The Spatial Origin of a Perceptual Transition in Binocular Rivalry

When the left and the right eye are simultaneously presented with incompatible images at overlapping retinal locations, an observer typically reports perceiving only one of the two images at a time. This phenomenon is called binocular rivalry. Perception during binocular rivalry is not stable; one of the images is perceptually dominant for a certain duration (typically in the order of a few seconds) after which perception switches towards the other image. This alternation between perceptual dominance and suppression will continue for as long the images are presented. A characteristic of binocular rivalry is that a perceptual transition from one image to the other generally occurs in a gradual manner: the image that was temporarily suppressed will regain perceptual dominance at isolated locations within the perceived image, after which its visibility spreads throughout the whole image. These gradual transitions from perceptual suppression to perceptual dominance have been labeled as traveling waves of perceptual dominance. In this study we investigate whether stimulus parameters affect the location at which a traveling wave starts. We varied the contrast, spatial frequency or motion speed in one of the rivaling images, while keeping the same parameter constant in the other image. We used a flash-suppression paradigm to force one of the rival images into perceptual suppression. Observers waited until the suppressed image became perceptually dominant again, and indicated the position at which this breakthrough from suppression occurred. Our results show that the starting point of a traveling wave during binocular rivalry is highly dependent on local stimulus parameters. More specifically, a traveling wave most likely started at the location where the contrast of the suppressed image was higher than that of the dominant one, the spatial frequency of the suppressed image was lower than that of the dominant one, and the motion speed of the suppressed image was higher than that of the dominant one. We suggest that a breakthrough from suppression to dominance occurs at the location where salience (the degree to which a stimulus element stands out relative to neighboring elements) of the suppressed image is higher than that of the dominant one. Our results further show that stimulus parameters affecting the temporal dynamics during continuous viewing of rival images described in other studies, also affect the spatial origin of traveling waves during binocular rivalry

Measurement of overall quality of life in nursing homes through self-report: the role of cognitive impairment

Measuring quality of life is a necessity for adequate interventions. This paper concerns the usefulness of six self-report measures for overall quality of life for nursing home residents with various levels of cognitive impairment. It was investigated which proportion of residents from four cognition groups could complete a scale, and internal consistency and construct validity of the scales were studied. Data collection took place in ten Dutch nursing homes (N = 227). The proportion of residents that could complete each scale varied. The Depression List could be administered most often to the cognitively most impaired group (43%; Mini Mental State Examination-scores 0–4). In the three cognition groups with MMSE-score >5, internal consistency of the Depression List, Geriatric Depression Scale and Negative Affect Scale was adequate in all three groups (alpha ≥.68). Intercorrelation was highest for the Philadelphia Geriatric Center Morale Scale, the Depression List, and the Geriatric Depression Scale (rho ≥.65). Nonetheless, self-report scales were not strongly correlated with two observational scales for depression, especially in cognitively severely impaired residents (rho ≤.30). In conclusion, it may not be possible to measure overall quality of life through self-report, and possibly also through observation, in many nursing home residents

Onnodige slechtziendheid onder ouderen in zorginstellingen: lessen uit een interventieproject in de regio Den Bosch

Introductie Veel ouderen in zorginstellingen in Nederland zijn onnodig blind of slechtziend (visus <0,3). Zij vallen vaker, zijn vaker depressief en hebben meer zorg nodig. In dit interventieproject werden slechtziende bewoners geïdentificeerd en doorverwezen voor adequate oogzorg. Het doel van het onderzoek is evaluatie van de interventie, waaronder validatie van de screening, bepalen van prevalentie en oorzaken van visuele beperkingen en bepalen van resultaten van de behandeling. Daarnaast wordt ook de effectiviteit van de zorgketen geëvalueerd. Materiaal en methode Aan 640 bewoners werd een eenvoudige oogscreening aangeboden en 210 van hen werden verwezen, via hun huisarts, naar de optiek (10), oogarts (98) of revalidatie-instelling (1). Resultaten De uitval in dit onderzoek was fors. De prevalentie van slechtziendheid (24%) was lager dan in vergelijkbare studies. Van de onderzochte bewoners had 51% cataract. Uiteindelijk zijn 17 (8,1%) van de 210 verwezen bewoners behandeld door de oogarts en negen (4,3%) naar een optiekzaak verwezen. Knelpunten in de effectiviteit van de zorgketen werden geïdentificeerd. Discussie Visusscreening in zorginstellingen voor ouderen is goed uitvoerbaar en zinvol. De organisatie van de zorgketen dient korter en eenvoudiger te worden. Daarmee zal de effectiviteit van deze interventie, en daarmee de kwaliteit van leven van veel bewoners, verbeteren

Low-level mediation of directionally specific motion after-effects: motion perception is not necessary

Previous psychophysical experiments with normal human observers have shown that adaptation to a moving dot stream causes directionally specific repulsion in the perceived angle of a subsequently viewed, moving probe. In this paper, we used a 2AFC task with roving pedestals to determine the conditions necessary and sufficient for producing directionally specific repulsion with compound adaptors, each ofwhich contains two oppositely moving, differently colored, component streams. Experiment 1 provides a demonstration of repulsion between single-component adaptors and probes moving at approximately 90° or 270°. In Experiment 2 oppositely moving dots in the adaptor were paired to preclude the appearance of motion. Nonetheless, repulsion remained strong when the angle betweeneach probe stream and one component was approximately 30°. In Experiment 3 adapting dot-pairs were kept stationary during their limited lifetimes. Their orientation content alone proved insufficient for producing repulsion. In Experiments 4-6 the angle between probe and both adapting components was approximately 90°or 270°. Directional repulsion was found when observers were asked to visually track one of the adapting components (Experiment 6), but not when observers were asked to attentionally track it (Experiment 5), nor while passively viewing the adaptor (Experiment 4). Our results are consistent with a low-level mechanism for motion adaptation. It is not selective for stimulus color and it is not susceptible to attentional modulation.The most likely cortical locus of adaptation is area V1

Modelling fast forms of visual neural plasticity using a modified second-order motion energy model

The Adelson-Bergen motion energy sensor is well established as the leading model of low-level visual motion sensing in human vision. However, the standard model cannot predict adaptation effects in motion perception. A previous paper Pavan et al.(Journal of Vision 10:1-17, 2013) presented an extension to the model which uses a first-order RC gain-control circuit (leaky integrator) to implement adaptation effects which can span many seconds, and showed that the extended model's output is consistent with psychophysical data on the classic motion after-effect. Recent psychophysical research has reported adaptation over much shorter time periods, spanning just a few hundred milliseconds. The present paper further extends the sensor model to implement rapid adaptation, by adding a second-order RC circuit which causes the sensor to require a finite amount of time to react to a sudden change in stimulation. The output of the new sensor accounts accurately for psychophysical data on rapid forms of facilitation (rapid visual motion priming, rVMP) and suppression (rapid motion after-effect, rMAE). Changes in natural scene content occur over multiple time scales, and multi-stage leaky integrators of the kind proposed here offer a computational scheme for modelling adaptation over multiple time scales. © 2014 Springer Science+Business Media New York

Visual Stability and the Motion Aftereffect: A Psychophysical Study Revealing Spatial Updating

Eye movements create an ever-changing image of the world on the retina. In particular, frequent saccades call for a compensatory mechanism to transform the changing visual information into a stable percept. To this end, the brain presumably uses internal copies of motor commands. Electrophysiological recordings of visual neurons in the primate lateral intraparietal cortex, the frontal eye fields, and the superior colliculus suggest that the receptive fields (RFs) of special neurons shift towards their post-saccadic positions before the onset of a saccade. However, the perceptual consequences of these shifts remain controversial. We wanted to test in humans whether a remapping of motion adaptation occurs in visual perception

Detection of Bovine Herpesvirus 1 Glycoprotein E Antibodies in Individual Milk Samples by Enzyme-Linked Immunosorbent Assays

The purpose of this study was to determine whether individual milk samples can replace serum samples for the detection of bovine herpesvirus 1 (BHV1) glycoprotein E (gE)-specific antibodies. Serum and milk samples were collected at the same time from cattle in BHV1-free herds, cattle in unvaccinated herds, and cattle in herds that were vaccinated twice with a BHV1 marker vaccine. The samples were tested in two gE enzyme-linked immunosorbent assay (ELISA) systems. In comparison to serum, the results showed that the gE-blocking ELISA was highly sensitive for testing milk samples (0.96). In contrast, the gE ELISA was less sensitive (0.79). The specificities of the gE-blocking ELISA and the gE ELISA for testing milk samples were very high (1.00 and 0.99, respectively). The presented results indicate that individual milk samples, which can be collected relatively easily and inexpensively, can be used instead of individual serum samples in the gE-blocking ELISA for the screening of cattle for BHV1 gE antibodies

The perceptions of women with breast cancer during treatment with chemotherapy on changes in weight; a mixed methods approach

Background: Weight gain and undesirable changes in body composition in women receiving chemotherapy (CT) for early stage breast cancer is a common, but poorly understood phenomenon. This sarcopenic obesity consists of an increase in fat mass and a decrease in lean body mass, which is associated with disease recurrence, an increased risk of cardiovascular disease and diabetes, lower quality of life, and a lower overall survival. The purpose of this study was to explore in-depth the perceptions of women with breast cancer on determinants of changes in body composition and muscle strength as dietary intake, physical activity and quality of life and their possible interventions on these potential changes. Interpreted against the individual measurements made during the treatment trajectory such as changes in weight, fat mass, lean body mass. Methods: As part of a greater mixed methods study, a longitudinal qualitative multiple case study was conducted. Newly diagnosed women with breast cancer were recruited and purposively selected (n = 18) from several hospitals in the Netherlands before the start of their treatment with CT. Semi structured face-to face interviews were conducted during the treatment trajectory at three time points: before start of CT, (T1), halfway (T2) and after CT (T3). Interviews (n = 54) were audiotaped and transcribed verbatim. A thematic content analysis approach was used to explore women's perceptions, such as changes in weight and taste and to interpret these qualitative findings against the individual quantitative data such as changes in weight, fat mass, lean body mass (DEXA scans), BMI, muscle strength and results of the Hospital Anxiety and Depression Scale (HADS). Results: All women, mean age 51 yr (26-65 yr) experienced known side effects from CT such as hair loss, nausea, sore mouth, mucositis. Fourteen out of 18 women gained weight between 2 and 7 kg; three women lost some weight (3-7 kg), whereas one woman lost 14 kg. All women said to be less physically active and complained about fatigue. They all experienced undesirable changes regarding taste, smell and food preferences sometimes leading to loss of appetite. Others experienced more appetite despite changes in food preferences or changes in taste and smell. Depending on their illness perception women differed in how they acted upon these changes. Some women monitored the impact of therapy reactively, other women tried to respond proactively and often creatively to all changes that happens to them. Results of the interviews were supplementary and explanatory to the weight and BMI changes and the results of the HADS. Conclusion: Suffering from weight changes, being less physically active, monitoring changes differently are important elements to take into account for the development of interventions to prevent weight gain in women with breast cancer during CT