VMAT2 availability in Parkinson’s disease with probable REM sleep behaviour disorder

REM sleep behaviour disorder (RBD) can be an early non-motor symptom of Parkinson’s disease (PD) with pathology involving mainly the pontine nuclei. Beyond the brainstem, it is unclear if RBD patients comorbid with PD have more affected striatal dopamine denervation compared to PD patients unaffected by RBD (PD-RBD−). To elucidate this, we evaluated the availability of vesicular monoamine transporter 2 (VMAT2), an index of nigrostriatal dopamine innervation, in 15 PD patients with probable RBD (PD-RBD+), 15 PD-RBD−, and 15 age-matched healthy controls (HC) using [11C]DTBZ PET imaging. This technique measured VMAT2 availability within striatal regions of interest (ROI). A mixed effect model was used to compare the radioligand binding of VMAT2 between the three groups for each striatal ROI, while co-varying for sex, cognitive function and depression scores. Multiple regressions were also computed to predict clinical measures from group condition and VMAT2 binding within all ROIs explored. We observed a significant main effect of group condition on VMAT2 availability within the caudate, putamen, ventral striatum, globus pallidus, substantia nigra, and subthalamus. Specifically, our results revealed that PD-RBD+ had lower VMAT2 availability compared to HC in all these regions except for the subthalamus and substantia nigra, while PD-RBD− was significantly lower than HC in all these regions. PD-RBD− showed a negative relationship between motor severity and VMAT2 availability within the left caudate. Our findings reflect that both PD patient subgroups had similar denervation within the nigrostriatal pathway. There were no significant interactions detected between radioligand binding and clinical scores in PD-RBD+. Taken together, VMAT2 and striatal dopamine denervation in general may not be a significant contributor to the pathophysiology of RBD in PD patients. Future studies are encouraged to explore other underlying neural chemistry mechanisms contributing to RBD in PD patients.

VMAT2 Availability in Parkinson’s Disease with REM Sleep Behaviour Disorder

REM sleep behaviour disorder (RBD) is an early sleep disturbance symptom of Parkinson’s disease (PD) thought to be caused by the disruption of normal basal ganglia function due to neurodegeneration. To further elucidate the neuropathological contribution of RBD in PD, we aimed to characterize the role of vesicular monoamine transporter 2 (VMAT2), an index of nigrostriatal dopamine innervation, in PD patients with RBD (PD-RBD+). We identified 15 PD-RBD+, 15 PD patients without RBD (PD-RBD–) and 15 age matched healthy controls (HC) who underwent [11C]DTBZ PET imaging. This technique measures VMAT2 availability within striatal regions of interest (ROI). Mixed effect model was used to compare the radioligand binding of VMAT2 between the three groups for each striatal ROI, while co-varying for sex, cognitive function and depression scores. Multiple regressions were also computed to predict clinical measures from group condition and VMAT2 binding within all ROIs explored. Significant level was set at p < 0.05 (Bonferroni corrected). We observed significant main effect of group condition on VMAT2 availability within the caudate, putamen, ventral striatum, globus pallidus, substantia nigra, and subthalamus. Specifically, we observed that both PD-RBD + and PD-RBD– group had lower VMAT2 availability compared to HC. PD-RBD– showed a negative relationship between motor severity and VMAT2 availability within the left caudate. This relationship was not found in the PD-RBD + group. Our findings reveal that both PD patient subgroups had reduced VMAT2 levels relative to HC—which reflects denervation within the nigrostriatal pathway. No significant interactions were detected between radioligand binding and clinical scores in PD-RBD+. Taken together, we found limited evidence that VMAT2 may contribute differently in PD-RBD + relative to PD-RBD–. Future studies are encouraged to explore other underlying neural chemistry mechanisms contributing to RBD in PD patients.

Sensitivity of discrete symmetry metrics: implications for metric choice

Gait asymmetry is present in several pathological populations, including those with Parkinson's disease, Huntington's disease, and stroke survivors. Previous studies suggest that commonly used discrete symmetry metrics, which compare single bilateral variables, may not be equally sensitive to underlying effects of asymmetry, and the use of a metric with low sensitivity could result in unnecessarily low statistical power. The purpose of this study was to provide a comprehensive assessment of the sensitivity of commonly used discrete symmetry metrics to better inform design of future studies. Monte Carlo simulations were used to estimate the statistical power of each symmetry metric at a range of asymmetry magnitudes, group/condition variabilities, and sample sizes. Power was estimated by repeated comparison of simulated symmetric and asymmetric data with a paired t-test, where the proportion of significant results is equivalent to the power. Simulation results confirmed that not all common discrete symmetry metrics are equally sensitive to reference effects of asymmetry. Multiple symmetry metrics exhibit equivalent sensitivities, but the most sensitive discrete symmetry metric in all cases is a bilateral difference (e.g. left - right). A ratio (e.g. left/right) has poor sensitivity when group/condition variability is not small, but a log-transformation produces increased sensitivity. Additionally, two metrics which included an absolute value in their definitions showed increased sensitivity when the absolute value was removed. Future studies should consider metric sensitivity when designing analyses to reduce the possibility of underpowered research.

Lying for Bonuses

This study aims to determine whether being in a group setting makes lying easier through the diffusion of responsibility. Participants in three separate conditions, two paired and one isolated control, were asked to roll dice and report results. Participants also had the incentive of earning extra money if the reported number was a four, regardless of the truthfulness of the response. The results showed that participants overwhelmingly reported rolling a four, statistically indicating that many chose to lie. Additionally, one of the two group conditions proved to have significantly higher rates of reported lying than the individual condition (with the other group condition directionally higher but not significantly). The findings suggest that people are more likely to engage in immoral behavior when placed in a group setting as opposed to when acting independently.

Out-group gestures can lower self-esteem

Culture-specific symbols can prime aspects of identity, like self-esteem, in bilingual-bicultural individuals. The purpose of the present studies was to test whether gestures that are specific to a culture prime self-esteem and, if so, whether it is due to in-group/out-group association. In Study 1, Chinese Canadians had higher self-esteem scores when primed by Chinese number gestures or characters than by English number gestures or words. In Study 2, we taught Chinese number gestures to non-Chinese adults, with half thinking they were Chinese gestures (out-group) and half that they were old fur traders’ gestures (in-group). The self-esteem scores were higher in the in-group condition than the out-group condition. Comparisons with self-esteem scores from previous studies suggest that the out-group conditions were significantly lower than baseline. These results suggest that out-group gesture primes can lower self-esteem.

Do demand characteristics contribute to minimal ingroup preferences?

“Minimal group” paradigms investigate social preferences arising from mere group membership. We asked whether demand characteristics contribute to children’s apparent minimal group bias in a preregistered experiment (N = 160). In a “group” condition, we attempted to replicate findings of bias following assignment to minimal groups. A second closely-matched “no-group” condition retained potential demand characteristics while removing group assignment. Parallel bias in the no-group condition would suggest that demand characteristics contribute to findings of apparent ingroup bias. Three main findings emerged. First, in the group condition, ingroup preference emerged in one of three bias measures only. Second, this preference emerged although participants evaluated ingroup/outgroup photos varying in race/ethnicity between trials. Third, the measure that yielded ingroup preferences in the group condition produced no parallel bias in the no-group condition, consistent with the view that mere membership in a group, not experimental demand, leads to minimal ingroup preferences.

Fostering Learners’ Perceived Presence and High-Level Learning Outcomes in Online Learning Environments

This study investigated the effects of using a teaching model enriched with presence on learners’ perceived presence and high-level learning outcomes in online learning environments. The study was conducted in an Iranian state university with 52 higher education students majoring in electronic IT management who were randomly divided into experimental or control group conditions. The research tools included a rubric to measure learner’s perceived presence and the researcher-made survey to measure learner’s high-level learning outcomes. The results showed that the frequency of the produced semantic units in different types of presence (cognitive, social, and teaching presence) was significantly higher for students in the experimental condition than those in the control group condition. In addition, students in the experimental condition showed more progression in the posttest in terms of their high-level learning outcomes as compared to the students in the control group condition.

Inequivalent Out-Groups in “The Decision III”: The Free Agency of LeBron James and the Power of Sport Rivalry

This study investigated how LeBron James’s free-agency decision in 2018 influences sport fans’ image impressions of him with in-groups (Cleveland Cavaliers) and out-groups (all other NBA teams) compared. In the months preceding James’s free-agency decision, an experimental design was employed to ask self-ascribed fans of LeBron James how they felt about 4 possible free-agency destinations: the Cleveland Cavaliers, the Houston Rockets, the Golden State Warriors, and his eventual selection, the Los Angeles Lakers. A total of 189 U.S. fans of LeBron James were recruited for the study. Results indicate that James’s image became worse (in terms of mean scores) for every out-group condition, while being slightly improved if opting to remain in the in-group; however, images were significantly different from other out-groups in the scenario in which LeBron James opted to join the Golden State Warriors—the Cavaliers most immediate rival at the time.

The cheerleader effect is robust to experimental manipulations of presentation time

The “cheerleader effect” occurs when the same face is perceived to be significantly more attractive when seen in a group of faces compared to alone. As perceptions of attractiveness decrease with additional viewing time, we investigated whether the cheerleader effect occurs simply because the target face is seen for less time in a group than it is alone. Observers rated the attractiveness of target faces twice; once in a group, and once alone. We manipulated the amount of time that each group image was presented for prior to the cue toward the target face (300, 1000, 2000, 3000, or 7000 milliseconds). Faces were perceived to be significantly more attractive in each group condition, regardless of presentation time, replicating the cheerleader effect. Furthermore, un-cued presentation time did not modulate the magnitude of this increase, demonstrating that a presentation time discrepancy does not contribute to the size of the typical cheerleader effect.

Predicting Choice Behavior of Group Members

Meaningful social interactions rest upon our ability to accurately infer and predict other people’s preferences. In doing so, we can separate two sources of information: knowledge we have about the particular individual (individual knowledge) and knowledge we have about the social group to which that individual belongs (categorical knowledge). However, it is yet unclear how these two types of knowledge contribute to making predictions about other people’s choice behavior. To fill this gap, we had participants learn probabilistic preferences by predicting object choices of agents that either belonged to a social group (Group condition) or not (Individual condition). We quantified how close predictions for a specific agent are relative to the objective individual preferences of that agent and how close these predictions are relative to the objective group-level preferences to which that agent belongs. As expected, we found that participants’ predictions in the Group condition, relative to the Individual condition, were more similar to the group-level preference, while less similar to the individual-level preferences. We interpret this pattern of results as indicative of a differential weighting of individual and categorical group knowledge when making predictions about individuals that belong to a social group. The results are interpreted in an assimilation account of categorization and stress the importance of group knowledge during daily social interactions.