Transcranial Direct Current Stimulation (tDCS) and the Face Inversion Effect: Anodal stimulation at Fp3 reduces recognition for upright faces

This is the final version of the article. Available from the publisher via the link in this record.Perceptual learning is a key perceptual skill that people possess, in particular, it contributes to their ability to distinguish between faces thus recognize individuals. Recently, we showed that anodal transcranial Direct Current Stimulation (tDCS) at Fp3 abolishes the inversion effect (that would otherwise exist) for familiar checkerboards created from a prototype. Because of the close analogy between the inversion effect obtained with checkerboards, which we use as a marker for perceptual learning, and the traditional face inversion effect (upright faces recognized better than inverted ones), we investigated the effects of anodal tDCS at Fp3 during an old/new recognition task for upright and inverted faces. Results showed that stimulation significantly reduced the face inversion effect compared to controls. The effect was strongest in reducing recognition performance to upright faces. This result supports our account of perceptual learning and its role as a key factor in face recognitio

Differential Motor Facilitation During Action Observation in Followers and Leaders on Instagram

High power and high socioeconomic status individuals have been found to exhibit less motor system activity during observation of another individual’s behavior. In the modern world, the use of online social networks for social interaction is increasing, and these social networks afford new forms of social status hierarchy. An important question is whether social status in an online setting affects social information processing in a way that resembles the known effects of real-world status on such processing. Using transcranial magnetic stimulation (TMS), we examined differences in motor cortical output during action observation between Instagram “leaders” and “followers.” Instagram Leaders were defined as individuals who have more followers than they are following, while Instagram Followers were defined as individuals who have fewer followers than they follow. We found that Followers exhibited increased Motor-evoked Potential (MEP) facilitation during action observation compared to Leaders. Correlational analyses also revealed a positive association between an individual’s Instagram follower/following ratio and their perceived sense of online status. Overall, the findings of this study provide some evidence in favor of the idea that our online sense of status and offline sense of status might be concordant in terms of their effect on motor cortical output during action observation.Statement of Significance: This study highlights the importance of examining the effects of online status on motor cortical output during action observation, and more generally alludes to the importance of understanding online and offline status effects on social information processing

Beyond the Libet clock: modality variants for agency measurements

The Sense of Agency (SoA) refers to our capability to control our own actions and influence the world around us. Recent research in HCI has been exploring SoA to provide users an instinctive sense of “I did that” as opposed to “the system did that”. However, current agency measurements are limited. The Intentional Binding (IB) paradigm provides an implicit measure of the SoA. However, it is constrained by requiring high visual attention to a “Libet clock” onscreen. In this paper, we extend the timing stimulus through auditory and tactile cues. Our results demonstrate that audio timing through voice commands and haptic timing through tactile cues on the hand are alternative techniques to measure the SoA using the IB paradigm. They both address limitations of the traditional method (e.g., lack of engagement and visual demand). We discuss how our results can be applied to measure SoA in tasks involving different interactive scenarios common in HCI

How a Lateralized Brain Supports Symmetrical Bimanual Tasks

A large repertoire of natural object manipulation tasks require precisely coupled symmetrical opposing forces by both hands on a single object. We asked how the lateralized brain handles this basic problem of spatial and temporal coordination. We show that the brain consistently appoints one of the hands as prime actor while the other assists, but the choice of acting hand is flexible. When study participants control a cursor by manipulating a tool held freely between the hands, the left hand becomes prime actor if the cursor moves directionally with the left-hand forces, whereas the right hand primarily acts if it moves with the opposing right-hand forces. In neurophysiological (electromyography, transcranial magnetic brain stimulation) and functional magnetic resonance brain imaging experiments we demonstrate that changes in hand assignment parallels a midline shift of lateralized activity in distal hand muscles, corticospinal pathways, and primary sensorimotor and cerebellar cortical areas. We conclude that the two hands can readily exchange roles as dominant actor in bimanual tasks. Spatial relationships between hand forces and goal motions determine hand assignments rather than habitual handedness. Finally, flexible role assignment of the hands is manifest at multiple levels of the motor system, from cortical regions all the way down to particular muscles

Physical and mental effort disrupts the implicit sense of agency

We investigated the effect of effort on implicit agency ascription for actions performed under varying levels of physical effort or cognitive load. People are able to estimate the interval between two events accurately, but they underestimate the interval between their own actions and their outcomes. This effect is known as ‘intentional binding’, and may provide feedback regarding the consequences of our actions. Concurrently with the interval reproduction task, our participants pulled sports resistance bands at high and low resistance levels (Experiments 1 and 2), or performed a working memory task with high and low set-sizes (Experiment 3). Intentional binding was greater under low than high effort. When the effort was task-related (Experiment 1), this effect depended on the individual’s explicit appraisal of exertion, while the effect of effort was evident at the group level when the effort was task-unrelated (physical, Experiment 2; mental, Experiment 3). These findings imply that the process of intentional binding is compromised when cognitive resources are depleted, either through physical or mental strain. We discuss this notion in relation to the integration of direct sensorimotor feedback with signals of agency and other instances of cognitive resource depletion and action control during strain

Free will debates: Simple experiments are not so simple

The notion that free will is an illusion has achieved such wide acceptance among philosophers and neuroscientists that it seems to be acquiring the status of dogma. Nonetheless, research in this area continues, and this review offers a new analysis of the design limitations and data interpretations of free-will experiments. This review presents 12 categories of questionable conclusions that some scholars use to promote the idea that free will is an illusion. The next generation of less ambiguous experiments is proposed

Top-down social modulation of interpersonal observation-execution.

Cyclical upper limb movement can involuntarily deviate from its primary movement axis when the performer concurrently observes incongruent biological motion (i.e. interpersonal observation-execution). The current study examined the social modulation of such involuntary motor interference using a protocol that reflected everyday social interactions encountered in a naturalistic social setting. Eighteen participants executed cyclical horizontal arm movements during the observation of horizontal (congruent) or curvilinear (incongruent) biological motion. Both prior to, and during the interpersonal observation-execution task, participants also received a series of social words designed to prime a pro-social or anti-social attitude. The results showed greater orthogonal movement deviation, and thus interference, for the curvilinear compared to horizontal stimuli. Importantly, and opposite to most of the previous findings from work on automatic imitation and mimicry, there was a greater interference effect for the anti-social compared to pro-social prime condition. These findings demonstrate the importance of interpreting the context of social primes, and strongly support predictions of a comparison between the prime construct and the self-concept/-schema and the top-down response modulation of social incentives

Protein Glycosylation in Helicobacter pylori: Beyond the Flagellins?

Glycosylation of flagellins by pseudaminic acid is required for virulence in Helicobacter pylori. We demonstrate that, in H. pylori, glycosylation extends to proteins other than flagellins and to sugars other than pseudaminic acid. Several candidate glycoproteins distinct from the flagellins were detected via ProQ-emerald staining and DIG- or biotin- hydrazide labeling of the soluble and outer membrane fractions of wild-type H. pylori, suggesting that protein glycosylation is not limited to the flagellins. DIG-hydrazide labeling of proteins from pseudaminic acid biosynthesis pathway mutants showed that the glycosylation of some glycoproteins is not dependent on the pseudaminic acid glycosylation pathway, indicating the existence of a novel glycosylation pathway. Fractions enriched in glycoprotein candidates by ion exchange chromatography were used to extract the sugars by acid hydrolysis. High performance anion exchange chromatography with pulsed amperometric detection revealed characteristic monosaccharide peaks in these extracts. The monosaccharides were then identified by LC-ESI-MS/MS. The spectra are consistent with sugars such as 5,7-diacetamido-3,5,7,9-tetradeoxy-L-glycero-L-manno-nonulosonic acid (Pse5Ac7Ac) previously described on flagellins, 5-acetamidino-7-acetamido-3,5,7,9-tetradeoxy-L-glycero-L-manno-nonulosonic acid (Pse5Am7Ac), bacillosamine derivatives and a potential legionaminic acid derivative (Leg5AmNMe7Ac) which were not previously identified in H. pylori. These data open the way to the study of the mechanism and role of protein glycosylation on protein function and virulence in H. pylori