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PubMed2006

Creating an organizational diversity vision: goals, outcomes, and future directions of the International Society of Psychiatric Nurses.

The aim of this article was to chronicle the development and status of a diversity vision within a psychiatric nursing organization. Organizational activities to support diversity and cultural competence, along with challenges to a full integration of these values, are presented. Psychiatric nurses need to be engaged in the process of developing personal and organizational cultural competence to eliminate barriers that contribute to disparities in effective mental health care.

Clinical Competence↗
PubMed1986

Comparison of Wesson and modified Sheedy fixation disparity tests. Do fixation disparity measures relate to normal binocular status?

A new fixation disparity measuring device, the Wesson Fixation Disparity Card, is compared with the modified Sheedy Disparometer. Twenty-eight subjects were divided into normal and abnormal categories of binocular status determined by classical clinical techniques rather than on patients' subjective symptomatology. Fixation disparity curves were generated on all subjects using both instruments. There were significant differences between the two instruments. Neither instrument was able to distinguish between normal and abnormal subjects but, over a five day period, each instrument produced repeatable results. The validity of fixation disparity measurements using either instrument on naive observers, especially children, is questioned.

Adolescent↗
PubMed2006

Deficits in movement planning and intrinsic coordinate control in ideomotor apraxia.

Two central issues in the field of motor control are the coordinate frame in which movements are controlled and the distinction between movement planning and online correction. In this study we used these issues to frame several hypotheses about the deficits underlying ideomotor apraxia (IMA). In particular, we examined whether ideomotor apraxics exhibited (1) deficits in movement control in intrinsic (body relative) coordinates with better control in extrinsic (workspace relative) coordinates, (2) deficits in movement planning that are compensated for by an overreliance on online correction, or (3) both deficits. Patients with IMA and two comparison groups performed movement tasks that relied preferentially on either intrinsic or extrinsic coordinate control when online correction was either possible or impossible. Participants performed posture imitation and grasp imitation movements to body- and object-relative end positions in the presence or absence of visual feedback. Consistent with the intrinsic coordinate control hypothesis, patients with IMA showed a significantly greater disparity than the other two groups between movements made to body-relative and object-relative targets as well as between imitation of meaningless postures and grasping. Consistent with the correction overreliance hypothesis, the IMA group was more disrupted than the other groups by the removal of vision. Thus, IMA patients exhibit behavioral patterns consistent with both deficient intrinsic coordinate control and overreliance upon visual feedback. Finally, lesion analysis suggests that damage to the left inferior parietal lobe (Brodmann's areas 39 and 40) may play a key role in both behavioral deficits.

Acoustic Stimulation↗
PubMed2000

Binocular three-dimensional motion detection: contributions of lateral motion and stereomotion.

When an object moves along a trajectory in three-dimensional (3-D) space, there are potentially two orthogonal components that could be used to detect its motion: stereomotion resulting from the difference or disparity between the images in the right and left eyes, and lateral motion from the sum or average of the image motions in the right and left eyes. Using a suprathreshold search task for a target moving amid 3-D distractors, we found a range of 3-D trajectories for which increasing the stereomotion component did not improve detection. However, with larger stereomotion components, performance improved. The addition of random-motion noise to only the lateral motion component adversely affected the detection of both lateral motion and stereomotion. These data suggest that the visual system uses the average of the monocular image motions for the detection of a range of 3-D trajectories. In addition, a mechanism sensitive to the changing disparity may also be used but only for a very restricted range of 3-D motions.

Adult↗
PubMed1984

Stereo-discrimination between diplopic images in clinically normal observers.

When retinal disparity exceeds the limits for fusion, the resulting images are perceived as diplopic. In a stereo test that allowed comparison of crossed and uncrossed disparity sensitivities, 74% of the subjects perceived convergent disparities more readily than divergent disparities. This asymmetric sensitivity to disparity did not appear to be related to measurements of phoria, vergence amplitudes, or clinical measurements of stereo acuity.

Depth Perception↗
PubMed1984

Color logic of apparent motion.

Two shapes of either the same or different color will seem to be in smooth apparent motion with like-colored mates, at proper conditions of flash timing and spacing. An experiment is reported in which the condition was tested for unlike-colored pairs, for example red-green alternated with green-red. The question of interest was how the visual system would resolve the disparity of color. An 'intelligent' solution would rotate the shapes in three dimensions. Like-colored and unlike-colored parts were found to move and transform similarly, however, the resolution being dependent more upon timing than upon color. The motion of intelligence as it might be applied to vision is discussed in light of these results.

Color Perception↗
PubMed1981

Mechanisms of static and dynamic stereopsis in foveal cortex of the rhesus monkey.

1. The sensation of stereoscopic depth rests on the central neural processing of signals evoked by the two retinal images of a single object in space. It was our purpose in this study to investigate in the behaving monkey the binocular cortical mechanisms that might underlie the ability to recognize the relative position and motion of objects in three-dimensional space.2. The large majority of neurones studied in A17 (n = 245), and all neurones studied in A18 (n = 21), were functionally connected to both eyes, and a substantial proportion (75%) of these neurones were sensitive to positional binocular disparity. On the basis of their depth sensitivity profile, four types of stereoscopic neurones were recognized, each type characteristically sensitive to visual contours appearing in depth farther than, at, or nearer than the point of binocular fixation.3. Tuned excitatory and tuned inhibitory neurones display binocular facilitation and binocular suppression respectively, to stimuli over a narrow range of small disparities, including zero disparity, with more or less pronounced reciprocal responses to stimuli with larger disparities. These neurones, the tuned excitatory in particular, may be considered to be the substrate for central fusion of slightly disparate retinal images, and to provide the basis for the neural mechanisms leading to three-dimensional perception of objects with high stereoacuity (fine stereopsis).4. Two other sets of reciprocally organized neurones, near and far neurones, respond differentially to wider ranges of crossed and uncrossed disparities. The near neurones are activated by stimuli in front of and inhibited by stimuli behind fixation. The far neurones have the reciprocal depth sensitivity. These neural elements may be regarded as active in the processing of binocular information leading to qualitative depth estimates in the presence of double vision (coarse stereopsis).5. Binocular response selectivity for the direction of object motion-in-depth depends chiefly upon monocular sensitivity to the direction of retinal image motion, a property we observed in about one half of the foveal neurones. Cortical neurones with the same directional sensitivity for monocular stimuli in both eyes display coarse binocular selectivity for the trajectory of object motion but provide unambiguous signals for the direction of motion, towards the right or towards the left within the depth domain of the neurone. A small group of neurones (3%) displays opposite and opponent directional sensitivity for stimuli in the two eyes. Their binocular response, therefore, is best when the two retinal images move in opposite directions at the same time, a condition that obtains with motion directly towards or away from the animal with little or no lateral movement. These directionally dual-opponent cells usually have coarse or no selectivity for position-in-depth.6. The results of this study indicate that basic mechanisms for the stereoscopic analysis of the position (static) and motion (dynamic) of objects in space relative to one another are present at early stages of binocular interaction in the visual cortex of primates, and that they are in effective action during normal binocular vision.

Animals↗
PubMedDate not supplied

The moving dynamic random dot stereosize test: validity and repeatability.

PURPOSE: We have developed a new test suitable for measuring stereopsis in young children and individuals with communication difficulties. It consists of a drifting, computer-generated red and green, dynamic random dot, disparate shape. The motion direction is indicated by the subject (subjective response) or by a naive observer judging the eye movements of the subject (objective response). Disparity is maintained at 616 sec arc and the dependent variable is the angular subtense of the target, which varies from 11 degrees to 11 ft. In this study, precision (ie, measuring repeatability and objective-subjective agreement) and validity were assessed. SUBJECTS AND METHODS: Sixteen subjects with normal vision participated in the repeatability study and 10 in the validity studies. A two-up/one-down, 2 alternative forced choice staircase procedure was used to measure objective and subjective threshold on two occasions with a 1-week separation. Sensitivity for detecting anisometropia was estimated with simulated anisometropia (0 to 3 D) and by comparison with the Randot test. Sensitivity for detecting amblyopia or strabismus was tested in 10 subjects. RESULTS: Subjective repeatability was 0.31 log units (2 levels of the test) and objective repeatability was 0.49 log units (3.2 levels of the test). The test was able to detect 2.0 D of simulated anisometropia in 8 of 10 cases (above the 95% confidence interval). None of the amblyopic subjects demonstrated stereopsis. CONCLUSION: This test of dynamic global stereopsis has potential as a clinical or screening tool for anisometropia, amblyopia, and strabismus.

Adult↗
PubMed1975

[Anthropologic foundation and psychologic consequences of political orientation toward right or left. An existential-psychoanalytic study on the phenomenology of political radicalism].

The author searches for an explanation for the fact that an originally only spatial and not "loaded" pair of concepts like "right and left" could gain in our time such high-tension content in political terms. He suspected underlying anthropologic connections and tried to elucidate them with existential analysis. He found that the basis can be seen in the physical constitution of man. Physical experience first transmits the concepts of right and left. The "asymmetric" symmetry of our bilateral physical organisation makes experiencing right and left possible. On this basis the mental concepts of our existence would be imposed in noethic-ethic categories. And these would become active in our political world. This is demonstrated on a case of H.E. Richter. Following Richter'd ideas the psychodynamic rules of political-structural disparities could be shown. The "rights" as repressors dominate the "lefts" as the depressed which now protest in their dispair. As extreme forms the two polarized radicals who now fanatically stylize the other as the enemy, will fight to the death their own denied opposite side psychodynamically. Bizarre ideal visions lead to legalization of terror and brutality. As missing how they are linked in psychiatric terminology paranoid types result extending to the formation of genuine (political) obsessions. For both catathymia of outlook and language are characteristic which show eminent loss of a picture of the world.

Adult↗
PubMed1979

A computational theory of human stereo vision.

An algorithm is proposed for solving the stereoscopic matching problem. The algorithm consists of five steps: (1) Each image is filtered at different orientations with bar masks of four sizes that increase with eccentricity; the equivalent filters are one or two octaves wide. (2) Zero-crossings in the filtered images, which roughly correspond to edges, are localized. Positions of the ends of lines and edges are also found. (3) For each mask orientation and size, matching takes place between pairs of zero-crossings or terminationss of the same sign in the two images, for a range of disparities up to about the width of the mask's central region. (4) Wide masks can control vergence movements, thus causing small masks to come into correspondence. (5) When a correspondence is achieved, it is stored in a dynamic buffer, called the 2 1/2-D sketch. It is shown that this proposal provides a theoretical framework for most existing psychophysical and neurophysiological data about stereopsis. Several critical experimental predictions are also made, for instance about the size of Panum's area under various conditions. The results of such experiments would tell us whether, for example, cooperativity is necessary for the matching process.

Humans↗
PubMed1995

Initiation of disjunctive smooth pursuit in monkeys: evidence that Hering's law of equal innervation is not obeyed by the smooth pursuit system.

Monkeys generated disjunctive smooth pursuit eye movements when they tracked visual targets that moved toward or away from them. Eye acceleration was computed during the initial 100 msec of pursuit (the open-loop interval) for various target trajectories. The initial acceleration of either eye was a function of the target's motion with respect to that eye, regardless of whether or not the pursuit was conjugate or disjunctive, or performed with one eye occluded. Eye movements produced by fusional vergence could be separated temporally from eye movements produced by smooth pursuit using step-ramp paradigms. The separation of the two responses demonstrates that the fusional vergence system operates in parallel with the smooth pursuit system, presumably to minimize disparity, but not to generate disjunctive components of smooth pursuit eye movements.

Animals↗
PubMed1999

Monocular focal retinal lesions induce short-term topographic plasticity in adult cat visual cortex.

Electrophysiological recording in primary visual cortex (VI) was performed both prior to and in the hours immediately following the creation of a discrete retinal lesion in one eye with an argon laser. Lesion projection zones (LPZs; 21-64 mm2) were defined in the visual cortex by mapping the extent of the lesion onto the topographic representation in cortex. There was no effect on neuronal responses to the unlesioned eye or on its topographic representation. However, within hours of producing the retinal lesion, receptive fields obtained from stimulation of the lesioned eye were displaced onto areas surrounding the scotoma and were enlarged compared with the corresponding field obtained through the normal eye. The proportion of such responsive recording sites increased during the experiment such that 8-11 hours post-lesion, 56% of recording sites displayed neurons responsive to the lesioned eye. This is an equivalent proportion to that previously reported with long-term recovery (three weeks to three months). Responsive neurons were evident as far as 2.5 mm inside the border of the LPZ. The reorganization of the lesioned eye representation produced binocular disparities as great as 15 degrees, suggesting interactions between sites in VI up to 5.5 mm apart.

Animals↗
PubMed1996

Convergence demands by spectacle magnifiers.

A general equation, c delta = k1b + k2sF, for finding the binocular convergence demands by spectacle magnifiers to view images at any distance is presented. Factor k1 in the equation yields the accommodative demand to view the image; factor k2 determines the actual reduction in convergence demand provided by the vendors' incorporation of base-in prism. When magnifiers from virtual images at finite distances, such as at the least distance of distinct vision or 25 cm, the interpupiliary distance (b), the separation between the lenses and the eyes (d), and the distance between the optical centers of the lenses (s) are basic quantities, according to this equation. The fundamental datum that the vendors should specify is the distance (s) between the optical centers of the lenses, rather than base-in prism. The specification of base-in prism is unrellable when images are formed at finite distances and the frame PD is not equal to the distance IPD. When the image is formed at infinity, that is when the angular magnification M = F/4, the convergence demand by spectacle magnifiers only depends on the separation between the optical centers of the lenses and the lens power, that is, c delta = sF. It is independent of the interpupillary distance (b) and the separation between the lenses and the eyes (d). We also present an equation, to find the disparity of the accommodative/convergence relation caused by spectacle magnifiers. Knowing the demands on convergence and accommodation, the practitioner can probably evaluate the potential for successful adaptation to spectacle magnifiers from routine measurements of positive and negative relative convergence and accommodation.

Accommodation, Ocular↗
PubMed1996

Visual loss in cytomegalovirus retinitis caused by cystoid macular edema in patients without the acquired immune deficiency syndrome.

PURPOSE: Although serous macular exudation has been described in patients with the acquired immune deficiency syndrome (AIDS) with active cytomegalovirus (CMV) retinitis, cystoid macular edema (CME) is not encountered in this clinical setting. In contrast to these findings, we describe vision loss due to CME occurring in immunosuppressed patients without AIDS treated for CMV retinitis. METHODS: Three patients (four eyes) with systemic immunodeficiency presenting with vision loss underwent ophthalmologic examination, including fundus photography and fluorescein angiography. Systemic evaluation was performed to establish the etiology of immunodeficiency and to rule out human immunodeficiency virus infection. Patients were treated with topical corticosteroid and nonsteroidal anti-inflammatory medications for CME. RESULTS: All patients had severe generalized immune deficiency, related either to drug-induced immunosuppression or primary immunodeficiency. Laboratory studies confirmed the presence of systemic CMV infection. Affected eyes had mild reduction of central vision (range, 20/40 to 20/60). Three of four affected eyes had resolving CMV retinitis outside the posterior pole with mild panuveitis. These eyes showed CME on clinical examination and fluorescein angiography. The CMV lesions regressed after reduction of immunosuppressive agents or after systemic antiviral treatment. Response of CME to topical anti-inflammatory medication was variable. CONCLUSIONS: Cystoid macular edema can occur in the setting of resolving CMV retinitis in patients with immunodeficiency other than AIDS. This entity is distinct from serous macular exudation, which can occur in patients with AIDS with active CMV retinitis involving the posterior pole. The disparity between patients with and without AIDS in the development of CME may be important in understanding the pathogenesis of CME.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Control of vergence: gating among disparity inputs by voluntary target selection.

The ability of human beings to shift their vergence between multiple disparity stimuli was investigated. The stimulus was a stereogram consisting of a single bar (1 x 0.3 degree) projected in the center of a larger circular pattern (28 degrees dia) of dots (0.3 degree dia). In the initial condition, the subjects perceived a single bar in the center of a cluster of dots, all lying in a single depth plane. The subjects were instructed to fixate either the bar or one of the dots close to the bar. Stepwise changes of target-vergence of either the bar, or of all dots, or of both configurations in opposite directions, were imposed in a random sequence. Under these conditions, ocular vergence was controlled by the target-vergence of the selected target at all times, even if this implied a loss of binocular fusion for the non-selected target. The effect of target selection per se, without concomitant changes in retinal position of the selected target, was studied in two experienced subjects with stabilized image techniques. The subjects viewed a configuration containing short vertical bars placed at either side of a long vertical bar. The short bars on different sides of the long bar had opposite (crossed or uncrossed) disparities. After stabilization of the configuration while the subject fixated the long bar, subjects attempted to fixate the short bars alternatingly. Due to the stabilization the ensuing eye movements did not affect the retinal positions, and thus the disparity, of the bars. Attempted fixation of a parafoveally viewed, short bar induced vergence responses in the appropriate direction.(ABSTRACT TRUNCATED AT 250 WORDS)

Attention↗
PubMed1993

Vertical disparities, differential perspective and binocular stereopsis.

To calculate the depth difference between a pair of points on a three-dimensional surface from binocular disparities, it is necessary to know the absolute distance to the surface. Traditionally, it has been assumed that this information is derived from non-visual sources such as the vergence angle of the eyes. It has been shown that the horizontal gradient of vertical disparity between the images in the two eyes also contains information about the fixation distance. Recent results, however indicated that manipulations of the vertical disparity gradient have no effect on either the perceived shape or the perceived depth of surfaces defined by horizontal disparities. Following the reasoning of Longuet-Higgins and Tyler, we suggest that vertical disparities are best understood as a consequence of perspective viewing from two different vantage points and the results we report here show that the human visual system is able to exploit vertical disparities and use them to scale the perceived depth and size of stereoscopic surfaces, if the field of view is sufficiently large.

Depth Perception↗
PubMed1993

[The Freiburg Stereotest. On assessment of stereovision in automobile driver examination].

BACKGROUND: The "Freiburg Stereotest" is a new instrument where disparate pictures are generated by a computer and displayed on one single high resolution video monitor. In the present work, the Freiburg Stereotest was used to check the stereo qualification for certain categories of driver's licence. For this purpose, a determination of the smallest detectable disparity is not reasonable. Rather, it should be checked whether or not a certain disparity, usually well above threshold, is recognized with a sufficient reliability. We have chosen a disparity of 100 arcsec; this value is considered to be an acceptable requirement for certain categories of driver's licence. SUBJECTS AND METHODS: 6 strabismic subjects were examined binocularly and 10 normal subjects were examined both binocularly and monocularly. Two targets ("busses"), side by side and different in depth by a disparity of 100 arcsec, were presented 78 times and, in a two-alternative forced-choice procedure, a minimum of 66 hits was required to pass the test. Monocular cues were excluded by a systematic variation of the lateral distance between the two targets. RESULTS: The strabismic subjects and the monocularly occluded normal subjects reached random scores only. With both eyes open, 8 of the 10 normal subjects reached scores near 100%, while 2 of them passed the test only when the lateral distance between the two targets was 15 minarc or less. For a lateral distance between the two targets of more than 15 minarc, these 2 subjects showed a learning effect. CONCLUSIONS: The Freiburg Stereotest allows to determine with statistical significance whether or not a proband can recognize a certain disparity which may be required for a driver's licence.

Adult↗