Absence Of Disparity Research Articles

Dissociating neural activity associated with the subjective phenomenology of monocular stereopsis: An EEG study

The subjective phenomenology associated with stereopsis, of solid tangible objects separated by a palpable negative space, is conventionally thought to be a by-product of the derivation of depth from binocular disparity. However, the same qualitative impression has been reported in the absence of disparity, e.g., when viewing pictorial images monocularly through an aperture. Here we aimed to explore if we could identify dissociable neural activity associated with the qualitative impression of stereopsis in the absence of the processing of binocular disparities. We measured EEG activity while subjects viewed pictorial (non-stereoscopic) images of 2D and 3D geometric forms under four different viewing conditions (binocular, monocular, binocular aperture, monocular aperture). EEG activity was analysed by oscillatory source localization (beamformer technique) to examine power change in occipital and parietal regions across viewing and stimulus conditions in targeted frequency bands (alpha: 8–13 Hz & gamma: 60–90 Hz). We observed expected event-related gamma synchronization and alpha desynchronization in occipital cortex and predominant gamma synchronization in parietal cortex across viewing and stimulus conditions. However, only the viewing condition predicted to generate the strongest impression of stereopsis (monocular aperture) revealed significantly elevated gamma synchronization within the parietal cortex for the critical contrasts (3D vs. 2D form). These findings suggest dissociable neural processes specific to the qualitative impression of stereopsis as distinguished from disparity processing.

With Equal Access and Utilization of Resources,Younger African American Patients Have Superior Survival Compared to Caucasian Patients Diagnosed with Multiple Myeloma at the Veterans Affairs Hospitals

Background: Multiple myeloma (MM) is a plasma cell neoplasm that constitutes approximately 1.8% of malignancies in the US. Recent studies have found significant and increasing racial disparities in survival outcomes since the introduction of novel targeted agents and increased use of autologous stem cell transplant in MM treatment, and concomitant disparity in access to these therapies. Here, we investigate whether these disparities hold in the Veterans Affairs (VA) healthcare system. We hypothesized that disparities seen in the general population might not appear in the VA, where differential access to treatment is less of an issue.Methods: We used the VA's nationwide Corporate Data Warehouse to identify patients diagnosed with symptomatic MM from 1999 to 2017. We extracted data on each patient's demographics, including their race and age at diagnosis, as well as comprehensive data on their treatment, from which we determined therapy at induction and stem-cell transplant status. Novel therapy at induction is defined as use of immunomodulatory drugs (IMiDs: thalidomide, lenalidomide, and pomalidomide) or proteasome inhibitors (PIs: bortezomib, carfilzomib, and ixazomib) within 3 months after therapy initiation. We compared overall survival between AA and Caucasians using Cox models. We assessed differences in treatment patterns using chi-squared tests.Results: We identified 3,254 AA and 8,845 Caucasian patients who fulfilled our criteria for symptomatic MM. We excluded 2486 Veterans with no race data, and 201 Veterans who were of other races. Without adjusting for age at diagnosis, there is a substantial difference in OS between AA and Caucasian patients. Median OS is 5.07 years (95% CI 4.70-5.44) for AA, which is significantly superior to 4.52 years (95% CI 4.38-4.65) for Caucasian patients (P<1e-15). Five year survival is 50.4% (95% CI 48.5-52.4%) for AA, compared to 45.9% (95% CI 44.7-47.1%) for Caucasians. This is illustrated in the survival plot in Figure 1A.However, age has a substantial effect on overall survival, decreasing from 7.5 years median survival among patients diagnosed in their 40s, to 5.9 years for those in their 50s, 5.2 years in 60s, 3.5 years in 70s, and 2.6 years in 80s (P<0.001).Among patients younger than 65 years old at diagnosis, we observed a significantly lower age-adjusted risk of death for AA compared to Caucasian patients (HR 0.86, 95% CI 0.79-0.94, P=0.001). However, in patients 65 and older, age-adjusted overall survival was similar between the two groups. This is illustrated in Figure 1B and 1C, where patients are stratified into two groups: age at diagnosis < 65 years old and ≥ 65 years old.We observed no racial disparity at the VA in the overall use of transplant or novel agents at induction (IMiD or PI), with 82.5% of AA patients and 81.5% of Caucasian patients receiving novel therapy (P=0.21). This includes patients diagnosed since the year 2000, when IMiDs and PIs were not widely available. Since 2010, patterns of usage still show equal utilization, but use of novel therapy at induction increased to 93% (94% AA, 93% Caucasian).Conclusions: In contrast to findings in the US population at large, at the VA, in absence of disparity in use of novel agents, no racial disparity was observed in overall survival between AA and Caucasian patients with MM. In fact, among patients <65 years old at diagnosis, we observed a significantly lower age-adjusted risk of death for AA compared to Caucasian patients. The difference in the younger population was not explained by access or utilization of resources. This analysis suggests that when healthcare access is neutralized, younger AA may even have improved overall survival, which may indicate the possibility of genetic differences that may drive the disease biology and therapeutic outcome in AA patients. [Display omitted] DisclosuresYellapragada:Takeda: Research Funding; Celgene: Research Funding; Novartis: Employment. Brophy:Novartis: Research Funding. Munshi:OncoPep: Other: Board of director.

A neural model for the integration of stereopsis and motion parallax in structure from motion

We introduce a model for the computation of structure from motion based on the physiology of visual cortical areas MT and MST. The model assumes that the perception of depth from motion is related to the firing of a subset of MT neurons tuned to both velocity and disparity. The model's MT neurons are connected to each other laterally to form modulatory receptive-field surrounds that are gated by feedback connections from area MST. This allows the building up of a depth map from motion in area MT, even in absence of disparity in the input. Depth maps from motion and from stereo are combined by a weighted average at a final stage. The model's predictions for the interaction between motion and stereo cues agree with previous psychophysical data, both when the cues are consistent with each other or when they are contradictory. In particular, the model shows nonlinearities as a result of early interactions between motion and stereo before their depth maps are averaged. The two cues interact in a way that represents an alternative to the “modified weak fusion” model of depth–cue combination.

Saccade amplitude disconjugacy induced by aniseikonia: role of monocular depth cues

The conjugacy of saccades is rapidly modified if the images are made unequal for the two eyes. Disconjugacy persists even in the absence of disparity which indicates learning. Binocular visual disparity is a major cue to depth and is believed to drive the disconjugacy of saccades to aniseikonic images. The goal of the present study was to test whether monocular depth cues can also influence the disconjugacy of saccades. Three experiments were performed in which subjects were exposed for 15–20 min to a 10% image size inequality. Three different images were used: a grid that contained a single monocular depth cue strongly indicating a frontoparallel plane; a random-dot pattern that contained a less prominent monocular depth cue (absence of texture gradient) which also indicates the frontoparallel plane; and a complex image with several overlapping geometric forms that contained a variety of monocular depth cues. Saccades became disconjugate in all three experiments. The disconjugacy was larger and more persistent for the experiment using the random-dot pattern that had the least prominent monocular depth cues. The complex image which had a large variety of monocular depth cues produced the most variable and less persistent disconjugacy. We conclude that the monocular depth cues modulate the disconjugacy of saccades stimulated by the disparity of aniseikonic images.

Immediate saccade amplitude disconjugacy induced by unequal images

We tested the ability of normal subjects to make changes in the conjugacy of their saccades. Subjects dichoptically viewed a grid the size of which was 10% larger in one eye. The grids were centred onto a flat screen at 57 cm or 1 m from the subject. Horizontal saccades immediately became larger in the eye viewing the larger grid. For some subjects this disconjugacy persisted even under subsequent monocular viewing. Such persistent changes occurred mainly in the field where the required disconjugacy was divergent for centrifugal saccades, convergent for centripetal saccades. Vertical saccades also developed compensatory disconjugacy; its amplitude was smaller but less variable. To explain these results we propose a fast associative learning mechanism that pairs peripheral disparity with saccades and is capable of producing saccade disconjugacy even in the absence of disparity. For horizontal saccades a secondary conditioning of monocular depth cues by the disparity would also be involved.

3-D in Pictorial Formats for Aircraft Cockpits

Sixteen military pilots flew simulated air-to-air and air-to-ground missions in a simulated fighter-attack cockpit. Three of the five color CRTs in the cockpit were capable of displaying retinal disparity and the major independent variable was presence or absence of disparity. Performance, workload, and opinion data were collected. A second objective of the study was to continue development of the display formats, which had evolved through earlier projects. The disparity results and the recommended format revisions are presented.

Histologic and hormonal documentation of the luteinized unruptured follicle syndrome

Histologic and hormonal documentation of a luteinized unruptured follicle that occurred during a spontaneous menstrual cycle in a rhesus monkey is presented. Frequent (every 2 hours) blood sampling to assess midcycle hormonal dynamics in the monkey with the luteinized unruptured follicle and in five monkeys with an ovulatory stigma revealed significant aberrations in the gonadotropin and steroid hormone profiles associated with a luteinized unruptured follicle. Although the midcycle 17β-estradiol surge was normal, the monkey with the luteinized unruptured follicle demonstrated (1) blunted midcycle bioassayable luteinizing hormone, immunoassayable luteinizing hormone, and follicle-stimulating hormone surges; (2) absence of disparity in the bioassayable luteinizing hormone: immunoassayable luteinizing hormone ratio during the gonadotropin surge; (3) absence of progesterone and 17α-hydroxyprogesterone secretion during the gonadotropin surge; and (4) delayed and blunted rise in progesterone and 17α-hydroxyprogesterone after the gonadotropin surge. These findings suggest that an impaired luteinizing hormone surge, perhaps mediated by insufficient midcycle progestin secretion, is one possible cause of the luteinized unruptured follicle syndrome.