The relationship between visually evoked effects and concussion in youth

ABSTRACTIncreased sensitivity to light is common following concussion. Viewing a flickering light can also produce uncomfortable somatic sensations like nausea or headache. Here we examined effects evoked by viewing a patterned, flickering screen in a cohort of 81 uninjured youth athletes and 84 youth with concussion. We used exploratory factor analysis and identified two primary dimensions of variation: the presence or absence of visually evoked effects, and variation in the tendency to manifest effects that localized to the eyes (e.g., eye watering), versus more generalized neurologic symptoms (e.g., headache). Based on these two primary dimensions, we grouped participants into three categories of evoked symptomatology: no effects, eye-predominant effects, and brain-predominant effects. A similar proportion of participants reported eye-predominant effects in the uninjured (33.3%) and concussion (32.1%) groups. By contrast, participants who experienced brain-predominant effects were almost entirely from the concussion group (1.2% of uninjured, 35.7% of concussed). The presence of brain-predominant effects was associated with a higher concussion symptom burden and reduced performance on visio-vestibular tasks. Our findings indicate that the experience of negative constitutional, somatic sensations in response to a dynamic visual stimulus is a salient marker of concussion and is indicative of more severe concussion symptomatology. We speculate that differences in visually evoked effects reflect varying levels of activation of the trigeminal nociceptive system.

Prehistoric Cave Art: From Image to Graphic Narration

This article examines cave art in France, arguing that the images created at many sites, but particularly Chauvet, can be analysed in terms of animation, storytelling, lighting and sound. Through superimposition and juxtaposition, and using the contours of the rock face, Palaeolithic artists invented a form of narration based on images, often then animated by the flickering light of lamps and torches. Drawing on semiological work by Philippe Sohet and his terms ‘narrative image’ and ‘iconic narration’, the article sees panels of cave art as constituting scenes and actions that can be discussed in relation to both bande dessinée and cinema. Finally, evidence suggests that the spectacles produced in these spaces, whatever their elusive meaning, also depended on sound and acoustics.

Optimal flickering light stimulation for entraining gamma waves in the human brain

Although light flickering at 40 Hz reduced Alzheimer’s disease (AD) pathologies in mice by entraining gamma waves, it failed to reduce cerebral amyloid burden in a study on six patients with AD or mild cognitive impairment. We investigated the optimal color, intensity, and frequency of the flickering light stimulus for entraining gamma waves in young adults. We compared the event-related synchronization (ERS) values of entrained gamma waves between four different light colors (white, red, green, and blue) in the first experiment and four different luminance intensities in the second experiment. In both experiments, we compared the ERS values of entrained gamma waves between 10 different flickering frequencies from 32 to 50 Hz. We also examined the severity of six adverse effects in both experiments. We compared the propagation of gamma waves in the visual cortex to other brain regions between different luminance intensities and flickering frequencies. We found that red light entrained gamma waves most effectively, followed by white light. Lights of higher luminance intensities (700 and 400 cd/m2) entrained stronger gamma waves than those of lower luminance intensities (100 and 10 cd/m2). Lights flickering at 34–38 Hz entrained stronger and more widely spread beyond the visual cortex than those flickering at 40–50 Hz. Light of 700 cd/m2 resulted in more moderate-to-severe adverse effects than those of other luminance intensities. In humans, 400 cd/m2 white light flickering at 34–38 Hz was most optimal for gamma entrainment.

Modeling of Voltage Fluctuations Generated by Arc Furnaces

Arc furnaces can be classified as electricity receivers, which largely affect the quality of electricity in the power system. Voltage fluctuations are the main disturbance generated by arc furnaces. The effects of voltage fluctuations include the phenomenon of flickering light. Apart from voltage fluctuations, arc devices, to a lesser extent, are the source of current and voltage asymmetry, voltage curve distortion, and voltage dips. The main purpose of theoretical considerations is to assess the voltage fluctuations generated by arc furnaces. The article presents a model of an arc device in which the arc has been replaced by a voltage whose value depends on the arc length. It presents also the results of the analysis of measurements of the parameters characterizing voltage fluctuations and flicker indicators.

The effects of colour and temporal frequency of flickering light on variability of the accommodation response in emmetropes and myopes

Background Myopia is hypothesized to be influenced by environmental light conditions. For example, it has been shown that colour and temporal frequency of flickering light affect emmetropisation in animals. Considering the omnipresence of flickering light in our daily life, we decided to analyze the effect of colour flickers on variability of the accommodation response (VAR) in emmetropes and myopes. Methods We measured the dynamic accommodative responses of 19 emmetropic and 22 myopic adults using a Grand Seiko WAM-5500 open-field autorefractor. The subjects focused for more than 20 s on a black Snellen E target against three different backgrounds made up of three colour flicker combinations (red/green, red/blue and blue/green) and under five frequency conditions (0.20 Hz, 0.50 Hz, 1.00 Hz, 1.67 Hz, and 5.00 Hz). Results Flicker frequency and colour both had a significant effect on VAR. Lower frequencies were associated with larger variability. Colour had an effect only at low frequencies, and red/blue colour flicker resulted in the largest variability. The variability in myopes were larger than those in emmetropes. Conclusions These findings support the hypothesis that further studies on the colour and temporal frequency of flickering light can lead to a better understanding of the development and progression of myopia.