In the depths of human circumstance.
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Adaptation, Psychological↗
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Results for “depth adaptation”
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[The visual depth acuity in twilight].
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Adaptation, Ocular↗
Autonomic neuropathy and the pathogenesis of glaucoma in diabetes mellitus.
In order to determine whether ocular hypertension and glaucoma may be a complication of autonomic neuropathy in diabetes mellitus, 30 asymptomatic diabetic patient volunteers were studied. A correlation was sought between reduced anterior chamber depth which is thought to predispose to the development of glaucoma, and two markers of autonomic dysfunction, loss of sinus arrhythmia and reduced diameter of dark adapted pupils. A significant correlation was found between reduced chamber depth and pupil diameter arrhythmia (r = 0.36, p = 0.025) and between chamber depth and pupil diameter (r = 0.45, p = 0.006). As expected, there was also a significant correlation between sinus arrhythmia and pupil diameter (r = 0.68, p less than 0.001). The correlation between pupil diameter and sinus arrhythmia, and between pupil diameter and chamber depth was preserved after the data were adjusted for age (r = 0.54, p less than 0.001 and r = 0.35, p = 0.03, respectively), while that between sinus arrhythmia and chamber depth was lost (r = 0.23, NS). No association was found between intraocular pressure and either marker of autonomic dysfunction, but intraocular pressure was not abnormal (less than 22 mmHg) in any individual case. These data suggest that autonomic denervation of the eye in diabetes may be associated with alteration of anterior chamber depth.
Adult↗
Ménière's disease: trauma, distress and adaptation studied through focus interview analyses.
In order to investigate, in depth, the role of psychological factors in Ménière's disease, i.e. how the patients experience and interpret their symptoms during the process of this illness, a qualitative method "focus group interviews" was used as a study design. The focus group included four subjects; one woman and three men. In addition, semi-structured interviews were performed with each of four more subjects having the disease, three women and one man, in order to guarantee representativity in terms of gender and age. Through the focus interview analyses eight final codes and a number of sub-codes were developed. Results clearly pointed out the significance of the first traumatic attack of the disease as well as early signs; different "psychosomatic" symptoms prior to the attacks. The recognition of fear and phobic reactions in the manifestation of the vertigo attack was considered as an important observation, as attacks often were triggered by distressing thoughts as well as by sensory sensations. Other areas, touched upon for future investigation, were crisis adaptation and illness function.
Adaptation, Psychological↗
Effects on the compensatory responses to positive and negative lenses of intermittent lens wear and ciliary nerve section in chicks.
This study examined the ocular compensation to lens-induced defocus in chick and the effect of interrupting lens wear on a daily basis. Eyes fitted with +10 D lenses at hatching compensated rapidly, with almost complete compensation after 4 days of lens wear; they had decreased vitreous chamber depth compared to normal eyes and were thus hyperopic when the lenses were removed. In contrast, adaptation to the -10 D lenses was much slower, was still incomplete after 9 days of lens wear, and in this case, eyes had increased vitreous chamber depth and were myopic without the lenses. Adaptation improved when lens wear was delayed until 7 days after hatching. The effect of interrupting lens wear by periods of normal vision varied with the sign of the lenses worn. Hyperopia was always seen in response to +10 D lenses, although the magnitude of the response decreased as the duration of lens wear was decreased. In contrast, even brief periods of normal vision, i.e., 3 hr, prevented the development of myopia in response to the -10 D lenses; this apparent sensitivity to normal vision is similar to that reported for form-deprivation myopia. Ciliary nerve section used here to eliminate accommodation did not alter these response patterns.
Accommodation, Ocular↗
Adaptive anterior hippocampal responses to oddball stimuli.
An efficient memory system requires the ability to detect and preferentially encode novel stimuli. Human electrophysiological recordings demonstrate differential hippocampal responses to novel vs. familiar stimuli, as well as to oddball stimuli. Although functional imaging experiments of novelty detection have demonstrated hippocampal activation, oddball-evoked hippocampal activation has not been demonstrated. Here we use event-related functional magnetic resonance imaging (fMRI) to measure hippocampal responses to three types of oddball words: perceptual, semantic, and emotional. We demonstrate left anterior hippocampal sensitivity to all three oddball types, with adaptation of responses across multiple oddball presentations. This adaptive hippocampal oddball response was not modulated by depth of processing, suggesting a high degree of automaticity in the underlying process. However, an interaction with depth of encoding for semantic oddballs was evident in a more lateral left anterior hippocampal region. We conclude that the hippocampal response to oddballs demonstrates a second-order novelty effect, being sensitive to the "novelty of novelty" of oddball stimuli. The data provide support for a more general theory that a function of the anterior hippocampus is to register mismatches between expectation and experience.
Adaptation, Physiological↗
Reversal of retinal feedback of binocular eye motions in depth vision.
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Adaptation, Ocular↗
Selective adaptation to frequency-modulated tones: evidence for an information-processing channel selectively sensitive to frequency changes.
Exposure to an FM tone elevates FM threshold but not AM threshold. This holds for a wide range of frequency deviations (delta F = +/- 0.4 Hz- +/- 30 Hz at least) provided that modulation frequency is low (fm = 2 Hz), but if fm is somewhat higher (e.g., 8 Hz) the finding only holds for small frequency deviations. FM threshold can rise with time up to an adapting duration of at least 1200 s, through this buildup depends on frequency deviation. Exposure to an AM tone elevates AM threshold, but not FM threshold, over a wide range of modulation depths (at least m = 5%--50%). Quasi-FM (QFM) adapting tones resemble FM adapting tones in their effects upon FM and AM sensitivities, even though QFM and AM adapting tones have identical power spectra. Exposure to a pure tone produces no difference between FM and AM threshold elevations. These data can be explained if the human auditory pathway contains separate information-processing channels for AM and FM signals whose sensitivities do not overlap even with suprathreshold stimuli. We suppose that the FM channel (but not the AM channel) is sensitive to changing differences (or ratios) between signals from different sites along the basilar membrane.
Adaptation, Psychological↗
The visual control of reaching and grasping: binocular disparity and motion parallax.
The primary visual sources of depth and size information are binocular cues and motion parallax. Here, the authors determine the efficacy of these cues to control prehension by presenting them in isolation from other visual cues. When only binocular cues were available, reaches showed normal scaling of the transport and grasp components with object distance and size. However, when only motion parallax was available, only the transport component scaled reliably. No additional increase in scaling was found when both cues were available simultaneously. Therefore, although equivalent information is available from binocular and motion parallax information, the latter may be of relatively limited use for the control of the grasp. Binocular disparity appears selectively important for the control of the grasp.
Adaptation, Physiological↗
Exposure to ultraviolet radiation delays photosynthetic recovery in Arctic kelp zoospores.
Seasonal reproduction in some Arctic Laminariales coincides with increased UV-B radiation due to stratospheric ozone depletion and relatively high water temperatures during polar spring. To find out the capacity to cope with different spectral irradiance, the kinetics of photosynthetic recovery was investigated in zoospores of four Arctic species of the order Laminariales, the kelps Saccorhiza dermatodea, Alaria esculenta, Laminaria digitata, and Laminaria saccharina. The physiology of light harvesting, changes in photosynthetic efficiency and kinetics of photosynthetic recovery were measured by in vivo fluorescence changes of Photosystem II (PSII). Saturation irradiance of freshly released spores showed minimal I ( k ) values (photon fluence rate where initial slope intersects horizontal asymptote of the curve) values ranging from 13 to 18 micromol photons m(-2) s(-1) among species collected at different depths, confirming that spores are low-light adapted. Exposure to different radiation spectra consisting of photosynthetically active radiation (PAR; 400-700 nm), PAR+UV-A radiation (UV-A; 320-400 nm), and PAR+ UV-A+UV-B radiation (UV-B; 280-320 nm) showed that the cumulative effects of increasing PAR fluence and the additional effect of UV-A and UV-B radiations on photoinhibition of photosynthesis are species specific. After long exposures, Laminaria saccharina was more sensitive to the different light treatments than the other three species investigated. Kinetics of recovery in zoospores showed a fast phase in S. dermatodea, which indicates a reduction of the photoprotective process while a slow phase in L. saccharina indicates recovery from severe photodamage. This first attempt to study photoinhibition and kinetics of recovery in zoospores showed that zoospores are the stage in the life history of seaweeds most susceptible to light stress and that ultraviolet radiation (UVR) effectively delays photosynthetic recovery. The viability of spores is important on the recruitment of the gametophytic and sporophytic life stages. The impact of UVR on the zoospores is related to the vertical depth distribution of the large sporophytes in the field.
Arctic Regions↗
The interaction of eye movements and retinal signals during the perception of 3-D motion direction.
When an object is tracked with the eyes, veridical perception of the motion of that object and other objects requires the brain to take account of and compensate for the eye movement. Here, I explore the effects of version and vergence eye movements on three-dimensional (3-D) motion perception. After demonstrating that eye movement compensation can be poor for detecting small objects moving in depth, I develop two models for how eye movement and visual signals may interact during the perception of 3-D motion direction. The first model assumes that the visual system is aiming to form an explicit representation of 3-D motion. From the results of a second experiment, on 3-D motion direction judgements, I show that this model could only hold with almost perfect 3-D motion compensation, contradicting the results from the first experiment. A second model assumes a much simpler strategy for estimating 3-D motion direction, based on recent experimental work. It predicts that compensation for vergence is not required because the Z-component of 3-D motion is not needed for direction judgements, consistent with the experimental results. This suggests that, for 3-D motion direction discrimination and angle judgements, extraretinal signals from vergence are not used.
Adaptation, Physiological↗
Prey capture and accommodation in the sandlance, Limnichthyes fasciatus (Creediidae; Teleostei).
The eyes of the sandlance, Limnichthyes fas ciatus (Creediidae, Teleostei) move independently and possess a refractive cornea, a convexiclivate fovea and a non-spherical lens giving rise to a wide separation of the nodal point from the axis of rotation of the eye much like that of a chameleon. To investigate this apparent convergence of the visual optics in these phylogenetically disparate species, we examine feeding behaviour and accommodation in the sandlance with special reference to the possibility that sandlances use accommodation as a depth cue to judge strike length. Frame-by-frame analysis of over 2000 strikes show a 100% success rate. Explosive strikes are completed in 50 ms over prey distances of four body lengths. Close-up video confirms that successful strikes can be initiated monocularly (both normally and after monocular occlusion) showing that binocular cues are not necessary to judge the length of a strike. Additional means of judging prey distance may also be derived from partallax information generated by rotation of the eye as suggested for chameleons. Using photorefraction on anaesthetised sandlances, accommodative changes were induced with acetylcholine and found to range between 120 D and 180 D at a speed of 600-720 D s(-1). The large range of accommodation (25% of the total power) is also thought to be mediated by corneal accommodation where the contraction of a unique cornealis muscle acts to change the corneal curvatures.
Adaptation, Physiological↗
Visual-motor optimization in binocular control.
When we view objects at various depths, the 3-D rotations of our two eyes are neurally yoked in accordance with a recently discovered geometric rule, here called the binocular extension of Listing's law; or L2. This paper examines the visual and motor consequences of this rule. Although L2 is a generalization of Listing's original, monocular law, it does not follow from current theories of the latter's function, which involve minimizing muscle work or optimizing certain aspects of retinal image flow. This study shows that a new optimization strategy that combines stereo vision with motor efficiency does explain L2, and describes the predictions of this new theory. Contrary to recent suggestions in the literature, L2 does not ensure vision of lines orthogonal to the visual plane, but rather reduces cyclodisparity of the visual plane itself; and L2 does not arise because a single, conjugate angular velocity command is sent to both eyes, but actually requires that the two eyes rotate with different speeds and axes when scanning an isovergence surface. This study shows that L2 is compatible with a 1-D control system for vergence alone (because horizontal and torsional vergence are yoked) and a 3-D system for combined, head-fixed saccades and vergence.
Adaptation, Ocular↗
Neural integration of information specifying structure from stereopsis and motion.
When one views a two-dimensional parallel projection of dots on the surface of a rotating globe, the direction of rotation is ambiguous, and the perceived direction of rotation of the two-dimensional figure is unstable over time. Stability can be temporarily induced by adaptation to a three-dimensional globe with a direction of rotation unambiguously specified by stereo disparity; adaptation causes the two-dimensional figure to appear to rotate in the direction opposite that experienced during stereoscopic adaptation. This adaptation effect is selective for axis of rotation but is not shape-specific. It does depend on simultaneous stimulation by multiple depth planes defined by elements moving in different directions. Evidently information about stereopsis and information about structure from motion are integrated within a common neural site in the brain.
Adaptation, Ocular↗
Slit-lamp-adapted optical coherence tomography of the anterior segment.
PURPOSE: To evaluate the diagnostic potential of a slit-lamp-adapted optical coherence tomography (OCT) system as an in vivo imaging device for routine clinical examination of the anterior segment of the eye. PATIENTS AND METHODS: In a pilot study, healthy volunteers and patients with different pathologies of the anterior segment were examined with a slit-lamp-adapted OCT system using 100-200 axial scans with 100-Hz line-scan frequency. The scan length is variable up to 7 mm, and the axial depth is 1.5 mm in tissue. RESULTS: The slit-lamp-adapted OCT system allowed direct biomicroscopic imaging of the measured area. Anatomic structures and morphological changes anterior to the attenuating iris pigment epithelium could be visualized with high accuracy. Biometric analyses of the cornea, the chamber angle, the iris and secondary cataract were possible. Complete demonstration of the chamber angle was difficult due to the backscattering properties of the anterior part of the sclera and the consequent shadowing of the most peripheral part of the iris. CONCLUSIONS: Slit-lamp-adapted OCT is a useful diagnostic tool which allows in vivo microscopic cross-sectional imaging of the anterior segment and precise measurement of ocular structures.
Anterior Eye Segment↗
Mechanisms for seeing transparency-from-motion and orientation-from-motion.
Structure-from-motion (SFM) perception is hypothesised to be mediated by units that sense the near-far relationships in transparency-from-motion (TFM) and orientation-from-motion (OFM). The frequency of subjective reversals during observation of ambiguous SFM displays is considerably decreased when either the direction of rotation or the surface orientation is oscillated during the inspection. Such manipulations impede adaptation of units selectively sensitive to TFM and OFM. The results show that both OFM and TFM units are direction-selective, and that the reversal rate is unaffected by reducing TFM to zero; and support the view that depth order, when both TFM and OFM are present, is estimated by common neural units.
Adaptation, Physiological↗
Stabilized structure from motion without disparity induces disparity adaptation.
3D structures can be perceived based on the patterns of 2D motion signals. With orthographic projection of a 3D stimulus onto a 2D plane, the kinetic information can give a vivid impression of depth, but the depth order is intrinsically ambiguous, resulting in bistable or even multistable interpretations. For example, an orthographic projection of dots on the surface of a rotating cylinder is perceived as a rotating cylinder with ambiguous direction of rotation. We show that the bistable rotation can be stabilized by adding information, not to the dots themselves, but to their spatial context. More interestingly, the stabilized bistable motion can generate consistent rotation aftereffects. The rotation aftereffect can only be observed when the adapting and test stimuli are presented at the same stereo depth and the same retinal location, and it is not due to attentional tracking. The observed rotation aftereffect is likely due to direction-contingent disparity adaptation, implying that stimuli with kinetic depth may have activated neurons sensitive to different disparities, even though the stimuli have zero relative disparity. Stereo depth and kinetic depth may be supported by a common neural mechanism at an early stage in the visual system.
Adaptation, Ocular↗
Intimate play and marital adaptation.
LITTLE attention has been given to the contribution of spontaneous, idiosyncratically elaborated "intimate play" to marital adjustment. This exploratory paper draws upon research and clinical interviews with married couples, ethological observations and children's play, and psychoanalytic object relations conceptions of adaptive regression. An understanding of intimate play is developed based on intrapsychic structures and interpersonal process, with several dimensions explored and illustrated in depth: its context, ritualizations, growth-potentiating aspects, and the range of adaptations it reflects. Intimate play is seen as having a role in positive bonding, communication, and conflict reduction, and more generally, as tending to stabilize a marital relationship. The clinical implications of the various phenomena associated with intimate play are also considered.
Adaptation, Psychological↗