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PubMed1996

The interaction of binocular disparity and motion parallax in the computation of depth.

Depth from binocular disparity and motion parallax has traditionally been assumed to be the product of separate and independent processes. We report two experiments which used classical psychophysical paradigms to test this assumption. The first tested whether there was an elevation in the thresholds for detecting the 3D structure of corrugated surfaces defined by either binocular disparity or motion parallax following prolonged viewing (adaptation) of supra-threshold surfaces defined by either the same or different cue (threshold elevation). The second experiment tested whether the depth detection thresholds for a compound stimulus, containing both binocular disparity and motion parallax, were lower than the thresholds determined for each of the components separately (sub-threshold summation). Experiment 1 showed a substantial amount of within- and between-cue threshold elevation and experiment 2 revealed the presence of sub-threshold summation. Together, these results support the view that the combination of binocular disparity and motion parallax information is not limited to a linear, weighted addition of their individual depth estimates but that the cues can interact non-linearly in the computation of depth.

Adaptation, Ocular↗
PubMedDate not supplied

Occupational adaptation: the experiences of older persons with physical disabilities.

The purpose of this phenomenological study was to explore the experiences of occupational adaptation among a small number of older Dutch persons with physical disabilities. Occupational adaptation was tentatively defined as overcoming disabling influences on occupational functioning. Eight occupational therapy clients, who were living in the community, were interviewed using an open in-depth interview format. A phenomenological analysis resulted in descriptions of occupational adaptation as a process that required these clients' active engagement. The clients recruited already familiar problem-solving strategies and personal resources as well as resources in their social and physical environments to identify prospects of potential solutions and to create solutions to overcome constraints on occupational functioning. Furthermore, participants strived for finding satisfaction through occupations, a meaning theme which emerged as the object of occupational adaptation. Satisfaction through occupations was found in maintaining daily routines and engaging in fulfilling occupations.

Adaptation, Physiological↗
PubMed1975

A gross and microscopic study of the respiratory anatomy of the Antarctic Weddell seal, Leptonychotes weddelli.

Four species of Phocidae, or true seals, inhabit the waters surrounding the Antarctic continent. These animals are thought to have different diving capabilities. The Weddell seal, Leptonychotes weddelli, is known to be capable of attaining depths up to 600 meters. The respiratiory system of the Weddell seal shows the usual adaptations to an aquatic environment characteristic of other marine. These include lungs that undergo compression acollapse at depths greater than 70 meters; hyaline cartilage in the tracheo-bronchial tree as far as the terminal bronchioles; and large amounts of smooth muscle surrounding the distal-most bronchioles. The collapsible lungs provide a mechanism by which air is forced from the alveoli adjacent to the pulmonary capillary beds thereby preventing the absorption of nitrogen gas into the bloodsteam. The presence of hyaline cartilage throughout most of the tracheo-bronchial tree increases the effective dead air space that accommodates most of the air forced from the collapsed lungs. The smooth muscle surrounding the respiratory bronchioles prevents their collapse while under the pressures of a deep dive. Collapse of the respiratory bronchioles not supported by cartilage would trap air in the lung alveoli during a dive. In addition, large- sac-like "diverticulae" are found in the submucosa throughout the tracheo-bronchial tree. These diverticulae, which open directly into the lumen of the tree, appear to be modified glands whose cells, in most cases, do not appear to be specialized for secretory function. They are most numerous in the more distal bronchi and terminal bronchioles where they are situated on both the luminal and adventitial sides of the hyaline cartilage supporting the walls of the air passages. Diverticulae are not found in the respiratory bronchioles or in the respiratory portion of the lungs.

Acclimatization↗
PubMedDate not supplied

Adaptive growth of tree root systems in response to wind action and site conditions.

Soil-root plate dimensions and structural root architecture were examined on 46-year-old Sitka spruce (Picea sitchensis (Bong.) Carr.) trees that had been mechanically uprooted. Rooting depth was restricted by a water table, and root system morphology had adapted to resist the wind movement associated with shallow rooting. The spread of the root system and the ratio of root mass to shoot mass (root/shoot ratio) were both negatively related to soil-root plate depth. Root systems had more structural root mass on the leeward side than the windward side of the tree relative to the prevailing wind direction. Cross sections of structural roots were obtained at distances of 0.5, 0.75, 1.0, and 1.25 m from the tree center. Buttressed parts of roots had greater lateral and vertical secondary thickening above rather than below the biological center. This uneven growth, which produced a shape similar in cross section to a T-beam, was greater on the leeward side of the tree, and was greatest at 0.5 m from the tree center of shallow rooted trees. Further from the tree, particularly on the windward side, many roots developed eccentric cross-sectional shapes comparable to I-beams, which would efficiently resist vertical flexing. Roots became more ovoid in shape with increasing distance from the tree, especially on deep rooted trees where lateral roots tapered rapidly to a small diameter. We conclude that these forms of adaptive growth in response to wind movement improve the rigidity of the soil-root plate and counteract the increasing vulnerability to windthrow as the tree grows.

Journal Article↗
PubMed1995

Familial patterns in patients with infrequent panic attacks.

OBJECTIVE: To evaluate the family environment in patients with infrequent panic attacks. DESIGN: Survey. SETTING: Waiting room of a family health center at a university-based family practice residency program. The center primarily serves low-income or underinsured patients, 80% of whom are Hispanic. PATIENTS OR OTHER PARTICIPANTS: Randomly selected patients completed the panic disorder section of the Structured Clinical Interview of the Diagnostic and Statistical Manual of Mental Disorders, Third Edition. Thirty patients with infrequent panic attacks were compared with 30 control patients without panic attacks matched for age, gender, and ethnicity. Both groups completed in-depth interviews. INTERVENTIONS: None. MAIN OUTCOME MEASURES: The in-depth structured interview included family environment instruments--Family Adaptability and Cohesion Evaluation Scales and Duke Social Support and Stress Scale--as well as a genogram. Family violence and sexual abuse were assessed by means of the Conflict Tactic Scales and the Sexual Stress Questionnaire. RESULTS: Although patients with infrequent panic attacks were of lower birth order than patients without panic attacks (Wilcoxon chi 2 = 2.13, P < or = .02), no differences in childhood or current family functioning were found. However, patients with infrequent panic attacks reported higher levels of childhood (paired t = 3.97, P < or = .001) and current (paired t = 3.05, P < or = .005) family stress. Although the prevalence of family violence was similar between groups, the group with infrequent panic attacks reported more violent events in the past year (paired t = 2.60, P < or = .02) than did the group with no panic attacks. Similarly, 60% of patients with infrequent panic attacks reported childhood sexual abuse, as opposed to 13% of patients without panic attacks (McNemar's chi 2 = 10.5, P < or = .005). CONCLUSIONS: Although no association between infrequent panic attacks and family functioning or support were found, the group with infrequent panic attacks reported more frequent violent events currently and higher levels of family stress. The high rate of childhood sexual abuse may have important causative implications for infrequent panic attacks.

Adult↗
PubMed1988

In vivo 31P NMR studies of rat salivary glands at 6.3 tesla.

In vivo 31P NMR spectra of rat submandibular glands were obtained. The glands were exposed, leaving the neurovascular system intact, and placed in a solenoidal coil. Resonances of nine phosphate metabolites were identified in the spectra and metabolite concentrations were estimated from the corresponding integrals ([ATP] = 3.4 +/- 0.7 mM). Tissue pH, as deduced from the chemical shift of the inorganic phosphate resonance, was 7.26 (+/- 0.07). T1 relaxation times of ATP, phosphocreatine, inorganic phosphate, and phosphomonoester 31P spin systems were examined. The effect of hypoxia was followed as a function of time. 31P NMR spectra of the glands have also been obtained noninvasively by the use of a surface coil, adapted to the dimensions of the glands, and depth pulses.

Animals↗
PubMed1995

Adapting to monocular vision: grasping with one eye.

The aim of the present study was to determine whether normal subjects with one eye covered and patients in whom one eye had been enucleated generate more head movements than subjects using binocular vision during the performance of a visually guided grasping movement. In experiment 1, 14 right-handed normal subjects were tested binocularly and monocularly in a task in which they were required to reach out and grasp oblong blocks of different sizes at different distances. Although the typical binocular advantage in reaching and grasping was observed, the overall head movement scores did not differ between these testing conditions. In experiment 2, seven right-handed enucleated patients were compared to seven age and sex-matched control subjects (tested under binocular and monocular viewing conditions), on the same task as used in experiment 1. While no differences were found in the kinematics of reaches produced by the enucleated patients and the control subjects, the patients did produce larger and faster resultant head movements, composed mainly of lateral and vertical movements. This suggests that enucleated patients may be generating more head movements in order to better utilize retinal motion cues to aid in manual prehension.

Adaptation, Physiological↗
PubMed1992

Chromatic adaptation to natural and incandescent illuminants.

A color CRT image display system was used to present adapting backgrounds that were spatially and temporally varied. Three observers adjusted the chromaticity of test stimuli to produce an achromatic appearance under a variety of adapting conditions. The achromatic-appearing chromaticities were used as measures of the observers' states of chromatic adaptation. The spatial configuration of the adapting background was varied to measure the spatial extent of the mechanisms responsible for chromatic adaptation. The temporal configuration of the adapting background was varied to measure the time-course of these mechanisms. The results show that chromatic adaptation is spatially localized with a time-course on the order of 10 sec. Since the mechanisms were shown to be spatially localized, the observed temporal integration across eye movements is required to allow these mechanisms to adjust to the spatially integrated scene chromaticity.

Adaptation, Ocular↗
PubMed1995

Control of vertical eye alignment in three-dimensional space.

A target that is nearer to one eye than the other subtends a larger visual angle in the closer eye. Consequently, when making saccades between vertically separated targets that are closer to one eye, there is a vertical retinal disparity that must be overcome by a change in the relative alignment of the eyes. We recorded eye movements in three normal subjects and showed that in such viewing circumstances subjects made unequal vertical saccades that led to a rapid change (peak velocity up to 30 deg/sec) in vertical eye alignment. On average, 81% of the required change in alignment occurred within the saccade for downward movements and 47% for upward movements. Such unequal vertical saccades occurred independently of immediate disparity cues; saccades remained unequal when refixing to the remembered locations of the vertically-oriented targets, or even when the natural vertical disparity was nullified by a prism. On the other hand, when subjects wore the nullifying prism in front of the inferior visual field of the left eye for 8-20 hr, they showed a decrease in saccade disconjugacy (to 12-35% of the preadaptation value) to targets closer to the left eye in the inferior but not in the superior visual field. We suggest that the brain develops a three-dimensional map (horizontal, vertical, depth) for vertical saccade yoking, which is under adaptive control, and which is used to preprogram automatically the relative excursions of the eyes during vertical saccades as a function of the current and the desired point of regard.

Adaptation, Ocular↗
PubMed1992

The amino acid sequence of the single hemoglobin of the high-antarctic fish Bathydraco marri Norman.

1. Bathydraco marri Norman is a cold-adapted Antarctic teleost (Family: Bathydraconidae), living preferably at depths between 400 and 1200 m. 2. The blood of this species contains a single hemoglobin, in which oxygen binding is pH-regulated (Bohr and Root effects). 3. The complete amino acid sequence of the alpha and beta chains of the hemoglobin of B. marri has been elucidated.

Acylation↗
PubMed2006

Blood-gas properties of plateau zokor (Myospalax baileyi).

Plateau zokor (Myospalax baileyi) is one of the blind subterranean mole rats that spend their life solely underground in sealed burrows. It is one of the special species of the Qinghai-Tibet plateau. In their burrows, oxygen is low and carbon dioxide is high and their contents fluctuate with the change of seasons, soil types, rain and depth of burrows. However, plateau zokors show successful adaptation to that extreme environment. In this study, their adapting mechanisms to the hypoxic hypercapnic environment were analyzed through the comparison of their blood-gas properties with that of pikas (Ochotona curzniae) and Sprague-Dawley rats. The results indicated that plateau zokors had higher red blood corpuscle counts (8.11+/-0.59 (10(12)/L)) and hemoglobin concentrations (147+/-9.85 g/L), but hematocrit (45.9+/-3.29%) and mean corpuscular volume (56.67+/-2.57 fL) were lower than the other rodents. Their arterial blood and venous blood pH were 7.46+/-0.07 and 7.27+/-0.07. Oxygen pressure in arterial blood of plateau zokors was about 1.5 times higher than that of pikas and rats, and it was 0.36 and 0.26 times in their venous blood. Partial pressure for carbon dioxide in arterial and venous blood of plateau zokors was 1.5-fold and 2.0-fold higher, respectively, than in rats and pikas. Oxygen saturation of plateau zokors was 5.7 and 9.3 times lower in venous blood than that of pikas and rats, respectively. As result, the difference of oxygen saturation in arterial blood to venous blood was 2- and 4.5-fold higher in plateau zokors as that of pikas and rats, respectively. In conclusion, plateau zokors had a high tolerance to pH changes in tissues, together with strong capabilities to obtain oxygen from their hypoxic-hypercapnic environment.

Adaptation, Physiological↗
PubMed1998

Stereodeficient subjects show substantial differences in interocular transfer of two motion adaptation aftereffects.

Interocular transfer (IOT) of two motion aftereffects was examined in subjects with normal and deficient stereopsis. Normal subjects showed complete (100%) IOT of motion adaptation on coherent motion thresholds, but only partial IOT of a conventional motion aftereffect, supporting suggestions that the latter aftereffect may be mediated at a lower level in the visual pathway than the extrastriate regions implicated in processing coherent motion. This idea was strengthened by an even greater dissociation between the extent of IOT of the two aftereffects among stereodeficient subjects who exhibited very low IOT of the conventional motion aftereffect, but high (> 87%) IOT of the coherence motion aftereffect.

Adaptation, Ocular↗
PubMed2003

The utilization of treatment and case management services by HIV-infected youth.

PURPOSE: This article describes the essential components for effective and comprehensive HIV care for youth who have tested positive and have been linked to HIV treatment. Descriptive profile data are also presented that detail the demographics, risk behaviors and health care barriers of youth served in the five Special Projects of National Significance (SPNS), which focused on adolescents and young adults. METHODS: Data presented are from the core multi-site data set, which was standardized across the five youth-oriented SPNS projects. Substance use and mental health symptoms were gathered using the Personal Problem Questionnaire (PPQ) screener, which was an adaptation of the PRIME-MD. In-depth qualitative interviews with enrolled HIV-positive youth were also conducted by several Projects. RESULTS AND CONCLUSIONS: Medical care alone is not enough and cannot be effective without supportive program components such as flexible scheduling, and a multi-disciplinary team approach that includes assertive case management. Case Managers help enrolled youth with concrete service needs such as housing, emergency financial assistance for food/utilities, transportation, child care, coverage for prescriptions, and public entitlements. They also help isolated youth to connect with a personal support system. Addressing those needs helps to facilitate and reinforce treatment adherence and retention. In addition to other identified needs such as stable housing and transportation, a significant number of enrolled youth self-reported having experienced physical, sexual, and/or emotional abuse in their lives and articulated a need for mental health services. Therefore, effective HIV care for youth must be multi-faceted; it must consist of more than a medical component.

Adolescent↗
PubMed1994

A new twist on the rotating-trapezoid illusion: evidence for neural-adaptation effects.

In a series of experiments, the selective-adaptation paradigm was applied to the rotating-trapezoid illusion in an effort to demonstrate neural-adaptation effects in the figural reversal of this classic illusion. Prior to viewing the standard trapezoid, the observer adapted to a rectangle rotating unambiguously in the same direction as the trapezoid or in the opposite direction. In accordance with the neural hypothesis, illusion strength was greatest when the two figures rotated in the same direction and weakest when the two figures rotated in opposite directions. Results were confirmed with two separate dependent variables: the observer's 'first look' at the illusion after adaptation and the observer's reversal rate during a test period. These findings were discussed in terms of (a) the basic similarity of results for the rotating trapezoid and reversible figures such as the Necker cube and (b) the need for a multiprocess model of both classes of illusions which emphasizes bottom-up and top-down processes.

Adaptation, Ocular↗