The rubber hand universe: On the impact of methodological differences in the rubber hand illusion.

The rubber hand illusion (RHI) is a widely applied paradigm to investigate changes in body representations. Extensive scientific interest has produced a great variability in the observed results and many contradictory findings have been reported. Taking into account the numerous variations in the experimental implementation of the RHI, many of these contradictive findings can be reconciled, but to date a thorough analysis of the methodological differences between RHI studies is lacking. Here we summarize and analyse methodological differences between RHI studies. In distinction from other reviews focusing on the integration of findings from various studies, the present paper is devoted to the differences in (i) the experimental setup, (ii) the method used to induce the RHI, (iii) the quantification of its effects, and (iv) aspects of the experimental design and data analysis. This approach will provide a reference frame for the interpretation of previous studies as well as for the design of future studies.

Closely Related Fruit Fly Species Living at Different Latitudes Diverge in Their Circadian Clock Anatomy and Rhythmic Behavior.

Recently, we reported differences in the expression pattern of the blue light-sensitive flavoprotein cryptochrome (CRY) and the neuropeptide pigment-dispersing factor (PDF) in the neuronal clock network of high-latitude Drosophila species, belonging to the Drosophila subgenus ( virilis-repleta radiation), compared with cosmopolitan D. melanogaster flies, belonging to the Sophophora subgenus. Alterations in rhythmic patterns of activity due to these differences might have adaptive significance for colonizing high-latitude habitats and, hence, adjusting to long photoperiods. Here, we show that these differing CRY/PDF expression patterns are only present in those species of the virilis-repleta radiation that colonized high latitudes. The cosmopolitan species D. mercatorum and D. hydei have a D. melanogaster-like clock network and behavior despite belonging to the virilis-repleta radiation. Similarly, 2 species of the holotropical Zaprionus genus, more closely related to the Drosophila subgenus than to the Sophophora subgenus, retain a D. melanogaster-like clock network and rhythmic behavior. We therefore suggest that the D. melanogaster-like clock network is the "ancestral fly clock phenotype" and that alterations in the CRY/PDF clock neurochemistry have allowed some species of the virilis-repleta radiation to colonize high-latitude environments.

Adaptation of Circadian Neuronal Network to Photoperiod in High-Latitude European Drosophilids.

The genus Drosophila contains over 2,000 species that, stemming from a common ancestor in the Old World Tropics, populate today very different environments [1, 2] (reviewed in [3]). We found significant differences in the activity pattern of Drosophila species belonging to the holarctic virilis group, i.e., D. ezoana and D. littoralis, collected in Northern Europe, compared to that of the cosmopolitan D. melanogaster, collected close to the equator. These behavioral differences might have been of adaptive significance for colonizing high-latitude habitats and hence adjust to long photoperiods. Most interestingly, the flies' locomotor activity correlates with the neurochemistry of their circadian clock network, which differs between low and high latitude for the expression pattern of the blue light photopigment cryptochrome (CRY) and the neuropeptide Pigment-dispersing factor (PDF) [4-6]. In D. melanogaster, CRY and PDF are known to modulate the timing of activity and to maintain robust rhythmicity under constant conditions [7-11]. We could partly simulate the rhythmic behavior of the high-latitude virilis group species by mimicking their CRY/PDF expression patterns in a laboratory strain of D. melanogaster. We therefore suggest that these alterations in the CRY/PDF clock neurochemistry might have allowed the virilis group species to colonize high-latitude environments.

Old friends, new story: The role of Slit2C signaling through PlexinA1.

Growth cone guidance is driven by attractive and repulsive signaling cues. Until recently, repulsive signaling by semaphorins was thought to be mediated through Plexin receptors, whereas Slits-induced repulsion was solely mediated through Robo receptors. In a recent report published in Nature Neuroscience, Celine Delloye-Bourgeois and colleagues (2015) combined phenotypic analyses of transgenic mouse lines and in vitro biochemical experiments to identify PlexinA1 as a novel receptor for Slits. Strikingly, they uncovered for the very first time that the Slit2C-terminal fragment possesses some unique biological activity as binding partner for PlexinA1. Even more excitingly, the signaling cascade triggered by SlitC binding to PlexinA1 mediates growth cone collapse of commissural axons both in vivo and ex vivo and nicely complements Robo-Slit signaling in the developing spinal cord midline to prevent midline recrossing.