SciCombinator

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Concept: Strobe light

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Transcranial focused ultrasound (FUS) is capable of modulating the neural activity of specific brain regions, with a potential role as a non-invasive computer-to-brain interface (CBI). In conjunction with the use of brain-to-computer interface (BCI) techniques that translate brain function to generate computer commands, we investigated the feasibility of using the FUS-based CBI to non-invasively establish a functional link between the brains of different species (i.e. human and Sprague-Dawley rat), thus creating a brain-to-brain interface (BBI). The implementation was aimed to non-invasively translate the human volunteer’s intention to stimulate a rat’s brain motor area that is responsible for the tail movement. The volunteer initiated the intention by looking at a strobe light flicker on a computer display, and the degree of synchronization in the electroencephalographic steady-state-visual-evoked-potentials (SSVEP) with respect to the strobe frequency was analyzed using a computer. Increased signal amplitude in the SSVEP, indicating the volunteer’s intention, triggered the delivery of a burst-mode FUS (350 kHz ultrasound frequency, tone burst duration of 0.5 ms, pulse repetition frequency of 1 kHz, given for 300 msec duration) to excite the motor area of an anesthetized rat transcranially. The successful excitation subsequently elicited the tail movement, which was detected by a motion sensor. The interface was achieved at 94.0±3.0% accuracy, with a time delay of 1.59±1.07 sec from the thought-initiation to the creation of the tail movement. Our results demonstrate the feasibility of a computer-mediated BBI that links central neural functions between two biological entities, which may confer unexplored opportunities in the study of neuroscience with potential implications for therapeutic applications.

Concepts: Brain, Neuroscience, Human brain, Frequency, Hertz, Sound, Amplitude, Strobe light

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Chronic mild stress can lead to negative health outcomes. Frequency, duration, and intensity of acute stressors can affect health-related processes. We tested whether the temporal pattern of daily acute stressors (clustered or dispersed across the day) affects depression-related physiology. We used a rodent model to keep stressor frequency, duration, and intensity constant, and experimentally manipulated the temporal pattern of acute stressors delivered during the active phase of the day. Adult male Sprague-Dawley rats were exposed to one of three chronic mild stress groups: Clustered: stressors that occurred within 1 hour of each other (n = 21), Dispersed: stressors that were spread out across the active phase (n = 21), and Control: no stressors presented (n = 21). Acute mild stressors included noise, strobe lights, novel cage, cage tilt, wet bedding, and water immersion. Depression-related outcomes included: sucrose preference, body weight, circulating glucocorticoid (corticosterone) concentration after a novel acute stressor and during basal morning and evening times, and endotoxin-induced circulating interleukin-6 concentrations. Compared to control rats, those in the Clustered group gained less weight, consumed less sucrose, had a blunted acute corticosterone response, and an accentuated acute interleukin-6 response. Rats in the Dispersed group had an attenuated corticosterone decline during the active period and after an acute stressor compared to the Control group. During a chronic mild stress experience, the temporal distribution of daily acute stressors affected health-related physiologic processes. Regular exposure to daily stressors in rapid succession may predict more depression-related symptoms, whereas exposure to stressors dispersed throughout the day may predict diminished glucocorticoid negative feedback.

Concepts: Biology, Physiology, Affect, Control theory, Frequency, Feedback, Strobe light, Stroboscope

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The stroboscopic visibility measure (SVM) is a method used to quantify the stroboscopic effect visibility in general illumination application. SVM has been defined previously based on a limited number of frequencies and participants. To validate and extend SVM, five perception experiments are presented, measuring the visibility threshold of light waveforms modulated at several frequencies, conducted in two different labs. A power function is fitted through the aggregated results to develop a stroboscopic effect contrast threshold function for a “standard observer,” which can be used to normalize SVM. An additional experiment shows the dependency on illumination level, extending the validity of SVM to other applications.

Concepts: Psychometrics, Test method, Laboratory, Strobe light, Stroboscope

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The development of a red, chlorine-/strontium-free pyrotechnic composition which serves as either a strobe or a flare is reported. The observed strobing behaviour of a red-light emitting composition of Mg/LiNO3/hexamine/binder was investigated. Additives like 5-amino-1H-tetrazole and nitrocellulose were used to increase the strobing frequency and achieve constant burning.

Concepts: Ammonia, Flare, Strobe light, Pyrotechnic composition

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The vestibulo-ocular reflex (VOR) acts to maintain images stable on the retina by rotating the eyes in exactly the opposite direction, but with equal magnitude, to head velocity. When viewing a near target, this reflex has an increased response to compensate for the translation of the eyes relative to the target that acts to reduce retinal image slip. Previous studies have shown that retinal velocity error provides an important visual feedback signal to increase the low-frequency (<1 Hz) VOR response during near viewing. We sought to determine whether initial eye position and retinal image position error could provide enough information to substantially increase the high-frequency VOR gain (eye velocity/head velocity) during near viewing. Ten human subjects were tested using the scleral search coil technique during horizontal head impulses under different lighting conditions (constant dark, strobe light at 0.5, 1, 2, 4, 10, 15 Hz, constant light) while viewing near (9.5 ± 1.3 cm) and far (104 cm) targets. Our results showed that the VOR gain increased during near viewing compared to far viewing, even during constant dark. For the near target, there was an increase in VOR gain with increasing strobe frequency from 1.17 ± 0.17 in constant dark to 1.36 ± 0.27 in constant light, a 21 ± 9 % increase. For the far target, strobe frequency had no effect. Presentation order of strobe frequency (i.e. 0.5-15 vs. 15-0.5 Hz) did not affect the gain, but it did affect the vergence angle (angle between the two eye's lines of sight). The VOR gain and vergence angles were constant during each trial. Our findings show that a retinal position error signal helps increase the vergence angle and could be invoking vestibular adaptation mechanisms to increase the high-frequency VOR response during near viewing. This is in contrast to the low-frequency VOR that depends more on retinal velocity error and predictive adaptation mechanisms.

Concepts: Retina, Eye, Vision, Vestibulo-ocular reflex, Frequency, Feedback, Lighting, Strobe light

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Vision helps humans in controlling bipedal stance, interacting mainly with vestibular and proprioceptive cues. This study investigates how postural compensation of support surface tilt is compromised by selectively reducing visual velocity cues by stroboscopic illumination of a stationary visual scene. Healthy adult subjects were presented with pseudorandom tilt sequences in the sagittal plane (tilt frequency range 0.017-2.2 Hz; velocity amplitude spectrum constant up to a frequency of 0.6 Hz, angular displacement amplitude spectrum increasing with decreasing frequencies). Center of mass (COM) sway responses were recorded for stroboscopic illuminations at 48, 32, 16, 8, and 4 Hz, as well as under continuous illumination and with eyes closed. With strobe duration (5 ms) and mean luminance (1 lx) kept constant, visual acuity and perceived brightness remained constant and the visual scene was perceived as stationary. Yet, tilt-evoked COM excursions increased with decreasing strobe frequency in a graded way, with largest effects occurring at tilt frequencies where large tilt velocities coincided with small displacements. In addition, COM excursions were reduced at the lowest strobe frequency compared to eyes closed, with the largest effect occurring at tilt frequencies where tilt displacements were large. We conclude that two mechanisms exist, a velocity mechanism that deals with tilt compensation and is foremost affected by the stroboscopic illumination and a displacement mechanism. This compares favorably to previous findings that, transferred to a stance control model, suggest a velocity mechanism for tilt compensation and a position mechanism for gravity compensation.

Concepts: Physical quantities, Frequency, Wavelength, Velocity, Sound, Displacement, Strobe light, Stroboscope

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Anticipatory postural adjustments (APAs) play an important role in the performance of many activities requiring the maintenance of vertical posture. However, little is known about how variation in the available visual information affects generation of APAs. The purpose of this study was to investigate the role of different visual cues on APAs. Ten healthy young subjects were exposed to external perturbations induced at the shoulder level in standing while the level of visual information about the forthcoming perturbation was varied. The external perturbations were provided by an aluminum pendulum attached to the ceiling. The visual conditions were (1) dynamic cues (full vision and high-frequency strobe light), (2) static cues (low-frequency strobe light) and (3) no cues (eyes open in dark room). Electrical activity of the trunk and leg muscles and center of pressure displacements were recorded and quantified within the time intervals typical for APAs. The results showed that significantly larger APAs were generated in conditions with dynamic visual cues as compared to the conditions with static cues (p < 0.05). Finally, no APAs were observed in the condition where there was complete absence of any visual cues. Principal component analysis further revealed different muscle coupling patterns in the full vision and high-frequency strobe light conditions. These findings suggest the importance of using appropriate visual cues in the generation of APAs.

Concepts: Electricity, Lightning, Muscle, Visual perception, Principal component analysis, Lighting, Book of Optics, Strobe light

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The present study (a) extended the assessment of an orientation program involving auditory cues (i.e., verbal messages automatically presented from the destinations) with five patients with Alzheimer’s disease, (b) compared the effects of this program with those of a program with light cues (i.e., a program in which strobe lights were used instead of the verbal messages) with the same five patients, and © conducted a social validation assessment of the two programs with 70 university psychology students employed as social raters. Results confirmed the effectiveness of the program with auditory cues and showed an equally strong impact of the program with light cues with all five patients. The psychology students involved in the social validation assessment provided significantly higher scores for the program involving light cues on a six-item questionnaire. Those scores suggested that this program was perceived as a practically and socially preferable choice. The implications of the findings for daily contexts dealing with patients with Alzheimer’s disease are discussed.

Concepts: Alzheimer's disease, Present, Clinical trial, Sociology, Unsolved problems in neuroscience, Lighting, Program, Strobe light