free) capacitive sensor. The nanoMIPs were produced by solid-phase synthesis for two templates with different sizes and properties, including a small molecule tetrahydrocannabinol (THC) and a protein (trypsin). NanoMIPs were deposited on the surface of the sensor and the change in capacitance (ΔC) upon binding of the target was measured. The significant improvement in the selectivity and limit of detection (one order of magnitude compared to previously used MIP microparticles) can be attributed to their increased surface-to-volume ratio and higher specificity of the nanoMIPs produced by the solid-phase method. The methodology described is also compatible with common sensor fabrication approaches, as opposed to methods involving in situ MIP polymerisation. The proposed sensor shows high selectivity, fast sensor response (45 min including injection, regeneration and re-equilibration with running buffer), and straightforward data analysis, which makes it viable for label-free monitoring in real-time. The set of targets assessed in this manuscript shows the general applicability of the biosensor platform.

A Target Tracking Algorithm Based on Mean Shift and Fast Template Matching

This paper proposes a target tracking algorithm based on mean shift and template matching. The algorithm is divided into three stages:prediction, template matching, target positioning, and template updating. In the prediction stage, combined with the target position obtained from the previous frame tracking, the target position is predicted using the mean shift method, and the template matching search gate is defined with the predicted position as the center and the corresponding size as the coverage area. At the template matching stage, using fast template matching algorithm, the target template and search gate are quickly matched from coarse to fine, and the matching degree between matching result and target template is calculated. If the matching degree is greater than the given threshold, the fast template matching will be performed and the result will be used as the tracking result of the current frame image. Otherwise, the target position predicted by the mean shift algorithm is used as the tracking results of the current frame image. Finally, the template updating process is controlled by the tracking results of the current frame to update the target template, and the stable tracking of the target is finally completed. At the same time, the algorithm improves the robust of tracking by combining the advantages of color and edge features to the insensitivity of rotation and deformation. The method has fast calculation speed and high accuracy, it can meet real-time requirements.

Dynamic Hand Gesture Tracking Method Based on Key Frame and Video Perceptual Hashing

Aiming at the common problems such as low tracking accuracy, robustness and poor real-time ability for the traditional tracking algorithm, a novel dynamic hand gesture tracking method based on key frame and video perceptual hashing has been proposed in this paper. Firstly, the proposed method is used to frame the video sequence and extract the key frames, in order to obtain a sequence of key frames. Secondly, the video perceptual hashing is used to extract the perceptual feature of the key frame and target template, thus the hash sequence is generated. Finally, the hamming distance is used to compare the similarities between the key frame and target template, therefore, the real-time tracking is carried out by using an online adaptive template update method to ensure the continuity of the hand gesture tracking. Experimental results show that the proposed method can realize the accurate and real-time tracking of the dynamic deformation gestures, and effectively reduce the time complexity of the algorithm, as well as ensure the stability and continuity of the moving target tracking.

Structure-Aware Local Sparse Coding for Visual Tracking.

Sparse coding has been applied to visual tracking and related vision problems with demonstrated success in recent years. Existing tracking methods based on local sparse coding sample patches from a target candidate and sparsely encode these using a dictionary consisting of patches sampled from target template images. The discriminative strength of existing methods based on local sparse coding is limited as spatial structure constraints among the template patches are not exploited. To address this problem, we propose a structure-aware local sparse coding algorithm, which encodes a target candidate using templates with both global and local sparsity constraints. For robust tracking, we show the local regions of a candidate region should be encoded only with the corresponding local regions of the target templates that are the most similar from the global view. Thus, a more precise and discriminative sparse representation is obtained to account for appearance changes. To alleviate the issues with tracking drifts, we design an effective template update scheme. Extensive experiments on challenging image sequences demonstrate the effectiveness of the proposed algorithm against numerous state-of-the-art methods.

Electrochemical Detection of SNP in Human Mitochondrial DNA Using Cyclic Primer Extension with Biotinylated Nucletides and Enzymatic Labeling at Disposable Pencil Graphite Electrodes

AbstractA novel method of SNP typing in human mitochondrial DNA utilizing enzymatic labeling and electrochemical detection at disposable pencil graphite electrodes is described. The procedure is based on amplification of DNA stretches by cyclic primer extension (PEx) of SNP‐specific diagnostic primers in a mixture of biotinylated and natural nucleotides. The diagnostic primers are designed to recognize, by its 3'‐terminal nucleotide, the SNP‐site in target template. Under optimized conditions of the PEx reaction, efficient polymerase synthesis of biotin‐labeled strands takes place only in the case of full complementarity between the diagnostic primer and the target SNP site. There is also benefit from introducing many biotin molecules per extended DNA strand, resulting in another level of signal amplification. After adsorption of biotinylated PEx products at the electrode surface, streptavidin‐alkaline phosphatase conjugate was bound to the biotin tags, 1‐naphthol was enzymatically produced and electrochemically detected. Several critical steps and parameters of the assay, including termination of 3’‐OH ends of residual amplification primers, temperature for annealing of diagnostic primers, relative amount of biotinylated deoxynucleoside triphosphate in the PEx mixture and number of PEx cycles were optimized in this study to attain best SNP resolution, and reduction of time needed for the analysis.

Multitarget tracking using multifeature model with acceleration feature

Multitarget tracking in video surveillance is challenging because the appearance features of the target are often unreliable in complicated scenes. To solve the problem, we propose a multitarget tracking method using multifeature model with acceleration feature. First, an acceleration feature descriptor is derived from the histograms of the optical flow features according to the background difference. Our approach filters and normalizes the descriptors of consecutive frames to establish acceleration feature models. Then, the multifeature models of target templates are initialized by combining acceleration and multiple spatial feature models. Second, we implement data association based on the tracklet confidence by integrating the acceleration and multiple spatial feature affinities. As a result, the optimal associated pairs between target tracklets and detections are solved by the Hungarian algorithm. Finally, our tracking system updates the multifeature models of target templates online depending on the reliability of the tracklets, and the trajectories of multiple targets are output. Experiments conducted on the challenging multiple object tracking benchmark confirm the effectiveness and superiority of the proposed method.

A photoswitchable “host-guest” approach for the selective enrichment of dimethoate from olive oil

This work describes the development of a new selective photocontrollable molecularly imprinted-based sorbent for the selective enrichment/pre-concentration of dimethoate from spiked olive oil samples. To achieve this goal an improved molecularly imprinted strategy relying on the embedding of a functional monomer containing an azobenzene chromophore as light-responsive element, on the crosslinked tridimensional molecular imprinted network, has been assessed. To address the mechanisms underlying template recognition and uptake/release of the analyte from the functional imprinted material, computational studies using a quantum chemical approach, have been explored. This new functional sorbent provides a straightforward controllable uptake/release of the target template using light as the stimuli tool, which is highly advantageous due to light manipulation characteristics, such as superior clean, precision and remote controllable properties. In general, this work will contribute to the implementation of a photoswitchable analytical methodology that proves to be suitable for the selective isolation and further quantification of dimethoate from olive oil matrices at levels similar to the maximum residues limits imposed by the legislation. The limits of detection, calculated based on 3σ, was 1.6 mgL−1 and the limit of quantification, based on 10σ, was 5.2 mgL−1. The implemented sample preparation shows high reproducibility and recoveries (93.3 ± 0.4%).

Working memory capacity predicts search accuracy for novel as well as repeated targets

ABSTRACTVisual search behaviour is guided by mental representations of targets that direct attention toward relevant features in the environment. Electrophysiological data suggests these target templates are maintained by visual working memory during search for novel targets and rapidly transfer to long term memory with target repetition. If this account is correct, an individual’s working memory capacity should be more predictive of search performance for novel targets than repeated targets. Across six experiments, we tested this hypothesis using both single (Experiments 5 and 6) and multiple (Experiments 1–4) target search tasks with three different types of stimuli (real world objects, letters, and triple conjunction shapes). Each target set was repeated for six consecutive trials. In addition, we estimated visual working memory capacity using a change detection working memory task. Overall, working memory capacity did not predict response time or efficiency in the visual search task. However, working memory capacity was equally predictive of search accuracy for both novel and repeated targets. These results suggest that working memory requirements do not substantially differ between novel and repeated target search, and working memory capacity may continue to play an important role in the encoding or maintenance of target representations after they are presumed to be in long term memory.

Learned suppression for multiple distractors in visual search.

Visual search for a target object occurs rapidly if there were no distractors to compete for attention, but this rarely happens in real-world environments. Distractors are almost always present and must be suppressed for target selection to succeed. Previous research suggests that one way this occurs is through the creation of a stimulus-specific distractor template. However, it remains unknown how information within such templates scale up with multiple distractors. Here we investigated the informational content of distractor templates created from repeated exposures to multiple distractors. We investigated this question using a visual search task in which participants searched for a gray square among colored squares. During "training," participants always saw the same set of colored distractors. During "testing," new distractor sets were interleaved with the trained distractors. The critical manipulation in each study was the distance (in color space) of the new test distractors from the trained distractors. We hypothesized that the pattern of distractor interference during testing would reveal the tuning of the suppression template: RTs should be commensurate with the degree to which distractor colors are encoded within the suppression template. Results from four experiments converged on the notion that the distractor template includes information about specific color values, but has broad "tuning," allowing suppression to generalize to new distractors. These results suggest that distractor templates, unlike target templates, encode multiple features and have broad representations, which have the advantage of generalizing suppression more easily to other potential distractors. (PsycINFO Database Record

PERCEPTUAL GUIDANCE IMPROVES VISUAL SEARCH IN AGING AND IN ALZHEIMER’S DISEASE: EVIDENCE FROM EYE-MOVEMENT BEHAVIOR WITHIN REAL-WORLD SCENES

Elderly people and, especially, patients with Alzheimer's disease (AD) show impaired performance in visual search. This seems to arise from inefficient strategies, with an increased number of eye fixations and longer fixation durations. As many activities of daily living require efficient search of objects within complex environments, visual search deficits of AD patients may have a key role in reducing their functional autonomy. However, while previous studies have examined patients’ search in simple object arrays, little is know about their search behaviour in real-world scenes. Using an EyeLink 1000, we recorded eye movements of 12 mild AD patients, 24 healthy age-matched individuals (“elderly controls”) and 32 young individuals (“young controls”) during search within real-world scenes. We examined whether any group difference in eye guidance during search depends on target template specificity (name vs. precise picture), target visual salience (low vs. high) and reliability of scene semantics (consistent vs. inconsistent targets). We analysed data using linear mixed effect models, considering search initiation (first search saccade), scene scanning (until first target fixations) and target verification (dwell time on target). Aging (elderly vs. young controls) and AD (patients vs. elderly controls) led to less effective behaviour in all search phases, with fewer first saccades directed toward the target, longer scanning time and longer verification time. While these patterns were not affected by scene semantic guidance, a greater amount of target perceptual guidance was especially beneficial for the elderly controls and, even more, for the AD patients. In particular, higher target salience reduced performance gaps between elderly and young controls during scene scanning and target verification, and – when combined with a pictorial template – between patients and elderly controls during scene scanning. Eye-movement analysis enables to examine the time course of fine impairments during real-world scene search. Enhancing target visual salience and providing a priori knowledge of the perceptual appearance of the specific target objects seem promising ways of improving visual search behaviour in healthy elderly individuals and in AD patients. This understanding may contribute to the development of more appropriate information systems and living places, promoting individual's everyday functional autonomy.

Visual search with varying versus consistent attentional templates: Effects on target template establishment, comparison, and guidance.

Attentional templates can be represented in visual working memory (VWM) when the target varies from trial-to-trial and can be represented in long-term memory (LTM) when the target is consistent during trial runs. Given that attentional templates can be represented in either VWM or LTM, are there any differences in how these representations impact visual search when targets are consistent compared with varying? The current study tested the consistent template hypothesis, which predicts faster performance with a consistent target compared with a varying target. Experiment 1 examined whether consistent targets could lead to consistent templates that would improve template establishment, guidance, and/or comparison of the template to search items. Search response time was faster for consistent targets, and consistent targets produced faster comparison processes, but not more efficient guidance. Experiment 2 examined the consistent template restoration hypothesis, which predicts faster template establishment and comparison processes for a previously encountered consistent target. Experiment 2 replicated the consistent template hypothesis and supported the consistent template restoration hypothesis. These studies demonstrate that although attentional guidance is similar with varying and consistent attentional templates, consistent templates improve search performance by speeding template establishment and comparison processes. (PsycINFO Database Record

Amodal Completion of a Target Template Enhances Attentional Guidance in Visual Search.

When searching for a target object in cluttered environments, our visual system appears to complete missing parts of occluded objects—a mechanism known as “amodal completion.” This study investigated how different variants of completion influence visual search for an occluded target object. In two experiments, participants searched for a target among distractors in displays that either presented composite objects (notched shapes abutting an occluding square) or corresponding simple objects. The results showed enhanced search performance when composite objects were interpreted in terms of a globally completed whole. This search benefit for global completions was found to be dependent on the availability of a coherent, informative simple-object context. Overall, these findings suggest that attentional guidance in visual search may be based on a target “template” that represents a globally completed image of the occluded (target) object in accordance with prior experience.

Robust Stabilised Visual Tracker for Vehicle Tracking

<p>Visual tracking is performed in a stabilised video. If the input video to the tracker algorithm is itself destabilised, incorrect motion vectors will cause a serious drift in tracking. Therefore video stabilisation is must before tracking. A novel algorithm is developed which simultaneously takes care of video stabilisation and target tracking. Target templates in just previous frame are stored in positive and negative repositories followed by Affine mapping. Then optimised affine parameters are used to stabilise the video. Target of interest in the next frame is approximated using linear combinations of previous target templates. Proposed modified L1 minimisation method is used to solve sparse representation of target in the target template subspace. Occlusion problem is minimised using the inherent energy of coefficients. Accurate tracking results have been obtained in destabilised videos.</p>

The JAVA Based Computational Tool for Pairwise Comparison of Protein Backbone Folds in Liganded and Apo 3D Structures of the alpha/beta Hydrolase Fold Proteins

Cholinesterases, carboxylesterases and lipases are some of prominent catalytically active proteins with specifically similar, globular tertiary structure fold termed “alpha/beta hydrolase fold”. Ligand binding, both reversible and covalent, frequently results in small, yet systematic and potentially functionally important changes in the conformation of their alpha carbon backbones that can be easily overseen by commonly used overlays based on overall minimization of backbone atom RMSD analysis. In particular, backbone conformations of cholinesterases ‐ acetylcholinesterase and butyrylcholinesterase ‐ show only small conformational changes. This is revealed in more than 200 PDB deposited cholinesterase X‐ray structures in complexes with structurally diverse ligands that affect their function.We developed a novel, reference point based principle for overlay‐independent pairwise comparison of liganded and non‐liganded alpha carbon backbone conformations from respective PDB (Protein Data Bank) deposited 3D structure entries and encoded it in JAVA based computer algorithm for quick analysis. Comparisons are based on differences in distances between each alpha carbon and chosen reference point in each pair of compared structures, as well as on differences in the angle between center of mass, reference point and each of alpha carbons in the comparison. Combination of the two comparison criteria reveals subset of backbone alpha carbons in two structures that maintains best their relative positions in the 3D space and that can be used as tethering points for overlay of compared structures. Created overlay has capacity to reveal small but systematic local changes in the backbone conformation frequently masked by the overall RMSD minimization approach.Our systematic analysis of a number of PDB deposited alpha/beta hydrolase fold structures revealed small, yet functionally important conformational changes in their backbone consistent with experimental observations and instrumental in revealing molecular mechanisms in respective catalytic reactions. These findings are important for complete molecular target template characterization in the structure based development of novel antidotes of exposure to organophosphates which covalently inhibit this family of enzymes.Support or Funding InformationThis work was supported by the CounterACT Program, National Institutes of Health Office of the Director, Grant R21 NS098998 from NINDS.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Whatever you do, don't look at the...: Evaluating guidance by an exclusionary attentional template.

People can use a target template consisting of one or more features to guide attention and gaze to matching objects in a search array. But can we also use feature information to guide attention away from known irrelevant items? Some studies found a benefit from foreknowledge of a distractor feature, whereas others found a cost. Importantly, previous work has largely relied on end-of-trial manual responses; it is unclear how feature-guided avoidance might unfold as candidate objects are inspected. In the current experiments, participants were cued with a distractor feature to avoid, then performed a visual search task while eye movements were recorded. Participants initially fixated a to-be-avoided object more frequently than predicted by chance, but they also demonstrated avoidance of cue-matching objects later in the trial. When provided more time between cue stimulus and search array, participants continued to be initially captured by a cued-color item. Furthermore, avoidance of cue-matching objects later in the trial was not contingent on initial capture by a cue-matching object. These results suggest that the conflicting findings in previous negative-cue experiments may be explained by a mixture of two independent processes: initial attentional capture by memory-matching items and later avoidance of known irrelevant items. (PsycINFO Database Record

Visual object tracking via the local soft cosine similarity

In this paper, we propose a robust visual tracking algorithm based on soft similarity under the Bayesian framework. Firstly, we propose a Local Soft Similarity based on Soft Cosine Measure (L3SCM) that measures the soft similarity between two vectors of features in Vector Space Model (VSM) by taking into account dependencies between these features. Secondly, we model the motion model component of the proposed tracker by using the Bayesian framework, then we apply the L3SCM measure into the observation model component to measure the local similarities between the template of the tracked target and the sampled candidates in incoming frame of a given image sequence. Finally, we integrate a simple scheme to update the target template throughout the tracking process in order to improve the robustness of the proposed tracker. Experimental results on several challenging image sequences illustrate that the proposed method performs better against several state-of-the-art trackers.

Washing-Free Electrochemical Detection of Amplified Double-Stranded DNAs Using a Zinc Finger Protein.

Recombinase polymerase amplification (RPA) has been combined with electrochemical detection for simple and rapid point-of-care testing. However, there are two major hindrances to this simple and rapid testing: (i) washing or purification steps are required to remove unbound labeled probes and interfering species in the sample; (ii) it is difficult to quantify double-stranded DNA (dsDNA) electrochemically by using biospecific affinity binding without dsDNA denaturation. In the present study, we describe a wash-free and rapid electrochemical method to detect RPA-amplified dsDNAs using a zinc finger protein, Zif268. Electrochemical detection is achieved using proximity-dependent electron mediation of ferrocenemethanol between a glucose-oxidase (GOx) label and an electrode, which differentiates the specifically electrode-bound and -unbound labels without a washing or purification step. RPA-amplified dsDNA containing a biotin-terminated forward primer is specifically bound to a neutravidin-modified electrode, and GOx-conjugated Zif268 is specifically bound to the dsDNA. The whole detection is performed within 17 min (15 min for the RPA reaction and <2 min for the electrochemical measurement). Electrochemical detection is carried out without an additional incubation period, because the specific binding between Zif268 and the dsDNA occurs during the RPA reaction. The detection method could discriminate between target template DNA of Piscirickettsia salmonis and nontarget DNAs (random sequence and calf thymus DNA). The detection limit for the target DNA is approximately 300 copies in 13.2 μL, indicating that the detection method is ultrasensitive. We believe that the method could offer a promising solution for simple and rapid point-of-care testing.

Early and late selection processes have separable influences on the neural substrates of attention

To improve our understanding of the mechanisms of target selection, we examined how the spatial separation of salient items and their similarity to a pre-defined target interact using lateralised electrophysiological correlates of visual spatial attention (N2pc component) and visual short-term memory (VSTM; SPCN component). Using these features of target selection, we sought to expand on previous work proposing a model of early and late selection, where the N2pc is suggested to reflect the selection probability of visual stimuli (Aubin and Jolicoeur, 2016). The authors suggested that early-selection processes could be enhanced when items are adjacent. In the present work, the stimuli were short oriented lines, all of which were grey except for two that were blue and hence salient. A decrease in N2pc amplitude with decreasing spatial separation between salient items was observed. The N2pc increased in amplitude with increasing similarity of salient distractors to the target template, but only in target-absent trials. There was no interaction between these two factors, suggesting that separable attentional mechanisms influenced the N2pc. The findings suggest that selection is initially based on easily-distinguished attributes (i.e., both blue items) followed by a later identification-based process (if necessary), which depends on feature similarity to a target template. For the SPCN component, the results were in line with previous work: for target-present trials, an increase in similarity of salient distractors was associated with an increase in SPCN amplitude, suggesting more information was maintained in VSTM. In sum, results suggest there is a need for further inspection of salient distractors when they are similar to the target, increasing the need for focal attention, demonstrated by an increase in N2pc amplitude, followed by a higher probability of transfer to VSTM, demonstrated by an increase in SPCN amplitude.

Modelling the Diclofenac and Indomethacin Recovery by Molecularly Imprinted Polymer

Pharmaceutical compounds in surface waters are an emerging environmental concern due to their biological activity, which consequently present a new challenge for drinking water and wastewater treatment systems. In this work, diclofenac (DCF) and indomethacin (IDM) have been used as target molecules or templates in order to be removed by means of molecularly imprinted polymers (MIP). MIP-DCF and MIP-IDM were synthesised and tested using two mathematical models, which are Lagergren and Thomas models. In addition, functional groups of the active functional sites and the target molecules have also been studied by using Fourier transform infrared spectroscopy. Both MIPs followed the Lagergren pseudo first order kinetic model. Comparing the original MIP-DCF and MIP-DCF after loading with DCF, differences in their functional groups were found. In conclusion, MIP-DCF and MIP-IDM work as good sorbents to recover these emerging pharmaceuticals persistent pollutants from water.