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At least 253 records · Page 14Linked to original sources
PubMed2005

Comparison of spatiotemporal cortical activation pattern during visual perception of Korean, English, Chinese words: an event-related potential study.

The aim of this study was to compare spatiotemporal cortical activation patterns during the visual perception of Korean, English, and Chinese words. The comparison of these three languages offers an opportunity to study the effect of written forms on cortical processing of visually presented words, because of partial similarity/difference among words of these languages, and the familiarity of native Koreans with these three languages at the word level. Single-character words and pictograms were excluded from the stimuli in order to activate neuronal circuitries that are involved only in word perception. Since a variety of cerebral processes are sequentially evoked during visual word perception, a high-temporal resolution is required and thus we utilized event-related potential (ERP) obtained from high-density electroencephalograms. The differences and similarities observed from statistical analyses of ERP amplitudes, the correlation between ERP amplitudes and response times, and the patterns of current source density, appear to be in line with demands of visual and semantic analysis resulting from the characteristics of each language, and the expected task difficulties for native Korean subjects.

Cerebral Cortex↗
PubMed2006

Effect of noise on the contrast detection threshold in visual perception.

It has recently been shown that noise can improve the detection of stimuli in several sensory modalities. We herein investigated whether visual contrast detection sensitivity can be improved by adding a certain amount of noise. The contrast detection thresholds of a light changing brightness periodically were measured either with or without overlapping noise in 22 normal participants. Sinusoidal modulating light at 1 or 15 Hz was used as a signal. White noise was used to produce random flickering light as the noise. Participants were required to detect any changes in the brightness of the signal with or without noise. The contrast detection threshold, which was measured using a psychophysical method, decreased at around the threshold level of the noise intensity. The maximum facilitatory effect was obtained at a noise intensity of 5 dB. This effect was consistently observed regardless of the frequency of the signal (1 and 15 Hz). These findings indicate that noise can improve the signal detection in human visual perception.

Adult↗
PubMed1999

Linking visual perception with human brain activity.

The past year has seen great advances in the use of functional magnetic resonance imaging (fMRI) to study the functional organization of the human visual cortex, to measure the neuronal correlates of visual perception, and to test computational theories of vision. Activity in particular visual brain areas, as measured with fMRI, has been found to correlate with psychophysical performance, with visual attention, and with subjective perceptual experience.

Animals↗
PubMed1996

The effect of anti-epileptic drugs on visual perception in patients with epilepsy.

We investigated the influence of the antiepileptic drugs carbamazepine (CBZ), phenytoin (PHT) and valproic acid (VPA) on different aspects of visual perception in patients with epilepsy by three different methods. (i) The colour arrangement test Farnsworth Munsell D100. (ii) A monitor system generating 24 different Gaussian dots and 24 different vertical sinusoidal gratings. Luminance increments and decrements for achromatic discrimination and four different colours for chromatic discrimination were investigated with four different sizes each adding up to 24 stimuli. (iii) A Maxwellian view system providing a foveal blue test light either superimposed on a yellow adaptation field (increment threshold) or after switching off this field (postadaptation threshold). Five different adaptation levels were investigated. Patients on PHT offered the most abnormalities, particularly in the D100 and in all Gaussian dots recordings. The individual differences between increment and postadaptation threshold (transient tritanopia effect) were significantly elevated at the four higher adaptation levels, whereas no change was found in the increment thresholds and only for the highest luminance level in the postadaptation thresholds. With VPA, chromatic and achromatic increment discrimination was impaired particularly for larger Gaussian stimuli on the monitor system. Valproic acid also induced a consistent increment threshold increase on the Maxwellian view system, an increase of the postadaptation threshold at the highest luminance level and, like PHT, an increase of the threshold differences at level 3 and 4, but not at the highest background level 5. Patients on CBZ provided normal results in all investigations, with the exception of a slight but significant increase in the D100 error score. Sinusoidal gratings turned out to be much less sensitive than Gaussian dots since they remained unchanged in patients on all three drug groups.

Adult↗
PubMed1978

Computer-based testing system for experiments in visual perception.

This paper discusses the increasing scope for the application of computing systems to the investigation of problems in the field of visual perception. A simple language for the generation of various perceptual testing schemes is described and some examples of possible applications are given.

Diagnosis, Computer-Assisted↗
PubMed2003

Visual perception in children: human, animal and virtual movement activates different cortical areas.

This study was designed to relate visual perception of motion (HUMAN, ANIMAL and VIRTUAL) to cortical activity (qEEG parameters). Thirty-four healthy right-handed children (29 months-94 months, mean age 5 years) viewed a video film showing a still image (a lake) and animated images with human, animal and virtual movement. EEGs were recorded while the children watched the video film. The power values of each frequency band theta 1: 3.5-5.5 Hz, theta 2: 5.5-7.5 Hz, alpha 1: 7.5-10.5 Hz, alpha 2: 10.5-13 Hz, beta 1: 13-18 Hz, beta 2: 18-25 Hz and beta 3: 25-35 Hz were analyzed in a four-way repeated-measures ANOVA (age x hemisphere x electrode x type of activation). Three main results were obtained: (1) younger children (< 5 years) showed higher power spectral values than older children; (2) there was specificity for real human movement in the left hemisphere; and (3) activations in the left- and right-hemispheres were different according to the movement visualized. These results indicate that in healthy children, human, animal and virtual movement activates different cortical areas.

Alpha Rhythm↗
PubMed1977

Impact of oculomotor retraining on the visual perception of curvature.

Observers viewed a computer-generated display consisting of horizontally oriented, concave-up curved lines. The position of these curves was contingent on the horizontal position of the eye so that, in order to change fixation errorlessly, from one point to another on the curve, the eye would have to execute a purely horizontal movement. In Condition H this was achieved by moving the curves horizontally, so that the minimum point was always at the horizontal eye position location, thus simulating the effect of viewing a line through a wedge prism on a contact lens. In Condition V it was achieved by moving the curves vertically so that the point fixated always had the same vertical location. In both conditions eye movements were reprogrammed rapidly to eliminate the vertical components of the saccades that were present at the start. While a small, but significant, amount of perceptual adaptation was obtained in Condition H, none at all was obtained in Condition V. The results are interpreted as not in support of such theories of perceptual adaptation to curvature distortion as require a close relationship between motor learning and perceptual change.

Adaptation, Ocular↗
PubMed1986

Note on nonveridical visual perception and pedestrian accidents at night.

It is sometimes supposed that increase of pedestrian conspicuity could lead to substantial reductions in pedestrian accidents at night. Available evidence is, however, not particularly encouraging. It is suggested that other factors affecting drivers' and pedestrians' perception may be involved.

Acceleration↗
PubMed1998

Deficits in complex visual perception following unilateral temporal lobectomy.

Although human temporal cortex is known to be important for short- and long-term memory, its role in visual perception is not well understood. In this study, we compared the performance of three patients with unilateral temporal lobectomies to that of normal controls on both "simple" and "complex" visual discriminations that did not involve explicit memory components. Two types of complex tasks were tested that involved discriminations secondary to texture segmentation. These were contrasted with simple discriminations using luminance-defined stimuli. Patients showed impaired thresholds only on tasks involving texture segmentation, performing as well as controls when the targets were defined by luminance rather than texture. The minimum stimulus presentation times for threshold performance were also measured for all tasks and found to be elevated in temporal lobectomy patients relative to controls. Although the magnitude of the deficits observed was substantial, loss was equivalent in ipsi- and contra-lesional regions of the visual field. Additional control experiments showed that the patients' perceptual deficits were not due, even in part, to disturbances of basic visual capacities such as acuity and contrast sensitivity. Our results indicate that temporal lobe damage disrupts complex, but not simple, visual discriminations throughout the visual field.

Case-Control Studies↗
PubMed2003

The function of stereotypes in visual perception.

Human vision is a product of both physiological and cultural dispositions. This cultural study investigates the role of cultural dispositions in visual perception. In particular, the study focuses on the role of stereotypes, which are involved in recognition. I propose that stereotypes are essential for basic functions of perception and human perception. However, stereotypes also introduce significant limitations on human experience. The fact that stereotypes are abstract simplifications of realities is not the limiting factor, since scientific and cultural progress continually refines stereotypes. The very principle of the stereotype appears to introduce the limitation, because the process of forming stereotypes requires both temporal and functional fragmentations of the continuum of our perception. This fragmentation can be a cause of sensory overload, a postmodern condition that generates cultural, perceptual and behavioral problems. To address this problem, I propose a cultural modification to our modality of perception. The modification shifts the emphasis of our perception from the recognition of stereotypes to the recognition of flows, processes and durations. References to the work of Henri Bergson and Martin Heidegger provide the philosophical basis for this modification and several empirical and experimental examples illustrate such modifications in practice.

Culture↗