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

The process of reading words depends heavily on efficient visual skills, including analyzing and decomposing basic visual features. Surprisingly, previous reading-related studies have almost exclusively focused on gross aspects of visual skills, while only very few have investigated the role of finer skills. The present study filled this gap and examined the relations of two finer visual skills measured by grating acuity (the ability to resolve periodic luminance variations across space) and Vernier acuity (the ability to detect/discriminate relative locations of features) to Chinese character-processing as measured by character form-matching and lexical decision tasks in skilled adult readers. The results showed that Vernier acuity was significantly correlated with performance in character form-matching but not visual symbol form-matching, while no correlation was found between grating acuity and character processing. Interestingly, we found no correlation of the two visual skills with lexical decision performance. These findings provide for the first time empirical evidence that the finer visual skills, particularly as reflected in Vernier acuity, may directly contribute to an early stage of hierarchical word processing.
Adolescent ; Decision Making ; Female ; Form Perception ; physiology ; Humans ; Male ; Pattern Recognition, Visual ; physiology ; Photic Stimulation ; Reading ; Semantics ; Statistics as Topic ; Visual Acuity ; physiology ; Vocabulary ; Young Adult

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

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

Event-related potential (ERP) studies report that early components P120, N170 and VPP are associated with face processing. Several lines of evidence suggest that VPP is the positive counterpart of N170, and they are generated by the same brain sources. However, whether P120 has a negative counterpart and the relations among these early components (i.e. P120, N170, VPP) remain unclear. In this study, the scalp electroencephalogram was recorded when the subjects passively viewed different stimuli, and ERP was calculated. The synchronization of electroencephalography signals between fronto-central and bilateral occipitotemporal sites was evaluated, and independent component analysis was employed to seek the face-sensitive independent components and their corresponding sources. We found that P120 had the negative counterpart, i.e., VN120; moreover, VN120-VPP and P120-N170 complexes were generated by the same sources located in fusiform gyrus, which reflected the same sequential neural activities of face processing.
Adolescent ; Brain ; physiology ; Electroencephalography ; Evoked Potentials ; physiology ; Face ; Female ; Humans ; Male ; Pattern Recognition, Visual ; physiology ; Perception ; physiology ; Sensation ; physiology ; Young Adult

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

OBJECTIVE: To explore the influence of visual attention in visual evoked potential (VEP) examination. METHODS: The pattern visual evoked potential (PVEP) and flash visual evoked potential (FVEP) were used to examine 110 normal subjects whose visual acuity or corrected visual acuity is in the range of 4.8-5.2, and age between 20 to 30 years old. In PVEP inspection, subjects were asked to watch with three ways, to stare at the central screen (at the same time count silently the number of alternating of black and white squares to improve the subjects' attention), to stare at the central screen at the same time thinking other things, to look sideways (the left eye stared at the left bottom corner of the screen or the right eye stared at the right one). In FVEP inspection, subjects were checked with eyes open and closed respectively. The latency and amplitude of P100 wave were recorded. The data were statistically analyzed by SPSS 13.0 software. RESULTS In PVEP inspection, the latency and amplitude of P100 wave were statistically different among three watching ways. In FVEP inspection, latency and amplitude of P100 wave were statistically different between eyes open and closed group. CONCLUSION Although the visual evoked potential test is an objective electrophysiological visual function test, it is susceptible to the influence of various subjective factors such as visual attention. It should arise the attention of forensic experts.
Adult ; Attention ; Cooperative Behavior ; Electroencephalography ; Electrophysiology ; Evoked Potentials, Visual/physiology* ; Female ; Forensic Medicine/methods* ; Humans ; Male ; Pattern Recognition, Visual ; Photic Stimulation ; Reaction Time ; Visual Acuity/physiology* ; Visual Fields/physiology* ; Young Adult

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

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

OBJECTIVETo investigate the spatiotemporal pattern of event-related potentials (ERPs) induced by emotional Stroop task.

METHODSThe ERPs of 19 channels were recorded from 13 healthy subjects while performing emotional Stroop task by pressing the buttons representing the colors in which the words denoting different emotions were displayed. A repeated-measures factorial design was adopted with three levels (word valence: positive, neutral and negative). The result of ERP analysis was presented in the form of statistical parametric mapping (SPM) of F value.

RESULTSNo significant difference was found in either reaction time or accuracy. The SPM of ERPs suggested significant emotional valence effects in the occipital region (200-220 ms), the left and central frontal regions (270-300 ms), and the bilateral temporal and parietal cortex (560-580 and 620-630 ms, respectively).

CONCLUSIONProcessing of task-irrelevant emotional valence information involves the dynamic operation of extensive brain regions. The ERPs are more sensitive than the behavioral indices in emotional evaluation.

Adult ; Attention ; physiology ; Brain ; physiology ; Brain Mapping ; Color ; Emotions ; physiology ; Evoked Potentials ; physiology ; Female ; Humans ; Male ; Neuropsychological Tests ; Pattern Recognition, Visual ; Psychomotor Performance ; physiology ; Reaction Time ; Semantics ; Young Adult