Using equiluminance settings to estimate the cardinal chromatic directions for individuals.

Color information is processed by the retina and lateral geniculate along principal dimensions known as the cardinal directions of color space. Normal differences in spectral sensitivity can impact the stimulus directions that isolate these axes for individual observers and can arise from variation in lens and macular pigment density, photopigment opsins, photoreceptor optical density, and relative cone numbers. Some of these factors that influence the chromatic cardinal axes also impact luminance sensitivity. We modeled and empirically tested how well tilts on the individual's equiluminant plane are correlated with rotations in the directions of their cardinal chromatic axes. Our results show that, especially for the SvsLM axis, the chromatic axes can be partially predicted by luminance settings, providing a potential procedure for efficiently characterizing the cardinal chromatic axes for observers.

Adapting to an enhanced color gamut - implications for color vision and color deficiencies.

One strategy for aiding color deficiencies is to use three narrow passbands to filter the light spectrum to increase the saturation of colors. This filtering is analogous to the narrow emission bands used in wide gamut lighting or displays. We examined how perception adapts to the greater color gamut area produced by such devices, testing color-normal observers and simulated environments. Narrowband spectra increased chromatic contrasts but also increased contrast adaptation, partially offsetting the perceived contrast enhancements. Such adaptation adjustments are important for understanding the perceptual consequences of exposure to naturally or artificially enhanced color gamut areas for both color-deficient and color-normal observers.

ENHANCED PERIPHERAL FACE PROCESSING IN DEAF INDIVIDUALS.

Studies of compensatory changes in visual functions in response to auditory loss have shown that enhancements tend to be restricted to the processing of specific visual features, such as motion in the periphery. Previous studies have also shown that deaf individuals can show greater face processing abilities in the central visual field. Enhancements in the processing of peripheral stimuli are thought to arise from a lack of auditory input and a subsequent increase in the allocation of attentional resources to peripheral locations, while enhancements in face processing abilities are thought to be driven by experience with ASL and not necessarily hearing loss. This combined with the fact that face processing abilities typically decline with eccentricity suggests that face processing enhancements may not extend to the periphery for deaf individuals. Using a face matching task, we examined whether deaf individuals' enhanced ability to discriminate between faces extends to the peripheral visual field. Deaf participants were more accurate than hearing participants in discriminating faces presented both centrally and in the periphery. Our results support earlier findings that deaf individuals possess enhanced face discrimination abilities in the central visual field and further extend them by showing that these enhancements also occur in the periphery for more complex stimuli.

Set size and ensemble perception of numerical value.

There is a growing body of research on ensemble perception, or our ability to form ensemble representations based on perceptual features for stimuli of varying levels of complexity, and more recently, on ensemble cognition, which refers to our ability to perceive higher-level properties of stimuli such as facial attractiveness or gaze direction. Less is known about our ability to form ensemble representations based on more abstract properties such as the semantic meaning associated with items in a scene. Previous work examining whether the meaning associated with digits can be incorporated into summary statistical representations suggests that numerical information from digit ensembles can be extracted rapidly, and likely using a parallel processing mechanism. Here, we further investigate whether participants can accurately generate summary representations of numerical value from digit sets and explore the effect of set size on their ability to do so, by comparing psychometric functions based on a numerical averaging task in which set size varied. Steeper slopes for ten- and seven-item compared to five-item digit sets provide evidence that displays with more digits yield more reliable discrimination between larger and smaller numerical averages. Additionally, consistent with previous reports, we observed a response bias such that participants were more likely to report that the numerical average was "greater than 5" for larger compared to smaller sets. Overall, our results contribute to evidence that ensemble representations for semantic attributes may be carried out via similar mechanisms as those reported for perceptual features.

Predicting color matches from luminance matches.

Color vision and spectral sensitivity vary among individuals with normal color vision; thus, for many applications, it is important to measure and correct for an observer's sensitivity. Full correction would require measuring color and luminance matches and is rarely implemented. However, luminance matches (equiluminance settings) are routinely measured and simple to conduct. We modeled how well an observer's color matches could be approximated by measuring only luminance sensitivity, since both depend on a common set of factors. We show that lens and macular pigment density and $L/M$L/M cone ratios alter equiluminance settings in different ways and can therefore be estimated from the settings. In turn, the density variations can account for a large proportion of the normal variation in color matching. Thus, luminance matches may provide a simple method to at least partially predict an observer's color matches without requiring more complex tasks or equipment.

Motion Parallax Improves Object Recognition in the Presence of Clutter in Simulated Prosthetic Vision.

PURPOSE: Efficacy of current visual prostheses in object recognition is limited. Among various limitations to be addressed, such as low resolution and low dynamic range, here we focus on reducing the impact of background clutter on object recognition. We have proposed the use of motion parallax via head-mounted camera lateral scanning and computationally stabilizing the object of interest (OI) to support neural background decluttering. Simulations in head-mounted displays (HMD), mimicking the proposed effect, were used to test object recognition in normally sighted subjects. METHODS: Images (24° field of view) were captured from multiple viewpoints and presented at a low resolution (20 × 20). All viewpoints were centered on the OI. Experimental conditions (2 × 3) included clutter (with or without) × head scanning (single viewpoint, 9 coherent viewpoints corresponding to subjects' head positions, and 9 randomly associated viewpoints). Subjects used lateral head movements to view OIs in the HMD. Each object was displayed only once for each subject. RESULTS: The median recognition rate without clutter was 40% for all head scanning conditions. Performance with synthetic background clutter dropped to 10% in the static condition, but it was improved to 20% with the coherent and random head scanning (corrected P = 0.005 and P = 0.049, respectively). CONCLUSIONS: Background decluttering using motion parallax cues but not the coherent multiple views of the OI improved object recognition in low-resolution images. The improvement did not fully eliminate the impact of background. TRANSLATIONAL RELEVANCE: Motion parallax is an effective but incomplete decluttering solution for object recognition with visual prostheses.

Word recognition: re-thinking prosthetic vision evaluation.

OBJECTIVE: Evaluations of vision prostheses and sensory substitution devices have frequently relied on repeated training and then testing with the same small set of items. These multiple forced-choice tasks produced above chance performance in blind users, but it is unclear if the observed performance represents restoration of vision that transfers to novel, untrained items. APPROACH: Here, we tested the generalizability of the forced-choice paradigm on discrimination of low-resolution word images. Extensive visual training was conducted with the same 10 words used in previous BrainPort tongue stimulation studies. The performance on these 10 words and an additional 50 words was measured before and after the training sessions. MAIN RESULTS: The results revealed minimal performance improvement with the untrained words, demonstrating instead pattern discrimination limited mostly to the trained words. SIGNIFICANCE: These findings highlight the need to reconsider current evaluation practices, in particular, the use of forced-choice paradigms with a few highly trained items. While appropriate for measuring the performance thresholds in acuity or contrast sensitivity of a functioning visual system, performance on such tasks cannot be taken to indicate restored spatial pattern vision.

Resistance Training Threshold for Elevating Bone Mineral Density in Growing Female Rats.

The purpose of this study was to determine the minimum amount of resistance exercise that would stimulate bone formation yielding an elevation in bone mineral density (BMD) during the growth period in female rats. Female rats were randomly divided into: Control (Con, n=8), 3 ladder climb resistance-trained group (3LC, n=8), 4 ladder climb resistance-trained group (4LC, n=8), 5 ladder climb resistance-trained group (5LC, n=8), and 6 ladder climb resistance-trained group (6LC, n=8). All exercised groups were conditioned to climb a vertical ladder with weights appended to their tail 3 days/wk for a total of 6 wks. After 6 wks, left tibia BMD (g/cm2) was significantly greater for 4LC (0.197±0.003), 5LC (0.200±0.004) and 6LC (0.202±0.003) when compared to Con (0.185±0.006). Left femur BMD (g/cm2) was significantly greater for 4LC (0.260±0.005), 5LC (0.269±0.004) and 6LC (0.272±0.006) when compared to Con (0.244±0.006). There were no significant differences in tibia and femur BMD between 4LC, 5LC, and 6LC groups. The results suggest that during growth, a high volume of resistance exercise was required to elicit an elevation in BMD in females.

Web-Based Alcohol Intervention in First-Year College Students: Efficacy of Full-Program Administration Prior to Second Semester.

BACKGROUND: Commercially available, web-based interventions for the prevention of alcohol use are being adopted for universal use with first-year college students, yet few have received empirical evaluation. OBJECTIVES: This randomized controlled trial investigated the effectiveness of a novel, commercially available, personalized web-based alcohol intervention, Alcohol-Wise (version 4.0, 3rd Millennium Classrooms), on multiple measures of alcohol consumption, alcohol consequences, alcohol expectancies, academic achievement, and adaptation to college in first-year students. METHOD: Participants received Alcohol-Wise either prior to first semester or were waitlisted and received the intervention second semester. As longitudinal effectiveness was of interest, follow-up surveys were conducted 10 weeks (n = 76) and 24 weeks (n = 64) following the web-based alcohol intervention. RESULTS: Completion of Alcohol-Wise had effects on academic achievement. Specifically, at the 24 week follow-up, academic achievement was higher in participants who received the intervention first semester of their freshman year as compared to the waitlist control. The incremental rise in heavy episodic drinking during the first semester of college was also reduced in waitlisted participants by Alcohol-Wise administration prior to second semester. Conclusion/Importance: Implications for the timing of web-based alcohol interventions to include administration prior to both first and second semesters of the freshman year are discussed.