Global Visual Perception Research Articles

Effect of Age and Refractive Error on Local and Global Visual Perception in Chinese Children and Adolescents.

PurposeThis study investigated the impact of age and myopia on visual form perception among Chinese school-age children.MethodsThis cross-sectional study included 1,074 students with a mean age of 12.1 ± 4.7 (range = 7.3–18.9) years. The mean spherical equivalence refraction (SER) of the participants was −1.45 ± 2.07 D. All participants underwent distance visual acuity (VA), refraction measurement and local and global visual form perception test including orientation, parallelism, collinearity, holes and color discrimination tasks.ResultsThe reaction times of emmetropes were slower than those of myopic and high myopic groups on both local (orientation, parallelism, and collinearity) and global discrimination tasks (all p < 0.05). A reduction in reaction times was found with increasing age on both local and global discrimination tasks (all p < 0.05). Age was significantly associated with both local and global visual perception performance after adjusting for gender, visual acuity and SER (orientation, β = −0.54, p < 0.001; parallelism, β = −0.365, p < 0.001; collinearity, β = −0.28, p < 0.001; holes, β = −0.319, p < 0.001; color, β = −0.346, p < 0.001).ConclusionsThis study revealed that both local and global visual perception improve with age among Chinese children and that myopes seem to have better visual perception than emmetropes.

Age-related changes in local and global visual perception

Over the past 40 years, research has addressed the impact of the aging process on various aspects of visual function. Most studies have focused on age-related visual impairment in low-level local features of visual objects, such as orientation, contrast sensitivity and spatial frequency. However, whether there are lifespan changes in global visual perception is still unclear. To suitably frame this question, we defined global visual patterns by a topological approach, and local visual patterns were manipulated with different levels of geometrical invariants in descending order of structural stability from projective, affine, and then Euclidean features. Using the Configural Superiority Effect, we investigated the influence of aging on local and global visual perception through a comparison of young and old adults in Experiment 1; moreover, we provided continuous-aging data from 21 to 78 years of age to investigate age-related changes in visual perception in Experiment 2. We found a large perceptual decline across increasing age groups in local geometrical perception: for example, Euclidean (orientation), affine (parallelism), and projective (collinearity) discrimination. Moreover, the study provides a counterintuitive finding that global topological perception resists the aging process and remains constant throughout adult lifespan. These findings highlight the possibility that for humans, global topology may be a stable and fundamental component by which visual systems represent and characterize objects.

Autistic Children Show a Surprising Relationship between Global Visual Perception, Non-Verbal Intelligence and Visual Parvocellular Function, Not Seen in Typically Developing Children.

Despite much current research into the visual processing style of individuals with Autism Spectrum Disorder (ASD), understanding of the neural mechanisms is lagging, especially with respect to the contributions of the overlapping dichotomies of magnocellular/parvocellular (afferent neural pathways), global/local (perception) and dorsal/ventral (cortical streams). Here, we addressed this deficiency by measuring inspection times (ITs) for novel global/local stimuli as well as recording nonlinear visually evoked potentials (VEPs), in particular, magnocellular and parvocellular temporal efficiencies. The study was conducted on a group of male ASD children and a typically developing (TD) group matched for mean age and mean non-verbal intelligence, as measured by the Raven’s Progressive Matrices. The IT results did not differ between groups, however a negative correlation between global IT and Raven’s score was found in the ASD group, that was not evident in the TD group. Nonlinear VEP showed the ASD group had smaller amplitude parvocellular-generated second order responses compared to the TD group. This is a sign of improved temporal responsiveness in ASD vs. TD groups. Principal Component Analysis linked global IT, non-verbal intelligence scores and VEP parvocellular efficiency in a single factor for the ASD but not the TD group. The results are suggestive of a constraint on pathways available for cognitive response in the ASD group, with temporal processing for those with ASD becoming more reliant on the parvocellular pathway.

Effect of heading perception on microsaccade dynamics

The present study shows the relationship between microsaccades and heading perception. Recent research demonstrates that microsaccades during fixation are necessary to overcome loss of vision due to continuous stimulation of the retinal receptors, even at the potential cost of a decrease in visual acuity. The goal of oculomotor fixational mechanisms might be not retinal stabilization, but controlled image motion adjusted to be optimal for visual processing. Thus, patterns of microsaccades may be exploited to help to understand the oculomotor system, aspects of visual perception, and the dynamics of visual attention. We presented an expansion optic flow in which the dot speed simulated a heading directed to the left or to the right of the subject, who had to signal the perceived heading by making a saccade toward the perceived direction. We recorded microsaccades during the optic flow stimulation to investigate their characteristics before and after the response. The time spent on heading perception was similar between right and left direction, and response latency was shorter during correct than incorrect responses. Furthermore, we observed that correct heading perception is associated with longer, larger and faster microsaccade characteristics. The time-course of microsaccade rate shows a modulation across the perception process similar to that seen for other local perception tasks, while the main direction is oriented toward the opposite side with respect to the perceived heading. Microsaccades enhance visual perception and, therefore, represent a fundamental motor process, with a specific effect for the build-up of global visual perception of space.

Magnocellular visual evoked potential delay with high autism spectrum quotient yields a neural mechanism for altered perception

Everyone has autistic characteristics to a greater or lesser degree, encapsulated in the Autism Spectrum Quotient, a scale that measures the degree to which an adult of normal intelligence displays traits associated with autism spectrum disorders. Recent psychophysical analyses of autism spectrum disorders point to superior local processing, and impaired or ignored global and contextual processing. The aim of this study was to test whether low- and high-scoring individuals on the Autism Spectrum Quotient differ on a measure of local and global processing, motion processing and visual pathway integrity. Fifteen low-scoring individuals and 14 high-scoring individuals derived from a normal population participated in the study. The results indicate that the initial cortical response to the magnocellular afferents is weaker at low contrast in the high autistic tendency group and that a second-order response, reflecting magnocellular activity, demonstrated a delay for high versus low scorers when the parvocellular pathway was also active in response to a high contrast stimulus. High-scoring individuals also demonstrated difficulty in identifying the global components of locally salient hierarchical Navon figures. Furthermore, cross-validated discriminant analysis, using four physiologically and three psychophysically derived parameters, correctly classified 83% of individuals who scored either high or low on the Autism Spectrum Quotient. These findings in the group scoring high on the Autism Spectrum Quotient indicate that a delay in primary visual/prestriate cortical processing of magnocellular input diminishes the advantage of its early arrival to primary visual cortex. This appears to be associated with impaired global visual perception, predicting with high accuracy behavioural tendencies associated with autism spectrum disorders. It has been proposed that perceptual impairment in autism may be attributed to a dysfunction of horizontal connections within early visual areas, presumably parvocellular in nature. However, the timing of such form processing aberrations is much later than the timing of abnormal magnocellular visual processing measured directly here. Thus it is proposed that a magnocellular processing delay decreases the ability of autistic individuals to benefit perceptually from feedback normally associated with the magnocellular advantage.

La mise en place de zone rétinienne préférentielle. Partie II : Quand ? Où ? Pourquoi s’installe-t-elle ?

The mechanisms underlying the localization of the preferred retinal locus (PRL) for visually impaired people has brought raised a number of hypotheses. In Part 1 we dissociated localizing the PRL from reading and writing tasks. Part 2 presents new hypotheses. and methods: This study was conducted on 100 partially sighted people consulting at our low-vision rehabilitation center. The technique used compares angiofluorographies with images recorded with the scanning laser ophthalmoscope during fixation tasks. It localizes the PRL with respect to the fovea. The PRL position was related to the size of the scotoma and the patient's visual damage. When there was only slight damage, the PRL was located on the left side or possibly in the superior position. When it worsened, the right position was significantly dominant; when it was severe, the PRL was generally located in the superior position or on the right. These positions were nearly always available for a given person. The new visual message must be integrated into the most suitable cerebral locations for low spatial frequencies, damaged forms, messages transmitted by retinal rods, and finally global visual perception. It must favor the peri-personal space and near vision. These elements correspond to the new visual surroundings of the visually impaired. We believe that these data are better processed if they are transmitted by the lower and left visual fields. The rehabilitation program must take into account the above considerations. If the vision therapist orients the PRL location using eccentric view training or by having the patient wear a prism, he must keep in mind that the partially sighted's activities of daily life are the most important. At first, the superior side position, which leaves the field open to a maximum of visual tasks, must be trained, followed by the right position. Of course, when this localization has already been achieved, it must be respected.

Dissociation of local and global processing in visual agnosia

Subsequent to strokes in the right and left inferomedial occipito-temporal lobes, two patients became prosopagnosic and alexic, respectively. They also show a complementary dissociation of the analysis of handwritten text. The patient with the right posterior stroke can read it but not recognize whose handwriting it is; the patient with the left posterior stroke cannot read the text but knows who wrote it. The analysis of spatial vision revealed that the prosopagnosic patient has no problem with seeing texture elements when presented in isolation. Yet she performs poorly with Moiréand texture perception, i.e. she suffers from a selective loss of global visual perception. The alexic patient performs well with Moirépatterns but neither with (complex) texture elements nor with textures. She seemingly can locally and globally process patterns composed of simple figural elements but fails with stimuli that require the integration of features. This finding of a concomitant dissociation of local and global visual processes in the two patients supports the view that prosopagnosia as well as alexia are the most conspicuous aspects of more general alterations of visual perception.