Travelling longitudinal waves provide a novel visual motion stimulus that supports the perception of stereoscopic travelling waves from a phased array of sinusoidal oscillations.

PURPOSE. The purposes of this study were to quantify the impact of degraded binocularity in keratoconus and its improvement with rigid contact lenses on a depth-related visuomotor task that emulates complex activities in daily living; and to determine whether visuomotor performance may be predicted from psychophysical estimates of stereo threshold. METHODS. Participants were instructed to pass a metal loop around a wire convoluted in depth. Error rate and speed were measured in 26 controls, 30 cases with keratoconus with best-corrected spectacles, a subset of 17 cases with rigid contact lenses, and 10 uncorrected myopes with acuity and stereo thresholds comparable to the keratoconic cohort. Stereo thresholds were determined using random-dot stimuli. RESULTS. Binocular error rates were lower than monocular error rates for controls, uncorrected myopes, and the better-performing half of cases (p < 0.001, for each), but not for the worst-performing half (p = 0.07). Error rates in cases improved with contact lenses (p < 0.001). Within each cohort, the error rate was poorly correlated with the stereo threshold (r2< 0.12, for each). Monocular speeds were significantly lower than binocular speeds for controls than for cases (p = 0.003) and for uncorrected myopes than cases (p = 0.001). CONCLUSIONS. Degraded binocularity in keratoconus may limit the ability to perform depth-related visuomotor tasks. A portion of this loss may be overcome by using rigid contact lenses. The attributes of visuomotor task performance are, however, not predictable from the psychophysical estimates of stereo thresholds.

Objective assessment of mindfulness requires increased precision in defining associated cognitive processes. Previous work argued that vipaśyanā-like mindfulness can be characterized as a specific attentional stance—how the felt sense of self is located relative to the body. We therefore studied effect of specific shifts in attentional stance on stress reduction, mindfulness, and interoceptive awareness indices in meditation novices and Mindfulness-Based Stress Reduction (MBSR) practitioners. This paper reports on three separate studies using a simple pre-test post-test design with meditation novices and MBSR practitioners, all of whom received brief instruction (≤1 hr) in an attentional stance expected to induce vipaśyanā-like mindfulness. Novices and MBSR practitioners then participated with a 10-min recorded version of the attentional stance exercise (ASE) and were assessed on measures of perceived stress and mindfulness. MBSR practitioners were similarly assessed after a 10-min MBSR practice. One group of novices was also assessed on measures of interoceptive awareness and three positive emotions. In novices, the 10-min ASE resulted in reductions in significant stress indices and increases in mindfulness and interoceptive awareness indices. In MBSR practitioners, the ASE and MBSR practices produced similar results in stress and mindfulness. In MBSR practitioners, attentional stance in the abdomen was associated with a modestly greater, and marginally significant, increase in mindfulness than that in the chest. Brief training and a short practice session entering a diffuse abdominal attentional stance yield stress reduction and increases in mindfulness similar to the impact of an MBSR meditation practice used by trained MBSR practitioners. Attentional stance is associated with specific biologically linked and cognitively relevant somatic markers, making it an effective behavioral instrument for obtaining objective data and mechanism assessment in vipaśyanā-like mindfulness.

Although the underlying principles of the spatiomotor dynamics during human movement execution are now broadly understood to conform to a minimum jerk principle, the question addressed in the present analysis is whether different principles operate during human drawing movements without visual input, deriving from studies of the Likova Cognitive-Kinesthetic Memory-Drawing Training. For two groups of participants, completely blind, and sighted but temporarily blindfolded, this analysis shows that the consensus model of arm-motion kinematics as a simple one-third power relationship of drawing speed to the local curvature of the line being drawn is not a sufficient characterization of their coupling. Instead, the drawing dynamics without visual feedback conform to a hyperbolic power relationship, with a coupling power of approximately 1.0 for regions of the highest curvature, asymptoting to curvature-independence for regions of shallow curvature, for both blind and blindfolded groups. Thus, the asymptotic power was much higher than the one-third power predicted by the minimum jerk principle. In detail, the maximum-velocity asymptote for both groups averaged about 6 cm/s for drawing from memory, increasing to more than twice as fast for mindless scribbling. We conclude that the more elaborate operating principle of a hyperbolic saturation function, with a power asymptote of about 1.0, may be interpreted as an adaptive implementation approximating the Minimum Jerk Principle of the simple one-third power law relating velocity and curvature.NEW & NOTEWORTHY This study reevaluates the one-third power law proposed to govern arm-motion kinematics relating drawing speed to the local curvature of the line being drawn. For complex drawings guided by memory without visual feedback, we find that the relationship is better characterized as a steeper power function that asymptotes to a constant speed for shallow curvatures, empirically approximating the predictions of the minimum jerk principle.

The electroretinogram (ERG) is a mass electrical response from all electrically activated components of the retina, recorded with the goal of identifying the individual contributions of relevant components for the purposes of electrodiagnosis of eye diseases and other systemic medical conditions. The primary hypothesis being tested was that the ERGs across the spectrum in the mesopic range of intensities could be fully accounted with a duplex (two-component) model of linear combinations of rod- and cone-pathway responses. Full-field square-wave ERGs were measured with the RETeval device at 2 Hz for 7 spectral bands: red, yellow, green, cyan, blue, magenta, and white, in increasing steps of 0.5 log units from 3 to 300 phot cd/m2, totaling 35 conditions for each eye of three neurotypical participants. A novel three-stage process termed Native Components Analysis (NCA), designed to overcome the distributive and orthogonality disadvantages of conventional linear component analysis, was implemented to identify the components contributing to the On-response of the overall ERG. The first step was select the ERG waveforms representative of each region of the response matrix. They were thus designated in terms of a) high and low intensities and b) the narrowband red, green and blue spectral regions. These 6 waveforms were taken as the native component candidates for an optimized fit to the full dataset. The second step was to determine the fit of these ERG components so-defined to the overall set of recorded ERG On-responses from each eye - a 140-parameter fit to the 10,500-parameter dataset. This approach was then compared with the standard approach of orthogonal Principal Components Analysis (PCA) to provide comparable compression. Over 6 datasets from the two eyes of three participants, the fit of the first 4 factors of the novel NCA approach accounted for 95.0 % of the overall variance in the data, compared with 97.5 % for the standard PCA approach. Adding components beyond the best 4 provided no significant improvement in the fits. For the individual datasets, the fit of the PCA accounted for 95.4 - 99.1 % of the variance, while the fit of the representative ERGs of the NCA approach accounted for 89.6-98.1 % of the variance across the individual datasets, validating the strategy of using representative ERG responses as the analytic components. The NCA fits strongly disconfirm the duplex rod/cone model that the ERG is a combination of just two temporal components, showing that as many as four separate components are required to account for the variance in the 35 waveforms in the participant group, with consistent structure across the spectral datasets. These results validate the utility of the novel Native Components Analysis approach to functional response analysis of retinal signals.

A key property of our environment is the mirror symmetry of many objects, although symmetry is an abstract global property with no definable shape template, making symmetry identification a challenge for standard template-matching algorithms. We therefore ask whether Deep Neural Networks (DNNs) trained on typical natural environmental images develop a selectivity for symmetry similar to that of the human brain. We tested a DNN trained on such typical natural images with object-free random-dot images of 1, 2, and 4 symmetry axes. Symmetry coding was negligible in the earliest DNN layers. The strongest discriminability occurred in the first fully connected layer, FC6, plausibly analogous to the human lateral occipital complex (LOC), matching many structural properties of human symmetry processing. These results support the homology between the feedforward DNN trained on natural images and the global processing of the extended visual hierarchy as it has evolved in the human brain.

We used the psychophysical summation paradigm to reveal some spatial characteristics of the mechanism responsible for detecting a motion-defined visual target in central vision. There has been much previous work on spatial summation for motion detection and direction discrimination, but none has assessed it in terms of the velocity threshold or used velocity noise to provide a measure of the efficiency of the velocity processing mechanism. Motion-defined targets were centered within square fields of randomly selected gray levels. The motion was produced within the disk-shaped target region by shifting the pixels rightwards for 0.2 s. The uniform target motion was perturbed by Gaussian motion noise in horizontal strips of 16 pixels. Independent variables were field size, the diameter of the disk target, and the variance of an independent perturbation added to the (signed) velocity of each 16-pixel strip. The dependent variable was the threshold velocity for target detection. Velocity thresholds formed swoosh-shaped (descending, then ascending) functions of target diameter. Minimum values were obtained when targets subtended approximately 2 degrees of visual angle. The data were fit with a continuum of models, extending from the theoretically ideal observer through various inefficient and noisy refinements thereof. In particular, we introduce the concept of sparse sampling to account for the relative inefficiency of the velocity thresholds. The best fits were obtained from a model observer whose responses were determined by comparing the velocity profile of each stimulus with a limited set of sparsely sampled “DoG” templates, each of which is the product of a random binary array and the difference between two 2-D Gaussian density functions.

Free-fusion stereograms are routinely used for demonstrating various stereoscopic effects. Yet, untrained observers find it challenging to perform this task. This study showed that only less than 1/3rd of sixty-one pre-presbyopic adults with normal binocular vision could successfully free-fuse random-dot image pairs and identify the stereoscopic shapes embedded in these patterns. Another one-third of participants performed the task with poor success rates, while the remaining could not perform the task. There was a clear dissociation of vergence and accommodative responses in participants who were successful with free-fusion, as recorded using a dynamic infrared eye tracker and photorefractor. Those in the unsuccessful cluster either showed strong vergence and accommodation or weak vergence and strong accommodation during the task. These response patterns, however, were specific to the free-fusion task because all these participants generated good convergence/accommodation to real-world targets and to conflicting vergence and accommodative demands stimulated with prisms or lenses. Task performance of the unsuccessful cluster also improved significantly following pharmacological paralysis of accommodation and reached the performance levels of the successful cluster. A minority of participants also appeared to progressively learn to dissociate one of the two directions of their vergence and accommodation crosslinks with repeated free-fusion trials. These results suggest that successful free-fusion might depend upon how well participants generate a combination of volitional and reflex vergence responses to large differences in disparity with conflicting static accommodative demands. Such responses would require that only one direction of the vergence-accommodation crosslinks be active at any given time. The sequence of near-responses could also be learnt through repeated trials to optimize task performance.

Purpose:Do one-eyed (uniocular) humans use monocular depth cues differently from those with intact binocularity to perform depth-related visuomotor tasks that emulate complex activities of daily living? If so, does performance depend on the participant's age, duration of uniocularity and head movements? Methods:Forty-five uniocular cases (age range 6-37 years; 2.4 months-31.0 years of uniocularity) and 46 age-similar binocular controls performed a task that required them to pass a hoop around an electrified wire convoluted in depth multiple times, while avoiding contact as indicated by auditory feedback. The task was performed with and without head restraint, in random order. The error rate and speed were calculated from the frequency of contact between the hoop and wire and the total task duration (adjusting for error time), respectively, all determined from video recordings of the task. Head movements were analyzed from the videos using face-tracking software. Results:Error rate decreased with age (P < 0.001) until the late teen years while speed revealed no such trend. Across all ages, the error rate increased and speed decreased in the absence of binocularity (P < 0.001). There was no additional error reduction with duration of uniocularity (P = 0.16). Head movements provided no advantage to task performance, despite generating parallax disparities comparable to binocular viewing. Conclusions:Performance in a dynamic, depth-related visuomotor task is reduced in the absence of binocular viewing, independent of age-related performance level. This study finds no evidence for a prolonged experience with monocular depth cues being advantageous for such tasks over transient loss of binocularity.

Purpose Heat adaptation (HA) is a popular strategy to combat the negative effects of thermal stress. The HA literature has expanded since a 2016 meta-analysis, and we provide an updated meta-analysis, incorporating 39 additional studies and advanced analysis. Methods Following Pubmed searches, full-text original articles using human participants were reviewed using the four-stage PRISMA process. Data were extracted by at least two of the authors. Hedges’ g effect sizes, 95% confidence intervals, and prediction intervals were calculated. Correlations were run where appropriate. Results One hundred and thirty-five total articles (96 previous, 39 new) were reviewed. Medium-term (8–14 days), active, constant work HA regimens remain the most common despite a recent focus on isothermal, passive, and short-term (≤ 7 days) alternatives. HA still improves subsequent exercise performance and capacity in the heat ( g = 0.7), reduces resting core temperature ( g = − 0.6) and heart rate ( g = − 0.5), and increases sweat rate ( g = 0.4) but the effect sizes are lower than previously reported. HA has a moderate or larger effect ( g > 0.5) on lowering sweat onset temperature, mean heart rate, sweat sodium and chloride concentrations, resting thermal sensation, and thirst sensation, and increasing resting plasma volume. There is considerable heterogeneity within the data for most variables. Conclusion HA regimens can reduce physiological and perceptual strain and improve subsequent exercise performance and capacity in the heat. Longer regimens may be more effect than shorter ones, but the data are lacking. Passive HA is a practical, effective alternative to active HA.

PURPOSE:The electroretinogram (ERG) is the summed response from all levels of the retinal processing of light, and exhibits several profound nonlinearities in the underlying processing pathways. Accurate computational models of the ERG are important, both for understanding the multifold processes of light transduction to ecologically useful signals by the retina, and for their diagnostic capabilities for the identification and characterization of retinal disease mechanisms. There are, however, very few computational models of the ERG waveform, and none that account for the full extent of its features over time. METHODS:This study takes the neuroanalytic approach to modeling the ERG waveform, defined as a computational model based on the main features of the transmitter kinetics of the retinal neurons. RESULTS:The present neuroanalytic model of the human rod ERG is elaborated from the same general principles as that of Hood and Birch (Vis Neurosci 8(2):107-126, 1992), but incorporates the more recent understanding of the early nonlinear stages of ERG generation by Robson and Frishman (Prog Retinal Eye Res 39:1-22, 2014). As a result, it provides a substantially better match than previous models of rod responses in six different waveform features of the ERG flash intensity series on which the Hood and Birch model was based. CONCLUSION:The neuroanalytic approach extends previous models of the component waves of the ERG, and can be structured to provide an accurate characterization of the full timecourse of the ERG waveform. The approach thus holds promise for advancing the theoretical understanding of the retinal kinetics of the light response.

Attentional stances are particular ways in which the location of the source or seat of attention is situated within bodily experience. The goal of the study is to use this untapped cognitive resource to refine the construct of mindfulness by providing objective measurement and experimental control of these aspects of mindfulness. Location of the seat of attention, also described as self-location or egocenter , has been shown to have measurable impact on cognitive skill, emotional temperament, and self-construal, as well as social and moral attitudes. Our recent study has shown that the seat of attention can be volitionally self-regulated into various internal attentional stances that are stably associated with distinct patterns of cortical activation as measured with EEG. These results suggest that control of attentional stance should provide direct management of specific cognitive and emotional resources. Two specific global cognitive states associated with mindfulness are the positive emotional states of vipaśyanā and śamatha . The current study of the correlations of 11 attentional stances for with positive emotions reveal the association of vipaśyanā with a diffuse attentional stance centered on the abdomen, and śamatha with a focused attentional stance situated along the midline of the body. In addition to advancing denotation and differentiation of these two distinct elements of mindfulness, these results provide the opportunity for more efficient mindfulness training. Such opportunity would benefit anyone needing stress-reducing mindfulness training, and in particular, for underserved individuals in society who are most in need of stress management.

Purpose: The purpose of this study was to evaluate the safety and efficacy of low dose cannabidiol (CBD; Epidiolex) as adjunctive therapy for idiopathic adult-onset blepharospasm (BPS), as well as develop a novel objective assessment methodology to gauge response. Methods: Prospective, randomized, double-masked, placebo-controlled crossover design of 6 months duration of 12 patients with BPS undergoing routine maximal botulinum toxin (BTX) therapy and experiencing breakthrough symptoms. Participants received their standard BTX every 3 months and were randomized to group A = CBD daily in cycle 1, followed by placebo in cycle 2 or group B = placebo followed by CBD. Videos recorded at days 0, 45, and 90 of each cycle were analyzed to quantify eyelid kinematics. The Jankovic Rating Scale (JRS) was used to provide a clinical rating. Results: All 12 patients completed the study without adverse events. CBD decreased median eyelid closure amplitude by 19.1% (−1.66 mm, confidence interval [CI] = −3.19 to −0.14 mm, P = 0.03), decreased median eyelid closure duration by 15.8% (−18.35 ms, CI = −29.37 to −7.32 ms, P = 0.001), and increased the maximum eyelid closure velocity by 34.8% (−13.26 mm/ms, CI = −20.93 to −5.58 mm/ms, P = 0.001). The JRS showed a 0.5 reduction in severity and frequency, which was not statistically significant. Conclusions: Low dose CBD was safely tolerated and improved several BPS kinematic parameters. The clinical scale suggested a direction of effect but may have been underpowered. Further studies are needed to better quantify the clinical relevance. Translational Relevance: This work describes a novel assessment methodology and therapeutic approach to bBPS.

Introduction. The primary rod pathway in human retina has a univariant rhodopsin spectral sensitivity peaking at ~500 nm; slower dynamics than cones with a b-wave time-to-peak of ~80 ms; no Off-bipolar cell contribution to decreases in intensity since the rod pathway lacks Off bipolars; and a response limit at ~10 cd/m2 due to some form of saturation mechanism. Beyond this limit the ERG switches to a cone response with a b-wave peak at ~40 ms. Methods. Full-field spectral ERGs were recorded with a RETeval device for 6 narrowband chromatic stimuli (magenta, red, yellow, green, cyan, blue) plus white, using 250 ms light pulses at 2Hz for 30 sec at 5 intensities from 6 to 600 cd/m2. Results. At the lowest (scotopic) intensity, the responses showed a surprising diversity, violating univariance. They were slow, with no Off-responses, but manifested two time courses. Blue, cyan and magenta responses had narrow b-waves peaking at ~60 ms, while those for green, yellow and white pulses had significantly slower b-waves peaking at ~90 ms. Negligible responses to red pulses confirmed the lack of a significant cone contribution to these dim (photopically-equated) stimuli. Conclusions. Paradoxically, the faster component was consistent with a mechanism maximal at ~500 nm (cyan) - a rod-like spectral sensitivity – despite being much faster than typical rod responses. Conversely, the spectral sensitivity of the slower component was maximal in the green (~540 nm), approximating that of the M-cones, even though they are expected to be inactive at this dim adaptation level. This spectral tuning for the slower component seems to imply cone intrusion at these low intensity levels, despite its slow, rod-like time course, suggesting the existence of an ancillary pathway with a slower response time but enhanced sensitivity, such as a cone-to-rod gap junction network specific to the M-cone pathway.