The precision of signals encoding active self-movement.

Everyday actions like moving the head, walking around and grasping objects are typically self-controlled. This presents a problem when studying the signals encoding such actions because active self-movement is difficult to control experimentally. Available techniques demand repeatable trials, but each action is unique, making it difficult to measure fundamental properties like psychophysical thresholds. We present a novel paradigm that recovers both precision and bias of self-movement signals with minimal constraint on the participant. The paradigm relies on linking image motion to previous self-movement, and two experimental phases to extract the signal encoding the latter. The paradigm takes care of a hidden source of external noise not previously accounted for in techniques that link display motion to self-movement in real time (e.g. virtual reality). We use head rotations as an example of self-movement, and show that the precision of the signals encoding head movement depends on whether they are being used to judge visual motion or auditory motion. We find that perceived motion is slowed during head movement in both cases. The 'non-image' signals encoding active head rotation (motor commands, proprioception and vestibular cues) are therefore biased towards lower speeds and/or displacements. In a second experiment, we trained participants to rotate their heads at different rates and found that the imprecision of the head rotation signal rises proportionally with head speed (Weber's Law). We discuss the findings in terms of the different motion cues used by vision and hearing, and the implications they have for Bayesian models of motion perception.

Effect of Pepper-Containing Diets on the Diversity and Composition of Gut Microbiome of Drosophila melanogaster.

One of the greatest impacts on the gastrointestinal microbiome is diet because the host and microbiome share the same food source. In addition, the effect of diet can diverge depending on the host genotype. Diets supplemented with phytochemicals found in peppers might cause shifts in the microbiome. Thus, understanding how these interactions occur can reveal potential health implications associated with such changes. This study aims to explore the gut microbiome of different Drosophila genetic backgrounds and the effects of dietary pepper treatments on its composition and structure. We analyzed the gut microbiomes of three Drosophila melanogaster genetic backgrounds (Canton-S, Oregon-RC, and Berlin-K) reared on control and pepper-containing diets (bell, serrano, and habanero peppers). Results of 16S rRNA gene sequencing revealed that the variability of Drosophila gut microbiome can be driven mainly by genetic factors. When the abundance of these communities is considered, pepper-containing diets also appear to have an effect. The most relevant change in microbial composition was the increment of Lactobacillaceae and Acetobacteraceae abundance in the pepper-containing diets in comparison with the controls in Oregon-RC and Berlin-K. Regression analysis demonstrated that this enhancement was associated with the content of phenolic compounds and carotenoids of the peppers utilized in this study; specifically, to the concentration of ß-carotene, ß-cryptoxanthin, myricetin, quercetin, and apigenin.