Recognition of halftone and contour figures under their lateralization and masking

Recognition of shape of natural objects was studied during lateralized tachistoscopic presentation and different degree of noise-like ("rain drops") masking in 15 healthy subjects. Two sets of figures were used: halftone and contour ones. In all masking conditions, the mean group data showed a significantly better recognition of contour images by the left hemisphere as compared to the right hemisphere. The probability of correct response decreased with increase in the degree of masking. Contour figures were recognized significantly better than halftone figures. Gender differences in recognition were revealed. Male subjects displayed no hemispheric preference in recognition of both types of stimuli in both masking conditions. Possible neurophysiological mechanisms and functional significance of the findings are discussed.     

Brain organization of the recognition of fragmented images in subjects who show different levels of task performance success

We studied the behavioral and EEG changes in healthy adults during recognition of fragmented images presented in a series beginning with a low fragmentation level up to a complete figure. Our sample was divided into two groups according to the recognition success. The first group made few mistakes. The other group made significantly more mistakes compared to the first group; this group had a shorter reaction time and a lower recognition threshold (i.e., the fragmentation level at which the object became recognizable). The ERP analysis showed the statistical dependence between the recognition success and the involvement of the frontal and caudal cortical areas. Compared to the second group, in the first one, we found no significant association between the recognition process and either early or late ERP components in the dorsolateral prefrontal cortex and found an increase of sensory-specific components P1 and P2 in the caudal areas. These results support the hypothesis on the impact of the prefrontal cortex on the successfulness of recognition of fragmented images.     

Noise effect on the recognition of fragmented contour images

We compared the results of recognition of fragmented contour images in the presence of noise and without noise. Both the contour images and the visual noise were synthesized with Gabor elements. The spacing between fragments in contour images and between noise elements, as well as the sizes of images, varied irrespective of one another. The percentage of recognition did not depend on the size of stimuli, but it differed for various objects in the presence and absence of noise. The percentage of recognition was higher for images with lots of turns in the absence of noise and, on the contrary, for images with lengthy contours with a lightly varying curvature in the presence of noise. The thresholds of recognition in noise depended, in general, on the ratio of the spacing between the elements in noise to the spacing between contour fragments.     

Segmentation of cervical cell images.

A major problem in the automation of cervical cytology screening is the segmentation of cell images. This paper describes various standard segmentation methods plus one which determines a segmentation threshold based on the stability of the perimeter of the cell as the threshold is varied. As well as contour, certain structural information is used to decide upon the threshold which separates cytoplasm from the background. Once the cytoplasm threshold is found, cytoplasm and nucleus are separated by simple clustering into three groups, cytoplasm, folded cytoplasm and nucleus. These techniques have been tested on 1500 cervical cells that belong to one of eight normal classes and five abnormal classes. A minimum Mahalanobis distance classifier was used to compare results. Manually thresholded cells were classified correctly 66.0% of the time for the 13 class problem and 95.2% of the time on the two (normal-abnormal) class problem. The contour tracing technique was 52.9% and 90.0% correct, respectively.     

Specificity of recognition of fragmented images in seven- to eight-year-old children: Analysis of event-related potentials

The topography and parameters of event-related potentials (ERPs) recorded during the presentation of incomplete images with different fragmentation were analyzed in seven- to eight-year-old children. The degree and mode of the involvement of different cortical zones at different stages of analysis and processing of fragmented images were determined. It was found in children that the prefrontal cortical areas were involved in the recognition of incomplete images in the same way as in adults. Age-related differences manifested themselves in a lower intensity of the slow positive complex in children, reflecting the decision-making and information retention processes required for the preparation of an answer.     

Contrast sensitivity and appearance in briefly presented illusory figures.

We examined the contributions of brightness enhancement, illusory figure formation and figural completion to changes in contrast sensitivity in contour gaps. The brightness on the border of a Kanizsa-square and an outline square was measured as the point of subjective equality with the background (PSE) for small line targets. Increment and decrement thresholds were measured at the same location. We found that contrast thresholds were lower than in a control condition without inducers, and that the threshold reduction was independent of the contrast polarity of the inducers. This reduction cannot be explained by a simple summation of stimulus contrast and induced brightness. In a second experiment the inducers that define the contour of the Kanizsa and the outline square were changed so that the figure was no longer closed, keeping the local stimulus surround constant. Thresholds were equally reduced for all conditions, independently of whether the figure was completed or not, or whether an illusory contour was perceived or not. The results suggest that the reduction of contrast threshold in contour gaps is independent of the brightness perceived in these gaps and of the formation of an illusory figure. Processes that cause contrast threshold reduction in contour gaps also seem to operate independently of figural completion.     

Recognition of forward-masked complex and simple images

The accuracy and time of motor response in tests for visual recognition of simple (sets of horizontal and vertical lines, angles, and crosses) and complex (contour images of animate and inanimate objects) images forward-masked with stimuli of varying complexity were estimated in psychophysiological experiments. It was found that forward masking impaired recognition, the mask whose complexity was close to that of the given test image being the most efficient in each particular case. The masking effect was the strongest in the experiments where the sets of test and masking images coincided. Recognition of complex images proved to be more resistant to masking than recognition of simple images. The observed effects of forward masking are assumed to be determined by lateral inhibition and changes in the excitability cycle. The relative contributions of these mechanisms depend on the degree of similarity between the test and masking stimuli, as well as the hierarchical level of the visual cortex at which the test stimulus is “targeted.”     

Recognition of fragmented images and mechanisms of memory

Analysis of the topography and parameters of event-related potentials (ERPs) recorded during the presentation of incomplete images with different fragmentation aided in study of the role of different cortical zones and the order of their involvement in the recognition process. The role of the frontal cortical areas at different stages of perception of fragmented images was established. The differences in the ERPs induced by recognized and unrecognized stimuli in the frontal and frontal-temporal derivations in the interval 30–83 ms were associated with the appearance of early positivity in response to recognized images and development of early negativity in response to unrecognized stimuli. The N300 component associated with recognition was stronger in these cortical zones during identification of images. A late positive complex appeared in the frontal areas earlier than in other areas. Involvement of the caudal visual areas in the recognition process was reflected by enhancement of the components P100, P250, and N400. Our results suggest that the frontal areas play the main role in the recognition of fragmented images because they are the structures that organize extraction of traces from long-term modality-specific memory using a system of afferent and efferent links and determine the strategy of information analysis necessary for the solution of a given task.     

Multi-Atlas Based Adaptive Active Contour Model with Application to Organs at Risk Segmentation in Brain MR Images

BackgroundAccurate delineation of organs at risk (OARs) is critical in radiotherapy. Manual delineation is tedious and suffers from both interobserver and intraobserver variability. Automatic segmentation of brain MR images has a wide range of applications in brain tumor radiotherapy. In this paper, we propose a multi-atlas based adaptive active contour model for OAR automatic segmentation in brain MR images.MethodsThe proposed method consists of two parts: multi-atlas based OAR contour initiation and an adaptive edge and local region based active contour evolution. In the adaptive active contour model, we define an energy functional with an adaptive edge intensity fitting force which is responsible for evaluating contour inwards or outwards, and a local region intensity fitting force which guides the evolution of the contour.ResultsExperimental results show that the proposed method achieved more accurate segmentation results in brainstem, eyes and lens automatic segmentation with the Dice Similar Coefficient (DSC) value of 87.19%, 91.96%, 77.11% respectively. Besides, the dosimetric parameters also demonstrate the high consistency of the manual OAR delineations and the auto segmentation results of the proposed method in brain tumor radiotherapy.ConclusionsThe geometric and dosimetric evaluations show the desirable performance of the proposed method on the application of OARs segmentations in brain tumor radiotherapy.     

Synthesis and cytotoxicity of a novel iridoid glucoside derived from aucubin

The novel iridoid glycoside 2 was prepared in six steps (15% overall yield) from natural aucubin (1) and fully characterized. Compound 2, which comprises the same conjugated cyclopentenone pharmacophore as known antitumor oxylipins and prostaglandins, displayed significant antiproliferative in vitro activity towards leukemia L1210 cells. The Michael addition of nucleophilic thiols to compound 2 occurred on a different position compared to classical delta7-prostaglandin A1 methyl ester. The resulting adducts 7a and 7b were fully characterized, and their MS fragmentation patterns were elucidated.     

Smaller Fixation Target Size Is Associated with More Stable Fixation and Less Variance in Threshold Sensitivity

The aims of this randomized observational case control study were to quantify fixation behavior during standard automated perimetry (SAP) with different fixation targets and to evaluate the relationship between fixation behavior and threshold variability at each test point in healthy young participants experienced with perimetry. SAP was performed on the right eyes of 29 participants using the Octopus 900 perimeter, program 32, dynamic strategy. The fixation targets of Point, Cross, and Ring were used for SAP. Fixation behavior was recorded using a wearable eye-tracking glass. All participants underwent SAP twice with each fixation target in a random fashion. Fixation behavior was quantified by calculating the bivariate contour ellipse area (BCEA) and the frequency of deviation from the fixation target. The BCEAs (deg²) of Point, Cross, and Ring targets were 1.11, 1.46, and 2.02, respectively. In all cases, BCEA increased significantly with increasing fixation target size (p < 0.05). The logarithmic value of BCEA demonstrated the same tendency (p < 0.05). A positive correlation was identified between fixation behavior and threshold variability for the Point and Cross targets (ρ = 0.413–0.534, p < 0.05). Fixation behavior increased with increasing fixation target size. Moreover, a larger fixation behavior tended to be associated with a higher threshold variability. A small fixation target is recommended during the visual field test.     

基于双模型融合的大熊猫头部图像分割

在大熊猫(Ailuropoda melanoleuca)的迁地保护和种群饲养管理中,及时、快速地进行个体识别和行为监测,对其健康管理具有至关重要的作用。圈养大熊猫健康状况通常由专门的饲养人员肉眼观测,人力成本高、效率低并且缺乏时效性。基于图像的动物个体识别与行为分析技术效率高、时间成本低,已经成为新的监测发展趋势。已有研究提出,通过大熊猫面部图像的检测和分析,可实现个体识别和行为分类。但该方法依然存在检测精度不足导致识别准确率难以提升的问题。本文提出一种基于YOLOv3和Mask R-CNN的双模型融合方法,实现了大熊猫头部图像分割和精准检测。包含3个部分：YOLOv3完成头部检测,Mask R-CNN完成大熊猫轮廓分割,然后将两个模型的输出进行交并比融合。结果显示,头部检测准确率为82.6%,大熊猫轮廓分割准确率为95.2%,总体头部轮廓分割准确率为87.1%。该方法对大熊猫头部图像的识别率和分割准确率高,为大熊猫的个体识别、性别分类提供了帮助,为行为分析提供了技术参考。     

An edge relocation segmentation algorithm

An automated procedure that refines the nuclear contour of a previously segmented nucleus is described. The algorithm makes use of intensity information, edge magnitude information and both object and edge connectivity information. This automated procedure generates a closed contour precisely along the edge of the nucleus. The procedure was tested on a database of 3,680 red-green-blue images of thionin-SO2 and orange II-stained cervical cells obtained from normal and dysplastic samples. When used in conjunction with a simple threshold selection algorithm and an artifact removal routine, this edge relocation algorithm resulted in the correct segmentation of over 98% of the nuclei. Only 63 (1.7%) of all nuclei were incorrectly segmented.     

Do alignment thresholds define a critical boundary in long-range detection facilitation with co-linear lines?

Thresholds for line contrast detection (experiment 2) were measured with a two-alternative temporal forced-choice procedure as a function of the spatial position of a vertical target line with regard to two co-linear context lines. The different spatial positions of the target line corresponded to values near the position discrimination threshold (experiment 1) reflecting the just detectable lateral offset, or non-co-linearity, between the context lines which were vertically separated by about 100 minutes of visual arc. Target and context lines were vertically separated by about 30 minutes of arc, had equal contrast polarity in one case, and opposite contrast polarity in the other. Strong line contrast detection facilitation is found at perceptually co-linear target locations. This facilitation decreases noticeably at a horizontal target offset that corresponds to the alignment threshold measured with the context lines. The effects are independent of the relative contrast polarity of target and context and, as shown in a third experiment, also independent of both the relative length or number of lines, and the magnitude of their absolute co-axial separation. This independence seems to hold, provided individual line length and co-axial distance between lines are larger than what appears to be the lower limit of the long-range spatial domain for orientation or contour integration (i.e. 20 minutes of arc), as determined by previous studies. The findings reported here suggest that alignment thresholds are likely to define a critical lateral boundary in long-range detection facilitation with co-linear lines. They support models of contour integration based on interactions between neural mechanisms that integrate local signals of contrast, orientation, and relative position or end-to-end alignment. Such mechanisms may help to explain the formation of representations of virtual contours and object contours in human perception.     

Energy model for contrast detection: spatiotemporal characteristics of threshold vision

A model for contrast detection of spatiotemporal stimuli is proposed which consists of a spatiotemporal linear filter, an energy device and a threshold device. Assuming the existence of independent intrinsic noise, the probability of stimulus detection was approximated by a Weibull function of the response energy. With this assumption, the stimulus energy is a constant at fixed detection probability. This energy model for contrast detection satisfactorily accounted for the elliptical threshold contours of line pairs at stimulus separations within the range 2–30 min and at stimulus onset asynchronies within the range 20–140 ms. The threshold contour at a large stimulus onset asynchrony (300 ms) was in the form of a rounded square. This finding was explained by assuming that the probability of seeing the line pair was determined by the joint probability that at least one stimulus had been detected. With the energy model, the temporal and spatial autocorrelation functions of the response to a flashed line were evaluated. The autocorrelation functions thus determined were used to predict the temporal contrast sensitivity function to a flickering line stimulus and the spatial contrast sensitivity function to flashed gratings, which were in agreement with the experimental data. The data obtained were fitted adequately by an impulse response approximated by a spatiotemporal Gabor-like function. Received: 08 December 1997 / Accepted in revised form: 26 January 1999     

Low-level aspects of segmentation and recognition.

This paper discusses two problems related to three-dimensional object recognition. The first is segmentation and the selection of a candidate object in the image, the second is the recognition of a three-dimensional object from different viewing positions. Regarding segmentation, it is shown how globally salient structures can be extracted from a contour image based on geometrical attributes, including smoothness and contour length. This computation is performed by a parallel network of locally connected neuron-like elements. With respect to the effect of viewing, it is shown how the problem can be overcome by using the linear combinations of a small number of two-dimensional object views. In both problems the emphasis is on methods that are relatively low level in nature. Segmentation is performed using a bottom-up process, driven by the geometry of image contours. Recognition is performed without using explicit three-dimensional models, but by the direct manipulation of two-dimensional images.     

A neural network based pattern recognition system for somatic embryos of Douglas fir

A pattern recognition system was developed to classify Douglas fir somatic embryos by employing an image analysis system and two neural network based classifiers. The contour of embryo images was segmented, digitalized and converted to numerical values after the discrete and fast Fourier transformation. These values, or Fourier features, along with some other shape factors, were used for embryo classification. The pattern recognition system used a hierarchical decision tree to classify Douglas fir embryos into three normal and one abnormal embryo classes. An accuracy of greater than 80% was achieved for normal embryos. This system provides an objective and efficient method of classifying embryos of Douglas fir. It will be a useful tool for kinetic studies and process optimization of conifer somatic embryogenesis.     

Proteomic analysis of bovine brain G protein gamma subunit processing heterogeneity

We characterized the variable processing of the G protein gamma subunit isoforms associated with bovine brain G proteins, a primary mediator of cellular communication. Ggamma subunits were isolated from purified brain G proteins and characterized by Edman sequencing, by MALDI MS, by chemical and/or enzymatic fragmentation assayed by MALDI MS, and by MS/MS fragmentation and sequencing. Multiple forms of six different Ggamma isoforms were detected. Significant variation in processing was found at both the amino termini and particularly the carboxyl termini of the proteins. All Ggamma isoforms contain a carboxyl-terminal CAAX motif for prenylation, carboxyl-terminal proteolysis, and carboxymethylation. Characterization of these proteins indicates significant variability in the normal processing of all of these steps in the prenylation reaction, including a new variation of prenyl processing resulting from cysteinylation of the carboxyl terminus. These results have multiple implications for intracellular signaling mechanisms by G proteins, for the role of prenyl processing variation in cell signaling, and for the site of action and consequences of drugs that target the prenylation modification.     

RECENT BIOACOUSTIC PUBLICATIONS—from 1991 and a few from 1990 and 1989

ABSTRACT

The focus of this study was to determine whether individual vocal identification of Scops Owls Otus scops was possible and if there was a stability of the hoot-calls over a short time period in the same individuals. Spontaneous vocalizations of 13 owls were recorded in 2004 in Southern Tuscany, Italy. Visual analysis of spectrograms and quantitative multivariate analysis of six vocal features showed marked individual differences. In some owls a repertoire of two different hoot types was found. In 2005, 10 Scops owls were recorded three times in the same breeding season (2 hours and 10 days after the first session). Statistical analysis of data showed that 60% of owls did not change call features over time. However a slight but significant variability between successive vocal performances of the same owl was found in 40% of cases. This variability may decrease the recognition power by acoustic analysis. To overcome this obstacle I suggest a multi step qualitative/quantitative approach. A Difference Index (DI) was calculated to set a threshold between the slight intra-individual and the very high inter-individual variability. This method allowed the recognition of calls of each owl recorded over time in 2005.     

Determination of Benefits of Cochlear Implantation in Children with Auditory Neuropathy

BackgroundAuditory neuropathy (AN) is a recently recognized hearing disorder characterized by intact outer hair cell function, disrupted auditory nerve synchronization and poor speech perception and recognition. Cochlear implants (CIs) are currently the most promising intervention for improving hearing and speech in individuals with AN. Although previous studies have shown optimistic results, there was large variability concerning benefits of CIs among individuals with AN. The data indicate that different criteria are needed to evaluate the benefit of CIs in these children compared to those with sensorineural hearing loss. We hypothesized that a hierarchic assessment would be more appropriate to evaluate the benefits of cochlear implantation in AN individuals.MethodsEight prelingual children with AN who received unilateral CIs were included in this study. Hearing sensitivity and speech recognition were evaluated pre- and postoperatively within each subject. The efficacy of cochlear implantation was assessed using a stepwise hierarchic evaluation for achieving: (1) effective audibility, (2) improved speech recognition, (3) effective speech, and (4) effective communication.ResultsThe postoperative hearing and speech performance varied among the subjects. According to the hierarchic assessment, all eight subjects approached the primary level of effective audibility, with an average implanted hearing threshold of 43.8 ± 10.2 dB HL. Five subjects (62.5%) attained the level of improved speech recognition, one (12.5%) reached the level of effective speech, and none of the subjects (0.0%) achieved effective communication.ConclusionCIs benefit prelingual children with AN to varying extents. A hierarchic evaluation provides a more suitable method to determine the benefits that AN individuals will likely receive from cochlear implantation.