double dissociation between the extrastriate body area and the posterior superior temporal sulcus during biological motion perception converging evidence from tms and fmri

Our brains engage numerous regions when exposed to biological motion, with the posterior superior temporal sulcus (pSTS) being the primary locus. The exact roles of hMT+ and the extrastriate body area (EBA) remain unclear. Here, we set out to determine the specific roles of pSTS and EBA during biological motion perception, focusing on walker orientation and walking direction. To obtain converging evidence, we conducted separate TMS and fMRI experiments within the same subjects (N = 12). Two separate tasks were used in the TMS study: walker orientation probing form processing and walking direction probing motion/sequence processing. Task performance was compared before and after applying repetitive offline TMS (1 Hz) over EBA and pSTS (based on fMRI-guided stereotaxy). In the fMRI study, EBA and pSTS were mapped in separate scans using standard localizers. Subsequently, runs with point-light walkers were subjected to MVPA, determining the amount of static (orientation) and dynamic (direction) information p..

Robust Henderson III estimators of variance components in the nested error model

Common methods for estimating variance components in Linear Mixed Models include Maximum Likelihood (ML) and Restricted Maximum Likelihood (REML). These methods are based on the strong assumption of multivariate normal distribution and it is well know that they are very sensitive to outlying observations with respect to any of the random components. Several robust altematives of these methods have been proposed (e.g. Fellner 1986, Richardson and Welsh 1995). In this work we present several robust alternatives based on the Henderson method III which do not rely on the normality assumption and provide explicit solutions for the variance components estimators. These estimators can later be used to derive robust estimators of regression coefficients. Finally, we describe an application of this procedure to small area estimation, in which the main target is the estimation of the means of areas or domains when the within-area sample sizes are small

Signature Movements Lead to Efficient Search for Threatening Actions

The ability to find and evade fighting persons in a crowd is potentially life-saving. To investigate how the visual system processes threatening actions, we employed a visual search paradigm with threatening boxer targets among emotionally-neutral walker distractors, and vice versa. We found that a boxer popped out for both intact and scrambled actions, whereas walkers did not. A reverse correlation analysis revealed that observers' responses clustered around the time of the “punch", a signature movement of boxing actions, but not around specific movements of the walker. These findings support the existence of a detector for signature movements in action perception. This detector helps in rapidly detecting aggressive behavior in a crowd, potentially through an expedited (sub)cortical threat-detection mechanism

Visual adaptation enhances action sound discrimination

Prolonged exposure, or adaptation, to a stimulus in one modality can bias, but also enhance, perception of a subsequent stimulus presented within the same modality. However, recent research has also found that adaptation in one modality can bias perception in another modality. Here we show a novel crossmodal adaptation effect, where adaptation to a visual stimulus enhances subsequent auditory perception. We found that when compared to no adaptation, prior adaptation to visual, auditory or audiovisual hand actions enhanced discrimination between two subsequently presented hand action sounds. Discrimination was most enhanced when the visual action ‘matched’ the auditory action. In addition, prior adaptation to a visual, auditory or audiovisual action caused subsequent ambiguous action sounds to be perceived as less like the adaptor. In contrast, these crossmodal action aftereffects were not generated by adaptation to the names of actions. Enhanced crossmodal discrimination and crossmodal perceptual aftereffects may result from separate mechanisms operating in audiovisual action sensitive neurons within perceptual systems. Adaptation induced crossmodal enhancements cannot be explained by post-perceptual responses or decisions. More generally, these results together indicate that adaptation is a ubiquitous mechanism for optimizing perceptual processing of multisensory stimuli

Safety and efficacy of a dapivirine vaginal ring for HIV prevention in women

BACKGROUND The incidence of human immunodeficiency virus (HIV) infection remains high among women in sub-Saharan Africa. We evaluated the safety and efficacy of extended use of a vaginal ring containing dapivirine for the prevention of HIV infection in 1959 healthy, sexually active women, 18 to 45 years of age, from seven communities in South Africa and Uganda. METHODS In this randomized, double-blind, placebo-controlled, phase 3 trial, we randomly assigned participants in a 2:1 ratio to receive vaginal rings containing either 25 mg of dapivirine or placebo. Participants inserted the rings themselves every 4 weeks for up to 24 months. The primary efficacy end point was the rate of HIV type 1 (HIV-1) seroconversion. RESULTS A total of 77 participants in the dapivirine group underwent HIV-1 seroconversion during 1888 person-years of follow-up (4.1 seroconversions per 100 person-years), as compared with 56 in the placebo group who underwent HIV-1 seroconversion during 917 person-years of follow-up (6.1 seroconversions per 100 person-years). The incidence of HIV-1 infection was 31% lower in the dapivirine group than in the placebo group (hazard ratio, 0.69; 95% confidence interval [CI], 0.49 to 0.99; P = 0.04). There was no significant difference in efficacy of the dapivirine ring among women older than 21 years of age (hazard ratio for infection, 0.63; 95% CI, 0.41 to 0.97) and those 21 years of age or younger (hazard ratio, 0.85; 95% CI, 0.45 to 1.60; P = 0.43 for treatment-by-age interaction). Among participants with HIV-1 infection, nonnucleoside reverse-transcriptase inhibitor resistance mutations were detected in 14 of 77 participants in the dapivirine group (18.2%) and in 9 of 56 (16.1%) in the placebo group. Serious adverse events occurred more often in the dapivirine group (in 38 participants [2.9%]) than in the placebo group (in 6 [0.9%]). However, no clear pattern was identified. CONCLUSIONS Among women in sub-Saharan Africa, the dapivirine ring was not associated with any safety concerns and was associated with a rate of acquisition of HIV-1 infection that was lower than the rate with placebo.Supported by the International Partnership for Microbicides (a not-for-profit product-development partnership), which receives support from the Bill and Melinda Gates Foundation, Irish Aid, the Ministry of Foreign Affairs of Denmark, the Ministry of Foreign Affairs of the Netherlands, the Norwegian Agency for Development Cooperation, the U.K. Department for International Development, the American people through the U.S. Agency for International Development, and the President’s Emergency Plan for AIDS Relief.http://www.nejm.org2017-06-01am2017Family Medicin

Neural Model for the Influence of Shading on the Multistability of the Perception of Body Motion

Body motion perception from impoverished stimuli shows interesting dynamic properties, such as multistability and spontaneous perceptual switching. Psychophysical experiments show that such multistability disappears when the stimulus includes also shading cues along the body surface. Classical neural models for body motion perception have not addressed perceptual multistability. We present an extension of a classical neurodynamic model for biological and body motion perception that accounts for perceptual switching, and its dependence on shading cues on the body surface. We demonstrate that a set of psychophysical observations can be accounted for in a unifying manner by a hierarchical neural model for body motion processing that includes an additional shading pathway, which processes luminance gradients within the individual body segments. The goal of our model is to explain psychophysics and neural mechanism in the brain

Perception of biological motion depends on lighting-from-above prior

Most research on biological motion perception has focused on the influences of 2D motion and form cues,and sometimes also of binocular disparity, while the influence of shading has been largely neglected.The perception of 3D static shapes from 2D images is strongly influenced by a lighting-from-aboveprior (Brewster, 1847; Ramachandran, 1988). We observed that for biological motion stimuli withperceptually ambiguous walking direction (Vanrie et al. 2004) the illumination direction can radicallyalter the perceived walking direction of walkers that consist of volumetric moving elements at thejoints. METHOD: We replaced the dots of a walker by volumetric elements that are rendered withdifferent positions of the illuminating light source. We studied the dependence of the perceived walkingdirection on the position of this light source. RESULTS/DISCUSSION: We found a radical change ofthe perceived walking direction (corresponding to a rotation by 180 deg) between lighting from aboveand lighting from below, while the physical structure of the walker remained exactly identical. Thisillusion demonstrates that biological motion perception is also substantially influenced by shading cues,where the processing of these cues is dependent on a lighting-from-above prior