Distance Discrimination Research Articles

Disrupted Tactile Acuity in People With Achilles Tendinopathy: A Preliminary Case-Control Investigation.

Study Design Controlled laboratory study, preliminary case-control design. Background The mechanisms that contribute to Achilles tendinopathy remain poorly understood. The disparity between pain experience and peripheral pathology demonstrated in patients with Achilles tendinopathy suggests that changes in central nervous system function may be involved. Objectives To investigate whether lower-limb tactile acuity is impaired in people with nonacute Achilles tendinopathy. Methods Thirteen consecutive participants with nonacute midportion Achilles tendinopathy and 13 healthy controls were enrolled. Two-point discrimination thresholds over the affected Achilles tendon, unaffected tendon, and tendon of healthy controls were evaluated. Independent and dependent t tests were used to compare group means. Results Two-point discrimination distance over the affected limb in participants with Achilles tendinopathy was significantly increased when compared to the unaffected limb (mean difference, 11.7 mm; 95% confidence interval [CI]: 1.9, 21.5; P = .02) and to healthy controls (mean difference, 13.1 mm; 95% CI: 1.6, 24.6; P = .03). There was no significant difference between the healthy controls and the unaffected side in people with Achilles tendinopathy (mean difference, 1.4 mm; 95% CI: -7.9, 5.1; P = .66). Conclusion These data provide the first evidence of reduced 2-point discrimination over the affected tendon in patients with Achilles tendinopathy. Further research is needed to determine the cause for the change in tactile acuity. J Orthop Sports Phys Ther 2016;46(12):1061-1064. Epub 30 Oct 2016. doi:10.2519/jospt.2016.6514.

Prototype-based Models for the Supervised Learning of Classification Schemes

AbstractAn introduction is given to the use of prototype-based models in supervised machine learning. The main concept of the framework is to represent previously observed data in terms of so-called prototypes, which reflect typical properties of the data. Together with a suitable, discriminative distance or dissimilarity measure, prototypes can be used for the classification of complex, possibly high-dimensional data. We illustrate the framework in terms of the popular Learning Vector Quantization (LVQ). Most frequently, standard Euclidean distance is employed as a distance measure. We discuss how LVQ can be equipped with more general dissimilarites. Moreover, we introduce relevance learning as a tool for the data-driven optimization of parameterized distances.

Clinical application of finger soft tissue defect coverage with dosal proximal digit fatty fasciocutaneous flap

Objective To discuss the coverage of finger soft tissue defect with dorsal proximal digit fasciocutaneous flap on the middle and distal digit. Methods From May, 2013 to December, 2014, 8 cases with soft tissue defects at 8 fingers were treated with dorsal proximal digit fasciocutaneous flap. The flap sizes ranged from 2.5 cm × 2.0 cm to 3.5 cm × 3.0 cm. The donor site were closed straightly. Results Eight flaps of 8 fingers survived. All the wounds at the donor sites healed well. Eight fingers in 8 cases were followed up for 6-12 months. The color, texture and contour of the flaps were satisfied. The two-point discrimination distances were 8-10 mm. Conclusion The skin defect in the middle and distal digit can be satisfied covered with dorsal proximal digit fasciocutaneous flap. This flap is a simple, reliable and safe management for digit defect and can be performed in the primary hospital. To ensure the surviving of the flap, ensure the surviving of the flap, the awareness of the anatomy of the flap should be known well. The limits of its reconstruction of sensation and coverage size exit in its application. Key words: Fasciocutaneous flap; Soft tissue defect of fingers; Dorsal metacarpal artery; Dorsal digit artery

A Simplified Form of the Psychometric Function for the m‐Alternative Forced Choice (mAFC) Method

AbstractThe m‐Alternative Forced Choice (mAFC), including the 2AFC, 3AFC, and mAFC where m > 3, are a type of widely used sensory discrimination method. This article offers an interesting finding for the psychometric function for the mAFC. The conventional general psychometric function for the mAFC, which is based on m independent normal distributions with one signal and m−1 noise observations, can be expressed as an elegant simplified form, i.e., a single cumulative distribution function (cdf) of the standard (m−1)‐variate normal distribution. This finding provides not only an alternative approach to calculate the probability of correct responses (Pc) and Thurstonian discriminal distance (δ) for the mAFC, but also an intuitive geometric interpretation for Pc in the mAFC. Moreover, the simplified form of the psychometric function for the mAFC may provide some insight for the decision strategies used in the mAFC.Practical ApplicationsThe simplified form of the psychometric function for the mAFC derived originally in this paper can be expressed in a built‐in S‐Plus program “pmvnorm” (for 3AFC) and R program “pmvnorm” (for mAFC where m > 2) in the R package “mvtnorm.” Two R codes “mAFCp” and “mAFCq,” which are based on the simplified form and the R package, were developed in the article. The codes can be used for calculations of Pc and δ for the mAFC easily. A table for Pc values in the mAFC is produced for m = 2 to 8, and δ from 0 to 4 with a step of 0.1. A table for δ values in the mAFC is produced for m = 2 to 8, and Pc from 0.01 to 0.99 with a step of 0.01. A table for the B values for calculation of variance of d‐prime obtained from the mAFC is also produced.

Learning a Distance Metric from Relative Comparisons between Quadruplets of Images

This paper is concerned with the problem of learning a distance metric by considering meaningful and discriminative distance constraints in some contexts where rich information between data is provided. Classic metric learning approaches focus on constraints that involve pairs or triplets of images. We propose a general Mahalanobis-like distance metric learning framework that exploits distance constraints over up to four different images. We show how the integration of such constraints can lead to unsupervised or semi-supervised learning tasks in some applications. We also show the benefit on recognition performance of this type of constraints, in rich contexts such as relative attributes, class taxonomies and temporal webpage analysis.

Event- and time-dependent decline of outcome information in the primate prefrontal cortex.

The prefrontal cortex (PF) is involved in outcome-based flexible adaptation in a dynamically changing environment. The outcome signal dissipates gradually over time, but the temporal dynamics of this dissipation remains unknown. To examine this issue, we analyzed the outcome-related activity of PF neurons in 2 monkeys in a distance discrimination task. The initial prestimulus period of this task varied in duration, allowing us to dissociate the effects of time and event on the decline in previous outcome-related activity —previous correct versus previous error. We observed 2 types of decline in previous outcome representation: PF neurons that ceased to encode the previous outcome as time passed (time-dependent) and neurons that maintained their signal but it decreased rapidly after the occurrence of a new external event (event-dependent). Although the time-dependent dynamics explained the decline in a greater proportion of neurons, the event-dependent decline was also observed in a significant population of neurons.

Person Re-Identification by Dual-Regularized KISS Metric Learning.

Person re-identification aims to match the images of pedestrians across different camera views from different locations. This is a challenging intelligent video surveillance problem that remains an active area of research due to the need for performance improvement. Person re-identification involves two main steps: feature representation and metric learning. Although the keep it simple and straightforward (KISS) metric learning method for discriminative distance metric learning has been shown to be effective for the person re-identification, the estimation of the inverse of a covariance matrix is unstable and indeed may not exist when the training set is small, resulting in poor performance. Here, we present dual-regularized KISS (DR-KISS) metric learning. By regularizing the two covariance matrices, DR-KISS improves on KISS by reducing overestimation of large eigenvalues of the two estimated covariance matrices and, in doing so, guarantees that the covariance matrix is irreversible. Furthermore, we provide theoretical analyses for supporting the motivations. Specifically, we first prove why the regularization is necessary. Then, we prove that the proposed method is robust for generalization. We conduct extensive experiments on three challenging person re-identification datasets, VIPeR, GRID, and CUHK 01, and show that DR-KISS achieves new state-of-the-art performance.

Repair of skin and soft tissue defects at distal end of finger with serrated flap with digital proper artery and nerve pedicle combined with bilaterally pedicled V-Y advancement flap of the injured finger

To investigate the therapeutic effects of repair of skin and soft tissue defects at distal end of finger with serrated flap with digital proper artery and nerve pedicle combined with bilaterally pedicled V-Y advancement flap of the injured finger. Thirteen patients with skin and soft tissue defects at distal end of 13 fingers were hospitalized from September 2013 to January 2015. After debridement, the wound area of finger ranged from 1.2 cm × 0.8 cm to 1.8 cm × 1.5 cm. Serrated flap with digital proper artery and nerve pedicle combined with bilaterally pedicled V-Y advancement flap of the injured finger were used to repair the defect. The flaps were interruptedly sutured. The areas of bilaterally pedicled V-Y advancement flap and serrated flap with digital proper artery and nerve pedicle ranged from 0.52 to 1.11 and 2.60 to 5.23 cm(2,) respectively. All flaps of 13 patients survived completely. The patients were followed up for 6 to 24 months. The color and texture of the flaps were good. After reconstruction, the finger tips were in round in shape. The appearance of the fingers was consistent with that of the normal fingers, and joint motility was normal. No hook-nail deformity or knuckle dysfunction was found. Sensation of the flaps was estimated as S4, and the distance of two-point discrimination ranged from 2 to 3 mm. The recovery of the joint motion function of the fingers was excellent. Serrated flap with digital proper artery and nerve pedicle, combined with bilaterally pedicled V-Y advancement flap from the injured finger can repair the skin and soft tissue defects at distal end of finger with reliable blood supply and simple operative technic. It also could avoid the formation of deformity subsequent to a linear scar, and a satisfactory appearance with good function could be obtained.

An online and incremental GRLVQ algorithm for prototype generation based on granular computing

In supervised classification, learning vector quantization (LVQ) methods are commonly used due to their intuitive structure based on prototypical instances that reduce considerably the computations in the classification process. Several improvements of LVQ have been proposed based on heuristics including LVQ3, and GLVQ. All these methods use the Euclidean distance to evaluate the similarity between prototypes and objects, which may be inappropriate if features are not equally scaled. Metric adaption techniques try to alleviate this problem by learning discriminative distance measures from the training data. Generalized relevance learning vector quantization is one of such improvements. However, in big data problems LVQ algorithms require incremental learning mechanisms. This paper introduces an LVQ-algorithm based on granular computing for prototye-based classification equipped with incremental learning mechanisms. The proposed algorithm is able to group entities with similar features, and at the same time proposes new prototypes to better cover the class distribution with prototyping elements. Two steps for the automatic control of prototypes are proposed: the first one controls the number of prototypes by a usage-frequency indicator; whereas the second one, is designed to learn the relevance of data dimensions, producing an automatic pruning of useless dimensions, avoiding a high computational load and increasing the interpretability of the resulting model. The proposed method is evaluated in benchmark data and obtains competitive performance with state-of-the-art solutions. In the case of big data sets, we obtained the best accuracy rate of about 72 % with a good compression rate of around 94 %.

Combined features for face recognition under illumination variation

A robust face recognition method that utilises a set of combined features is proposed to effectively conduct face recognition with images taken under diverse illumination variations. This method extracts discriminant features from different methods, both of which have different characteristics. To exploit the respective advantage of each method, the respective discriminability of the features extracted by each method is measured based on the discriminant distance criterion of each method. The experimental results show that the proposed features result in improved recognition performance under illumination variation.

Effects of Auditory-Somatosensory Interactions on Auditory Distance Discrimination Accuracy(<Special issue>VR Psychology VI)

Effects of Auditory-Somatosensory Interactions on Auditory Distance Discrimination Accuracy(<Special issue>VR Psychology VI)

Sensory Measurements for the Method of “M+N” with Larger M and N

Abstract In a recent paper in the sensory literature, the method of “M+N” with larger M and N is proposed to be a new kind of sensory discrimination method. Fisher's exact test is used for the method for discrimination testing. The current article focuses on sensory measurements for the method. Five indices for sensory measurements and effect-sizes are derived, estimated, and proposed. The indices include log odds ratio, R-index, Thurstonian discriminal distance δ (or d′), Cohen's Δ (or d) and Gini-index. Variances of the estimators of the indices are also produced. With the proposed indices, the method of “M+N” with larger M and N can be connected to and compared with the conventional sensory discrimination methods based on common sensory measurements. Practical Applications The method of “M+N” with larger M and N can be used for both sensory discrimination tests and measurements. The method is particularly suitable for a range of nonfatiguing discrimination tasks, e.g., visual inspection and, to a certain extent, manual inspection. With the indices proposed in this article, sensory effects can be measured for the new method. Built-in R programs are used in the article for the analysis. R codes for estimations of the indices and their variances for the method are developed and provided. Tables for two important sensory indices, R-index and d′, corresponding to the observed odds ratio are presented and used in the article.

Reconstruction of soft tissue defects at finger tip with relay flaps pedicled by perforator from digital artery

To investigate the application of relay flaps pedicled by perforator from digital artery for reconstruction of soft tissue defects at finger tip. From Mar. 2012 to Jun. 2014, 9 cases with soft tissue defects at finger tip were reconstructed with relay flaps at one side of finger pedicled by perforator from digital artery. The flap size ranged from 1.3 cm x 1.6 cm to 1.6 cm x 2.2 cm. The defects at donor sites were covered by adjacent web perforator V-Y advanced flaps. All the 18 flaps in 9 cases survived completely with primary healing both in recipient and donor sites. The patients were followed up for 5 months to 2 years ( average, 12 months) with good elasticity and cosmetic results. No pain happened in the treated finger. The 2-point discrimination distance was 7-8 mm in fingertip flaps, and 10-12 mm in web perforator flaps. Hand function was graded as excellent in 7 cases, good in 2 cases, based on ATM assessment. The affected fingers had normal temperature and cold-resistance during winter. The width and depth of web in the donor site were not affected. The relay flaps pedicled by perforator from digital artery can be applied for reconstruction of soft tissue defects at finger tip. The procedure is easy with satisfactory results and reservation of main artery. No skin graft is necessary for closure of defects on donor sites.

Efficacy observation on repair of finger pulp defects and sensory reconstruction of children with the perforator propeller flaps based on the end dorsal branch of digital proper artery in the same finger

To investigate the clinical outcomes of the use of the perforator propeller flaps based on the end dorsal branch of digital proper artery in the same finger in repair of finger pulp defects and sensory reconstruction in children. Twenty-three children (31 fingers) with index, middle, ring or little finger pulp defects were hospitalized from September 2012 to December 2013. The area of finger pulp defects ranged from 1.2 cm × 1.0 cm to 2.0 cm × 1.5 cm. The perforator propeller flaps based on the end dorsal branch of digital proper artery in the same finger were used to repair the defects, with the flap size ranging from 1.3 cm × 1.2 cm to 2.2 cm × 1.6 cm. The dorsal branch of the digital proper nerve of the flap was conducted end-to-end anastomosis with the broken end of the nerve of the wound to reconstruct sensation. The donor sites were covered with autologous full-thickness skin obtained from inner aspect of the thigh. Primary healing of the wounds and donor sites were achieved in all 23 children. All the flaps and skin grafts of donor sites survived. All the patients were followed up for 6 to 20 months, with mean time of 14 months. At the last follow-up, the flaps and donor sites were in good appearance, the finger pulps were mellow and plump, with no obvious pigmentation or cicatricial contracture. The sensation of finger pulps reached S3(+), and the distance of two-point discrimination ranged from 4.5 to 6.0 mm, with mean distance of 5.1 mm. Twenty-one parents of the patients were strongly satisfied with the appearance of the repaired fingers, and the other 2 parents also expressed satisfaction. Transplantation of the perforator propeller flap based on the end dorsal branch of digital proper artery in the same finger is a safe and reliable method for the repair of index, middle, ring, and little finger pulp defects and sensory reconstruction of children. The flaps are with good blood supply, appearance and sensory function after operation.

Simultaneous two color image capture for sub-diffraction localization fluorescence microscopy

A sub-diffraction limit fluorescence localization microscope was constructed using a standard cooled 1.4 mega-pixel fluorescence charge-coupled device (CCD) camera to simultaneously resolve closely adjacent paired quantum dots on a flat surface with emissions of 540 and 630nm. The images of the overlapping Airy discs were analyzed to determine the center of the point spread function after noise reduction using Fourier transformation analysis. The Cartesian coordinates of the centers of the point spread functions were compared in serial images. Histograms constructed from serial images fit well to Gaussian functions for resolving two quantum dots separated by as little as 10nm in the x–y coordinates. Statistical analysis of multiple pairs validated discrimination of inter-fluorophore distances that vary by 10nm. The method is simple and developed for x–y resolution of dilute fluorophores on a flat surface, not serial z sectioning.

Repairing of limb extremity wounds with free descending genicular artery perforator flap without saphenous vein

Objective To explore the surgical technique and the efficacy of free descending genicular artery perforator flap without saphenous vein for tissue defect. Methods 18 cases of extremity tissue defect were involved in this study from August 2010 to April 2014, including 16 males and 2 females with an average age of 32.4 years (8 plantar or heel soft tissue defect, 10 back of hand or palm soft tissue defect). 2 old injury cases that had soft tissue defect after scar release were treated by free flaps and the other 16 were open injury with infection, among which 5 cases were combined with fractures or bone defect. Sizes of the skin and soft tissue defect were 2.0 cm×8.0 cm to 9.0 cm×12.0 cm. All wounds were treated by free descending genicular artery perforator flap from the contralateral limb. Medial femoral cutaneous nerve was kept in flaps as far as possible. The projection points of descending genicular artery perforator and saphenous vein were detected by Doppler, then the flaps were cut with reverse approach, and saphenous vein and saphenous nerve were preserved. Results All 18 flaps were survived and all cases were followed up for 3 to 30 months (average, 10.3 months). The flap sizes varied from 2.5 cm×9.0 cm-9.5 cm×13.0 cm. 2 cases with bone defect were healed 3 months later without infection, and the other 3 cases with fractures were healed 2-3 months after operation. The two point's discrimination distance was 7.0-12.0 mm on the flap. The disabilities of the arm, shoulder, and hand questionnaire score averaged 51, and the mean Japanese Orthopaedic Association's foot rating scale was 70.5. Most patients were satisfied with appearance of the recipient and donor sites, among which 5 cases had skin-graft on the donor sites, and the other 12 cases had small scars on the donor sites. Poor healing was detected in 1 case on the thigh which was healed 3 weeks later. There was no paresthesia and rash on the donor sites. The mean distance between projection points of descending genicular artery perforator and saphenous vein was 3.7 cm. Conclusion Free descending genicular artery perforator flap without saphenous vein is an optimal therapy for the extremity tissue defect, which has the advantage of covert donor site, less invasion, less variation of perforator, and could recover the skin sense of recipient site. Key words: Surgical flaps; Wounds and injuries; Extremities

Effects of electrode size and spacing on sensory modalities in the phantom thumb perception area for the forearm amputees.

Tactile sensory feedback plays a key role in accomplishing the dexterous manipulation of prosthetic hands for the amputees, and the non-invasive transcutaneous electrical nerve stimulation (TENS) of the phantom finger perception (PFP) area would be an effective way to realize sensory feedback clinically. In order to realize the high-spatial-resolution tactile sensory feedback in the PFP region, we investigated the effects of electrode size and spacing on the tactile sensations for potentially optimizing the surface electrode array configuration. Six forearm-amputated subjects were recruited in the psychophysical studies. With the diameter of the circular electrode increasing from 3 mm to 12 mm, the threshold current intensity was enhanced correspondingly under different sensory modalities. The smaller electrode could potentially lead to high sensation spatial resolution. Whereas, the smaller the electrode, the less the number of sensory modalities. For an Φ-3 mm electrode, it is even hard for the subject to perceive any perception modalities under normal stimulating current. In addition, the two-electrode discrimination distance (TEDD) in the phantom thumb perception area decreased with electrode size decreasing in two directions of parallel or perpendicular to the forearm. No significant difference of TEDD existed along the two directions. Studies in this paper would guide the configuration optimization of the TENS electrode array for potential high spatial-resolution sensory feedback.

Asymptotic properties of the misclassification rates for Euclidean Distance Discriminant rule in high-dimensional data

Performance accuracy of the Euclidean Distance Discriminant rule (EDDR) is studied in the high-dimensional asymptotic framework which allows the dimensionality to exceed sample size. Under mild assumptions on the traces of the covariance matrix, our new results provide the asymptotic distribution of the conditional misclassification rate and the explicit expression for the consistent and asymptotically unbiased estimator of the expected misclassification rate. To get these properties, new results on the asymptotic normality of the quadratic forms and traces of the higher power of Wishart matrix, are established. Using our asymptotic results, we further develop two generic methods of determining a cut-off point for EDDR to adjust the misclassification rates. Finally, we numerically justify the high accuracy of our asymptotic findings along with the cut-off determination methods in finite sample applications, inclusive of the large sample and high-dimensional scenarios.

Prediction of Internal Defect Area in Wooden Components by Stress Wave Velocity Analysis

In this study, wooden components torn down from ancient buildings were used as the experimental materials. With methodology based on reverse simulation testing, some artificial holes making up different proportional areas of their cross-section were chiseled and tested with a six-sensor-point stress wave testing device. The results indicated that two-dimensional analog images could be used to judge the internal defects of wooden components qualitatively but did not provide quantitative, accurate determination. By comparing and contrasting the attenuation tendency of stress wave velocities among adjacent sensor points, separated sensor points, and diagonal sensor points, the defect grade of wooden components can be classified. Six variations were chosen as discriminant factors. These were the attenuation coefficients of the stress wave velocities via three propagation paths and the relative proportions of their absolute values. The Mahalanobis distance discrimination model was adopted for the in-grade estimation of the internal defects present in the component’s cross-section. This method had high operability and no misjudgment ratio.

Is plantar foot sensation associated with standing balance in type 2 diabetes mellitus patients

To examine the relationship between one-leg standing balance (OLSB) and different modalities of foot sole sensation in patients with type 2 diabetes mellitus (T2DM). Forty patients diagnosed with T2DM (mean age, 53.96 ± 15.31 years) and ten healthy control subjects were included. Duration of OLSB was measured with digital chronometer. Threshold of light-touch pressure (LTP), evaluated with full Semmes-Weinstein Monofilament Test Kit, and distance of two-point discrimination (TPD), evaluated with aesthesiometer, were assessed at six different regions of the foot sole. Thresholds of the LTP at all regions were significantly correlated with duration of OLSB (p 0.05). LTP at the plantar side of the great toe was the most related area with the OLSB (r = −0.48, p < 0.05). In patients with T2DM, LTP, and TPD sensations of foot sole and duration of OLSB were decreased compared to healthy controls. In this study, there was a moderate correlation between LTP sensation and balance. Other factors that would affect the balance in patients with T2DM should be investigated.