Experimental-analytical approach to assessing mechanosensitive cartilage blood marker kinetics in healthy adults: dose-response relationship and interrelationship of nine candidate markers

Purpose: To determine the suitability of selected blood biomarkers of articular cartilage as mechanosensitive markers and to investigate the dose-response relationship between ambulatory load magnitude and marker kinetics in response to load. Methods: Serum samples were collected from 24 healthy volunteers before and at three time points after a 30-minute walking stress test performed on three test days. In each experimental session, one of three ambulatory loads was applied: 100% body weight (BW); 80%BW; 120%BW. Serum concentrations of COMP, MMP-3, MMP-9, ADAMTS-4, PRG-4, CPII, C2C and IL-6 were assessed using commercial enzyme-linked immunosorbent assays. A two-stage analytical approach was used to determine the suitability of a biomarker by testing the response to the stress test (criterion I) and the dose-response relationship between ambulatory load magnitude and biomarker kinetics (criterion II). Results. COMP, MMP-3 and IL-6 at all three time points after, MMP-9 at 30 and 60 minutes after, and ADAMTS-4 and CPII at immediately after the stress test showed an average response to load or an inter-individual variation in response to load of up to 25% of pre-test levels. The relation to load magnitude on average or an inter-individual variation in this relationship was up to 8% from load level to load level. There was a positive correlation for the slopes of the change-load relationship between COMP and MMP-3, and a negative correlation for the slopes between COMP, MMP-3 and IL-6 with MMP-9, and COMP with IL6. Conclusions: COMP, MMP-3, IL-6, MMP-9, and ADAMTS-4 warrant further investigation in the context of articular cartilage mechanosensitivity and its role in joint degeneration and OA. While COMP seems to be able to reflect a rapid response, MMP-3 seems to reflect a slightly longer lasting, but probably also more distinct response. MMP-3 showed also the strongest association with the magnitude of load.

EEG signatures change during unilateral Yogi nasal breathing

Airflow through the left-and-right nostrils is said to be entrained by an endogenous nasal cycle paced by both poles of the hypothalamus. Yogic practices suggest, and scientific evidence demonstrates, that right-nostril breathing is involved with relatively higher sympathetic activity (arousal states), while left-nostril breathing is associated with a relatively more parasympathetic activity (stress alleviating state). The objective of this study was to further explore this laterality by controlling nasal airflow and observing patterns of cortical activity through encephalographic (EEG) recordings. Thirty subjects participated in this crossover study. The experimental session consisted of a resting phase (baseline), then a period of unilateral nostril breathing (UNB) using the dominant nasal airway, followed by UNB using the non-dominant nasal airway. A 64-channel EEG was recorded throughout the whole session. The effects of nostril-dominance, and nostril-lateralization were assessed using the power spectral density of the neural activity. The differences in power-spectra and source localization were calculated between EEG recorded during UNB and baseline for delta, theta, alpha, beta and gamma bands. Cluster-based permutation tests showed that compared to baseline, EEG spectral power was significantly (1) decreased in all frequency bands for non-dominant nostril UNB, (2) decreased in alpha, beta and gamma bands for dominant nostril UNB, (3) decreased in all bands for left nostril UNB, and (4) decreased in all bands except delta for right nostril UNB. The beta band showed the most widely distributed changes across the scalp. our source localisation results show that breathing with the dominant nostril breathing increases EEG power in the left inferior frontal (alpha band) and left parietal lobule (beta band), whereas non-dominant nostril breathing is related to more diffuse and bilateral effects in posterior areas of the brain.These preliminary findings may stimulate further research in the area, with potential applications to tailored treatment of brain disorders associated with disruption of sympathetic and parasympathetic activity.

Detecting the Speed Change Intention from EEG Signals: From the Offline and Pseudo-Online Analysis to an Online Closed-Loop Validation

Control of assistive devices by voluntary user intention is an underdeveloped topic in the Brain–Machine Interfaces (BMI) literature. In this work, a preliminary real-time BMI for the speed control of an exoskeleton is presented. First, an offline analysis for the selection of the intention patterns based on the optimum features and electrodes is proposed. This is carried out comparing three different classification models: monotonous walk vs. increasing and decreasing change speed intentions, monotonous walk vs. only increasing intention, and monotonous walk vs. only decreasing intention. The results indicate that, among the features tested, the most suitable parameter to represent these models are the Hjorth statistics in alpha and beta frequency bands. The average offline classification accuracy for the offline cross-validation of the three models obtained is 68 ± 11%. This selection is also tested following a pseudo-online analysis, simulating a real-time detection of the subject’s intentions to change speed. The average results indices of the three models during this pseudoanalysis are of a 42% true positive ratio and a false positive rate per minute of 9. Finally, in order to check the viability of the approach with an exoskeleton, a case of study is presented. During the experimental session, the pros and cons of the implementation of a closed-loop control of speed change for the H3 exoskeleton through EEG analysis are commented.

EVM: An Educational Virtual Reality Modeling Tool; Evaluation Study with Freshman Engineering Students

Educational Virtual Modeling (EVM) is a novel VR-based application for sketching and modeling in an immersive environment designed to introduce freshman engineering students to modeling concepts and reinforce their understanding of the spatial connection between an object and its 2D projections. It was built on the Unity 3D game engine and Microsoft’s Mixed Reality Toolkit (MRTK). EVM was designed to support the creation of the typical parts used in exercises in basic engineering graphics courses with a special emphasis on a fast learning curve and a simple way to provide exercises and tutorials to students. To analyze the feasibility of using EVM for this purpose, a user study was conducted with 23 freshmen and sophomore engineering students that used both EVM and Trimble SketchUp to model six parts using an axonometric view as the input. Students had no previous experience in any of the two systems. Each participant went through a brief training session and was allowed to use each tool freely for 20 min. At the end of the modeling exercises with each system, the participants rated its usability by answering the System Usability Scale (SUS) questionnaire. Additionally, they filled out a questionnaire for assessment of the system functionality. The results demonstrated a very high SUS score for EVM (M = 92.93, SD = 6.15), whereas Trimble SketchUp obtained only a mean score of 76.30 (SD = 6.69). The completion time for the modeling tasks with EVM showed its suitability for regular class use, despite the fact that it usually takes longer to complete the exercises in the system than in Trimble SketchUp. There were no statistically significant differences regarding functionality assessment. At the end of the experimental session, participants were asked to express their opinion about the systems and provide suggestions for the improvement of EVM. All participants showed a preference for EVM as a potential tool to perform exercises in the engineering graphics course.

Metamemory for Prospective Memory Performance in Younger and Older Adults: Does the Reference Point Affect our Judgments?

The present study investigated age differences in the ability to predict prospective memory (PM) performance. A sample of younger (N = 88) and older (N = 88) participants completed an event-based PM task embedded in an ongoing task. Metamemory was measured by asking participants to predict their performance before completing the PM task and complete some questionnaires on self-perceptions of everyday memory ability. We manipulated A) the reference point used to evaluate performance and B) the order of presentation of the instruments. One group of participants predicted their upcoming performance with a general confidence rating (performance condition) whereas a different group predicted their performance in comparison to other people of their age (peers condition). The metamemory questionnaires were completed either at the beginning of the experimental session or after the PM task, in a counterbalanced order. In terms of performance, we did not observe age differences in PM. In terms of metamemory, younger and older participants were similarly underconfident in the performance condition and overconfident in the peers condition. Moreover, older adults reported significantly better PM abilities than younger adults, and participants generally reported more memory failures when the metamemory questionnaires were administered after the PM task and in the performance condition. These findings show that both younger and older adults have limited metacognitive insights, and point to reactive effects of metamemory to metacognitive reference point and order of administration of the instruments.

Stress and the Cardiovascular System

<p>The research reported in this thesis is primarily concerned with systemic arterial pulse transit time (PTT) which is of physiological significance because it is the most appropriate indicator of arterial compliance, the primary determinant of cardiac load, PTT acceleration or deceleration being associated with an increase or decrease in cardiac load respectively. Initially, PTT was investigated in the context of active/passive coping. Obrist, et al., (1978) proposed that active coping is generated by tasks of moderate difficulty and is characterized by large, sustained cardiac accelerations. Interbeat interval (IBI) was measured as the reference response for active/passive coping. The assumption is that active coping is the behavioural state which provides the link between psychological stress and hypertension. However, contemporary cardiovascular physiologists put more emphasis on arterial compliance than IBI because it is not only significant in essential hypertension, but is also a critical determinant of circulation efficiency in health and disease. In Experiment 1 men and women completed mental arithmetic, problem solving, reaction time and personal tempo (voluntary button pressing). Acceleratory and deceleratory PTT changes were found during all tasks; IBI changes were predominantly acceleratory and their magnitude was determined by task difficulty. In Experiment 2 subjects completed problem solving tasks at two levels of difficulty. The results confirmed that unexplained directional variability characterized PTT changes and acceleration characterized IBI changes. It was hypothesized that subject state could be a determinant of PTT response direction. In Experiment 3 the State-Trait Anxiety Inventory, the Stress Arousal Checklist, the Eysenck Personality Inventory and the Jenkins Activity Survey were administered before problem solving at three levels of difficulty and personal tempo were completed. PTT directional variability was not accounted for by any of the measures used. IBI changes were again acceleratory and their magnitude was determined by task difficulty. Two extensions of the active/passive coping hypothesis were proposed: 1) that task difficulty and magnitude of IBI change are related along a continuum of behavioural coping; 2) that task type, not difficulty, determines the frequency of IBI acceleration. The effect of task contingency on IBI change was identified as requiring more detailed investigation. It was further hypothesized that relative subject state as measured by a change in resting IBI (Malmo, 1959) could predict the direction of PTT change during task. In Experiment 4 subjects completed all tasks from Experiment 3 in both parts of an extended experimental session. Half the subjects ingested caffeine. IBI decelerated during baseline from part 1 to part 2 and deceleratory PTT changes dominated task responding in part 2. However, a caffeine-induced deceleration in IBI across baselines was not associated with deceleratory PTT change, and directional variability continued to characterize PTT changes. In order to eliminate the directional variability of PTT changes during tasks a further experiment was undertaken which manipulated relative behavioural state prior to task by informing subjects on their first attendance at the laboratory that they would be required to perform a demanding problem solving task on their fifth attendance. From sessions 1 to 4 subjects attended the laboratory for short rest periods only during which cardiovascular activity was recorded. On the fifth session subjects also completed a task. In that experiment (Experiment 5), IBI acceleration over multiple session baselines in anticipation of a task was associated with uniformly acceleratory PTT changes during tasks, supporting the hypothesis that subject initial state is an important determinant of the direction of PTT change, and hence in whether cardiac load increases or decreases under stress.</p>

Stress and the Cardiovascular System

<p>The research reported in this thesis is primarily concerned with systemic arterial pulse transit time (PTT) which is of physiological significance because it is the most appropriate indicator of arterial compliance, the primary determinant of cardiac load, PTT acceleration or deceleration being associated with an increase or decrease in cardiac load respectively. Initially, PTT was investigated in the context of active/passive coping. Obrist, et al., (1978) proposed that active coping is generated by tasks of moderate difficulty and is characterized by large, sustained cardiac accelerations. Interbeat interval (IBI) was measured as the reference response for active/passive coping. The assumption is that active coping is the behavioural state which provides the link between psychological stress and hypertension. However, contemporary cardiovascular physiologists put more emphasis on arterial compliance than IBI because it is not only significant in essential hypertension, but is also a critical determinant of circulation efficiency in health and disease. In Experiment 1 men and women completed mental arithmetic, problem solving, reaction time and personal tempo (voluntary button pressing). Acceleratory and deceleratory PTT changes were found during all tasks; IBI changes were predominantly acceleratory and their magnitude was determined by task difficulty. In Experiment 2 subjects completed problem solving tasks at two levels of difficulty. The results confirmed that unexplained directional variability characterized PTT changes and acceleration characterized IBI changes. It was hypothesized that subject state could be a determinant of PTT response direction. In Experiment 3 the State-Trait Anxiety Inventory, the Stress Arousal Checklist, the Eysenck Personality Inventory and the Jenkins Activity Survey were administered before problem solving at three levels of difficulty and personal tempo were completed. PTT directional variability was not accounted for by any of the measures used. IBI changes were again acceleratory and their magnitude was determined by task difficulty. Two extensions of the active/passive coping hypothesis were proposed: 1) that task difficulty and magnitude of IBI change are related along a continuum of behavioural coping; 2) that task type, not difficulty, determines the frequency of IBI acceleration. The effect of task contingency on IBI change was identified as requiring more detailed investigation. It was further hypothesized that relative subject state as measured by a change in resting IBI (Malmo, 1959) could predict the direction of PTT change during task. In Experiment 4 subjects completed all tasks from Experiment 3 in both parts of an extended experimental session. Half the subjects ingested caffeine. IBI decelerated during baseline from part 1 to part 2 and deceleratory PTT changes dominated task responding in part 2. However, a caffeine-induced deceleration in IBI across baselines was not associated with deceleratory PTT change, and directional variability continued to characterize PTT changes. In order to eliminate the directional variability of PTT changes during tasks a further experiment was undertaken which manipulated relative behavioural state prior to task by informing subjects on their first attendance at the laboratory that they would be required to perform a demanding problem solving task on their fifth attendance. From sessions 1 to 4 subjects attended the laboratory for short rest periods only during which cardiovascular activity was recorded. On the fifth session subjects also completed a task. In that experiment (Experiment 5), IBI acceleration over multiple session baselines in anticipation of a task was associated with uniformly acceleratory PTT changes during tasks, supporting the hypothesis that subject initial state is an important determinant of the direction of PTT change, and hence in whether cardiac load increases or decreases under stress.</p>

Emergent Prosocial Behavior During Dynamic Human Group Formation

For scientists, policy makers, and the general population, there is increasing interest in how humans form cooperative groups. However, how group-oriented behavior emerges during the dynamic process of group formation is still unknown. We hypothesize that humans will exhibit emergent prosocial behavior as their immediate group size increases. Using a network-embedded-dyad prisoner dilemma task, with periodic opportunities to retain or remove group members, we find subjects consistently follow a well-performing reciprocal base policy (tit-for-tat-like) across the experimental session. However, subjects’ strategies also became more forgiving and less exploitative as group size increased, with a default preference shift to cooperation. Thus, human cooperation may emerge from a desire to create and maintain larger and more cooperative groups, and multiscale strategy that considers both self-interest and group-interest.

Struggles and strategies in anaerobic and aerobic cycling tests: A mixed-method approach with a focus on tailored self-regulation strategies

Endurance sports pose a plethora of mental demands that exercisers have to deal with. Unfortunately, investigations of exercise-specific demands and strategies to deal with them are insufficiently researched, leading to a gap in knowledge about athletic requirements and strategies used to deal with them. Here, we investigated which obstacles exercisers experience during an anaerobic (Wingate test) and an aerobic cycling test (incremental exercise test), as well as the strategies they considered helpful for dealing with these obstacles (qualitative analysis). In addition, we examined whether thinking of these obstacles and strategies in terms of if-then plans (or implementation intentions; i.e., “If I encounter obstacle O, then I will apply strategy S!”) improves performance over merely setting performance goals (i.e., goal intentions; quantitative analysis). N = 59 participants (age: M = 23.9 ± 6.5 years) performed both tests twice in a 2-within (Experimental session: 1 vs. 2) × 2-between (Condition: goal vs. implementation intention) design. Exercisers’ obstacles and strategies were assessed using structured interviews in Session 1 and subjected to thematic analysis. In both tests, feelings of exertion were the most frequently stated obstacle. Motivation to do well, self-encouragement, and focus on the body and on cycling were frequently stated strategies in both tests. There were also test-specific obstacles, such as boredom reported in the aerobic test. For session 2, the obstacles and strategies elicited in Session 1 were used to specify if-then plans. Bayesian mixed-factor ANOVA suggests, however, that if-then plans did not help exercisers to improve their performance. These findings shed novel light into the mental processes accompanying endurance exercise and the limits they pose on performance.

Positive moods are all alike? Differential affect amplification effects of ‘elated’ versus ‘calm’ mental im-agery in young adults reporting hypomanic-like experiences

Positive mood amplification is a hallmark of the bipolar disorder spectrum (BPDS). We need bet-ter understanding of cognitive mechanisms leading to such elevated mood. Generation of vivid, emo-tionally compelling mental imagery is proposed to act as an ‘emotional amplifier’ in BPDS.We used a positive mental imagery generation paradigm to manipulate affect in a subclinical BPDS-relevant sample reporting high (n=31) vs. low (n=30) hypomanic-like experiences on the Mood Dis-order Questionnaire (MDQ). Participants were randomized to an ‘elated’ or ‘calm’ mental imagery condi-tion, rating their momentary affect four times across the experimental session. We hypothesized greater affect increase in the high (vs. low) MDQ group assigned to the elated (vs. calm) imagery generation condition. We further hypothesized that this change would be driven by increases in the types of affect typically associated with (hypo)mania, i.e., suggestive of high activity lev-els.Mixed model and time-series analysis showed that for the high MDQ group, affect increased steeply and in a sustained manner over time in the ‘elated’ imagery condition, and more shallowly in ‘calm’. The low-MDQ group did not show this amplification effect. Analysis of affect clusters showed high-MDQ mood amplification in the ‘elated’ imagery condition was most pronounced for active affective states. This experimental model of BPDS-relevant mood amplification shows evidence that positive men-tal imagery drives changes in affect in the high MDQ group in a targeted manner. Findings inform cogni-tive mechanisms of mood amplification, and spotlight prevention strategies targeting elated imagery, while potentially retaining calm imagery to preserve adaptive positive emotionality.