The human visual system efficiently extracts local elements from cluttered backgrounds and integrates these elements into meaningful contour perception. This process is a critical step before object recognition, in which contours often play an important role in defining the shapes and borders of the to-be-recognized objects. However, the neural mechanism of the contour integration is still under debate. The investigation of the neural mechanism underlying contour integration could deepen our understanding of perceptual grouping in the human visual system and advance the development of the algorithms for image grouping and segmentation in computer vision. Here, we review two theoretical frameworks that were proposed over the past decades. The first framework is based on hardwired horizontal connection in primary visual cortex, while the second one emphasizes the role of recurrent connections within intra- and inter-areas. At the end of review, we also raise the unsolved issues that need to be addressed in future studies.
Form Perception ; Humans ; Models, Neurological ; Pattern Recognition, Visual ; Visual Cortex ; physiology ; Visual Perception

OBJECTIVES: To study the characteristic of contrast visual evoked potentials （CVEP） in patients with ocular trauma. METHODS: Sixty patients defined as ocular trauma by forensic clinical examination in our center were selected, and split into 0.2-0.3 （Group A）, 0.3-0.5 （Group B） and ≥0.5 （Group C） according to the best corrected visual acuity. The variation characteristics of wave amplitude and latency of CVEP under 100%, 25% and 10% contrast were observed and analyzed statistically. RESULTS: （1） Under the same contrast, the wave amplitude of P₁₀₀ decreased with the decrease of stimulus perspective. （2） Under the same stimulus perspective, the wave amplitude of P₁₀₀ decreased with the decrease of contrast （P<0.05）. （3） Under the contrast of 100% and 25% with the same stimulus perspective （except 100% 7' perspective stimulus）, the difference between group A and group B had no statistical significance （P>0.05）. Between group A and group C, group B and group C, the wave amplitude of P₁₀₀ gradually increased with the increase of vision （P<0.05）. Under the contrast of 10% with 15' stimulus perspective, the wave amplitude of P₁₀₀ increased with the increase of vision （P<0.05）. （4） Under the same contrast with the same stimulation perspective, the latency of P₁₀₀ wave shortened with the increase of vision, while the difference had no statistical significance （P>0.05）. Under the same stimulus perspective, the latency of P₁₀₀ wave was prolonged with the decrease of contrast （P>0.05）. CONCLUSIONS CVEP may become one of the possible methods for the evaluation of contrast visual acuity.
Evoked Potentials, Visual/physiology* ; Eye Injuries/physiopathology* ; Humans ; Pattern Recognition, Visual/physiology* ; Photic Stimulation ; Vision, Ocular ; Visual Acuity

Animal's numerical competence has been one of the central issues in comparative psychology, cognitive psychology and cognitive neuroscience. A great number of studies indicate that animals have the capability to subitize small numerousness and judge relative numerousness. However, it is pendent if they have the counting ability. There is no evidence that animals can estimate numerousness. Neurophysiological studies show that the posterior parietal cortex and the prefrontal cortex in monkeys are involved in the neural mechanisms underlying numerical competence.
Animals ; Behavior, Animal ; Cerebral Cortex ; physiology ; Cognition ; Macaca mulatta ; Mathematics ; Mental Competency ; Pattern Recognition, Visual ; physiology ; Verbal Behavior ; physiology

A modified "cross-modal delayed response" paradigm was used to investigate whether the visual mismatch negativity can be elicited by cartoon facial expressions, and to define the mechanism underlying automatic processing of facial expressions. Subjects taking part in the tests were instructed to discriminate the type of the tones they heard as quickly and accurately as possible, and to act merely when they heard the response imperative signal. Neutral, happy and angry faces were presented during intervals between a tone and a response imperative signal. Visual mismatch negativity (VMMN) was obtained by subtracting the event - related potential (ERP) elicited by neutral faces from that elicited by happy faces or angry faces. The angry-related VMMN was more negative than happy-related VMMN, and both were more negative in the left than in the right cerebral hemisphere. The results indicated that VMMN can be elicited by the cartoon facial expressions, and the facial expressions can be processed automatically.
Adult ; Brain ; physiology ; Cartoons as Topic ; Evoked Potentials, Visual ; physiology ; Facial Expression ; Female ; Humans ; Male ; Pattern Recognition, Visual ; physiology ; Photic Stimulation ; Visual Perception ; physiology ; Young Adult

The method of event-related potentials (ERP) was used to study the gender difference in face recognition. The stimuli in the experiment were 10 upright and 10 inverted face photos. The subjects, half female and half male, were asked to judge whether the face was upright or inverted. The results showed that the N170 wave forms were observed in the occipito-temporal regions and they were found exhibiting brain's right hemispheric dominance. The stimuli of different gender photos were noticed to have no significant impact on the N170 wave forms, but there were significant differentce in the amplitude and latency period of N170 between different gender participants. Moreover, there was marked difference in the latency period of the male participants watching the same gender face and different gender face. Similar results were not found in the ERP's latency period of female participants.
Adult ; Brain ; physiology ; Electroencephalography ; Evoked Potentials ; Face ; Facial Expression ; Female ; Form Perception ; physiology ; Humans ; Male ; Pattern Recognition, Visual ; physiology ; Recognition (Psychology) ; Sex Factors ; Young Adult

OBJECTIVE: To compare the vision objectively assessed by SPVERA with the illiterate E Acuity in normal subjects. METHODS: The effect of artificially induced image defocusing on visual acuities (Vas) measured by SPVEP and illiterate E chart measurement was studied in 14 normal subjects. SPVEP was recorded using vertical gratings of 8 different spatial frequencies ranging from 0.235 9 to 30.203 2 c/deg. The responses were averaged and displayed through the discrete Fourier transform on the monitor display. SPVERA was determined by extrapolating the PVER amplitude -spatial frequency function to baseline. SPVERA was compared with illiterate E visual acuity measured under the same conditions of optical defocus. RESULTS: With moderate defocusing (<+1.0 diopter (D),VA > 0.42), the SPVERA were equal to or poorer than the illiterate E visual acuity. With more defocus (> +2.0 diopter (D), VA < 0.3),the SPVERA became better than the illiterate E chart Visual Acuity. The correlation between the two acuities was r2 = 0.919. CONCLUSION SPVERA and the illiterate E visual acuity correlated to a certain degree. We conclude that the SPVERA is effective in estimating vision objectively.
Adult ; Evoked Potentials, Visual/physiology* ; Female ; Fourier Analysis ; Humans ; Male ; Middle Aged ; Pattern Recognition, Visual/physiology* ; Photic Stimulation ; Vision Disorders/physiopathology* ; Vision Tests/methods* ; Visual Acuity/physiology*

OBJECTIVE: To explore pattern reversal visual evoked potential (PRVEP) P100 components in the patients with different visual acuity and the correlation of P100 components with visual acuity using different visual simulation angles. METHODS: PRVEPs were recorded at Oz point in the patients (100 eyes) with different visual acuity including 0.2, 0.4, 0.6, 0.8 and 1.0 and induced by pattern reversal visual simulation with the different spatial frequencies(check sizes: 8 degrees-7.5'). The latency and amplitude of components P100 were analyzed and statistical analysis was performed using SPSS 13.0 software. RESULTS: The latency and amplitude of P100 wave showed a curvilinear relationship with check sizes. With check size 10 simulation in 0.2 visual acuity group, the P100 latency reached to the minimum and the P100 amplitude showed peak value. Other groups displayed the best value with check size 30'. The P100 latency and amplitude showed a linear correlation with visual acuity. With the increase of visual acuity, the P100 wave latency decreased and the amplitude increased gradually. Regression models between visual acuity and the Pic wave latency and amplitude were also established. CONCLUSION The regression functions can be an objective and accurate method to evaluate the visual acuity based on the better simulation angles using PRVEP examination.
Adult ; Evoked Potentials, Visual/physiology* ; Female ; Forensic Medicine/methods* ; Humans ; Male ; Myopia/physiopathology* ; Pattern Recognition, Visual/physiology* ; Photic Stimulation ; Reaction Time/physiology* ; Reference Values ; Regression Analysis ; Visual Acuity

Dynamic color is an important carrier that takes information in some special occupations. However, up to the present, there are no available and objective tests to evaluate dynamic color processing. To investigate the characteristics of dynamic color processing, we adopted two patterns of visual stimulus called "onset-offset" which reflected static color stimuli and "sustained moving" without abrupt mode which reflected dynamic color stimuli to evoke event-related brain potentials (ERPs) in primary color amblyopia patients (abnormal group) and subjects with normal color recognition ability (normal group). ERPs were recorded by Neuroscan system. The results showed that in the normal group, ERPs in response to the dynamic red stimulus showed frontal positive amplitudes with a latency of about 180 ms, a negative peak at about 240 ms and a peak latency of the late positive potential (LPP) in a time window between 290 and 580 ms. In the abnormal group, ERPs in response to the dynamic red stimulus were fully lost and characterized by vanished amplitudes between 0 and 800 ms. No significant difference was noted in ERPs in response to the dynamic green and blue stimulus between the two groups (P>0.05). ERPs of the two groups in response to the static red, green and blue stimulus were not much different, showing a transient negative peak at about 170 ms and a peak latency of LPP in a time window between 350 and 650 ms. Our results first revealed that some subjects who were not identified as color blindness under static color recognition could not completely apperceive a sort of dynamic red stimulus by ERPs, which was called "dynamic red blindness". Furthermore, these results also indicated that low-frequency ERPs induced by "sustained moving" may be a good and new method to test dynamic color perception competence.
Adult ; Color Perception ; physiology ; Color Vision Defects ; diagnosis ; physiopathology ; Event-Related Potentials, P300 ; physiology ; Evoked Potentials, Visual ; physiology ; Female ; Humans ; Male ; Pattern Recognition, Visual ; physiology ; Young Adult

OBJECTIVE: To study and compare several measures of pattern visual evoked potential in measuring normal adults' real visual acuity. METHODS: Forty normal eyes were selected to test the pattern reversal visual evoked potential, black-white scanning pattern visual evoked potential, red-black scanning pattern visual evoked potential, respectively. Their experiment visual acuity was compared with their real visual acuity. RESULTS: The black-white scanning pattern visual evoked potential and the red-black sweep pattern visual evoked potential were more accurate, more convenient, and much faster in measuring real visual acuity than the pattern reversal visual evoked potential. CONCLUSION Pattern reversal visual evoked potential, black-white scanning pattern visual evoked potential, and red-black scanning pattern visual evoked potential all can be used in forensic medical examination of eye injuries.
Adolescent ; Adult ; Analysis of Variance ; Evoked Potentials, Visual/physiology* ; Female ; Forensic Medicine/methods* ; Humans ; Male ; Middle Aged ; Pattern Recognition, Visual ; Vision Tests/methods* ; Visual Acuity/physiology* ; Young Adult

OBJECTIVE: To explore the different brain areas activated by Chinese, English, and Nepali word tasks in Nepalese by using the functional magnetic resonance image (fMRI). METHODS: To determine the neuroanatomic functional brain areas responsible for Chinese, English and Nepali reading as well as sentence-formation, blood oxygenation level dependent (BOLD) block design by fMRI was performed in 6 healthy Nepalese volunteers. RESULTS: During Chinese reading, the activated areas included bilateral motor area, subfrontal gyri, superior temporal gyri, and superior parietal lobule; during English reading, the activated areas were left motor area, left subfrontal gyrus, left supra temporal gyrus, left insula and bilateral cerebellum; and the Nepali task demonstrated the activation of left anterior central gyrus, superior frontal gyrus, superior temporal gyrus. Aside from the bilateral occipital lobes, both English and Nepali activated areas were the left cerebral hemisphere dominant. CONCLUSION The more familiar with the language, the fewer areas are activated. Superior temporal gyrus might be involved in sentence-formation.
Adult ; Brain ; physiology ; China ; England ; Female ; Humans ; Image Processing, Computer-Assisted ; Language ; Magnetic Resonance Imaging ; Nepal ; Pattern Recognition, Visual ; Reading