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Do multielement visual tracking and visual search draw continuously on the same visual attention resources?

Multielement visual tracking and visual search are 2 tasks that are held to require visual-spatial attention. The authors used the attentional operating characteristic (AOC) method to determine whether both tasks draw continuously on the same attentional resource (i.e., whether the 2 tasks are mutually exclusive). The authors found that observers can search and track within the same trial significantly better than would be predicted if the 2 tasks were mutually exclusive. In fact, the AOC for tracking and search is similar to that for tracking and auditory monitoring. The results of additional experiments support an attention-switching account for this high level of dual-task performance in which a single attentional resource is efficiently switched between the tracking and search. The results provide important constraints for architectures of visual selective attention and the mechanisms of multielement tracking.

Adolescent↗

Reversal of visual discrimination and visual acute extinction in cats with poor or limited early visual experience.

Transformation of visual instrumental conditioned reflexes rewarded with food was compared in cats binocularly deprived of pattern vision in the early period of life (BD cats), control cats reared also in the laboratory but with open eyes (C cats) and cats reared in normal environment (N cats). In Expt. I the cats were given 4 sequential reversal trainings of cross vs. disc discrimination and in Expt. II a response to a gate marked with a cross or a disc was submitted to 4 sequential acute extinctions and restorations. The results show that both visual deprivation and rearing in monotonous laboratory environment moderately affect transformation of associations between visual stimuli and hunger drive and instrumental responses. However, in BD cats transformation learning is less impaired than previously studied visual discrimination learning.

Animals↗

Plasticity in the kitten's visual cortex: effects of the suppression of visual experience upon the orientational properties of visual cortical cells.

The orientation selectivity of visual cortical cells was tested in two groups of kittens. In one group the animals were reared normally for the first 4-6 weeks of life then kept in darkness. Those in the other group were dark-reared for the first 6 weeks then exposed to light for 6 h and returned to the dark. The properties of the receptive fields of visual cortical cells were examined in these kittens after periods of dark-rearing ranging from 3 days to 12 weeks. In both groups, the proportion of orientation selective cells was found to decrease with time spent in the dark. The critical period for orientation appeared to end at 10-12 weeks of age. Two populations of visual cells were distinguished functionally by their different behaviour during prolonged dark-rearing. Most of the cells which retained their orientation specificity longest during dark-rearing were tuned to horizontal or vertical orientations and more of them were monocular than in normal kittens. These functional characteristics resemble those exhibited by neurons of very young kittens. Changes in specificity observed during loss of selectivity are compared to those observed during early development. We suggest that the extent to which the orientation selectivity of a cell is plastic depends very largely upon the time, during the course of development, at which its selectivity was acquired.

Animals↗

Visual scotoma and visual afterimages: some evidence that the perceived visual afterimage may not be a purely retinal phenomenon: a single case study.

Observations of the differential appearance and behaviour of a deliberately induced visual scotoma and a patterned visual afterimage are reported. Although a retinal scotoma behaves like a visual afterimage in some ways, there are sufficient differences to suggest that the perceived visual afterimage may not be just the simple consequence of prolonged retinal stimulation.

Afterimage↗

[Effect of various light sources on visual functions in the age aspect. II. Visual acuity, the range of accommodation and fusion and the visual field].

The authors performed examinations in 15 middle aged persons and in 13 persons of older productive age in conditions of equivalent illumination, first the glow one, then the sodium one of 600 lx value at the stand of examination. They observed the dynamics of selected visual functions as the time went by in the forenoon hours. The group of older persons tolerated worse the sodium light and in both age groups one could observe the receding of the visual near point. The authors analyze the remaining visual functions in both conditions of illumination.

Accommodation, Ocular↗

Selective visual attention, visual search and visual awareness.

In a previous study, Butter and Goodale (2000) reported that visual search increases the identification of targets relative to distracters. The present series of studies investigated further this effect of search. Search increased identification of Ls when they were targets and decreased their identification when Ls were distracters in concurrent search involving feature conjunctions (Exp. 1). Subjects in Experiment 2 showed increases in sensitivity, but not in response bias, to Ls. Search had a weaker effect on d' for identification of Ts. Increasing the difficulty of searching for Ts or Ls by increasing the number of distracters enhanced identification of targets versus distracters relative to the effect of search involving eight distracters (Exp. 3). Two studies investigated the effects on probe identification of easy search tasks involving differences in stimulus features. In Experiment 4, there were no reliable effects of search on probe identification when targets were distinguished from distracters by straight versus curved lines (Z vs. O). When horizontal and vertical lines were targets and distracters, subjects showed weak and inconsistent effect on probe identification (Exp. 5). These findings, together with results of neurophysiological studies, support the view that executive mechanisms play a role in visual search by augmenting the activity of goal representations in working memory, thus increasing the likelihood of identifying goal stimuli and enhancing the efficiency of visual search.

Adult↗

Influences of visual pitch and visual yaw on visually perceived eye level (VPEL) and straight ahead (VPSA) for erect and rolled-to-horizontal observers.

Localization within the space in front of an observer can be specified along two orthogonal physical dimensions: elevation ('up', 'down') and horizontal ('left','right'). For the erect observer, these correspond to egocentric dimensions along the long and short axes of the body, respectively. However, when subjects are rolled-to-horizontal (lying on their sides), the correspondence between the physical and egocentric dimensions is reversed. Employing egocentric coordinates, localization can be referred to a central perceptual point-visually perceived eye level (VPEL) along the long axis of the body, and visually perceived straight ahead (VPSA) along the short axis of the body. In the present experiment, measurements of VPEL and of VPSA were made on each of eight subjects who were either erect or rolled-to-horizontal while monocularly viewing a long 2-line stimulus (two parallel, 64 degrees -long lines separated by 50 degrees ) in otherwise complete darkness that was centered on the eye of the observer and was tilted out of the frontoparallel plane by a variable amount and direction (from -30 degrees to +30 degrees in 10 degrees steps). The stimulus tilt was either around an axis through the center of the two eyes (pitch; VPEL was measured) or around the long axis of the body that passed through the center of the viewing eye (yaw; VPSA was measured). Large variations in the localization settings were measured that were systematic with stimulus tilt. The slopes of the functions plouing the deviations from veridicality against the orientation of the 2-line stimulus ('induction functions') were larger for the rolled-to-horizontal observer than for the erect observer for both VPEL and VPSA, and for a given body orientation were larger for the VPEL discrimination than for the VPSA discrimination; the influences of body orientation in physical space and the direction of the discrimination relative to the body were lineraly additive. Both the y-intercepts of the induction functions and the central perceptual point measured in complete darkness were lower when the norm setting by the subject was along the vertical than when it was along the horizontal; this held for both the VPEL and VPSA discriminations. The systematic effects of body orientation on the slopes and of line orientation on the y-intercepts and dark values result from an effect of gravity on the settings and fit well to a general principle: any departure from erect posture increases the induction effects of the visual stimulus. The effect of gravity is consistent with the effect of gravity in previous work in high-g environments with the VPEL discrimination.

Analysis of Variance↗

Factor structure of Benton's tests of visual retention, visual construction, and visual form discrimination.

The standard drawing and multiple-choice versions of the Benton Visual Retention Test (BVRT), the Visual Form Discrimination Test (VFDT), the Rey Auditory Verbal Learning Test (AVLT), and the Wechsler Adult Intelligence Scale-Revised Digit Span subtest were administered to a mixed sample of 97 psychiatric, neurologic, and control subjects. Factor analysis of the Benton test battery measures alone showed that the standard and multiple-choice BVRT protocols performed very similarly. Scoring of the standard BVRT for errors and number of correct items was shown to be statistically redundant for this sample. Possible simplification of standard BVRT scoring was suggested. Copying and immediate visual-memory skills emerged as separable factors on the standard BVRT. When the AVLT and Digit Span measures were factor analyzed with the Benton lest battery measures, however, simple factorial structure emerged only for the AVLT measures (one factor) and the BVRT copying measures that were grouped with the VFDT. A verbal mediation component was thought to be associated with the multifactorial BVRT and multiple-choice BVRT results in this analysis.

Journal Article↗

Visual search, visual streams, and visual architectures.

Most psychological, physiological, and computational models of early vision suggest that retinal information is divided into a parallel set of feature modules. The dominant theories of visual search assume that these modules form a "blackboard" architecture: a set of independent representations that communicate only through a central processor. A review of research shows that blackboard-based theories, such as feature-integration theory, cannot easily explain the existing data. The experimental evidence is more consistent with a "network" architecture, which stresses that: (1) feature modules are directly connected to one another, (2) features and their locations are represented together, (3) feature detection and integration are not distinct processing stages, and (4) no executive control process, such as focal attention, is needed to integrate features. Attention is not a spotlight that synthesizes objects from raw features. Instead, it is better to conceptualize attention as an aperture which masks irrelevant visual information.

Attention↗

Visual load of working with visual display terminals--introduction of VDT to newspaper editing and visual effect.

In the Japanese newspaper industry, since the late 1970s, computerization has been started in large scale. The system, called Computerized Typesetting System (CTS), has been introduced. With this system, all information in the newspaper is input into a computer, called up on a cathode ray display (CRT) to edit, and then output to film or printing plates by CTS. Thus, the work of newspaper production has undergone a major transformation from industrial work to clerical work. It was reported that newspaper production staff working with VDTs complained more than staff working with the older key system about visual and physical problems which affected their job and their daily life. The complaint rates were highest for editors, who used VDT constantly throughout the day. This study was performed to clarify the health impact of VDT use and to prevent health disorders caused by the introduction of CTS. It is concluded that 5 m corrected vision and sphere refraction of CTS workers who used CTS over 2 or 4 hr daily, significantly became worse in a year after the introduction. Therefore, it is indicated that the control of CTS work time is important to prevent the visual disorder.

Adult↗

[Dynamics of visual functions in the conditions of glow and sodium lighting. I. Visual acuity, accommodation, flicker fusion, visual field and heterophoria].

Investigations of the functions cited in the title were performed in 23 persons with a normal visual system in conditions of equal illumination, first the glow and the next day or later--the sodium one. All the tests were carried out three times in the morning hours evaluating in this way their dynamics as the time goes. The authors are analyzing the degree of the variability of the discussed functions in the time, as well as their behaviour in conditions of applied illumination. The results obtained suggest that in conditions of illumination by a high-pressure sodium lamp no negative characteristics of this source of light emerged. Deterioration of a small degree was observed only in the range of accommodation for near.

Accommodation, Ocular↗

Comparison of visual field progression in patients with normal pressure glaucoma between eyes with and without visual field loss that threatens fixation.

AIM: To compare the frequency and site of visual field progression and changes in visual acuity in patients with normal pressure glaucoma (NPG) with and without pre-existing visual field loss. METHOD: Patients with normal tension glaucoma were selected who had at least 10 visual fields over 5 or more years of follow up and no other condition that might influence the visual field or visual acuity. Alternate left and right eyes were selected from patients in random order. These eyes were then subdivided according to visual field defect threatening fixation, visual field defect not threatening fixation, and no visual field defect (fellow eyes). Eyes were defined as showing a threat to fixation according to the presence of a visual field defect involving one of more of four paracentral visual field locations. Pointwise linear regression analysis was applied to each visual field series using PROGRESSOR software. Progression of visual field loss was defined as the appearance of a regression slope 1 dB per year or more with a significance of p<0.01, which remained consistent with the addition of two of three successive visual fields to the series. The number of patients showing progression and the number where progression occurred in one of the four paracentral visual field locations was noted. The number of eyes losing two or more lines of Snellen visual acuity over the follow up period was also noted. RESULTS: 174 eyes of 174 patients were selected. 106 eyes had visual field loss threatening fixation, 46 eyes had visual field loss that did not threaten fixation, and 22 were fellow eyes with normal visual fields. The median follow up was 7.2 years. Eight eyes (36.4%) in the "normal visual fields" group, 31 eyes (67.4%) in the "visual field loss away from fixation" group, and 87 eyes (82.1%) in the "threat to fixation" group showed progression in any part of the visual field. Two eyes (9.1%) in the "normal visual fields" group, nine eyes (19.6%) in the "visual field loss away from fixation" group, and 45 eyes (42.5%) in the "threat to fixation" group showed progression at "threat to fixation". The Cox proportional hazards regression model showed an increased risk of progression at any part of the visual field for female sex and a decreased risk for eyes with normal visual fields. For progression at threat to fixation this model showed an increased risk with pre-existing threat to fixation. Eyes from older patients and those that went on to have progressive visual field loss at fixation were more likely to lose two lines of Snellen visual acuity over the follow up period. CONCLUSION: Since 20-30% of previously field damaged eyes and over 60% without prior field loss fail to demonstrate progressive visual field damage over a long follow up it is recommended that normal pressure glaucoma patients be monitored for progression and that potentially harmful therapy be withheld until progression is demonstrated. Although the presence of visual field loss that threatens fixation does not constitute an increased risk of visual field progression it does indicate an increased risk of further loss of visual field close to fixation which is in turn associated with loss of central acuity. In the light of this finding, patients with visual field loss that threatens fixation should be managed more aggressively.

Aged↗

Visual acuity and visual field impairment in Usher syndrome.

OBJECTIVE: To determine the extent of visual acuity and visual field impairment in patients with types 1 and 2 Usher syndrome. METHODS: The records of 53 patients with type 1 and 120 patients with type 2 Usher syndrome were reviewed for visual acuity and visual field area at their most recent visit. Visual field areas were determined by planimetry of the II4e and V4e isopters obtained with a Goldmann perimeter. Both ordinary and logistic regression models were used to evaluate differences in visual acuity and visual field impairment between patients with type 1 and type 2 Usher syndrome. RESULTS: The difference in visual acuity of the better eye between patients with type 1 and type 2 varied by patient age (P=.01, based on a multiple regression model). The maximum difference in visual acuity between the 2 groups occurred during the third and fourth decades of life (with the type 1 patients being more impaired), while more similar acuities were seen in both younger and older patients. Fifty-one percent (n=27) of the type 1 patients had a visual acuity of 20/40 or better in at least 1 eye compared with 72% (n=87) of the type 2 patients (age-adjusted odds ratio, 3.9). Visual field area to both the II4e (P=.001) and V4e (P<.001) targets was more impaired in the better eye of type 1 patients than type 2 patients. A concentric central visual field greater than 20 degrees in at least 1 eye was present in 20 (59%) of the available 34 visual fields of type 1 patients compared with 70 (67%) of the available 104 visual fields of type 2 patients (age-adjusted odds ratio, 2.9) with the V4e target and in 6 (21%) of the available 29 visual fields of type 1 patients compared with 36 (38%) of the available 94 visual fields of type 2 patients (age-adjusted odds ratio, 4.9) with the II4e target. The fraction of patients who had a visual acuity of 20/40 or better and a concentric central visual field greater than 20 degrees to the II4e target in at least 1 eye was 17% (n=5) in the type 1 patients and 35% (n=33) in the type 2 patients (age-adjusted odds ratio, 3.9). CONCLUSIONS: Visual acuity and visual field area were more impaired in patients with type 1 than type 2 Usher syndrome. Of note, 27 of 53 type 1 (51%) and 87 of 120 type 2 (72%) patients had a visual acuity of 20/40 or better in at least 1 eye. These data are useful for overall counseling of patients with Usher syndrome.

Adult↗

Increased rate of visual field loss associated with larger initial visual field threshold values on follow-up of open-angle glaucoma.

PURPOSE: To determine the changes in the visual field over time and the factors that contribute to these changes on follow-up of open-angle glaucoma patients. PATIENTS AND METHODS: From a retrospective review of patients' charts and visual fields, 30 eyes from 30 patients with open-angle glaucoma with a minimum of 3 years of follow-up were chosen. Visual fields were obtained with the Octopus perimeter about every 4 months. Regression analysis was used to obtain the slope for all the threshold values for each eye for the total field and nine different regions over time. Optic disc area was measured from single fundus photographs obtained at the beginning of the period of observation. RESULTS: The open-angle glaucomas were observed for a mean of 6.7 +/- 2.3 years. The number of visual fields per eye was 20.7 +/- 8.0. The mean threshold value of the total field for the first three visual fields was 18.0 +/- 5.2 dB. The visual fields of the 30 eyes with a mean intraocular pressure of 18 +/- 2 mm Hg during follow-up showed a significant decrease in their visual field slope of -0.384 dB/y for the total visual field. On multivariate analysis, the slope or rate of visual field loss was significantly correlated with the average of the first three initial visual field thresholds for the total visual field, temporal, and central regions so that the greater the threshold value the more rapid the rate of the visual field loss. For the total visual field and for the nasal, superior nasal, and temporal regions with lower initial threshold values, the rate of visual field loss was curvilinear with the rate of visual field loss increasing at greater initial mean threshold values. The other regions of the visual field showed a linear increasing rate of visual field loss with larger initial threshold values. Other factors significantly associated with progression of visual field loss were refractive error, race, the slope of the pulse rate, and the mean percent false positives and false negatives for initial to final observations. The mean and the slope of intraocular pressure from initial to final observation were not significant variables. CONCLUSION: In open-angle glaucomas observed for 6.7 +/- 2.3 years, there was a more rapid rate of visual field loss associated with larger initial threshold values and a less rapid rate of visual field loss associated with smaller initial threshold values indicating that the progression of visual field loss is greater in an earlier stage of disease.

Differential Threshold↗

The relationship between visual disability and visual field in patients with glaucoma.

PURPOSE: To evaluate the relationship between visual disability and the remaining visual field in glaucoma patients. DESIGN: Prospective noncomparative survey. PARTICIPANTS: One hundred forty-seven Japanese patients with glaucoma were examined. METHODS: Using a previously developed questionnaire, we assessed the relationship between visual disability indices and both the visual field examined using program 30-2 of the Humphrey Field Analyzer and visual acuity. MAIN OUTCOME MEASURES: Pearson's correlation coefficients between visual disability indices and the 22 visual field and 2 visual acuity measurements were calculated. Multiple regression analysis with stepwise variable selection identified factors significantly contributing to visual disability. RESULTS: We identified a significant correlation between visual disability and both the visual field and visual acuity measurements collected. Of the factors examined, retinal sensitivity in the lower hemifield within 5 degrees of the fixation and visual acuity in the better eye significantly contributed to all the item and total disability indices (DIs), measurements of the degree of visual disability as evaluated by the questionnaire; visual acuity in the worse eye contributed to two of the seven item DIs, as well as the total DI. The R value for total DI (R = 0.87, P < 0.0001) indicated that approximately 76% of the visual disability could be explained by these factors. CONCLUSIONS: The Japanese glaucoma patients' visual disability is explained primarily by retinal sensitivity in the lower hemifield within 5 degrees of the fixation and visual acuity in the better eye and secondarily by visual acuity in the worse eye.

Adult↗

Five-year change in visual acuity and incidence of visual impairment: the Blue Mountains Eye Study.

PURPOSE: To describe the 5-year change in visual acuity and the incidence of visual impairment in a population-based cohort. DESIGN: Population-based epidemiologic study. PARTICIPANTS: Of the 3654 participants of the Blue Mountains Eye Study (BMES I) baseline examination (aged 49 years+ during 1992-1994), 2335 were reexamined during the 5-year follow-up examinations from 1997 to 1999 (BMES II), and 543 persons had died since BMES I. METHODS: Visual acuity was measured using a logarithm of the minimum angle of resolution chart in both eyes separately before and after standardized refraction. Pupils were dilated and a detailed examination was performed. MAIN OUTCOME MEASURES: Visual impairment, after best refractive correction, was defined as any (visual acuity </=20/40; </=41 letters) and severe (visual acuity </=20/200; 0-5 letters) in keeping with the Beaver Dam Eye Study. Incident binocular visual impairment was defined as visual acuity </=20/40 in both eyes at follow-up, where visual acuity was >20/40 in both eyes at baseline. Incident binocular severe visual impairment was defined as visual acuity </=20/200 in both eyes at follow-up, where visual acuity was >20/200 in both eyes at baseline. The incidence for three other levels of visual impairment is also given: <20/40, <20/70, and <20/200. Monocular visual impairment was defined as impairment in one eye only at follow-up, where both eyes were unimpaired at baseline. Incident doubling and halving of the visual angle were calculated. RESULTS: Incidence rates for visual impairment increased significantly with age. Any incident impairment </=20/40 occurred binocularly in 41 persons (1.9%) and monocularly in 150 persons (7.1%). Severe incident impairment </=20/200 occurred binocularly in 3 persons (0.1%) and monocularly in 44 persons (2.1%). Incident impairment <20/40 occurred binocularly in 37 persons (1.7%) and monocularly in 134 persons (6.3%). Impairment <20/70 occurred binocularly in 15 persons (0.7%) and monocularly in 84 persons (3.8%). Impairment <20/200 occurred binocularly in 3 persons (0.1%) and monocularly in 44 persons (1.9%). Women consistently had a higher incidence of visual impairment than men, although this was often not statistically significant after adjusting for age. Increasing age was a strong predictor of visual impairment. CONCLUSIONS: This study has documented the 5-year incidence and causes of visual impairment in an older Australian population.

Age Distribution↗

Small lateral suprasylvian cortex lesions produce visual neglect and decreased visual activity in the superior colliculus.

Previous experiments in cats have shown that complete contralateral visual neglect is produced by removing all known visual cortex on one side of the brain, which can then be reversed by damaging the opposite superior colliculus. Presumably, descending facilitatory influences from the visual cortex to the ipsilateral superior colliculus are counterbalanced by intercollicular inhibition (Sprague: Science 153:1544-1546, '66). However, not all of visual cortex or all of the superior colliculus needs to be involved in this circuit. It is the deep rather than the superficial laminae of the superior colliculus that are primarily involved in visual attentive and orientation behaviors, and these laminae are largely independent of primary visual cortex. However, they do depend on corticotectal influences from a comparatively small extraprimary visual area of the posterior region of the lateral suprasylvian cortex (PSSC-Ogasawara et al: J. Neurophysiol. 52:1226-1245, '84). The present experiments demonstrate that lesions only a few millimeters in diameter in this corticotectal zone of the PSSC can produce profound visual neglect. While damage to this area has little, if any, effect on superficial laminae visual activity, it produces a dramatic decrease in the visual activity of the deep laminae. These cats with PSSC lesions fail to orient to a visual stimulus that is introduced suddenly into the contralateral visual field, yet they respond on nearly 100% of the trials to this same stimulus when it is presented in the ipsilateral visual field. The lesion-induced visual neglect produced by PSSC lesions is long-lasting but can be abruptly ameliorated by a midbrain lesion that primarily involves, or undercuts, the deep laminae of the contralateral superior colliculus. Thus, 1) visual neglect can be produced by depriving the deep laminae of the superior colliculus of visual inputs from the cortex, even when the principal visual cortical regions (17, 18, and 19) and their target structures are intact, and 2) visually guided behavior can be restored by eliminating afferents originating in, or passing through, the deep laminae of the contralateral superior colliculus.

Animals↗

Visual stabilization of posture in retinitis pigmentosa and in artificially restricted visual fields.

PURPOSE: To investigate the relationship between retinitis pigmentosa (RP) progression and the visual contribution to posture stabilization; to examine the extent to which visual-field diameter affects the visual contribution to posture stabilization. METHODS: Posture information was recorded in 35 subjects with well-characterized RP and in 20 subjects with normal vision. Data were collected as each subject stood in a dark environment and as each subject viewed a stationary visual display. In both conditions, somatosensory feedback was concurrently altered. Data were also collected on 10 additional subjects with normal vision wearing field-restricting goggles (visual-field diameters ranged from 26.5 down to 6 degrees). RESULTS: RP progression is accompanied by a steady decrease of the visual stabilization of posture, from normal values at the onset of the disease to the absence of visual stabilization and, eventually, to visual destabilization of posture. Decreasing visual field diameter in the subject with normal vision resulted in a linear decrease of the visual stabilization of posture. However, subjects with RP with comparable visual-field loss showed significantly lower visual stabilization than normal subjects with artificially restricted fields. Moreover, subjects with normal vision with restricted visual fields as small as 6 degrees failed to show visual destabilization of posture. CONCLUSIONS: Most likely, the additional reduction in the visual stabilization of posture shown in subjects with RP, as well as the visual destabilizing effect manifest in the late stages of RP, is caused by anomalous processing of visual information in the remaining visual field.

Adult↗