Just noticeable differences for elbow joint torque feedback.

Joint torque feedback is a new and promising means of kinesthetic feedback imposed by a wearable device. The torque feedback provides the wearer temporal and spatial information during a motion task. Nevertheless, little research has been conducted on quantifying the psychophysical parameters of how well humans can perceive external torques under various joint conditions. This study aims to investigate the just noticeable difference (JND) perceptual ability of the elbow joint to joint torques. The paper focuses on the ability of two primary joint proprioceptors, the Golgi-tendon organ (GTO) and muscle spindle (MS), to detect elbow torques, since touch and pressure sensors were masked. We studied 14 subjects while the arm was isometrically contracted (static condition) and was moving at a constant speed (dynamic condition). In total there were 10 joint conditions investigated, which varied the direction of the arm's movement and the preload direction as well as torque direction. The JND torques under static conditions ranged from 0.097 Nm with no preload to 0.197 Nm with a preload of 1.28 Nm. The maximum dynamic JND torques were 0.799 Nm and 0.428 Nm, when the arm was flexing and extending at 213 degrees per second, respectively.

Unsupervised learning predicts human perception and misperception of gloss.

Reflectance, lighting and geometry combine in complex ways to create images. How do we disentangle these to perceive individual properties, such as surface glossiness? We suggest that brains disentangle properties by learning to model statistical structure in proximal images. To test this hypothesis, we trained unsupervised generative neural networks on renderings of glossy surfaces and compared their representations with human gloss judgements. The networks spontaneously cluster images according to distal properties such as reflectance and illumination, despite receiving no explicit information about these properties. Intriguingly, the resulting representations also predict the specific patterns of 'successes' and 'errors' in human perception. Linearly decoding specular reflectance from the model's internal code predicts human gloss perception better than ground truth, supervised networks or control models, and it predicts, on an image-by-image basis, illusions of gloss perception caused by interactions between material, shape and lighting. Unsupervised learning may underlie many perceptual dimensions in vision and beyond.

A flexible geometry for panoramic visual and optogenetic stimulation during behavior and physiology.

BACKGROUND: To study visual processing, it is necessary to precisely control visual stimuli while recording neural and behavioral responses. It can be important to present stimuli over a broad area of the visual field, which can be technically difficult. NEW METHOD: We present a simple geometry that can be used to display panoramic stimuli. A single digital light projector generates images that are reflected by mirrors onto flat screens that surround an animal. It can be used for behavioral and neurophysiological measurements, so virtually identical stimuli can be presented. Moreover, this geometry permits light from the projector to be used to activate optogenetic tools. RESULTS: Using this geometry, we presented panoramic visual stimulation to Drosophila in three paradigms. We presented drifting contrast gratings while recording walking and turning speed. We used the same projector to activate optogenetic channels during visual stimulation. Finally, we used two-photon microscopy to record responses in direction-selective cells to drifting gratings. COMPARISON WITH EXISTING METHOD(S): Existing methods have typically required custom hardware or curved screens, while this method requires only flat back projection screens and a digital light projector. The projector generates images in real time and does not require pre-generated images. Finally, while many setups are large, this geometry occupies a 30 × 20 cm footprint with a 25 cm height. CONCLUSIONS: This flexible geometry enables measurements of behavioral and neural responses to panoramic stimuli. This allows moderate throughput behavioral experiments with simultaneous optogenetic manipulation, with easy comparisons between behavior and neural activity using virtually identical stimuli.

NIMH MonkeyLogic: Behavioral control and data acquisition in MATLAB.

BACKGROUND: Computerized control of behavioral paradigms is an essential element of neurobehavioral studies, especially physiological recording studies that require sub-millisecond precision. Few software solutions provide a simple, flexible environment to create and run these applications. MonkeyLogic, a MATLAB-based package, was developed to meet these needs, but faces a performance crisis and obsolescence due to changes in MATLAB itself. NEW METHOD: Here we report a complete redesign and rewrite of MonkeyLogic, now NIMH MonkeyLogic, that natively supports the latest 64-bit MATLAB on the Windows platform. Major layers of the underlying real-time hardware control were removed and replaced by custom toolboxes: NIMH DAQ Toolbox and MonkeyLogic Graphics Library. The redesign resolves undesirable delays in data transfers and limitations in graphics capabilities. RESULTS: NIMH MonkeyLogic is essentially a new product. It provides a powerful new scripting framework, has dramatic speed enhancements and provides major new graphics abilities. COMPARISON WITH EXISTING METHOD: NIMH MonkeyLogic is fully backward compatible with earlier task scripts, but with better temporal precision. It provides more input device options, superior graphics and a new real-time closed-loop programming model. Because NIMH MonkeyLogic requires no commercial toolbox and has a reduced hardware requirement, implementation costs are substantially reduced. CONCLUSION: NIMH MonkeyLogic is a versatile, powerful, up-to-date tool for controlling a wide range of experiments. It is freely available from https://monkeylogic.nimh.nih.gov/.

Shady: A software engine for real-time visual stimulus manipulation.

BACKGROUND: Precise definition, rendering and manipulation of visual stimuli are essential in neuroscience. Rather than implementing these tasks from scratch, scientists benefit greatly from using reusable software routines from freely available toolboxes. Existing toolboxes work well when the operating system and hardware are painstakingly optimized, but may be less suited to applications that require multi-tasking (for example, closed-loop systems that involve real-time acquisition and processing of signals). NEW METHOD: We introduce a new cross-platform visual stimulus toolbox called Shady (https://pypi.org/project/Shady)-so called because of its heavy reliance on a shader program to perform parallel pixel processing on a computer's graphics processor. It was designed with an emphasis on performance robustness in multi-tasking applications under unforgiving conditions. For optimal timing performance, the CPU drawing management commands are carried out by a compiled binary engine. For configuring stimuli and controlling their changes over time, Shady provides a programmer's interface in Python, a powerful, accessible and widely-used high-level programming language. RESULTS: Our timing benchmark results illustrate that Shady's hybrid compiled/interpreted architecture requires less time to complete drawing operations, exhibits smaller variability in frame-to-frame timing, and hence drops fewer frames, than pure-Python solutions under matched conditions of resource contention. This performance gain comes despite an expansion of functionality (e.g. "noisy-bit" dithering as standard on all pixels and all frames, to enhance effective dynamic range) relative to previous offerings. CONCLUSIONS: Shady simultaneously advances the functionality and performance available to scientists for rendering visual stimuli and manipulating them in real time.

Influence of the wearable posture correction sensor on head and neck posture: Sitting and standing workstations.

BACKGROUND: Flexed head and neck postures are associated with the development of neck pain in the office environment. There is little evidence regarding whether a wearable posture sensor would improve the head and neck postures of office workers. OBJECTIVE: The aim of this study was to evaluate the effect of the wearable posture sensor on the posture and physical demands on the head and neck during office work. METHODS: Nineteen participants performed a typing task with and without the wearable sensor in the sitting and standing positions. They were allowed to adjust their workstation during the experiment based on a psychophysical method. The flexion angles of the head and neck, the gravitational moment on the neck, and the positions of the workstation components were measured. RESULTS: On average, participants with the wearable sensor had 8% lower neck flexion angles and 14% lower gravitational moments on the neck than those of participants without the wearable sensor. The effect of the wearable sensor on reducing postural stress of the neck was more significant when using the standing workstation compared to the sitting workstation. CONCLUSIONS: The wearable posture sensor could be an effective tool to alleviate the postural stress of the neck in the office setting.

Vibration testing: Optimizing methods to improve reliability.

INTRODUCTION: In this study we assessed the test-retest reliability of a Rydel-Seiffer tuning fork and an electronic vibrameter with hand-held and fixed probes. METHODS: Fifty healthy volunteers were assessed twice in the upper and lower limb 15 minutes apart. Reliability was assessed by intraclass correlation coefficient (ICC) and standard error of measurement (SEM). The effect of stimulus parameters on vibration disappearance threshold (VDT) was assessed by analysis of variance. RESULTS: All 3 tools showed good reliability (ICCs = 0.65-0.95). Vibrameter recordings with the fixed probe showed high variability. The vibrameter was more sensitive in detecting body-site and age differences in vibration thresholds than the tuning fork. Significantly higher VDT was observed when higher starting amplitudes and slower rates of change were used. DISCUSSION: The hand-held vibrameter is a superior tool to monitor vibration sense. The stimulus amplitude and rate of change are important to control as they alter VDT. Muscle Nerve 59:229-235, 2019.

Numerosity representation is encoded in human subcortex.

Certain numerical abilities appear to be relatively ubiquitous in the animal kingdom, including the ability to recognize and differentiate relative quantities. This skill is present in human adults and children, as well as in nonhuman primates and, perhaps surprisingly, is also demonstrated by lower species such as mosquitofish and spiders, despite the absence of cortical computation available to primates. This ubiquity of numerical competence suggests that representations that connect to numerical tasks are likely subserved by evolutionarily conserved regions of the nervous system. Here, we test the hypothesis that the evaluation of relative numerical quantities is subserved by lower-order brain structures in humans. Using a monocular/dichoptic paradigm, across four experiments, we show that the discrimination of displays, consisting of both large (5-80) and small (1-4) numbers of dots, is facilitated in the monocular, subcortical portions of the visual system. This is only the case, however, when observers evaluate larger ratios of 3:1 or 4:1, but not smaller ratios, closer to 1:1. This profile of competence matches closely the skill with which newborn infants and other species can discriminate numerical quantity. These findings suggest conservation of ontogenetically and phylogenetically lower-order systems in adults' numerical abilities. The involvement of subcortical structures in representing numerical quantities provokes a reconsideration of current theories of the neural basis of numerical cognition, inasmuch as it bolsters the cross-species continuity of the biological system for numerical abilities.

Do dichromats see colours in this way? Assesing simulation tools without colorimetric measurements / ¿Son estos los colores que ven los dicrómatas? Evaluando herramientas de simulación sin mediciones colorimétricas

BACKGROUND: Simulcheck evaluates Colour Simulation Tools (CSTs, they transform colours to mimic those seen by colour vision deficients). Two CSTs (Variantor and Coblis) were used to know if the standard Simulcheck version (direct measurement based, DMB) can be substituted by another (RGB values based) not requiring sophisticated measurement instruments. METHOD: Ten normal trichromats performed the two psychophysical tasks included in the Simulcheck method. The Pseudoachromatic Stimuli Identification task provided the huv (hue angle) values of the pseudoachromatic stimuli: colours seen as red or green by normal trichromats but as grey by colour deficient people. The Minimum Achromatic Contrast task was used to compute the LR (relative luminance) values of the pseudoachromatic stimuli. RESULTS AND CONCLUSIONS: Simulcheck DMB version showed that Variantor was accurate to simulate protanopia but neither Variantor nor Coblis were accurate to simulate deuteranopia. Simulcheck RGB version provided accurate huv values, so this variable can be adequately estimated when lacking a colorimeter -an expensive and unusual apparatus-. Contrary, the inaccuracy of the LR estimations provided by Simulcheck RGB version makes it advisable to compute this variable from the measurements performed with a photometer, a cheap and easy to find apparatus

ANTECEDENTES: Simulcheck evalúa Herramientas de Simulación del Color (HSCs, transforman los colores para imitar lo que ven las personas con deficiencias en la visión cromática). Se utilizaron dos HSCs (Variantor y Coblis) para evaluar si la versión estándar de Simulcheck (basada en mediciones directas, BMD) puede sustituirse por otra que no requiere instrumentos de medición sofisticados (basada en valores RGB). MÉTODO: diez tricrómatas realizaron las tareas psicofísicas incluidas en el método Simulcheck. La de Identificación de Estímulos Pseudoacromáticos proporcionó el ángulo cromático (huv) de los estímulos que los observadores comunes ven rojos o verdes, pero grises las personas con deficiencias en la visión cromática. La de Mínimo Contraste Acromático proporcionó los valores LR (luminancia relativa) de los estímulos pseudoacromáticos. RESULTADOS Y CONCLUSIONES: la versión BMD mostró que Variantor simuló adecuadamente la protanopia, pero que ni Variantor ni Coblis fueron adecuados para la deuteranopia. La Versión RGB del método Simulcheck proporcionó valores huv adecuados, consecuentemente se concluyó que esta variable puede estimarse adecuadamente sin un colorímetro -aparato caro e inusual-. Por el contrario, la inadecuación de las estimaciones de LR proporcionadas por la versión RGB recomienda computar esta variable usando mediciones realizadas con un fotómetro, un aparato barato y fácil de encontrar

Optical Measurement of Straylight in Eyes With Cataract.

PURPOSE: To measure straylight in a cohort of patients with cataract using a novel optical instrument and to correlate optical straylight values with clinical grade of cataracts and psychophysical straylight values. METHODS: Measurements were performed on 53 eyes of 44 patients with cataract admitted to the ophthalmology service of the university hospital in Murcia, Spain, and 9 young volunteers with no known ophthalmic pathology. Lens opacities were classified according to the Lens Opacities Classification System Ill (LOCS III) under slit-lamp examination. Intraocular straylight was additionally assessed psychophysically using the C-Quant straylight meter (Oculus Optikgeräte GmbH, Wetzlar, Germany). RESULTS: Optical measurements of the logarithm of the straylight parameter ranged from 1.01 to 2.01 (mean: 1.43 ± 0.244) in patients with cataract and 0.80 to 1.08 (mean: 0.92 ± 0.104) in healthy young volunteers. Straylight differed by a statistically significant amount among different LOCS III groups (P < .05). Moreover, the optically measured straylight parameter was positively correlated to the psychophysically estimated value (r = 0.803, P < .05). CONCLUSIONS: A new compact optical instrument suitable for clinical measurements of straylight in the human eye has been developed. Optically measured straylight values were highly correlated to those that were obtained psychophysically. Optical measurement of straylight can be used for the objective classification of cataract opacities based on their optical impact. [J Refract Surg. 2016;32(12):846-850.].

The Simplest Chronoscope V: A Theory of Dual Primary and Secondary Reaction Time Systems.

Extending work by Montare, visual simple reaction time, choice reaction time, discriminative reaction time, and overall reaction time scores obtained from college students by the simplest chronoscope (a falling meterstick) method were significantly faster as well as significantly less variable than scores of the same individuals from electromechanical reaction timers (machine method). Results supported the existence of dual reaction time systems: an ancient primary reaction time system theoretically activating the V5 parietal area of the dorsal visual stream that evolved to process significantly faster sensory-motor reactions to sudden stimulations arising from environmental objects in motion, and a secondary reaction time system theoretically activating the V4 temporal area of the ventral visual stream that subsequently evolved to process significantly slower sensory-perceptual-motor reactions to sudden stimulations arising from motionless colored objects.

Perceptual shrinkage of a one-way motion path with high-speed motion.

Back-and-forth motion induces perceptual shrinkage of the motion path, but such shrinkage is hardly perceived for one-way motion. If the shrinkage is caused by temporal averaging of stimulus position around the endpoints, it should also be induced for one-way motion at higher motion speeds. In psychophysical experiments with a high-speed projector, we tested this conjecture for a one-way motion stimulus at various speeds (4-100 deg/s) along a straight path. Results showed that perceptual shrinkage of the motion path was robustly observed in higher-speed motion (faster than 66.7 deg/s). In addition, the amount of the forwards shift at the onset position was larger than that of the backwards shift at the offset position. These results demonstrate that high-speed motion can induce shrinkage, even for a one-way motion path. This can be explained by the view that perceptual position is represented by the integration of the temporal average of instantaneous position and the motion representation.

LCD Monitors as an Alternative for Precision Demanding Visual Psychophysical Experiments.

Precise timing and presentation of stimuli is critical in vision research, still, the limiting factor in successful recognition is often the monitor itself that is used to present the stimuli. The most widespread method is the use of monitors controlled by personal computers. Traditionally, most experiments used cathode-ray tubes but they are more and more difficult to access, and instead, liquid-crystal displays are getting more and more popular. The two types have fundamentally different working principles and limitations in displaying the stimulus.In our experiments, the temporal precision of the stimulus presentation was in focus. We investigated whether liquid-crystal displays, which are not considered to be fit to display fast successive stimuli, can represent an alternative choice for cathode-ray tubes. We used the double flash and the flicker illusion to compare the technical capabilities of the two monitor types. These illusions not only do require a precise timing but also a very short exposure to the stimuli. At the same time, the interstimulus interval is also of extreme importance. In addition, these illusions require peripheral stimulation of the retina, which is more sensitive to the temporal aspects of the visual stimulus. On the basis of previous studies and our own psychophysical results, we suggest that liquid-crystal displays might be a good alternative for precise, frame-to-frame stimulus presentation even if parts of the stimuli are projected on the peripheral retina.

Engañando a las células on-off: evolución histórica de nuestra compresión del modo en que los animales se camuflan / Deceiving the on-off cells: Historic evolution of our comprehension of the way animals camouflage themselves

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Psychophysical evaluation of haptic perception under augmentation by a handheld device.

OBJECTIVE: This study investigated the effectiveness of force augmentation in haptic perception tasks. BACKGROUND: Considerable engineering effort has been devoted to developing force augmented reality (AR) systems to assist users in delicate procedures like microsurgery. In contrast, far less has been done to characterize the behavioral outcomes of these systems, and no research has systematically examined the impact of sensory and perceptual processes on force augmentation effectiveness. METHOD: Using a handheld force magnifier as an exemplar haptic AR, we conducted three experiments to characterize its utility in the perception of force and stiffness. Experiments 1 and 2 measured, respectively, the user's ability to detect and differentiate weak force (<0.5 N) with or without the assistance of the device and compared it to direct perception. Experiment 3 examined the perception of stiffness through the force augmentation. RESULTS: The user's ability to detect and differentiate small forces was significantly improved by augmentation at both threshold and suprathreshold levels. The augmentation also enhanced stiffness perception. However, although perception of augmented forces matches that of the physical equivalent for weak forces, it falls off with increasing intensity. CONCLUSION: The loss in the effectiveness reflects the nature of sensory and perceptual processing. Such perceptual limitations should be taken into consideration in the design and development of haptic AR systems to maximize utility. APPLICATION: The findings provide useful information for building effective haptic AR systems, particularly for use in microsurgery.

A validated set of tool pictures with matched objects and non-objects for laterality research.

Neuropsychological and neuroimaging research has established that knowledge related to tool use and tool recognition is lateralized to the left cerebral hemisphere. Recently, behavioural studies with the visual half-field technique have confirmed the lateralization. A limitation of this research was that different sets of stimuli had to be used for the comparison of tools to other objects and objects to non-objects. Therefore, we developed a new set of stimuli containing matched triplets of tools, other objects and non-objects. With the new stimulus set, we successfully replicated the findings of no visual field advantage for objects in an object recognition task combined with a significant right visual field advantage for tools in a tool recognition task. The set of stimuli is available as supplemental data to this article.

Macular pigment optical density measured by heterochromatic modulation photometry.

PURPOSE: To psychophysically determine macular pigment optical density (MPOD) employing the heterochromatic modulation photometry (HMP) paradigm by estimating 460 nm absorption at central and peripheral retinal locations. METHODS: For the HMP measurements, two lights (B: 460 nm and R: 660 nm) were presented in a test field and were modulated in counterphase at medium or high frequencies. The contrasts of the two lights were varied in tandem to determine flicker detection thresholds. Detection thresholds were measured for different R:B modulation ratios. The modulation ratio with minimal sensitivity (maximal threshold) is the point of equiluminance. Measurements were performed in 25 normal subjects (11 male, 14 female; age: 30 ± 11 years, mean ± sd) using an eight channel LED stimulator with Maxwellian view optics. The results were compared with those from two published techniques - one based on heterochromatic flicker photometry (Macular Densitometer) and the other on fundus reflectometry (MPR). RESULTS: We were able to estimate MPOD with HMP using a modified theoretical model that was fitted to the HMP data. The resultant MPODHMP values correlated significantly with the MPODMPR values and with the MPODHFP values obtained at 0.25° and 0.5° retinal eccentricity. CONCLUSIONS: HMP is a flicker-based method with measurements taken at a constant mean chromaticity and luminance. The data can be well fit by a model that allows all data points to contribute to the photometric equality estimate. Therefore, we think that HMP may be a useful method for MPOD measurements, in basic and clinical vision experiments.

Rapid material appearance acquisition using consumer hardware.

A photo-realistic representation of material appearance can be achieved by means of bidirectional texture function (BTF) capturing a material's appearance for varying illumination, viewing directions, and spatial pixel coordinates. BTF captures many non-local effects in material structure such as inter-reflections, occlusions, shadowing, or scattering. The acquisition of BTF data is usually time and resource-intensive due to the high dimensionality of BTF data. This results in expensive, complex measurement setups and/or excessively long measurement times. We propose an approximate BTF acquisition setup based on a simple, affordable mechanical gantry containing a consumer camera and two LED lights. It captures a very limited subset of material surface images by shooting several video sequences. A psychophysical study comparing captured and reconstructed data with the reference BTFs of seven tested materials revealed that results of our method show a promising visual quality. Speed of the setup has been demonstrated on measurement of human skin and measurement and modeling of a glue dessication time-varying process. As it allows for fast, inexpensive, acquisition of approximate BTFs, this method can be beneficial to visualization applications demanding less accuracy, where BTF utilization has previously been limited.

Clinical feasibility of fast psychophysical tuning curves evaluated using normally hearing adults: success rate, range of tip shift, repeatability, and comparison of methods used for estimation of frequency at the tip.

OBJECTIVE: Psychophysical tuning curves (PTCs) have been used predominantly in laboratory settings to assess frequency selectivity in the auditory system. Recently, a fast-PTC procedure has been developed for diagnosis of cochlear dead regions. In this study the clinical feasibility of using fast PTCs in adults was investigated. Success rate (the number of successes per number of attempts) and repeatability were assessed. The range of the tip frequency (ftip) shift was established and different methods of ftip estimation compared. DESIGN: Fast PTCs were measured for signal frequencies (fs) of 500, 1000, 2000, 3000, and 4000 Hz on two occasions using an upward-sweeping masker. Five methods were used to estimate ftip for each PTC. STUDY SAMPLE: Thirty-two adults with normal hearing were tested. RESULTS: All participants were able to successfully complete the task, the majority of them with minimal training. The moving average, quadratic function, and double lowpass filtering methods had the highest success rate in ftip estimation. The quadratic function method had the smallest 95% range of - 3.4% fs to 10.2% fs and the best test-retest reliability of 5.1% fs. CONCLUSIONS: Fast PTCs show potential for clinical use due to a high success rate with minimal training required. We suggest the quadratic function method for routine clinical use as it had the smallest 95% range, a high success rate in ftip estimation and the best test-retest reliability. For fast PTCs measured for signal frequencies from 500 to 4000 Hz using an upward-sweeping masker, we suggest the normative range of ftip to be - 3% fs to 10% fs with a test-retest reliability of 5% fs.

Schumann's wheel tachistoscope: its reconstruction and its operation.

In the fall and winter of 1910, Max Wertheimer (1880-1943) performed his famous experiments on perceived motion, published in 1912. Besides slider experiments he mainly used a wheel tachistoscope developed by Friedrich Schumann (1863-1940) at the end of the 19th century. The Adolf-Wuerth-Center for the History of Psychology has several wheel tachistoscopes in its collection of instruments. Their provenance can be traced back to the Institute of Psychology of the University of Frankfurt and the University of Zurich. It is very plausible that Wertheimer, who performed his experiments at the Frankfurt Institute, used one of them. But the wheel tachistoscope alone is not sufficient to reconstruct Wertheimer's original experiments. As always, the devil is in the details. Wertheimer's descriptions of the necessary accessories, a prism, a viewing device, and an electric motor to move the wheel, are rather sparse. This article describes the results of a search for traces in the literature, in archives, and in literary depositories to shed some light on Wertheimer's experimental equipment. As a result, it was possible to reconstruct the entire apparatus and to obtain the same optical impressions with the reconstructed devices as Wertheimer's observers reported. In addition, one of his results was replicated with new participants exactly 100 years after its first publication.