An integrated reweighting theory of perceptual learning.

Improvements in performance on visual tasks due to practice are often specific to a retinal position or stimulus feature. Many researchers suggest that specific perceptual learning alters selective retinotopic representations in early visual analysis. However, transfer is almost always practically advantageous, and it does occur. If perceptual learning alters location-specific representations, how does it transfer to new locations? An integrated reweighting theory explains transfer over retinal locations by incorporating higher level location-independent representations into a multilevel learning system. Location transfer is mediated through location-independent representations, whereas stimulus feature transfer is determined by stimulus similarity at both location-specific and location-independent levels. Transfer to new locations/positions differs fundamentally from transfer to new stimuli. After substantial initial training on an orientation discrimination task, switches to a new location or position are compared with switches to new orientations in the same position, or switches of both. Position switches led to the highest degree of transfer, whereas orientation switches led to the highest levels of specificity. A computational model of integrated reweighting is developed and tested that incorporates the details of the stimuli and the experiment. Transfer to an identical orientation task in a new position is mediated via more broadly tuned location-invariant representations, whereas changing orientation in the same position invokes interference or independent learning of the new orientations at both levels, reflecting stimulus dissimilarity. Consistent with single-cell recording studies, perceptual learning alters the weighting of both early and midlevel representations of the visual system.

Grating acuity and contrast tests for clinical trials of severe vision loss.

PURPOSE: To evaluate the reliability and validity of grating visual acuity (VA) and contrast sensitivity (CS) tests, which could be useful outcome measures to assess changes in severely reduced vision. METHODS: The Grating Acuity Test (GAT) and Grating Contrast Sensitivity (GCS) tests, which involve the detection of grating orientation in a four-Alternative Forced Choice paradigm on a liquid crystal display screen, were compared with the well-validated Early Treatment of Diabetic Retinopathy Study (ETDRS) and Pelli-Robson (PR) charts. Grating tests were repeated two or three times within-visit, across three or four sessions, in 20 legally blind subjects: 8 with retinitis pigmentosa (RP) (16 eyes) and 12 with other retinal diseases (OR) (16 eyes). RESULTS: VA determined by ETDRS and GAT was in good agreement and scaled very similarly, as shown by regression of the within-session difference between the two measures against their mean [RP group: slope (m) = 0.11; 95% confidence interval [CI]: -0.06, 0.29; p = 0.21; OR group: m = -0.07; 95% CI: 0.33, 0.20; p = 0.62]. On average, higher logCS levels were obtained using the GCS than the PR in both groups. The two CS measures scaled similarly in the RP group (m = 0.07; 95% CI: -0.09, 0.22; p = 0.39) but not in the OR group (m = 0.41; 95% CI: 0.12, 0.70; p = 0.005). The within- and between-visit 95% coefficient of repeatability (CR.95) were 0.11 to 0.17 log units for the ETDRS charts and GAT in both groups and 0.14 to 0.15 log units for the PR and GCS in the RP group, whereas the OR group demonstrated more variability in CS. Between-visit CR.95 did not significantly change with mean VA or CS for the ETDRS, PR, or GCS tests, but RP patients' CR.95 on the GAT increased significantly with decreasing VA. Floor effects occurred for some RP eyes with ETDRS and PR charts but not with the GAT and GCS. CONCLUSIONS: Computer-driven grating tests appear to be reliable, capable of evaluating vision that may fall outside of the range of standard clinical tests and may be useful during clinical trials for advanced eye disease.

Task precision at transfer determines specificity of perceptual learning.

Perceptual learning, the improvement in performance with practice, reflects plasticity in the adult visual system. We challenge a standard claim that specificity of perceptual learning depends on task difficulty during training, instead showing that specificity, or conversely transfer, is primarily controlled by the precision demands (i.e., orientation difference) of the transfer task. Thus, for an orientation discrimination task, transfer of performance improvement is observed in low-precision transfer tasks, while specificity of performance improvement is observed in high-precision transfer tasks, regardless of the precision of initial training. The nature of specificity places important constraints on mechanisms of transfer in visual learning. These results contribute to understanding generalization of practiced improvements that may be key to the development of expertise and for applications in remediation.

Optimizing the ULV-VFQ for Clinical Use Through Item Set Reduction: Psychometric Properties and Trade-Offs.

PURPOSE: We examine the dimensionality of the 150-item visual functioning questionnaire for individuals with ultralow vision (ULV-VFQ) and develop representative abbreviated versions, facilitating clinical use, while retaining compatibility with a 17-item performance assessment. METHODS: Subsets with 50 and 23 items covering the full difficulty range were selected, with evenly spaced item measures (IMs) and good representation of visual aspects and functional domains. Person measures (PMs) for the anchored subsets were derived through Rasch analysis of data from 80 respondents. RESULTS: Fit statistics for the reduced item sets were similar to those for the full set, with reliabilities at or above 95%. Mean PMs in the reduced sets were within 0.8 standard errors (SEs) of those in the full set. SEs of the PMs increased from the SE for 150 items, roughly in inverse proportion with the square root of the set size. Unexplained variance levels (24%-27%) and variance of the first unexplained factor (3.3%-3.9%) were close to those (30% and 2.6%) for 150 items. Differential item functions for omitted items were negligible. Aspects and domains are adequately represented in the reduced sets. CONCLUSIONS: Self-reported visual ability can be measured accurately using appropriately chosen anchored subsets of the ULV-VFQ. Functional ability of individuals with ULV is characterized adequately by a single dimension. TRANSLATIONAL RELEVANCE: The ULV-VFQ50 and ULV-VFQ23, using anchored IMs from the 150-item ULV-VFQ, provide an efficient and reliable self-report assessment of visual ability in individuals whose visual impairment is too severe for assessment with VFQs currently in use.

The importance of research literacy for yoga therapists.

Evidence-Informed Practice (EIP) utilizes the three components of expert opinion, research evidence, and client values. It is a recommended training competency for integrative health practitioners in diverse fields, such as acupuncture and massage therapy. Research Literacy (RL) is a necessary pre-requisite to EIP. Many yoga therapists have limited training in these skills, which negatively impacts inter-professional communication and collaboration, as well as further advancement of yoga therapy research and practice. In this article, we propose inclusion of RL and EIP in the training of yoga therapists. Benefits for client care, collaborative care, and the field of yoga therapy are discussed.

Development of the Ultra-Low Vision Visual Functioning Questionnaire (ULV-VFQ).

PURPOSE: To develop and psychometrically evaluate a visual functioning questionnaire (VFQ) in an ultra-low vision (ULV) population. METHODS: Questionnaire items, based on visual activities self-reported by a ULV population, were categorized by functional visual domain (e.g., mobility) and visual aspect (e.g., contrast) to ensure a representative distribution. In Round 1, an initial set of 149 items was generated and administered to 90 participants with ULV (visual acuity [VA] ≤ 20/500; mean [SD] age 61 [15] years), including six patients with a retinal implant. Psychometric properties were evaluated through Rasch analysis and a revised set (150 items) was administered to 80 participants in Round 2. RESULTS: In Round 1, the person measure distribution (range, 8.6 logits) was centered at -1.50 logits relative to the item measures. In Round 2, the person measure distribution (range, 9.5 logits) was centered at -0.86 relative to the item mean. The reliability index in both rounds was 0.97 for Items and 0.99 for Persons. Infit analysis showed four underfit items in Round 1, five underfit items in Round 2 with a z-score greater than 4 cutoff. Principal component analysis on the residuals found 69.9% explained variance; the largest component in the unexplained variance was less than 3%. CONCLUSIONS: The ULV-VFQ, developed with content generated from a ULV population, showed excellent psychometric properties as well as superior measurement validity in a ULV population. TRANSLATIONAL RELEVANCE: The ULV-VFQ, part of the Prosthetic Low Vision Rehabilitation (PLoVR) development program, is a new VFQ developed for assessment of functional vision in ULV populations.

Living with Ultra-Low Vision: An Inventory of Self-Reported Visually Guided Activities by Individuals with Profound Visual Impairment.

PURPOSE: To understand how individuals with profound visual impairment (ultra-low vision, ULV) use their remaining vision. METHODS: Forty-six participants with ULV (visual acuity ≤ 200/500 in the better seeing eye) were divided into nine focus groups (4-6 individuals per group) and met either in person (n = 2) or over the phone (n = 7). Discussions were guided by the Massof Activity Inventory. Audio recordings were transcribed and analyzed for visual activities that were then classified along two visual categorizations - functional domains and visual aspects. The latter was based on a Grounded Theory classification of participants' descriptions. RESULTS: Seven hundred sixty activities were reported. By functional domain they were classified as reading/shape recognition (10%), mobility (17%), visual motor (24%), and visual information gathering (49%). By visual aspects, they were classified as contrast (43%), luminance (17%), environmental lighting (9%), familiarity (3%), motion perception (5%), distance (7%), size (9%), eccentricity (5%), depth perception (1%), and other/miscellaneous (1%). More than one visual aspect may be critical for an activity: participants reported that contrast plays a role in 68% of visual activities, followed by luminance (27%), environmental lighting (14%), and size (14%). CONCLUSIONS: Visual aspects, primarily contrast, were found to be critical factors enabling ULV individuals to perform visual activities. TRANSLATIONAL RELEVANCE: This inventory, part of the Prosthetic Low Vision Rehabilitation (PLoVR) curriculum development study, provides a unique perspective into the visual world of the nearly blind, and can be used in the development of a Visual Functioning Questionnaire (VFQ) and visual performance measures suited for ULV populations.

Ashtanga-Based Yoga Therapy Increases the Sensory Contribution to Postural Stability in Visually-Impaired Persons at Risk for Falls as Measured by the Wii Balance Board: A Pilot Randomized Controlled Trial.

OBJECTIVE: Persons with visual impairment (VI) are at greater risk for falls due to irreparable damage to visual sensory input contributing to balance. Targeted training may significantly improve postural stability by strengthening the remaining sensory systems. Here, we evaluate the Ashtanga-based Yoga Therapy (AYT) program as a multi-sensory behavioral intervention to develop postural stability in VI. DESIGN: A randomized, waitlist-controlled, single-blind clinical trial. METHODS: The trial was conducted between October 2012 and December 2013. Twenty-one legally blind participants were randomized to an 8-week AYT program (n = 11, mean (SD) age = 55(17)) or waitlist control (n=10, mean (SD) age = 55(10)). AYT subjects convened for one group session at a local yoga studio with an instructor and two individual home-based practice sessions per week for a total of 8 weeks. Subjects completed outcome measures at baseline and post-8 weeks of AYT. The primary outcome, absolute Center of Pressure (COP), was derived from the Wii Balance Board (WBB), a standalone posturography device, in 4 sensory conditions: firm surface, eyes open (EO); firm surface, eyes closed (EC); foam surface, EO; and foam surface, EC. Stabilization Indices (SI) were computed from COP measures to determine the relative visual (SIfirm, SIfoam), somatosensory (SIEO, SIEC) and vestibular (SIV, i.e., FoamEC vs. FirmEO) contributions to balance. This study was not powered to detect between group differences, so significance of pre-post changes was assessed by paired samples t-tests within each group. RESULTS: Groups were equivalent at baseline (all p > 0.05). In the AYT group, absolute COP significantly increased in the FoamEO (t(8) = -3.66, p = 0.01) and FoamEC (t(8) = -3.90, p = 0.01) conditions. Relative somatosensory SIEO (t(8) = -2.42, p = 0.04) and SIEC (t(8) = -3.96, p = 0.01), and vestibular SIV (t(8) = -2.47, p = 0.04) contributions to balance increased significantly. As expected, no significant changes from EO to EC conditions were found indicating an absence of visual dependency in VI. No significant pre-post changes were observed in the control group (all p > 0.05). CONCLUSIONS: These preliminary results establish the potential for AYT training to develop the remaining somatosensory and vestibular responses used to optimize postural stability in a VI population. TRIAL REGISTRATION: www.ClinicalTrials.gov NCT01366677.

Yoga as a Therapeutic Intervention: A Bibliometric Analysis of Published Research Studies from 1967 to 2013.

OBJECTIVE: A comprehensive bibliometric analysis was conducted on publications for yoga therapy research in clinical populations. METHODS: Major electronic databases were searched for articles in all languages published between 1967 and 2013. Databases included PubMed, PsychInfo, MEDLINE, IndMed, Indian Citation Index, Index Medicus for South-East Asia Region, Web of Knowledge, Embase, EBSCO, and Google Scholar. Nonindexed journals were searched manually. Key search words included yoga, yoga therapy, pranayama, asana. All studies met the definition of a clinical trial. All styles of yoga were included. The authors extracted the data. RESULTS: A total of 486 articles met the inclusion criteria and were published in 217 different peer-reviewed journals from 29 different countries on 28,080 study participants. The primary result observed is the three-fold increase in number of publications seen in the last 10 years, inclusive of all study designs. Overall, 45% of the studies published were randomized controlled trials, 18% were controlled studies, and 37% were uncontrolled studies. Most publications originated from India (n=258), followed by the United States (n=122) and Canada (n=13). The top three disorders addressed by yoga interventions were mental health, cardiovascular disease, and respiratory disease. CONCLUSION: A surge in publications on yoga to mitigate disease-related symptoms in clinical populations has occurred despite challenges facing the field of yoga research, which include standardization and limitations in funding, time, and resources. The population at large has observed a parallel surge in the use of yoga outside of clinical practice. The use of yoga as a complementary therapy in clinical practice may lead to health benefits beyond traditional treatment alone; however, to effect changes in health care policy, more high-quality, evidence-based research is needed.

Intra-session test-retest reliability of magnitude and structure of center of pressure from the Nintendo Wii Balance Board™ for a visually impaired and normally sighted population.

Individuals with visual impairment (VI) have irreparable damage to one of the input streams contributing to postural stability. Here, we evaluated the intra-session test-retest reliability of the Wii Balance Board (WBB) for measuring Center of Pressure (COP) magnitude and structure, i.e. approximate entropy (ApEn) in fourteen legally blind participants and 21 participants with corrected-to-normal vision. Participants completed a validated balance protocol which included four sensory conditions: double-leg standing on a firm surface with eyes open (EO-firm); a firm surface with eyes closed (EC-firm); a foam surface with EO (EO-foam); and a foam surface with EC (EC-foam). Participants performed the full balance protocol twice during the session, separated by a period of 15min, to determine the intraclass correlation coefficient (ICC). Absolute reliability was determined by the standard error of measurement (SEM). The minimal difference (MD) was estimated to determine clinical significance for future studies. COP measures were derived from data sent by the WBB to a laptop via Bluetooth. COP scores increased with the difficulty of sensory condition indicating WBB sensitivity (all p<0.01). ICCs in the VI group ranged from 0.73 to 0.95, indicating high to very high correlations, and the normal group showed moderate to very high ICCs (0.62-0.94). The SEM was comparable between groups regardless of between-subject variability. The reliability of the WBB makes it practical to screen for balance impairment among VI persons.

A systematic review of yoga for balance in a healthy population.

OBJECTIVE: A systematic review was done of the evidence on yoga for improving balance. DESIGN: Relevant articles and reviews were identified in major databases (PubMed, MEDLINE(®), IndMed, Web of Knowledge, EMBASE, EBSCO, Science Direct, and Google Scholar), and their reference lists searched. Key search words were yoga, balance, proprioception, falling, fear of falling, and falls. Included studies were peer-reviewed articles published in English before June 2012, using healthy populations. All yoga styles and study designs were included. Two (2) raters individually rated study quality using the Downs & Black (DB) checklist. Final scores were achieved by consensus. Achievable scores ranged from 0 to 27. Effect size (ES) was calculated where possible. RESULTS: Fifteen (15) of 152 studies (age range 10-93, n=688) met the inclusion criteria: 5 randomized controlled trials (RCTs), 4 quasi-experimental, 2 cross-sectional, and 4 single-group designs. DB scores ranged from 10 to 24 (RCTs), 14-19 (quasi-experimental), 6-12 (cross-sectional), and 11-20 (single group). Studies varied by yoga style, frequency of practice, and duration. Eleven (11) studies found positive results (p<0.05) on at least one balance outcome. ES ranged from -0.765 to 2.71 (for 8 studies) and was not associated with DB score. CONCLUSIONS: Yoga may have a beneficial effect on balance, but variable study design and poor reporting quality obscure the results. Balance as an outcome is underutilized, and more probing measures are needed.

Evaluation of the benefits of a kripalu yoga program for police academy trainees: a pilot study.

BACKGROUND: Law enforcement ranks as one of the most stressful occupations in the world. Yoga is a mind-body practice composed of postures, breathing, and meditation techniques, and is known for its beneficial effects on stress and mood disturbance. OBJECTIVES: This pilot study evaluated the effects of Kripalu yoga on perceived stress, mood, and mindfulness during police academy training. METHOD: Forty-two recruits participated in a 6-class yoga intervention. Participants completed the Profile of Mood States-Short Form, Perceived Stress Scale, and the Five Facet Mindfulness Questionnaire prior to and immediately following completion of the yoga program, as well as an exit survey. RESULTS: Paired samples t-tests revealed significant postintervention changes in perceived stress and mood, reductions in tension and fatigue, and a trend toward reduced anger. Changes in mindfulness were not detected. The exit survey indicated perceived benefits of yoga for some participants. CONCLUSIONS: This preliminary study suggests that yoga may be beneficial for reducing stress, tension, and fatigue among police academy trainees. Future longitudinal randomized controlled trials are needed to evaluate its full potential as a permanent component of police academy training.

Specificity of perceptual learning increases with increased training.

Perceptual learning often shows substantial and long-lasting changes in the ability to classify relevant perceptual stimuli due to practice. Specificity to trained stimuli and tasks is a key characteristic of visual perceptual learning, but little is known about whether specificity depends upon the extent of initial training. Using an orientation discrimination task, we demonstrate that specificity follows after extensive training, while the earliest stages of perceptual learning exhibit substantial transfer to a new location and an opposite orientation. Brief training shows the best performance at the point of transfer. These results for orientation-location transfer have both theoretical and practical implications for understanding perceptual expertise.