Sensitizing the Viewer:The Impact of New Techniques and the Art Experience

To create a new understanding of the experience of techniques in art, Sensitizing the Viewer reframes the avant-gardes within the realm of powerful early and later cinema experiences. Sensitizing the Viewer was written in the wake of working on Ostrannenie which was published by Amsterdam University Press in 2010

Left parietal tACS at alpha frequency induces a shift of visuospatial attention

Background Voluntary shifts of visuospatial attention are associated with a lateralization of parieto-occipital alpha power (7-13Hz), i.e. higher power in the hemisphere ipsilateral and lower power contralateral to the locus of attention. Recent noninvasive neuromodulation studies demonstrated that alpha power can be experimentally increased using transcranial alternating current stimulation (tACS). Objective/Hypothesis We hypothesized that tACS at alpha frequency over the left parietal cortex induces shifts of attention to the left hemifield. However, spatial attention shifts not only occur voluntarily (endogenous/ top-down), but also stimulus-driven (exogenous/ bottom-up). To study the task-specificity of the potential effects of tACS on attentional processes, we administered three conceptually different spatial attention tasks. Methods 36 healthy volunteers were recruited from an academic environment. In two separate sessions, we applied either high-density tACS at 10Hz, or sham tACS, for 35–40 minutes to their left parietal cortex. We systematically compared performance on endogenous attention, exogenous attention, and stimulus detection tasks. Results In the endogenous attention task, a greater leftward bias in reaction times was induced during left parietal 10Hz tACS as compared to sham. There were no stimulation effects in either the exogenous attention or the stimulus detection task. Conclusion The study demonstrates that high-density tACS at 10Hz can be used to modulate visuospatial attention performance. The tACS effect is task-specific, indicating that not all forms of attention are equally susceptible to the stimulation

Continuous Planetary Polar Observation from Hybrid Pole-Sitters at Venus, Earth, and Mars

A pole-sitter is a satellite that is stationed along the polar axis of the Earth, or any other planet, to generate a continuous, hemispherical view of the planet’s polar regions. In order to maintain such a vantage point, a low-thrust propulsion system is required to counterbalance the gravitational attraction of the planet and the Sun. Previous work has considered the use of solar electric propulsion (SEP) or a hybrid configuration of an SEP thruster and a solar sail to produce the required acceleration. By subsequently optimising the propellant consumption by the thruster, estimates of the mission performance in terms of the payload capacity and mission lifetime have been obtained. This paper builds on these results and aims at lifting the pole-sitter concept to the next level by extending the work both from a technical and conceptual perspective: from a technical perspective, this paper will further improve the mission performance by optimising the pole-sitter orbits for the payload capacity or mission lifetime instead of for the propellant consumption. The results show that, at Earth, this allows improvements in the order of 5-10 percent in terms of payload capacity and mission lifetime. Furthermore, on a conceptual level, this paper will, for the first time, investigate the possibility of so-called quasi-pole-sitter orbits. For quasi-pole-sitter orbits the requirement to be exactly on the polar axis is relaxed to allow some movement around the polar axis as long as continuous observation of the entire polar region at a desired minimum elevation angle is achieved. This ultimately enables solar sail-only pole-sitter orbits that are no longer limited in performance by the SEP propellant consumption. Finally, this paper extends all analyses to other inner Solar System planets, showing that Mars provides excellent conditions for a pole-sitter platform with its low mass and relatively far distance from the Sun. With this extension of the pole-sitter concept to other planets as well as considering, for the first time, the option of quasi-pole-sitter orbits, the concept is lifted to the next level, strengthening the feasibility and utility of these orbits for continuous planetary polar observation

Relating alpha power modulations to competing visuospatial attention theories

Visuospatial attention theories often propose hemispheric asymmetries underlying the control of attention. In general support of these theories, previous EEG/MEG studies have shown that spatial attention is associated with hemispheric modulation of posterior alpha power (gating by inhibition). However, since measures of alpha power are typically expressed as lateralization scores, or collapsed across left and right attention shifts, the individual hemispheric contribution to the attentional control mechanism remains unclear. This is, however, the most crucial and decisive aspect in which the currently competing attention theories continue to disagree. To resolve this long-standing conflict, we derived predictions regarding alpha power modulations from Heilman's hemispatial theory and Kinsbourne's interhemispheric competition theory and tested them empirically in an EEG experiment. We used an attention paradigm capable of isolating alpha power modulation in two attentional states, namely attentional bias in a neutral cue condition and spatial orienting following directional cues. Differential alpha modulations were found for both hemispheres across conditions. When anticipating peripheral visual targets without preceding directional cues (neutral condition), posterior alpha power in the left hemisphere was generally lower and more strongly modulated than in the right hemisphere, in line with the interhemispheric competition theory. Intriguingly, however, while alpha power in the right hemisphere was modulated by both, cue-directed leftward and rightward attention shifts, the left hemisphere only showed modulations by rightward shifts of spatial attention, in line with the hemispatial theory. This suggests that the two theories may not be mutually exclusive, but rather apply to different attentional states

Phase of beta-frequency tACS over primary motor cortex modulates corticospinal excitability

The assessment of corticospinal excitability by means of transcranial magnetic stimulation-induced motor evoked potentials is an established diagnostic tool in neurophysiology and a widely used procedure in fundamental brain research. However, concern about low reliability of these measures has grown recently. One possible cause of high variability of MEPs under identical acquisition conditions could be the influence of oscillatory neuronal activity on corticospinal excitability. Based on research showing that transcranial alternating current stimulation can entrain neuronal oscillations we here test whether alpha or beta frequency tACS can influence corticospinal excitability in a phase-dependent manner. We applied tACS at individually calibrated alpha- and beta-band oscillation frequencies, or we applied sham tACS. Simultaneous single TMS pulses time locked to eight equidistant phases of the ongoing tACS signal evoked MEPs. To evaluate offline effects of stimulation frequency, MEP amplitudes were measured before and after tACS. To evaluate whether tACS influences MEP amplitude, we fitted one-cycle sinusoids to the average MEPs elicited at the different phase conditions of each tACS frequency. We found no frequency-specific offline effects of tACS. However, beta-frequency tACS modulation of MEPs was phase-dependent. Post hoc analyses suggested that this effect was specific to participants with low (<19 Hz) intrinsic beta frequency. In conclusion, by showing that beta tACS influences MEP amplitude in a phase-dependent manner, our results support a potential role attributed to neuronal oscillations in regulating corticospinal excitability. Moreover, our findings may be useful for the development of TMS protocols that improve the reliability of MEPs as a meaningful tool for research applications or for clinical monitoring and diagnosis. (C) 2018 Elsevier Ltd. All rights reserved

Plant parasitic nematodes associated with crops grown by smallholders in Mozambique

Des enquêtes effectuées sur les cultures du Mozambique de 1992 à 1996 ont révélé la présence et l'importance de nombreux nématodes phytoparasites, #Meloidogyne spp. et #Pratylenchus spp. étant les plus répandus et prédominants. Plusieurs espèces ont été trouvées pour la première fois au Mozambique, tandis que d'autres étaient relevées sur d'autres plantes que celles signalées lors des enquêtes précédentes. #Pratylenchus zeae est fréquent sur le maïs, mais aussi sur le haricot (#Phaseolus vulgaris L.), la canne à sucre et le tournesol. #Meloidogyne spp. sont de sérieux ennemis du haricot commun lorsqu'il est interplanté avec le maïs dans la province de Niassa, et également du niébé dans les champs expérimentaux et les zones irriguées du sud, du tournesol dans la province du Niassa, du tabac dans les provinces de Nampula et Manica, et enfin des plantes maraïchères en de nombreuses localités. Mais au Mozambique ces nématodes ne constituent pas un problème pour le manioc. #Ditylenchus africanus, qui attaque les gousses d'arachide, a été trouvé dans les provinces de Maputo et Gaza et pourrait y avoir été introduit lors de l'importation d'arachides utilisées comme semences ou pour la consommation humaine. (Résumé d'auteur

Does alpha phase modulate visual target detection? Three experiments with tACS-phase-based stimulus presentation

In recent years, the influence of alpha (7–13 Hz) phase on visual processing has received a lot of attention. Magneto‐/encephalography (M/EEG) studies showed that alpha phase indexes visual excitability and task performance. Studies with transcranial alternating current stimulation (tACS) aim to modulate oscillations and causally impact task performance. Here, we applied right occipital tACS (O2 location) to assess the functional role of alpha phase in a series of experiments. We presented visual stimuli at different pre‐determined, experimentally controlled, phases of the entraining tACS signal, hypothesizing that this should result in an oscillatory pattern of visual performance in specifically left hemifield detection tasks. In experiment 1, we applied 10 Hz tACS and used separate psychophysical staircases for six equidistant tACS‐phase conditions, obtaining contrast thresholds for detection of visual gratings in left or right hemifield. In experiments 2 and 3, tACS was at EEG‐based individual peak alpha frequency. In experiment 2, we measured detection rates for gratings with (pseudo‐)fixed contrast. In experiment 3, participants detected brief luminance changes in a custom‐built LED device, at eight equidistant alpha phases. In none of the experiments did the primary outcome measure over phase conditions consistently reflect a one‐cycle sinusoid. However, post hoc analyses of reaction times (RT) suggested that tACS alpha phase did modulate RT for specifically left hemifield targets in both experiments 1 and 2 (not measured in experiment 3). This observation requires future confirmation, but is in line with the idea that alpha phase causally gates visual inputs through cortical excitability modulation