Measuring task-related changes in heart rate variability

Identifying physiological indicators of the cognitive, thermal, and combined (cognitive-thermal) stress conditions

Physiologically based stress detection systems have proven to be effective in identifying different stress conditions in the body to determine the source of stress and be able to counteract it. However, some stress conditions have not been widely studied, including thermal stress, cognitive stress, and combined (thermal-cognitive) stress conditions, which are frequently encountered in work or school environments. In order to develop systems to detect and differentiate these conditions, it is necessary to identify the physiological indicators that characterize each of them. The present research aims to identify which physiological indicators (heart rate, respiratory rate, galvanic skin response, and local temperature) could differentiate different stress conditions (no-stress, cognitive stress, thermal stress, and combined (thermal-cognitive) stress conditions). Thirty participants were exposed to cognitive, thermal, and combined stress sources while recording their physiological signals. The findings indicate that both mean heart rate and mean galvanic skin response identify moderate thermal and cognitive stress conditions as distinct from a no-stress condition, yet they do not differentiate between the two stress conditions. Additionally, heart rate uniquely identifies the cognitive-thermal stress condition, effectively distinguishing this combined stress condition from the singular stress conditions and the no-stress condition. Mean local temperature specifically signals thermal stress conditions, whereas mean respiratory rate accurately identifies cognitive stress conditions, with both indicators effectively separating these conditions from each other and from the no-stress condition. This is the first basis for differentiating thermal and cognitive stress conditions through physiological indicators.

Investigating the effectiveness of immersive VR skill training and its link to physiological arousal

This paper details the motivations, design, and analysis of a study using a fine motor skill training task in both VR and physical conditions. The objective of this between-subjects study was to (a) investigate the effectiveness of immersive virtual reality for training participants in the 'buzz-wire' fine motor skill task compared to physical training and (b) investigate the link between participants' arousal with their improvements in task performance. Physiological arousal levels in the form of  electro-dermal activity (EDA) and ECG (Electrocardiogram) data were collected from 87 participants, randomly distributed across the two conditions. Results indicated that VR training is as good as, or even slightly better than, training in physical training in improving task performance. Moreover, the participants in the VR condition reported an increase in self-efficacy and immersion, while marginally significant differences were observed in the presence and the temporal demand (retrieved from NASA-TLX measurements). Participants in the VR condition showed on average less arousal than those in the physical condition. Though correlation analyses between performance metrics and arousal levels did not depict any statistically significant results, a closer examination of EDA values revealed that participants with lower arousal levels during training, across conditions, demonstrated better improvements in performance than those with higher arousal. These findings demonstrate the effectiveness of VR in training and the potential of using arousal and training performance data for designing adaptive VR training systems. This paper also discusses implications for researchers who consider using biosensors and VR for motor skill experiments.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10055-022-00699-3.

Association between distinct coping styles and heart rate variability changes to an acute psychosocial stress task

Modern life comprises a myriad of stressful situations, ranging from life-threatening ones to others not so deadly, all of which activate a physiologic stress response. Engaging in healthy ways to cope can prevent us from wearing out our physiological systems. Heart rate variability (HRV) is often used as an index of emotion regulation response. Hence, our goal is to investigate whether the habitual use of coping strategies is related to a distinct pattern of HRV changes when the individual is exposed to a moderate psychosocial stressor. In this study, 60 female participants performed a psychosocial stress task-oral speech preparation-while ECG signals were collected during the whole experimental procedure. Heart rate (HR), HRV parameters (SDNN, RMSSD, LF, HF) and coping strategies (Brief COPE) were registered. Participants were divided into two groups (low and high groups) as a function of their scores on the maladaptive and adaptive coping strategies of the Brief COPE. As expected, the task alone induced increases in heart rate and reductions in HRV parameters. Additionally, the analyses revealed a different pattern of HRV (SDNN, RMSSD, LF and HF) changes in response to the stressor, with participants using less maladaptive strategies being able to maintain the HRV at baseline levels when confronting the stressor, while those using more maladaptive strategies reducing HRV during the task. These results show a different pattern of HRV changes as a function of the coping style, suggesting a possible autonomic advantage, namely, the maintenance of HRV, in individuals who use maladaptive coping strategies less frequently.

Effects of Dynamic Resilience on the Reactivity of Vagally Mediated Heart Rate Variability

Dynamic resilience is a novel concept that aims to quantify how individuals are coping while operating in dynamic and complex task environments. A recently developed dynamic resilience measure, derived through autoregressive modeling, offers an avenue toward dynamic resilience classification that may yield valuable information about working personnel for industries such as defense and elite sport. However, this measure classifies dynamic resilience based upon in-task performance rather than self-regulating cognitive structures; thereby, lacking any supported self-regulating cognitive links to the dynamic resilience framework. Vagally mediated heart rate variability (vmHRV) parameters are potential physiological measures that may offer an opportunity to link self-regulating cognitive structures to dynamic resilience given their supported connection to the self-regulation of stress. This study examines if dynamic resilience classifications reveal significant differences in vagal reactivity between higher, moderate and lower dynamic resilience groups, as participants engage in a dynamic, decision-making task. An amended Three Rs paradigm was implemented that examined vagal reactivity across six concurrent vmHRV reactivity segments consisting of lower and higher task load. Overall, the results supported significant differences between higher and moderate dynamic resilience groups' vagal reactivity but rejected significant differences between the lower dynamic resilience group. Additionally, differences in vagal reactivity across vmHRV reactivity segments within an amended Three Rs paradigm were partially supported. Together, these findings offer support toward linking dynamic resilience to temporal self-regulating cognitive structures that play a role in mediating physiological adaptations during task engagement.

Non-contact imaging of peripheral hemodynamics during cognitive and psychological stressors

Peripheral hemodynamics, measured via the blood volume pulse and vasomotion, provide a valuable way of monitoring physiological state. Camera imaging-based systems can be used to measure these peripheral signals without contact with the body, at distances of multiple meters. While researchers have paid attention to non-contact imaging photoplethysmography, the study of peripheral hemodynamics and the effect of autonomic nervous system activity on these signals has received less attention. Using a method, based on a tissue-like model of the skin, we extract melanin [Formula: see text] and hemoglobin [Formula: see text] concentrations from videos of the hand and face and show that significant decreases in peripheral pulse signal power (by 36% ± 29%) and vasomotion signal power (by 50% ± 26%) occur during periods of cognitive and psychological stress. Via three experiments we show that similar results are achieved across different stimuli and regions of skin (face and hand). While changes in peripheral pulse and vasomotion power were significant the changes in pulse rate variability were less consistent across subjects and tasks.

StressFoot: Uncovering the Potential of the Foot for Acute Stress Sensing in Sitting Posture

Stress is a naturally occurring psychological response and identifiable by several body signs. We propose a novel way to discriminate acute stress and relaxation, using movement and posture characteristics of the foot. Based on data collected from 23 participants performing tasks that induced stress and relaxation, we developed several machine learning models to construct the validity of our method. We tested our models in another study with 11 additional participants. The results demonstrated replicability with an overall accuracy of 87%. To also demonstrate external validity, we conducted a field study with 10 participants, performing their usual everyday office tasks over a working day. The results showed substantial robustness. We describe ten significant features in detail to enable an easy replication of our models.

Assessing Physiological Stress Responses to Word Retrieval in Individuals with Aphasia: A Preliminary Study

OBJECTIVE

Word retrieval difficulty can be distressing for individuals with aphasia. However, physiological stress responses to word retrieval are relatively unstudied. This study aims to measure the physiological response (i.e., heart rate and respiratory rate) and perceived stress in individuals with aphasia during a naming task to understand whether word retrieval may be a stressor to them.

METHOD

An aphasia group (n = 7) and a healthy group (n = 38) participated in 4 experimental conditions, including rest, counting, and high-frequency and low-frequency word conditions, while their physiological parameters were measured throughout the sessions. Stress ratings were also obtained for each condition.

RESULTS

Significant differences in heart rate were found while participants were engaged in speech and/or language tasks, compared to the rest condition, for both groups. Significant differences in respiratory rate were found between the rest and low-frequency word conditions in the aphasia group. No significant difference was found in heart rate between 2 groups, but a difference in respiratory rate was found between 2 groups in the low-frequency word condition. There were some discrepancies between stress level and physiological parameters.

CONCLUSIONS

Individuals with aphasia perceived greater stress in the naming tasks, however, the perceived stress was not necessarily parallel to the physiological parameters.

The mediating role of hippocampal networks on stress regulation in amnestic mild cognitive impairment

Objectives

To examine the role of the hippocampus in stress regulation in older adults with amnestic mild cognitive impairment (aMCI).

Methods

This study combined resting-state functional MRI, structural MRI, self-reported chronic stress exposure, and an electrocardiography-based acute stress protocol to compare aMCI group (n = 17) to their cognitively healthy counterparts (HC, n = 22).

Results

For the entire sample, there was a positive correlation between chronic stress exposure and acute stress regulation. The aMCI group showed significantly smaller volumes in the right hippocampus than HC. The two groups did not differ in chronic stress exposure or acute stress regulation. In the HC group, the left hippocampal connectivity with inferior parietal lobe was significantly correlated with both the chronic stress and acute stress. In the aMCI group, the left hippocampal connectivity with both the right insula and the left precentral gyrus was significantly correlated to chronic stress exposure and acute stress regulation. Additionally, the left hippocampal connectivity with right insula significantly mediated the relationship between chronic stress exposure and acute stress regulation in aMCI group.

Conclusions

Extra hippocampal networks may be recruited as compensation to attend the maintenance of relatively normal stress regulation in aMCI by alleviating the detrimental effects of chronic stress exposure on acute stress regulation.

Mental Workload Alters Heart Rate Variability, Lowering Non-linear Dynamics

Mental workload is known to alter cardiovascular function leading to increased cardiovascular risk. Nevertheless, there is no clear autonomic nervous system unbalance to be quantified during mental stress. We aimed to characterize the mental workload impact on the cardiovascular function with a focus on heart rate variability (HRV) non-linear indexes. A 1-h computerized switching task (letter recognition) was performed by 24 subjects while monitoring their performance (accuracy, response time), electrocardiogram and blood pressure waveform (finger volume clamp method). The HRV was evaluated from the beat-to-beat RR intervals (RRI) in time-, frequency-, and informational- domains, before (Control) and during the task. The task induced a significant mental workload (visual analog scale of fatigue from 27 ± 26 to 50 ± 31 mm, p < 0.001, and NASA-TLX score of 56 ± 17). The heart rate, blood pressure and baroreflex function were unchanged, whereas most of the HRV parameters markedly decreased. The maximum decrease occurred during the first 15 min of the task (P1), before starting to return to the baseline values reached at the end of the task (P4). The RRI dimension correlation (D2) decrease was the most significant (P1 vs. Control: 1.42 ± 0.85 vs. 2.21 ± 0.8, p < 0.001) and only D2 lasted until the task ended (P4 vs. Control: 1.96 ± 0.9 vs. 2.21 ± 0.9, p < 0.05). D2 was identified as the most robust cardiovascular variable impacted by the mental workload as determined by posterior predictive simulations (p = 0.9). The Spearman correlation matrix highlighted that D2 could be a marker of the generated frustration (R = -0.61, p < 0.01) induced by a mental task, as well as the myocardial oxygen consumption changes assessed by the double product (R = -0.53, p < 0.05). In conclusion, we showed that mental workload sharply lowered the non-linear RRI dynamics, particularly the RRI correlation dimension.

Decreased Task-Related HRV Is Associated With Inhibitory Dysfunction Through Functional Inter-Region Connectivity of PFC in Major Depressive Disorder

The regulation of the autonomic nervous system (ANS) can improve cognitive function in major depressive disorders (MDD). Heart rate variability (HRV) derives from the dynamic control of the ANS and reflects the balance between the activities of the sympathetic and parasympathetic nervous systems by measuring tiny changes in adjacent heart beats. Task-related HRV may reflect the association between the flexibility of cognition and ANS function. The study was to investigate the neural mechanism of interactions between ANS and cognitive function in MDD with Magnetoencephalography (MEG) measurements. Participants included 20 MDD patients and 18 healthy controls (HCs). All participants were measured with a go/no-go task MEG. HRV indices, the standard deviation of the average normal-to-normal (NN) interval calculated over short periods (SDANN) and the square root of the mean squared differences of successive NN intervals (RMSSD), were derived from the raw MEG data. Results showed that MDD patients showed decreased SDANN and RMSSD. In MDD patients, both resting-state and task-related RMSSD were related to inhibitory and control dysfunction. In the go/no-go task, many areas in the prefrontal cortex (PFC) are responsible for an individual's inhibitory function. A brain MEG functional connectivity analysis revealed that there were significant differences in four brain regions within the prefrontal cortex (PFC) between MDD patients and HCs. Task-related RMSSD in HCs were related to the functional connectivity between the left middle frontal gyrus and the anterior cingulate cortex (ACC), while in MDD patients, these values were not related to the above functional connectivity but were related to the functional connectivity between the left middle frontal gyrus and insula. However, the resting-state RMSSD value was not related to these significant difference functional connectivity networks in all participants. It concludes that the decreased task-related HRV is associated with inhibitory dysfunction through functional inter-region connectivity in the PFC in MDD, and the task-related HRV can be used as an index of the association between MDD and autonomic dysregulation.

Combined effect of prefrontal transcranial direct current stimulation and a working memory task on heart rate variability

Prefrontal cortex activity has been associated with changes to heart rate variability (HRV) via mediation of the cortico-subcortical pathways that regulate the parasympathetic and sympathetic branches of the autonomic nervous system. Changes in HRV due to altered prefrontal cortex functioning can be predicted using the neurovisceral integration model, which suggests that prefrontal hyperactivity increases parasympathetic tone and decreases contributions from the sympathetic nervous system. Working memory (WM) tasks and transcranial direct current stimulation (tDCS) have been used independently to modulate brain activity demonstrating changes to HRV in agreement with the model. We investigated the combined effects of prefrontal tDCS and a WM task on HRV. Bifrontal tDCS was administered for 15 minutes at 2mA to 20 participants in a sham controlled, single-blind study using parallel groups. A WM task was completed by participants at three time points; pre-, during-, and post-tDCS, with resting state data collected at similar times. Frequency-domain HRV was computed for high frequency (HF; 0.15-0.4Hz) and low frequency (LF; 0.04-0.15Hz) power reflecting parasympathetic and sympathetic branch activity, respectively. Response time on the WM task, but not accuracy, improved from baseline to during-tDCS and post-tDCS with sham, but not active, stimulation. HF-HRV was significantly increased in the active tDCS group compared to sham, lasting beyond cessation of stimulation. Additionally, HF-HRV showed a task-related reduction in power during performance on the WM task. Changes in LF-HRV were moderately inversely correlated (r > 0.4) with changes in WM accuracy during and following tDCS compared to baseline levels. Stimulation of the prefrontal cortex resulted in changes to the parasympathetic branch of the nervous system in agreement with a linearly additive interpretation of effects. Sympathetic activity was not directly altered by tDCS, but was correlated with changes in WM performance. This suggests that the parasympathetic and sympathetic branches respond differentially due to similar, but distinct neural pathways. Given the ease of HRV data collection, studies of prefrontal tDCS would benefit from collection of this data as it provides unique insight into tDCS effects resulting from propagation through brain networks.

Remote measurement of cognitive stress via heart rate variability

Remote detection of cognitive load has many powerful applications, such as measuring stress in the workplace. Cognitive tasks have an impact on breathing and heart rate variability (HRV). We show that changes in physiological parameters during cognitive stress can be captured remotely (at a distance of 3m) using a digital camera. A study (n=10) was conducted with participants at rest and under cognitive stress. A novel five band digital camera was used to capture videos of the face of the participant. Significantly higher normalized low frequency HRV components and breathing rates were measured in the stress condition when compared to the rest condition. Heart rates were not significantly different between the two conditions. We built a person-independent classifier to predict cognitive stress based on the remotely detected physiological parameters (heart rate, breathing rate and heart rate variability). The accuracy of the model was 85% (35% greater than chance).

Effects of hearing loss on heart rate variability and skin conductance measured during sentence recognition in noise

OBJECTIVE

The purpose of the study was to determine the effects of hearing loss and noise on (1) two autonomic nervous system measures associated with stress (skin conductance and heart rate variability) and on (2) subjective ratings of workload/stress. The authors hypothesized that hearing loss would increase psychophysiological and subjective reactivity to noise during speech recognition tasks. Both psychophysiological and subjective indicators of workload/stress were expected to increase with a reduction in signal-to-noise ratio.

DESIGN

Sentence recognition in the presence of babble noise was assessed in 15 adults with clinically normal hearing and 18 adults with sensorineural hearing loss. Mean sentence recognition was equalized for the two groups using an adaptive procedure to estimate 80% recognition of words in sentences. Sentences were then presented in quiet and at four fixed signal-to-noise ratios: -6, -3, 0, and +3 dB relative to the individually determined signal-to-noise thresholds. Electrocardiography and skin conductance recordings were obtained during each listening condition. The high-frequency spectral component of heart rate variability was extracted from the electrocardiographic recordings as a measure of parasympathetic nervous system activity. Subjective ratings of effort, mental demand, stress, and perceived performance were obtained after each listening condition using the National Aeronautics and Space Administration Task Load Index.

RESULTS

Recognition scores referenced to the adaptive threshold were similar for the two groups. Participants with hearing loss showed a decrease in high-frequency heart rate variability at lower signal-to-noise ratios, whereas those with normal hearing did not. Skin conductance levels were not sensitive to changes in signal-to-noise ratio. However, overall skin conductance reactivity to noise (relative to quiet) was higher for those with hearing loss than for those with normal hearing. In contrast to the psychophysiological findings, there were no significant differences between subjective ratings for the two groups.

CONCLUSIONS

Listeners with hearing loss show greater autonomic nervous system reactivity to babble noise during speech recognition than do listeners with normal hearing, when recognition performance is equal. The findings are consistent with the conclusion that listeners with hearing loss experience increased effort and/or stress during speech recognition in noise.

Immediate effect of yogic visual concentration on cognitive performance

The ancient Indian yoga text, Hatha Yoga Pradipika, describes six cleansing techniques. The objective of cleansing techniques is to purify and prepare the body for the practice of yoga postures, breath regulation, and meditation. Yogic visual concentration technique (trataka) is one of these techniques. A previous study showed an increase in critical flicker fusion (CFF) following yogic visual concentration (trataka). The present study planned to assess the immediate effect of trataka on cognitive performance using the Stroop color-word test. Performance on the Stroop color-word test was assessed in 30 healthy male volunteers with ages ranging from 18 years to 31 years old (22.57 ± 3.65 years). The participants were tested before and after yogic visual concentration (trataka) and during a control session on two separate days. There was a significant improvement in performance on the Stroop color-word test after trataka compared to the control session [repeated measures analysis of variance (RM ANOVA) with Bonferroni adjustment; p < 0.001]. Performance on the Stroop color-word test was better after trataka compared to the control session suggesting that the trataka technique increased the selective attention, cognitive flexibility, and response inhibition.

Investigating the autonomic nervous system and cognitive functions as potential mediators of an association between cardiovascular disease and driving performance

Cardiovascular disease (CVD) impacts the autonomic nervous system and cognitive functions related to activities of daily living, including driving an automobile. Although CVD has been linked to unsafe driving, mechanisms underlying this relationship remain elusive. The aim of this study was to examine the role of cognitive functions and the autonomic nervous system as potential mediators of driving performance. Nineteen individuals having recently suffered a cardiac event and 16 individuals with no history of CVD completed a simulated drive using a STISIM simulator to assess driving performance. Heart rate was recorded throughout testing using a Polar RS800CX heart rate monitor, and measures of executive, orienting, and alerting functions were obtained through the Attention Network Test. We used the Baron and Kenny analysis method to assess potential mediating effects of the relationship between CVD and driving performance. Executive function was the only potential mediator investigated to be associated with driving (p < 0.01) and CVD (p < 0.05); however, it did not appear to play a mediating role (p = 0.28). These results suggest that individuals with CVD exhibit decrements in complex cognitive tasks such as driving and that further research is needed to better understand the mechanisms underlying this relationship.

The response of the human circulatory system to an acute 200-μT, 60-Hz magnetic field exposure

PURPOSE

Recent research by the authors on the effects of extremely low-frequency (ELF) magnetic field (MF) exposure on human heart rate (HR), heart rate variability (HRV), and skin blood perfusion found no cardiovascular effects of exposure to an 1,800-μT, 60-Hz MF. Research from our group using rats, however, has suggested a microcirculatory response to a 200-μT, 60-Hz MF exposure. The present pilot study investigated the effects of 1 h of exposure to a 200-μT, 60-Hz MF on the human circulation. Microcirculation (as skin blood perfusion) and HR were measured using laser Doppler flowmetry. Mean arterial pressure was monitored with a non-invasive blood pressure system.

METHODS

Ten volunteers were recruited to partake in a counterbalanced, single-blinded study consisting of two testing sessions (real and sham exposure) administered on separate days. Each session included four consecutive measurement periods separated by rest, allowing assessment of cumulative and residual MF effects.

RESULTS

A within-subjects analysis of variance did not reveal session by time period interactions for any of the parameters which would have been suggestive of a MF effect (p > 0.05). Perfusion, HR, and skin surface temperature decreased over the course of the experiment (p < 0.05).

CONCLUSIONS

The MF used in this experiment did not affect perfusion, HR, or mean arterial pressure. Decreasing perfusion and HR trends over time were similar to our previous results and appear to be associated with a combination of inactivity (resulting in decreasing body temperatures) and reduced physiological arousal.