A systematic examination of the neural correlates of subjective time perception with fMRI and tDCS.

The ability to keep track of time is one of the fundamental human behaviours that enhance survival in the wild. It is still an essential skill that enables an individual to function well in modern society. In the present study, we tested the attentional gate model, one of the most common conceptual frameworks in studies of subjective time perception. Its utility has been well established, but it has been criticised for its lack of neurophysiological support; few studies attempted to systematically identify its components and their neural correlates. Previous studies established that the dorsolateral prefrontal cortex (DLPFC) was associated with working memory tasks and a correlation between activity in the cerebellum and the timing of tasks. An fMRI study was conducted to confirm that these two cortical regions were activated during the execution of a new time discrimination task that considers individual variations in subjective time perception. Simulations were conducted to optimize the electrode placement in order to maximize the electric fields of tDCS perturbation to these two areas. According to the attentional gate model, hypotheses about tDCS perturbation to subjective time perception, attention and working memory were formulated and tested. Attention and working memory were measured by the attention network and N-back tasks. There are weak effects to the perceived subjective equivalent and the reaction time in the attention network task, but both are not statistically significant after correction for multiple comparisons. Exploration analyses show a link between attention and subjective time perception after tDCS perturbation. To conclude, the results do not support the attentional gate model, but show a linkage between attention and subjective time perception in terms of similar neural circuits and their relationships under certain circumstances.

Examining social context and the pathways to mental wellness in young adults during social movement: A parallel mediation analysis.

BACKGROUND: Good family relationships are important for mental health. However, the mechanism linking family perceptions to mental wellness during political and social turmoil remains unclear. This study aimed to examine whether psychological and social factors could protect university students from detrimental mental health conditions in a time of social chaos. METHODS: Participants included young adults (n = 1874, mean age = 22.19 years) who had been enrolled in Hong Kong local tertiary intuitions during Hong Kong's 2019 social movement. An online survey assessing various conditions, including family satisfaction, social support, personal resilience, negative moods, sense of school belonging, and mental health conditions before and during the movement, was administered to these students. Mediation analyses were performed to examine the role of negative affect, support from family, and school belongingness as mediators of the association between family satisfaction and mental health condition during the movement overall and by resilience subgroups. RESULTS: Higher levels of satisfaction with family relationships before the onset of movement was associated with lower levels of negative affect and higher levels of support from family and school belongingness during the movement, in turn benefiting the student's mental health. The links of family satisfaction and school belongingness with mental wellness were particularly strong among low-resilient students. LIMITATIONS: Mediation analysis using retrospective survey data CONCLUSIONS: Family conditions would interact with personal resilience to influence mental health status during social turmoil. The findings underscore the importance of early interventions particularly for those students facing family difficulties to enhance their social chaos and emergency preparedness.

The perception of time while perceiving dynamic emotional faces.

Emotion plays an essential role in the perception of time such that time is perceived to "fly" when events are enjoyable, while unenjoyable moments are perceived to "drag." Previous studies have reported a time-drag effect when participants are presented with emotional facial expressions, regardless of the emotion presented. This effect can hardly be explained by induced emotion given the heterogeneous nature of emotional expressions. We conducted two experiments (n = 44 and n = 39) to examine the cognitive mechanism underlying this effect by presenting dynamic sequences of emotional expressions to participants. Each sequence started with a particular expression, then morphed to another. The presentation of dynamic facial expressions allows a comparison between the time-drag effect of homogeneous pairs of emotional expressions sharing similar valence and arousal to heterogeneous pairs. Sequences of seven durations (400, 600, 800, 1000, 1200, 1400, 1600 ms) were presented to participants, who were asked to judge whether the sequences were closer to 400 or 1600 ms in a two-alternative forced choice task. The data were then collated according to conditions and fit into cumulative Gaussian curves to estimate the point of subjective equivalence indicating the perceived duration of 1000 ms. Consistent with previous reports, a feeling of "time dragging" is induced regardless of the sequence presented, such that 1000 ms is perceived to be longer than 1000 ms. In addition, dynamic facial expressions exert a greater effect on perceived time drag than static expressions. The effect is most prominent when the dynamics involve an angry face or a change in valence. The significance of this sensitivity is discussed in terms of emotion perception and its evolutionary significance for our attention mechanism.

A basic need theory approach to problematic Internet use and the mediating effect of psychological distress.

The Internet provides an easily accessible way to meet certain needs. Over-reliance on it leads to problematic use, which studies show can be predicted by psychological distress. Self-determination theory proposes that we all have the basic need for autonomy, competency, and relatedness. This has been shown to explain the motivations behind problematic Internet use. This study hypothesizes that individuals who are psychologically disturbed because their basic needs are not being met are more vulnerable to becoming reliant on the Internet when they seek such needs satisfaction from online activities, and tests a model in which basic needs predict problematic Internet use, fully mediated by psychological distress. Problematic Internet use, psychological distress, and basic needs satisfaction were psychometrically measured in a sample of 229 Hong Kong University students and structural equation modeling was used to test the hypothesized model. All indices showed the model has a good fit. Further, statistical testing supported a mediation effect for psychological distress between needs satisfaction and problematic Internet use. The results extend our understanding of the development and prevention of problematic Internet use based on the framework of self-determination theory. Psychological distress could be used as an early predictor, while preventing and treating problematic Internet use should emphasize the fulfillment of unmet needs.

Interaction between complex motion patterns in the perception of shape.

We investigated how different types of complex motion patterns interact in the perception of shape. We used global dot-motion stimuli which consisted of two superimposed groups of dots; one group of dots moved along an ellipsoidal trajectory (target pattern), while the other group of dots was divided into quadrants with dots in alternating sectors moving in radial expanding and radial contracting directions (background pattern). In the first experiment, observers judged whether the major axis of an ellipsoidal motion pattern oriented at 45 degrees or -45 degrees from vertical lay to the right or to the left of a central vertical line. Ellipsoids with different aspect ratios, which controlled both the tilt (left or right of vertical) and the extent of ellipsoidal curvature, were presented to observers using method of constant stimuli. The appearance of the ellipsoidal target pattern was distorted in the presence of background motion. The aspect ratio of the target at which observers perceived the figure to be circular was approximately 0.86 (an aspect ratio of 1.0 indicates a circle), with the pattern's major axis lying in the two sectors that contained contracting motion. This finding may constitute evidence that background motion distorts the perception of space, resulting in a distorted target pattern. However, the distortion effect is limited to conditions for which the speed of the target pattern and background pattern was slow and high contrast, and for when dots forming the target and background patterns were of the same luminance polarity.

Global speed averaging is tuned for binocular disparity.

The extent to which local speeds at different depths are averaged to determine global speed was determined using a version of the Global Dot Motion (GDM) stimulus. Judgments of the apparent speed of fast moving dots (4.05-10.53 deg/s) in the presence of slow moving dots (4.05 deg/s) were measured using GDM stimuli which simulated radially expanding motion, and which confined slow and fast speed dots exclusively to alternating wedge shaped sectors. The presence of slow moving dots in the stimulus reduced the apparent speed of high-speed dots in a manner consistent with speed averaging. However with increases in depth, produced by a difference in binocular disparity between dots in alternating sectors, speed averaging became less effective, and the relationship between speed and disparity resembled a tuning function. We discuss our results in light of research that clarifies the functional properties of global motion mechanisms in the primate cortex.