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PubMed2001

The neuroanatomy of phenomenal vision: a psychological perspective.

Somewhere in the visual system, phenomenal vision--the seeing of colors, brightness, depths, shades, and motion--is generated not only from the distribution of light on the retina, but also when the eyes are closed, in dreams, hallucinations, phosphenes, and (possibly) imagery. Whether these different forms of phenomenal vision share a common substrate although their origins are different (optical, mechanical, electrical, endogenous) is discussed in the light of evidence from neuropsychological and functional imaging studies. Whereas extrastriate visual cortical areas appear to be involved in all types of phenomenal vision that have been studied, the necessity of a contribution from primary visual cortex is demonstrated by the loss of conscious vision that follows its destruction. If both extrastriate and primary cortical activation are needed, the latter may not just provide an indispensable input, but may also need to receive the output of the extrastriate processing via reentrant connections.

Blindness, Cortical↗
PubMed1987

Screening of colour vision defects in diabetic patients.

The colour vision of 50 diabetic patients was examined with two screening tests, Standard Pseudoisochromatic Plates part 2 (SPP 2) and Farnsworth Panel D 15 (Panel D 15) test and with two diagnostic tests, Nagel anomaloscope and Farnsworth-Munsell 100-hue test. The performance of the diabetic patients in colour vision tests was compared to their performance in colour dependent urine and blood glucose tests. Fourteen of the patients failed the glucose tests, and they failed both of the screening tests as well. The diagnostic tests showed that all of them had a blue-yellow defect and 10 of them also had a red-green defect. The rest of the patients, 36, read the glucose tests correctly, but 17 of them failed the SPP 2 screening test, and 5 failed the Panel D 15 screening test. In diagnostic tests there were 15 patients with normal colour vision, one patient with a red-green defect, 13 patients with a blue-yellow defect, and 7 patients with both a red-green and a blue-yellow defect. The colour vision defect in diabetic patients is most often a blue-yellow defect or a combined blue-yellow and red-green defect. Therefore, the usual pseudoisochromatic plates, e.g. the Ishihara test, are not sufficient in screening because they screen only red-green defects. The screening tests should contain both a red-green and a blue-yellow part.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Impairment of colour vision associated with amiodarone keratopathy.

Objective changes in colour vision have not been demonstrated previously in patients on long-term amiodarone therapy, although the occurrence of blurring of vision and seeing coloured haloes around lights has been widely reported. In a masked study, colour vision was assessed in 15 patients who had been treated with amiodarone for 16-72 months. Subjects with extensive corneal microdeposits (Miller stage 3) had worse colour vision than subjects with mild or moderate corneal changes (Miller stages 1 and 2) (P = 0.02), and higher serum concentrations of the metabolite desethlyamiodarone (P = 0.008). The only subject with marked asymmetry of corneal changes had a long-standing unilateral ptosis, suggesting that exposure to light might influence the development of corneal changes.

Adult↗
PubMed1989

Colour vision and dark adaptation in diabetic patients after photocoagulation.

Colour vision and dark adaptation were studied in 60 diabetic patients treated with photocoagulation. An acquired colour vision defect was found in 50% and a defective dark adaptation in 77% of the patients. Both colour vision and dark adaptation were defective in 47% of the patients. Colour vision defect only was found in 3% and dark adaptation defect only in 30% of the patients. Neither of these defects was found in 20% of the patients. The Farnsworth-Munsell 100-hue test showed a blue-yellow axis in 24 of the 30 colour defective patients. In the patients with an impaired dark adaptation, the range of the cone and rod threshold elevations from the normal upper limit was from 0.2 to 1.4 log units. The Farnsworth-Munsell 100-hue test scores showed a significant positive correlation to the values of both cone and rod thresholds.

Adult↗
PubMed1986

Reproduction of complex movements: the effects of the presence of vision during encoding or at recall.

This study investigated the role of vision in the encoding and reproduction of movement. Kinaesthetic reproductions of a kinaesthetically presented two-dimensional movement were compared with reproductions where vision was present either during the standard or at reproduction. The main finding was that the presence of vision during the standard resulted in poorer accuracy and greater underestimation of movement size than when it was absent throughout or present during reproduction. The presence of vision during the standard, however, resulted in less distortion of the linear components of movement shape although no such effect was found for the angular components. The initial direction of movement was reproduced more accurately where visual experience of the movement was given, either during the standard or during reproduction.

Adult↗
PubMed1978

The rate of recovery of vision after early monocular deprivation in kittens.

1. Fifteen kittens were monocularly deprived of vision by suturing the lids of the right eye together for various periods of time at different ages. A simple behavioural technique was used to assess the immediate effects of the period of monocular deprivation on the visual acuity of the deprived eye as well as the time course of any subsequent recovery.2. The extent of the recovery of vision was measured under conditions where the animal was either forced to use its deprived eye by performing a reverse suture or where the animal had both eyes open after the initial period of monocular occlusion.3. The initial effects of monocular deprivation were graded in severity according to the age at which the deprivation was imposed, ranging from apparent blindness in animals deprived at 6 weeks of age to only a small loss of acuity in kittens deprived at 12 weeks of age.4. The effects of deprivation imposed from birth were particularly severe, leading to a temporary blindness. Nevertheless after a period of time that became progressively longer with increasing deprivation, all animals showed some recovery of pattern vision over the course of the next 2 or 3 months. The extent of this recovery became progressively less as the period of deprivation was prolonged. There was even some recovery of vision (an acuity of 2.5 cycles/deg) in animals that were deprived throughout the duration of the ;critical period' to 4 months of age.5. Direct comparison of the rate of behavioural recovery between animals that were reverse sutured with that of litter-mates that received binocular input after monocular occlusion to either 45 or 60 days of age proved to be remarkably similar, although the acuity that was eventually attained by the reverse sutured animals was always slightly higher.6. The recoveries observed after reverse suturing were reasonably well correlated with changes observed in the ocular dominance of visual cortical cells under similar circumstances.7. Although the recovery in these animals can be accounted for by the simple notion of a competitive interaction between the two eyes, the recovery observed in animals that had both eyes open after the initial period of deprivation cannot be so readily explained. Evidently there must be an additional non-competitive mechanism of recovery.

Age Factors↗
PubMed1995

Sensory integration in the bottlenosed dolphin: immediate recognition of complex shapes across the senses of echolocation and vision.

In matching-to-sample tests, a bottlenosed dolphin (Tursiops truncatus) was found capable of immediately recognizing a variety of complexly shaped objects both within the senses of vision or echolocation and, also, across these two senses. The immediacy of recognition indicated that shape information registers directly in the dolphin's perception of objects through either vision or echolocation, and that these percepts are readily shared or integrated across the senses. Accuracy of intersensory recognition was nearly errorless regardless of whether the sample objects were presented to the echolocation sense and the alternatives to the visual sense (E-V matching) or the reverse, with samples presented to the visual sense and alternatives to the echolocation sense (V-E matching). Furthermore, during V-E matching, the dolphin was equally facile at recognition whether the sample objects exposed to vision were "live," presented in air in the real world, or were images displayed on a television screen placed behind an underwater window. Overall, the results suggested that what a dolphin "sees" through echolocation is functionally similar to what it sees through vision.

Animals↗
PubMed2001

The role of vision in control of orientation in a back tuck somersault.

During a back tuck somersault, the angular velocity of the head is thought to surpass the visual system's ability to maintain a distinct and continuous picture of the environment. The primary objectives of this research were to determine if differences existed with regard to trunk and lower body kinematics, as well as landing balance, when gymnasts perform back tuck somersaults under different vision conditions. Ten female gymnasts (age = 11.6 +/- 2.67 years, competitive level = 8 +/- 1.15, and training time in gymnastics = 5.9 +/- 1.63 years) performed back tuck somersaults under 4 vision conditions while wearing electromagnetic sensors that allowed automatic digitizing. Although no significant differences were found between vision conditions with regard to timing, joint angles, and joint angular velocities, gymnasts were more stable at landing under conditions that allowed vision during either the entire somersault or the last half of the sumersault.

Acceleration↗
PubMed2001

Frontal eye field sends delay activity related to movement, memory, and vision to the superior colliculus.

Many neurons within prefrontal cortex exhibit a tonic discharge between visual stimulation and motor response. This delay activity may contribute to movement, memory, and vision. We studied delay activity sent from the frontal eye field (FEF) in prefrontal cortex to the superior colliculus (SC). We evaluated whether this efferent delay activity was related to movement, memory, or vision, to establish its possible functions. Using antidromic stimulation, we identified 66 FEF neurons projecting to the SC and we recorded from them while monkeys performed a Go/Nogo task. Early in every trial, a monkey was instructed as to whether it would have to make a saccade (Go) or not (Nogo) to a target location, which permitted identification of delay activity related to movement. In half of the trials (memory trials), the target disappeared, which permitted identification of delay activity related to memory. In the remaining trials (visual trials), the target remained visible, which permitted identification of delay activity related to vision. We found that 77% (51/66) of the FEF output neurons had delay activity. In 53% (27/51) of these neurons, delay activity was modulated by Go/Nogo instructions. The modulation preceded saccades made into only part of the visual field, indicating that the modulation was movement-related. In some neurons, delay activity was modulated by Go/Nogo instructions in both memory and visual trials and seemed to represent where to move in general. In other neurons, delay activity was modulated by Go/Nogo instructions only in memory trials, which suggested that it was a correlate of working memory, or only in visual trials, which suggested that it was a correlate of visual attention. In 47% (24/51) of FEF output neurons, delay activity was unaffected by Go/Nogo instructions, which indicated that the activity was related to the visual stimulus. In some of these neurons, delay activity occurred in both memory and visual trials and seemed to represent a coordinate in visual space. In others, delay activity occurred only in memory trials and seemed to represent transient visual memory. In the remainder, delay activity occurred only in visual trials and seemed to be a tonic visual response. In conclusion, the FEF sends diverse delay activity signals related to movement, memory, and vision to the SC, where the signals may be used for saccade generation. Downstream transmission of various delay activity signals may be an important, general way in which the prefrontal cortex contributes to the control of movement.

Animals↗
PubMed2004

Quantification of spatial vision in the Royal College of Surgeons rat.

PURPOSE: To examine how spatial vision deteriorates in the RCS rat over time as a background to experimental studies aimed at limiting photoreceptor degeneration. METHODS: The Visual Water Task was used to quantify the grating acuity of pigmented dystrophic RCS rats as they aged and to compare both grating acuity and contrast sensitivity in nondystrophic RCS rats with those parameters in normal pigmented laboratory rats (Long-Evans). RESULTS: Nondystrophic rats had grating acuities and contrast sensitivity functions that were similar to those obtained from Long-Evans rats. The grating acuity of dystrophic rats deteriorated from 80% of normal at 1 month of age to blindness by 11 months. Acuity declined rapidly to 0.32 cyc/deg over the first 4 months, with a slower decline thereafter. CONCLUSIONS: Robust measures of vision can be achieved in RCS rats using the Visual Water Task, and with this test, no visual dysfunction can be detected in the background strain. The course of functional deterioration in dystrophic rats is highly predictable, allowing the approach to be used to explore the substrates of the deterioration in vision and to monitor the effects of therapeutic retinal interventions on spatial vision.

Aging↗
PubMed2004

Rapid quantification of adult and developing mouse spatial vision using a virtual optomotor system.

PURPOSE: To develop a simple, rapid method of quantifying the spatial vision of mice. METHODS: A rotating cylinder covered with a vertical sine wave grating was calculated and drawn in virtual three-dimensional (3-D) space on four computer monitors facing to form a square. C57BL/6 mice standing unrestrained on a platform in the center of the square tracked the grating with reflexive head and neck movements. The spatial frequency of the grating was clamped at the viewing position by repeatedly recentering the cylinder on the head. Acuity was quantified by increasing the spatial frequency of the grating until an optomotor response could not be elicited. Contrast sensitivity was measured at spatial frequencies between 0.03 and 0.35 cyc/deg. RESULTS: Grating acuity was measurable on the day of eye opening (postnatal day [P]15: mean acuity, 0.031 cyc/deg) and reached a maximum (approximately 0.4 cyc/deg) by P24. A peak in the contrast sensitivity function emerged on P16 (4.7, or 21% contrast at 0.064 cyc/deg). The peak remained at 0.064 cyc/deg and climbed to a maximum sensitivity of 24.5, or 4% contrast, by P29. Acuity was obtained in each mouse in <10 minutes, and a detailed contrast sensitivity curve was generated in approximately 30 minutes. CONCLUSIONS: The virtual optomotor system provides a simple and precise method for rapidly quantifying mouse vision. Behavioral measures of vision in mice are essential for interpreting the results of experiments designed to reveal the cellular and molecular mechanisms of vision and visual development and for evaluating potential treatments for visual diseases.

Animals↗
PubMedDate not supplied

Theory is the cart, vision is the horse: reflections on research in diabetes patient education.

PURPOSE: In this paper, we examine the nature of vision and the role it plays in helping educators identify and use theories productively. We also discuss the role of theory in diabetes education and provide criteria for selecting appropriate theories. METHODS: The vision of diabetes education developed at the Michigan Diabetes Research and Training Center was used to illustrate how our vision has influenced our use of educational and behavioral theories. RESULTS: Both our vision and our theoretical assumptions should be articulated, discussed, debated, and studied. CONCLUSIONS: Diabetes patient education research can systematically contribute to the development of a sound, coherent, and progressive body of knowledge that will truly serve diabetes patient education.

Behavioral Sciences↗
PubMed2007

How humans reach: distinct cortical systems for central and peripheral vision.

Lesions of the posterior parietal cortex in humans can produce a specific disruption of visually guided hand movements termed optic ataxia. The fact that the deficit mainly occurs in peripheral vision suggests that reaching in foveal and extrafoveal vision relies on two different anatomical substrates. Using fMRI in healthy subjects, the authors demonstrated the existence of two systems, differently modulated by the two reaching conditions. Reaching in central vision involves a restricted network, including the medial intraparietal sulcus (mIPS) and the caudal part of the dorsal premotor cortex (PMd). Reaching in peripheral vision engages a more extensive network, including the parieto-occipital junction (POJ). Interestingly, POJ corresponds to the site of the lesion overlap that the authors recently found to be responsible for optic ataxia. These two sets of results converge to show that there is not a unique cortical network for reaching control but instead two systems engaged in reaching to targets in the central and peripheral visual field.

Adult↗
PubMed2005

Dissemination of health technology assessments: identifying the visions guiding an evolving policy innovation in Canada.

Health technology assessment (HTA) has received increasing support over the past twenty years in both North America and Europe. The justification for this field of policy-oriented research is that evidence about the efficacy, safety, and cost-effectiveness of technology should contribute to decision and policy making. However, concerns about the ability of HTA producers to increase the use of their findings by decision makers have been expressed. Although HTA practitioners have recognized that dissemination activities need to be intensified, why and how particular approaches should be adopted is still under debate. Using an institutional theory perspective, this article examines HTA as a means of implementing knowledge-based change within health care systems. It presents the results of a case study on the dissemination strategies of six Canadian HTA agencies. Chief executive officers and executives (n = 11), evaluators (n = 19), and communications staff (n = 10) from these agencies were interviewed. Our results indicate that the target audience of HTA is frequently limited to policy makers, that three conflicting visions of HTA dissemination coexist, that active dissemination strategies have only occasionally been applied, and that little attention has been paid to the management of diverging views about the value of health technology. Our discussion explores the strengths, limitations, and trade-offs associated with the three visions. Further efforts should be deployed within agencies to better articulate a shared vision and to devise dissemination strategies that are consistent with this vision.

Canada↗
PubMed2001

Behavioural responses of the tiger beetle larva to moving objects: role of binocular and monocular vision.

The larva of the tiger beetle Cicindela chinensis is an ambushing hunter with a body length of 15-22 mm that lives in a tunnel in the ground. It ambushes prey, keeping its head horizontal at the opening of the tunnel. When prey approaches the tunnel, the larva jumps to snap at it. When an object moves beyond its jumping range (approximately 15 mm), however, the larva quickly withdraws deep into the tunnel. These responses are mediated by two of six pairs of stemmata. How does the larva judge the hunting range using such a simple visual system? A previous study suggested that both binocular and monocular vision are used for distance estimation. Range estimation by binocular vision was further confirmed in the present behavioural observations: larvae jumped towards objects beyond the normal hunting range when virtual images of such distant objects were formed close to the larva using prisms or a narrow window. A possible mechanism involved in range estimation by monocular vision was also examined in behavioural experiments. The depth of the image in the retina appears to play a role in distance estimation because a larva with one functional stemma, the other stemmata being occluded, changed its response to a very distant object from an escape to a predatory jump when a concave lens was placed above its head. Two alternative ideas, based on optical and morphological data, are proposed to explain this behavioural change by the one-stemma larvae. First, as for myopic people, the larva might see clearly only objects that are close. Second, an infinitely distant object might produce a focused image only on the central part of the retina, whereas an object within hunting range (<15 mm) might do so on surrounding regions of the retina. The latter idea implies that the region of the retina at which the larva perceives a clear image is concerned with which type of behaviour is released, a predatory jump or an escape. We conclude that visual information about hunting range in the tiger beetle larva is extracted both peripherally by the spatial pattern of image clarity and centrally by binocular vision.

Animals↗
PubMed2006

Psychological distress and visual functioning in relation to vision-related disability in older individuals with cataracts.

OBJECTIVE: To determine whether demographic, health status and psychological functioning measures, in addition to impaired visual acuity, are related to vision-related disability. METHODS: Participants were 105 individuals (mean age=73.7 years) with cataracts requiring surgery and corrected visual acuity in the better eye of 6/24 to 6/36 were recruited from waiting lists at three public out-patient ophthalmology clinics. Visual disability was measured with the Visual Functioning-14 survey. Visual acuity was assessed using better and worse eye logMAR scores and the Melbourne Edge Test (MET) for edge contrast sensitivity. Data relating to demographic information, depression, anxiety and stress, health care and medication use and numbers of co-morbid conditions were obtained. RESULTS: Principal component analysis revealed four meaningful factors that accounted for 75% of the variance in visual disability: recreational activities, reading and fine work, activities of daily living and driving behaviour. Multiple regression analyses determined that visual acuity variables were the only significant predictors of overall vision-related functioning and difficulties with reading and fine work. For the remaining visual disability domains, non-visual factors were also significant predictors. Difficulties with recreational activities were predicted by stress, as well as worse eye visual acuity, and difficulties with activities of daily living were associated with self-reported health status, age and depression as well as MET contrast scores. Driving behaviour was associated with sex (with fewer women driving), depression, anxiety and stress scores, and MET contrast scores. CONCLUSION: Vision-related disability is common in older individuals with cataracts. In addition to visual acuity, demographic, psychological and health status factors influence the severity of vision-related disability, affecting recreational activities, activities of daily living and driving.

Activities of Daily Living↗
PubMed1992

Immobility of some second-order stimuli in human peripheral vision.

Real-world objects and events are often demarcated and defined by changes of luminance. Such stimuli are easily noticed by human beings whether the stimuli occur in central or in peripheral vision. It is also possible to use differences of color, texture, contrast, or temporal characteristics to create visual stimuli (so-called non-luminance-domain or second-order stimuli). Here I report the discovery that a variety of spatially periodic, second-order patterns, when set in motion in peripheral vision, appear stationary even though their structure is clearly visible. The immobility of the second-order stimuli is evidenced by the striking inability of observers to report their direction of motion. Special signal transformations are required to reveal the motion of second-order stimuli to higher-stage motion mechanisms, and the immobility of second-order stimuli in peripheral but not in central vision suggests that the processing of the transformed signals by higher-stage motion mechanisms changes radically from central to peripheral vision.

Color Perception↗
PubMed1998

Vision and driving: selective effect of optical blur on different driving tasks.

A test of static (high-contrast) visual acuity is the most prevalent vision test used to screen driver license applicants worldwide, even though research has largely failed to provide convincing empirical evidence for its role in traffic accidents. The purpose of this research was to evaluate the effect of visual acuity degradation on different components of the driving task. Participants were 24 young licensed drivers (15 men, 9 women) with normal vision. Driving performance was measured while participants wore modified swimmer's goggles to which blurring lenses were affixed in amounts necessary to produce binocular visual acuity levels of 20/20, 20/40 (the prevalent acuity standard for driving), 20/100, and 20/200. Driving performance was measured using the closed-road method of Wood and Troutbeck (1994). Acuity degradation produced significant decrements in road sign recognition and road hazard avoidance as well as significant increments in total driving time. Participants' abilities to estimate whether clearances between pairs of traffic cones were sufficiently wide to permit safe passage of the vehicle and to slalom through a series of traffic cones were relatively unaffected by acuity degradation. Thus the latter tasks appear to be mediated by aspects of central and peripheral vision that are relatively unaffected by optical blur. Potential applications of this type of research include the development of procedures for defining empirically justifiable vision standards for driver licensure.

Adult↗