Optical motions and transformations as stimuli for visual perception.
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Humans↗
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Asymmetric color matching: how color appearance depends on the illuminant.
We report the results of matching experiments designed to study the color appearance of objects rendered under different simulated illuminants on a CRT monitor. Subjects set asymmetric color matches between a standard object and a test object that were rendered under illuminants with different spectral power distributions. For any illuminant change, we found that the mapping between the cone coordinates of matching standard and test objects was well approximated by a diagonal linear transformation. In this sense, our results are consistent with von Kries's hypothesis [Handb. Physiol. Menschen 3, 109 (1905) [in Sources of Color Vision, D. L. MacAdam, ed. (MIT Press, Cambridge, Mass., 1970)]] that adaptation simply changes the relative sensitivity of the different cone classes. In addition, we examined the dependence of the diagonal transformation on the illuminant change. For the range of illuminants tested, we found that the change in the diagonal elements of the linear transformation was a linear function of the illuminant change.
Color Perception↗
The case for transforming governmental public health.
Changing threats to the public's health necessitate a profound transformation of the public health enterprise. Despite recent attention to the biodefense role of public health, policymakers have not developed a clear, realistic vision for the structure and functionality of the governmental public health system. Lack of leadership and organizational disconnects across levels of government have prevented strategic alignment of resources and undermined momentum for meaningful change. A transformed public health system is needed to address the demands of emergency preparedness and health protection. Such transformation should include focused, risk-based resource allocation; regional planning; technological upgrades; workforce restructuring; improved integration of private-sector assets; and better performance monitoring.
Health Promotion↗
Genes expressed in the human trabecular meshwork during pressure-induced homeostatic response.
Physiological pressure inside the eye is maintained by a resistance mechanism provided by the trabecular meshwork tissue. In most cases, prolonged, elevated pressure leads to an eye pathology characterized by retinal ganglion cell (RGC) degeneration, optic nerve damage, and non-remedial blindness. We are investigating the regulation of trabecular meshwork genes in response to elevated pressure. Using perfused organ cultures from postmortem human donors, we have previously demonstrated the presence of a homeostatic mechanism at 2-4 days of pressure insult (Borrás et al. 2002, Invest Ophthalmol Vis Sci 43:33-40). Here, we sought to identify trabecular meshwork genes whose expression was altered during this homeostatic period. By macroarray hybridization, we compared the expression profiles of high-pressure (HP) and normal-pressure (NP) treated eyes from the same individual (n = 3 pairs). Our results identified 40 upregulated and 14 downregulated genes. The highest proportion of upregulated genes encoded proteins involved in signal transduction (32%). Among the potentially relevant genes, PIP 5K1C, VIP, tropomodulin, and MMP2 encoded mediators known to influence outflow resistance. Others encoded functions which are new for the trabecular meshwork, but which are intrinsic to unrelated tissues. These new mechanisms appear as they could be of benefit for trabecular meshwork function. Matrix Gla protein (MGP), perlecan, osteomodulin, and osteoblast-specific factor are essential in cartilage and bone physiology whereas spectrin and ICAM4 are specific for blood cells and crucial in maintaining their shape and adhesion. In addition, MGP transcripts were stimulated by extracellular calcium and downregulated by TGF-beta1. We propose that MGP might be an important player in the adaptive homeostatic mechanism by contributing to maintain a softer trabecular meshwork tissue and facilitate aqueous humor outflow.
Aged↗
Test-retest reliability of trunk accelerometry during standing and walking.
OBJECTIVE: To investigate repeatability of acceleration measured by a portable, triaxial accelerometer over the lumbar spine as a measure of balance during standing and walking. DESIGN: Acceleration was measured along three axes and transformed to a horizontal-vertical coordinate system. Standing was tested on two feet, vision unobstructed and obstructed, and on one foot, vision unobstructed. Walking was tested in five different self-selected speeds on even and uneven ground. Retest was performed after 2 days. SETTING: A flat floor with a 7m uneven mat. SUBJECTS: Nineteen healthy students. MAIN OUTCOME MEASURES: Standing: Acceleration root mean square (RMS). Walking: Point estimate of acceleration RMS for a reference walking speed (1.2m/sec). All tests: Within-subject standard deviation (sw), intraclass correlation coefficients (ICCs). RESULTS: The sw indicated high absolute test-retest repeatability for standing on two feet. Because of restricted ranges of value, relative reliability was low, however, with ICC(3,1) < .56. For standing on one foot, absolute and relative reliability were highest in the mediolateral direction, with ICC(3,1) = .84. For the walking tests, ICC(3,1) ranged from .79 to .94 for the three axes. Reliability was on the same level for even and uneven ground. CONCLUSION: The results indicate that accelerometry without need for stationary instrumentation is a reliable method that may be useful for studying standing balance and gait in the clinic.
Acceleration↗
Processing of polarized light by squid photoreceptors.
Behavioural tests have demonstrated that cephalopods can discriminate light polarized in different planes, and the receptors have been localized by electrophysiological studies of the eye. Discrimination of the plane of polarization is a consequence of both the structure of the microvilli in the outer segments of the photoreceptors and the orientation of the photosensitive chromophore on these membranes. However, between the depolarizing receptor response resulting from photoreception and the behaviour of the animal, nothing is known about neuronal processing of polarized light by cephalopods. Here we show that some squid photoreceptors discriminate the plane of polarization within the spike train, and that any particular plane is seen as a variable intensity. Given the well known orthogonal orientation of microvilli in outer segments of adjacent photoreceptors and the physiological preference for one of two mutually perpendicular planes of polarization by single photoreceptors, we conclude that cephalopod vision is based on two complementary views of the world, each determined by the transformation of polarization-sensitive receptors into complementary intensity scales. A visual system based on this transformation would lead to enhanced contrast underwater and visualization of object details obscured by confounding highlights.
Action Potentials↗
Is there a role of visual cortex in spatial hearing?
The integration of auditory and visual spatial information is an important prerequisite for accurate orientation in the environment. However, while visual spatial information is based on retinal coordinates, the auditory system receives information on sound location in relation to the head. Thus, any deviation of the eyes from a central position results in a divergence between the retinal visual and the head-centred auditory coordinates. It has been suggested that this divergence is compensated for by a neural coordinate transformation, using a signal of eye-in-head position. Using functional magnetic resonance imaging, we investigated which cortical areas of the human brain participate in such auditory-visual coordinate transformations. Sounds were produced with different interaural level differences, leading to left, right or central intracranial percepts, while subjects directed their gaze to visual targets presented to the left, to the right or straight ahead. When gaze was to the left or right, we found the primary visual cortex (V1/V2) activated in both hemispheres. The occipital activation did not occur with sound lateralization per se, but was found exclusively in combination with eccentric eye positions. This result suggests a relation of neural processing in the visual cortex and the transformation of auditory spatial coordinates responsible for maintaining the perceptual alignment of audition and vision with changes in gaze direction.
Acoustic Stimulation↗
Task transfer: another pressure for evolution of the medical profession.
Since the 1960s, Australian society and the medical profession have undergone enormous change. Our society has moved from a relatively homogeneous and conservative community, supported by limited government services, to one that is multicultural, focused on the individual and consumerism, and supported by extensive government programs, with health care a top public and political priority. A defining feature of contemporary society is its mistrust of institutions, professionals, public servants and politicians. The medical profession has changed from a cohesive entity, valuing generalism and with limited specialisation, to one splintered by ultra-specialisation and competing professional agendas. The medical workforce shortage and efforts to maintain the safety and quality of health services are putting acute pressure on the profession. Task transfer or role substitution of medical services is mooted as a potential solution to this pressure. This has the potential to drastically transform the profession. How task transfer will evolve and change medicine depends on the vision and leadership of the profession and a flexible pragmatism that safeguards quality and safety and places patient priorities above those of the profession.
Australia↗
Ubiquitous computing technology for just-in-time motivation of behavior change.
This paper describes a vision of health care where "just-in-time" user interfaces are used to transform people from passive to active consumers of health care. Systems that use computational pattern recognition to detect points of decision, behavior, or consequences automatically can present motivational messages to encourage healthy behavior at just the right time. Further, new ubiquitous computing and mobile computing devices permit information to be conveyed to users at just the right place. In combination, computer systems that present messages at the right time and place can be developed to motivate physical activity and healthy eating. Computational sensing technologies can also be used to measure the impact of the motivational technology on behavior.
Health Behavior↗
[Allergic vasculitis caused by Vigabatrin].
A patient with focal epilepsy that was resistant to medical treatment received add-on therapy with vigabatrin. Six months after commencement of vigabatrin therapy, allergic vasculitis caused by vigabatrin was diagnosed. The patient displayed unilateral anterior ischaemic optic neuropathy with impairment of vision and concentric loss of visual field. The diagnosis was based on the lymphocyte transformation test and the clinical course. The allergic vasculitis was healed by cortisone therapy.
Adult↗
The complete pattern of ocular dominance stripes in the striate cortex and visual field of the macaque monkey.
Ocular dominance stripes in the striate cortex of a macaque monkey were labeled by autoradiography after injection of [3H]proline into one eye. The stripes were reconstructed on a representation of the flattened cortical surface by two independent techniques: one used computer graphics, and the other was the manual unfolding procedure of Van Essen and Maunsell (VanEssen, D. C., and J. H. R. Maunsell (1980) J. Comp. Neurol. 191: 255-281). The two reconstructions differed in many details of the pattern but were in agreement on its general features. As described in earlier studies, the stripes formed a system of parallel bands, with numerous branches and islands. They were roughly orthogonal to the V1/V2 border throughout the binocular segment of the cortex. In the lateral part of the operculum, where the fovea is represented, the stripes were less orderly than elsewhere. In the calcarine fissure the stripes ran directly across the striate cortex from its dorsal to its ventral margin. In the far periphery the stripes for the ipsilateral eye became progressively narrower, eventually fragmenting into small islands at the edge of the monocular segment. The overall periodicity (width of a left- plus right-eye pair of stripes) averaged 0.88 mm but decreased by a factor of about 2 from center to periphery. This decrease was not accounted for solely by shrinkage of the ipsilateral eye stripes. The flattened cortical reconstruction was transformed back into visual field coordinates, using information about visual field topography obtained from the detailed mapping study of Van Essen et al. (Van Essen, D.C., W.T. Newsome, and J.H.R. Maunsell (1984) Vision Res. 24: 429-448), as well as from more limited mapping done in the same monkey that was used for the reconstruction. In the transformed map, the stripes increased in width about 40-fold from the fovea to the far periphery. As deduced previously (LeVay, S., D. H. Hubel, and T. N. Wiesel (1975) J. Comp. Neurol. 159: 559-576; Hubel, D. H., and D. C., Freeman (1977) Brain Res. 122: 336-343), there were portions of the map in which the stripes followed curves approximating isoeccentricity lines, but this relationship was not very exact or consistent. The pattern of stripes appears to be more meaningfully related to the geometry of the cortical surface. This has significant implications for understanding the developmental mechanisms involved in stripe formation.
Animals↗
Reversal of visual discrimination and visual acute extinction in cats with poor or limited early visual experience.
Transformation of visual instrumental conditioned reflexes rewarded with food was compared in cats binocularly deprived of pattern vision in the early period of life (BD cats), control cats reared also in the laboratory but with open eyes (C cats) and cats reared in normal environment (N cats). In Expt. I the cats were given 4 sequential reversal trainings of cross vs. disc discrimination and in Expt. II a response to a gate marked with a cross or a disc was submitted to 4 sequential acute extinctions and restorations. The results show that both visual deprivation and rearing in monotonous laboratory environment moderately affect transformation of associations between visual stimuli and hunger drive and instrumental responses. However, in BD cats transformation learning is less impaired than previously studied visual discrimination learning.
Animals↗
[Phantom vision phenomenon].
The subject of the paper is the phenomenon of phantom vision. It occurs among the blind (or almost blind) and is characterised by perceiving various visual sensations, for example: light, geometrical shapes, buildings, people, flowers etc. The paper presents views explaining the generation of phantom vision. According to Melzack's theory, the occurrence of these sensations is explained in relation to the phenomenon of transforming the neuro-activity of the brain in a specific--for each organ--neuronal network called neuromatrix. Even if some organs do exist but have ceased to function completely (or to a significant degree) and consequently the brain does not receive any sensory stimuli from them, the neuromatrix in brain can generate visual sensations constituting the phantom vision phenomenon. The paper also presents three cases of phantom vision.
Aged↗
[Phantom vision sensation].
The paper presents the phenomenon of phantom sensation including in particular, a phantom vision. These unusual sensations occur among the blind (or almost blind) and are characterised by the perception of various visual impressions, for example, light, geometrical shapes, buildings, people, flowers etc. The paper presents views explaining the generation of phantom vision. According to Melzack's theory, the occurrence of these sensations is explained in relation to the phenomenon of transforming the neuro-activity of the brain in a specific--for each organ--neuronal network called neuromatrix. Even if some organs do exist but have ceased to function completely (or to a significant degree) and consequently the brain does not receive any sensory stimuli from them, the neuromatrix in brain can generate visual sensations constituting the phantom vision phenomenon. The article also includes commentaries on such visual and mental sensations like hallucinations, Pick's visions and so called "scotoma of the leg".
Humans↗
How can we improve the nursing work environment?
It has been suggested by many recently that the nursing work environment needs to be altered to make it more responsive to both nurse and patient needs. One essential aspect of this change would be to increase patient safety. This article suggests that to improve patient safety as well as satisfaction of nurses, the culture of the nursing organization should be transformed into one of a "learning organization." Using this model of an organization, every member of the nursing organization would be encouraged to reach his or her greatest potential, the welfare of the team would become paramount, and a shared vision of where the organization needs to go would emerge, thus maximizing productivity, safety, and job satisfaction for all healthcare team members. This transformation could mean that the terms "Nursing Organizations" and "Learning Organizations" would not have to be oxymorons.
Attitude of Health Personnel↗
Transformations between visual and kinesthetic coordinate systems in reaches to remembered object locations and orientations.
The abilities of human subjects to perform reach and grasp movements to remembered locations/orientations of a cylindrical object were studied under four conditions: (1) visual presentation of the object-reach with vision allowed; (2) visual presentation-reach while blindfolded; (3) kinesthetic presentation of the object-reach while blindfolded and (4) kinesthetic presentation-reach with vision. The results showed that subjects were very accurate in locating the object in the purely kinesthetic condition and that directional errors were low in all four conditions; but, predictable errors in reach distance occurred in conditions 1,2, and 4. The pattern of these distance errors was similar to that identified in previous research using a pointing task to a small target (i.e., overshoots of close targets, undershoots of far targets). The observation that the pattern of distance errors in condition 4 was similar to that of conditions 1 and 2 suggests that subjects transform kinesthetically defined hand locations into a visual coordinate system when vision is available during upper limb motion to a remembered kinesthetic target. The differences in orientation of the upper limb between target and reach positions in condition 3 were similar in magnitude to the errors associated with kinesthetic perceptions of arm and hand orientations in three-dimensional space reported in previous studies. However, fingertip location was specified with greater accuracy than the orientation of upper limb segments. This was apparently accomplished by compensation of variations in shoulder (arm) angles with oppositely directed variations in elbow joint angles. Subjects were also able to transform visually perceived object orientation into an appropriate hand orientation for grasp, as indicated by the relation between hand roll angle and object orientation (elevation angle). The implications of these results for control of upper limb motion to external targets are discussed.
Adolescent↗
Automated registration of multimodal brain image sets using computer vision methods.
We present a new method of registering three dimensional image volumes of the brain of a given patient acquired at different times or with different imaging modalities, or both. Registration is an essential requirement for fusing the data from the two image sets so as to either increase the available information by exploiting complementary imaging modalities, or to measure small changes over time for prognostication, disease assessment, etc. The new technique exploits an external, removable, remountable reference frame which is attached to the head. Computer vision techniques are used to determine the positions of fiducial marks in every image. The transformation required to map each image of one image volume onto the other image volume is developed using the theory of quaternions. The results indicate that the new technique is robust and practical in a clinical setting.
Algorithms↗
Skewness and transformations of Farnsworth-Munsell 100-hue test scores.
In the past, suggested transformations of Farnsworth-Munsell 100-Hue Test (FM 100-Hue) test scores distributions have been limited to a square root transformation. In this study, the choice of transformations of total error scores (TES) are considered by identifying a possible source of skewness. Several distributions of FM100-Hue Test TES were assessed for skewness (third moment). The error score (ES) distributions for the 85 individual caps in each of the populations were also analysed for skewness (Figs. 3 and 4). There is no single transformation which will normalise all TES distributions. The single cap ES distributions with low mean ES (such as those achieved normals and, for some regions of the test, by anomalous trichromats and dichromats) are symmetrical because most subjects can organise the cap perfectly (and could do even better given smaller colour differences). The distributions of ESs where the mean ES is in the moderate range (such as those achieved by diabetics) are skewed because some ESs at the lower end of the range represent performance which could also be better than the test allows. ES distributions with a high mean (such as random distributions and some regions of the test by congenital dichromats) are symmetrical being unaffected by the limitations of the test. TES distributions of diabetics are asymmetrical and comprise skewed cap ES distributions. A suggestion for a transformation is made.
Color Perception Tests↗