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At least 1,351 records · Page 75Linked to original sources
PubMed1977

Visual observing behavior in the albino rat: effects of nature and complexity of visual stimuli and stage of estrus.

The effect of varying levels of complexity within two types of visual stimuli on observing behavior of albino rats (60 females, 30 males, CD Strain, Charles River) was examined. Measures of frequency and duration of looking, as well as measures of general activity, were recorded. Differences in duration of observing as a function of group membership and type of stimuli were obtained. Activity was affected by the level of complexity. A re-examination of the concept of complexity is suggested. Further delineation of variables affecting observing behavior is also needed.

Animals↗
PubMed2003

Word identification and eye fixation locations in visual and visual-plus-auditory presentations of spoken sentences.

In this study, we investigated where people look on talkers' faces as they try to understand what is being said. Sixteen young adults with normal hearing and demonstrated average speechreading proficiency were evaluated under two modality presentation conditions: vision only versus vision plus low-intensity sound. They were scored for the number of words correctly identified from 80 unconnected sentences spoken by two talkers. The results showed two competing tendencies: an eye primacy effect that draws the gaze to the talkers eyes during silence and an information source attraction effect that draws the gaze to the talker's mouth during speech periods. Dynamic shifts occur between eyes and mouth prior to speech onset and following the offset of speech, and saccades tend to be suppressed during speech periods. The degree to which the gaze is drawn to the mouth during speech and the degree to which saccadic activity is suppressed depend on the difficulty of the speech identification task. Under the most difficult modality presentation condition, vison only, accuracy was related to average sentence difficulty and individual proficiency in visual speech perception, but not to the proportion of gaze time directed toward the talkers mouth or toward other parts of the talker's face.

Adolescent↗
PubMed2005

Visual working memory for simple and complex visual stimuli.

Does the magical number four characterize our visual working memory (VWM) capacity for all kinds of objects, or is the capacity of VWM inversely related to the perceptual complexity of those objects? To find out how perceptual complexity affects VWM, we used a change detection task to measure VWM capacity for six types of stimuli of different complexity: colors, letters, polygons, squiggles, cubes, and faces. We found that the estimated capacity decreased for more complex stimuli, suggesting that perceptual complexity was an important factor in determining VWM capacity. However, the considerable correlation between perceptual complexity and VWM capacity declined significantly if subjects were allowed to view the sample memory display longer. We conclude that when encoding limitations are minimized, perceptual complexity affects, but does not determine, VWM capacity.

Adolescent↗
PubMed2005

[Subjective decrease of visual acuity after photodynamic therapy: documentation by optical coherence tomography and its correlation with visual acuity].

CASE REPORT: A 68-year-old patient complained of decreased visual acuity (VA) two days after photodynamic therapy (PDT) had been performed. VA decreased from the pre-operative value of 0.4 to 0.1 on the second postoperative day. With additional + 1.75 diopters, VA was 0.32. Optical coherence tomography (OCT) disclosed a subneuroretinal fluid accumulation causing a serous retinal detachment 600 microm in height. One week postoperatively, neither decreased vision nor retinal elevation were noted. DISCUSSION: The temporary subjective decreased VA could be predominantly reduced by adequate refraction. OCT and VA measurements excluded ischemia of the neuroretina or the choroid as a causative factor.

Aged↗
PubMedDate not supplied

[Work of the human visual system. I. Adequate visual stimulus].

It is shown that the adequate stimulus permitting to detect the presence of colour differentiation in the visual field is the change of relative space-time differences of light actions in different retinal points. Differences only in space or only in time are not sufficient for perception.

Color Perception↗
PubMedDate not supplied

The importance of the phase transfer function to visual function and visual quality metrics.

PURPOSE: To propose a vision quality metric that directly incorporates the phase transfer function. METHODS: The process of retinal image formation from the pupil to the retina is presented to identify possible domains for calculating vision quality metrics. These domains are pupil plane metrics using ocular aberrations, and retinal plane metrics using the point spread function or optical transfer function. The importance of the phase transfer function to visual performance is demonstrated and a method is proposed for directly including phase in a vision quality metric based on ocular wavefront error. RESULTS: A family of vision quality metrics is proposed, which directly incorporates the Stiles-Crawford effect, contrast sensitivity function, and the phase transfer function. CONCLUSION: The phase transfer function is an important aspect of the quality of an image, and it may be directly included in metrics intended to quantify vision quality.

Contrast Sensitivity↗
PubMed1991

Visual stimulation increases technetium-99m-HMPAO distribution in human visual cortex.

The ability of changes in the distribution of technetium-99m-hexamethylpropylene amine oxime (99mTc-HMPAO) to reflect physiologic changes in regional cerebral blood flow (rCBF) was evaluated using photic stimulation, a procedure known to increase rCBF in the striate cortex. Seven healthy subjects were injected with 740 MBq 99mTc-HMPAO on two separate days. On one day, the injection was performed following closure of the eyes and patching for 5 min. On the other day, subjects were exposed to a stroboscopic light to produce photic simulation. Images of distribution of 99mTc-HMPAO were obtained using a Strichman 810X single-photon emission computed tomogram (SPECT) brain scanner. Comparison of images obtained during light occluded versus stimulation conditions revealed a significant increase in distribution of radiopharmaceutical in visual cortex relative to whole brain (peak increase corrected for radiopharmaceutical backdiffusion 36.7% +/- 6.6%). HMPAO appears to provide a useful method for detecting relative rCBF increases with SPECT.

Adult↗
PubMedDate not supplied

[Description of an unusual clinical picture of visual hallucinations (polyopsia, erythropsia) as expression of right temporo-occipital ischemia (visual association cortex, Brodman area 37].

An unusual clinical picture (polypsia and erythropsia) as a consequence of an ischaemic lesion of the temporo-occipital junction, known as Brodman area 37 is reported. CT images showed that the lesion area was linked with the two particular function of visual association and memory peculiar to area 37 and, as is well known in the literature, predominant in right hemisphere damage.

Aged↗
PubMed1982

[Visual selectivity in infants. Study of visual preference for new images in normal infants].

The authors report and assess a method for the study of the development of visual selectivity in 9 infants aged 11 to 41 weeks. This study confirms previous results and shows that from 11 weeks, infants who are offered a choice between a new or a familiar picture look preferentially at the new one. The authors propose to apply this method to the early evaluation of cognitive development in infants.

Attention↗
PubMed1994

Onset and offset of a visual cue have different effects on manual reaction time to a visual target.

Simple reaction time (RT) to a peripheral visual target is shortened when a non-informative cue is flashed at target location 100-150 ms before target onset (early facilitation). Afterwards, RT to targets appearing at cue location is lengthened (inhibition of return). In the present study we have investigated if these effects arise from the onset and/or from the offset of the cue and the time-dependence of these effects. Twelve subjects were asked not to respond to a non-informative cue (S1) appearing on a computer screen 6 degrees to the right or to the left of a fixation point (FP), but to respond, by pressing a key, to a target (S2) occurring at 4 degrees from the FP in the same hemifield as S1 or in the opposite hemifield. There were two different types of trials. In both, a brief auditory stimulus (W) occurring 700 ms after the onset of FP warned the subject that S2 would appear 100, 200, 300, 500 or 800 ms later. Trials where the onset of S1 coincides with W and S1 remains on until the response to S2 are called ON trials. In OFF trials, S1 onset occurs at the beginning of the trial and its offset coincides with W. We found that in ON trials, RTs to S2 occurring ipsi- or contralaterally to S1 did not differ. In contrast, S1 offset elicited an inhibition of its hemifield beginning at least 100 ms after S1 offset and extending up to 800 ms.

Acoustic Stimulation↗