Real-Time Quality Index to Control Data Loss in Real-Life Cardiac Monitoring Applications.

Wearable cardiac sensors pave the way for advanced cardiac monitoring applications based on heart rate variability (HRV). In real-life settings, heart rate (HR) measurements are subject to motion artifacts that may lead to frequent data loss (missing samples in the HR signal), especially for commercial devices based on photoplethysmography (PPG). The current study had two main goals: (i) to provide a white-box quality index that estimates the amount of missing samples in any piece of HR signal; and (ii) to quantify the impact of data loss on feature extraction in a PPG-based HR signal. This was done by comparing real-life recordings from commercial sensors featuring both PPG (Empatica E4) and ECG (Zephyr BioHarness 3). After an outlier rejection process, our quality index was used to isolate portions of ECG-based HR signals that could be used as benchmark, to validate the output of Empatica E4 at the signal level and at the feature level. Our results showed high accuracy in estimating the mean HR (median error: 3.2%), poor accuracy for short-term HRV features (e.g., median error: 64% for high-frequency power), and mild accuracy for longer-term HRV features (e.g., median error: 25% for low-frequency power). These levels of errors could be reduced by using our quality index to identify time windows with few or no data loss (median errors: 0.0%, 27%, and 6.4% respectively, when no sample was missing). This quality index should be useful in future work to extract reliable cardiac features in real-life measurements, or to conduct a field validation study on wearable cardiac sensors.

Human or not human? Performance monitoring ERPs during human agent and machine supervision.

Performance monitoring is a critical process which allows us to both learn from our own errors, and also interact with other human beings. However, our increasingly automated world requires us to interact more and more with automated systems, especially in risky environments. The present EEG study aimed at investigating and comparing the neuro-functional correlates associated with performance monitoring of an automated system and a human agent using a vertically-oriented arrowhead version of the flanker task. Given the influence of task difficulty on performance monitoring, two levels of difficulty were considered in order to assess their impact on supervision activity. A large N2-P3 complex in fronto-central regions was observed for both human agent error detection and system error detection during supervision. Using a cluster-based permutation analysis, a significantly decreased P3-like component was found for system compared to human agent error detection. This variation is in line with various psychosocial behavioral studies showing a difference between human-human and human-machine interactions, even though it was not clearly anticipated. Finally, the activity observed during error detection was significantly reduced in the difficult condition compared to the easy one, for both system and human agent supervision. Overall, this study is a first step towards the characterization of the neurophysiological correlates underlying system supervision, and a better understanding of their evolution in more complex environments. To go further, these results need to be replicated in other experiments with various paradigms to assess the robustness of the pattern and decrease during system supervision.

Microsaccades are modulated by both attentional demands of a visual discrimination task and background noise.

Microsaccades are miniature saccades occurring once or twice per second during visual fixation. While microsaccades and saccades share similarities at the oculomotor level, the functional roles of microsaccades are still debated. In this study, we examined the hypothesis that the microsaccadic activity is affected by the type of noisy background during the execution of a particular discrimination task. Human subjects had to judge the orientation of a tilted stimulus embedded in static or dynamic backgrounds in a forced choice-task paradigm, as adapted from Rucci, Iovin, Poletti, and Santini (2007). Static backgrounds induced more microsaccades than dynamic ones only during the execution of the discrimination task. A directional bias of microsaccades, dictated by the stimulus orientation, was temporally coupled with this period of increased activity. Both microsaccade rates and orientations were comparable across background types after the response time although subjects maintained fixation until the end of the trial. This represents a background-specific modulation of the microsaccadic activity driven by attentional demands. The visual influence of microsaccades on discrimination performances was modeled at the retinal level for both types of backgrounds. A higher simulated microsaccadic activity was necessary for static backgrounds in order to achieve discrimination performance scores comparable to that of dynamic ones. Taken together, our experimental and theoretical findings further support the idea that microsaccades are under attentional control and represent an efficient sampling strategy allowing spatial information acquisition.

Brain mechanisms of automated conflict avoidance simulator supervision.

Supervision of automated systems is an ubiquitous aspect of most of our everyday life activities which is even more necessary in high risk industries (aeronautics, power plants, etc.). Performance monitoring related to our own error making has been widely studied. Here we propose to assess the neurofunctional correlates of system error detection. We used an aviation-based conflict avoidance simulator with a 40% error-rate and recorded the electroencephalographic activity of participants while they were supervising it. Neural dynamics related to the supervision of system's correct and erroneous responses were assessed in the time and time-frequency domains to address the dynamics of the error detection process in this environment. Two levels of perceptual difficulty were introduced to assess their effect on system's error detection-related evoked activity. Using a robust cluster-based permutation test, we observed a lower widespread evoked activity in the time domain for errors compared to correct responses detection, as well as a higher theta-band activity in the time-frequency domain dissociating the detection of erroneous from that of correct system responses. We also showed a significant effect of difficulty on time-domain evoked activity, and of the phase of the experiment on spectral activity: a decrease in early theta and alpha at the end of the experiment, as well as interaction effects in theta and alpha frequency bands. These results improve our understanding of the brain dynamics of performance monitoring activity in closer-to-real-life settings and are a promising avenue for the detection of error-related components in ecological and dynamic tasks.

Spatio-temporal attention toward emotional scenes across adulthood.

Research on emotion suggests that the attentional preference observed toward the negative stimuli in young adults tends to disappear in normal aging and, sometimes, to shift toward a preference for positive stimuli. The current eye-tracking study investigated visual exploration of paired natural scenes of different valence (Negative-Neutral, Positive-Neutral, and Negative-Positive pairs) in three age groups (young, middle-aged, and older adults). Two arousal levels of stimuli (high and low arousal) were also considered given role of this factor in age-related effects on emotion. Results showed the automatic attentional orienting toward the negative stimuli was relatively preserved in our three age groups although reduced in the elderly, in both arousal conditions. A similar negativity bias was also observed in initial attention focusing but shifted toward a positivity bias over time in the three age groups. Moreover, it appeared the spatial exploration of emotional scenes evolved over time differently for older adults compared with other age groups. No difference between young adults and middle-aged adults in ocular behavior was observed. This study confirms the interest of studying both spatial and temporal characteristics of oculomotor behaviors to better understand the age-related effects on emotion. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Similar cerebral networks in language, music and song perception.

Two fMRI experiments were conducted using song to investigate the domain specificity of linguistic and musical processing. In Experiment 1, participants listened to pairs of spoken words, "vocalise" (i.e., singing without words), and sung words while performing a same-different task. Results revealed bilateral involvement of middle and superior temporal gyri and inferior and middle frontal gyri while listening to spoken words, sung words and vocalise, although to different degrees. In Experiment 2, participants listened to pairs of sung words that were similar or different in terms of the linguistic and musical dimensions (2x2 factorial event-related design) while performing a same-different task. Results showed widespread interactions between the linguistic and musical dimensions of sung words mainly within the network of brain areas identified in Experiment 1. Consequently, the activity in these brain regions cannot be considered as specific to either language or music processing. Taken together, results of both experiments argue against domain specificity and provide additional evidence for a common cerebral network involved in both lexical/phonological and melodic processing.

Evaluation of performance monitoring ERPs through difficulty manipulation in a response-feedback paradigm.

Performance monitoring is an amply studied function, since it is of major importance in carrying out actions in our everyday life. No consensus has been reached on the functional role and the relationship between each event-related potential (ERP) characterizing this function. In this study, we used a modified version of the flanker task, measuring the impact of task difficulty on the amplitudes of response-locked and feedback-locked performance monitoring ERPs in a single trial. We observed a functional differentiation between fronto-central (ERN/CRN and FRN) and centro-parietal (Pe/Pc and P300) components: the former seem to be only sensitive to accuracy, whereas the latter seem to be mainly modulated by task difficulty. The use of a surface Laplacian transformation, estimating current source density, on our data also supported an effect of difficulty on centro-parietal response-locked and feedback-locked ERPs. This technique allowed the spatial resolution to be improved and provided clarity, associated with the difficulty manipulation, on the activity of response-locked and feedback-locked performance monitoring ERPs.

Performance Monitoring Applied to System Supervision.

Nowadays, automation is present in every aspect of our daily life and has some benefits. Nonetheless, empirical data suggest that traditional automation has many negative performance and safety consequences as it changed task performers into task supervisors. In this context, we propose to use recent insights into the anatomical and neurophysiological substrates of action monitoring in humans, to help further characterize performance monitoring during system supervision. Error monitoring is critical for humans to learn from the consequences of their actions. A wide variety of studies have shown that the error monitoring system is involved not only in our own errors, but also in the errors of others. We hypothesize that the neurobiological correlates of the self-performance monitoring activity can be applied to system supervision. At a larger scale, a better understanding of system supervision may allow its negative effects to be anticipated or even countered. This review is divided into three main parts. First, we assess the neurophysiological correlates of self-performance monitoring and their characteristics during error execution. Then, we extend these results to include performance monitoring and error observation of others or of systems. Finally, we provide further directions in the study of system supervision and assess the limits preventing us from studying a well-known phenomenon: the Out-Of-the-Loop (OOL) performance problem.

Efficient Workload Classification based on Ignored Auditory Probes: A Proof of Concept.

Mental workload is a mental state that is currently one of the main research focuses in neuroergonomics. It can notably be estimated using measurements in electroencephalography (EEG), a method that allows for direct mental state assessment. Auditory probes can be used to elicit event-related potentials (ERPs) that are modulated by workload. Although, some papers do report ERP modulations due to workload using attended or ignored probes, to our knowledge there is no literature regarding effective workload classification based on ignored auditory probes. In this paper, in order to efficiently estimate workload, we advocate for the use of such ignored auditory probes in a single-stimulus paradigm and a signal processing chain that includes a spatial filtering step. The effectiveness of this approach is demonstrated on data acquired from participants that performed the Multi-Attribute Task Battery - II. They carried out this task during two 10-min blocks. Each block corresponded to a workload condition that was pseudorandomly assigned. The easy condition consisted of two monitoring tasks performed in parallel, and the difficult one consisted of those two tasks with an additional plane driving task. Infrequent auditory probes were presented during the tasks and the participants were asked to ignore them. The EEG data were denoised and the probes' ERPs were extracted and spatially filtered using a canonical correlation analysis. Next, binary classification was performed using a Fisher LDA and a fivefold cross-validation procedure. Our method allowed for a very high estimation performance with a classification accuracy above 80% for every participant, and minimal intrusiveness thanks to the use of a single-stimulus paradigm. Therefore, this study paves the way to the efficient use of ERPs for mental state monitoring in close to real-life settings and contributes toward the development of adaptive user interfaces.

Cerebral Correlates of Emotional and Action Appraisals During Visual Processing of Emotional Scenes Depending on Spatial Frequency: A Pilot Study.

Visual processing of emotional stimuli critically depends on the type of cognitive appraisal involved. The present fMRI pilot study aimed to investigate the cerebral correlates involved in the visual processing of emotional scenes in two tasks, one emotional, based on the appraisal of personal emotional experience, and the other motivational, based on the appraisal of the tendency to action. Given that the use of spatial frequency information is relatively flexible during the visual processing of emotional stimuli depending on the task's demands, we also explored the effect of the type of spatial frequency in visual stimuli in each task by using emotional scenes filtered in low spatial frequency (LSF) and high spatial frequencies (HSF). Activation was observed in the visual areas of the fusiform gyrus for all emotional scenes in both tasks, and in the amygdala for unpleasant scenes only. The motivational task induced additional activation in frontal motor-related areas (e.g. premotor cortex, SMA) and parietal regions (e.g. superior and inferior parietal lobules). Parietal regions were recruited particularly during the motivational appraisal of approach in response to pleasant scenes. These frontal and parietal activations, respectively, suggest that motor and navigation processes play a specific role in the identification of the tendency to action in the motivational task. Furthermore, activity observed in the motivational task, in response to both pleasant and unpleasant scenes, was significantly greater for HSF than for LSF scenes, suggesting that the tendency to action is driven mainly by the detailed information contained in scenes. Results for the emotional task suggest that spatial frequencies play only a small role in the evaluation of unpleasant and pleasant emotions. Our preliminary study revealed a partial distinction between visual processing of emotional scenes during identification of the tendency to action, and during identification of personal emotional experiences. It also illustrates flexible use of the spatial frequencies contained in scenes depending on their emotional valence and on task demands.

Useful visual field reduction as a function of age and risk of accident in simulated car driving.

PURPOSE: To study the relationships between the reduction of the useful visual field, age, and driving performance. METHODS: Forty-eight subjects, aged from 23 to 77 years performed a test to evaluate the size of their useful visual fields. The test involved the detection and localization of peripheral signals that could appear in an area of 70 degrees of visual angle. The subjects then performed a simulated car-driving task involving the management of a situation that could lead to an accident. RESULTS: The analysis of the data revealed that the ability to process peripheral signals and simulated driving performance (vehicle speed) deteriorate with age. Simulated driving performance and useful visual field measurement have been analyzed jointly. The results indicate that the reduction of the useful visual field, estimated using a target-localization task, is related to the individual's ability to manage the simulated driving situation (correlation coefficient with speed = -0.43 and with reaction time for avoidance of a mobile obstacle = +0.30) and the deterioration of the useful visual field estimated using a target detection task is related only to vehicle speed (correlation coefficient = -0.32). CONCLUSIONS: The adoption of a lower speed by the drivers with a reduced visual field (the elderly ones) is probably an adaptation strategy to process the peripheral information. All useful visual field measurements do not seem to be equivalent to estimate the ability to process information relative to the mobile obstacle. The risk of collision should be estimated only with a useful visual field test using a target localization task.

A comparison of ERP spatial filtering methods for optimal mental workload estimation.

Mental workload estimation is of crucial interest for user adaptive interfaces and neuroergonomics. Its estimation can be performed using event-related potentials (ERPs) extracted from electroencephalographic recordings (EEG). Several ERP spatial filtering methods have been designed to enhance relevant EEG activity for active brain-computer interfaces. However, to our knowledge, they have not yet been used and compared for mental state monitoring purposes. This paper presents a thorough comparison of three ERP spatial filtering methods: principal component analysis (PCA), canonical correlation analysis (CCA) and the xDAWN algorithm. Those methods are compared in their performance to allow for an accurate classification of mental workload when applied in an otherwise similar processing chain. The data of 20 healthy participants that performed a memory task for 10 minutes each was used for classification. Two levels of mental workload were considered depending on the number of digits participants had to memorize (2/6). The highest performances were obtained using the CCA filtering and the xDAWN algorithm respectively with 98% and 97% of correct classification. Their performances were significantly higher than that obtained using the PCA filtering (88%).

Correlation between driving errors and vigilance level: influence of the driver's age.

During long and monotonous driving at night, most drivers progressively show signs of visual fatigue and loss of vigilance. Their capacity to maintain adequate driving performance usually is affected and varies with the age of the driver. The main question is to know, on one hand, if occurrence of fatigue and drowsiness is accompanied by a modification in the driving performance of the driver and, on the other hand, if this relationship partially depends on the driver's age. Forty-six male drivers, divided into three age categories: 20-30, 40-50, and 60-70 years, performed a 350-km motorway driving session at night on a driving simulator. Driving errors were measured in terms of number of running-off-the-road incidents (RORI) and large speed deviations. The evolution of physiological vigilance level was evaluated using electroencephalography (EEG) recording. In older drivers, in comparison with young and middle-aged drivers, the degradation of driving performance was correlated to the evolution of lower frequency waking EEG (i.e., theta). Contrary to young and middle-aged drivers, the deterioration of the vigilance level attested by EEG correlated with the increase in gravity of all studied driving errors in older drivers. Thus, depending on the age category considered, only part of the driving errors would constitute a relevant indication as for the occurrence of a state of low arousal.

Brain processing of emotional scenes in aging: effect of arousal and affective context.

Research on emotion showed an increase, with age, in prevalence of positive information relative to negative ones. This effect is called positivity effect. From the cerebral analysis of the Late Positive Potential (LPP), sensitive to attention, our study investigated to which extent the arousal level of negative scenes is differently processed between young and older adults and, to which extent the arousal level of negative scenes, depending on its value, may contextually modulate the cerebral processing of positive (and neutral) scenes and favor the observation of a positivity effect with age. With this aim, two negative scene groups characterized by two distinct arousal levels (high and low) were displayed into two separate experimental blocks in which were included positive and neutral pictures. The two blocks only differed by their negative pictures across participants, as to create two negative global contexts for the processing of the positive and neutral pictures. The results show that the relative processing of different arousal levels of negative stimuli, reflected by LPP, appears similar between the two age groups. However, a lower activity for negative stimuli is observed with the older group for both tested arousal levels. The processing of positive information seems to be preserved with age and is also not contextually impacted by negative stimuli in both younger and older adults. For neutral stimuli, a significantly reduced activity is observed for older adults in the contextual block of low-arousal negative stimuli. Globally, our study reveals that the positivity effect is mainly due to a modulation, with age, in processing of negative stimuli, regardless of their arousal level. It also suggests that processing of neutral stimuli may be modulated with age, depending on negative context in which they are presented to. These age-related effects could contribute to justify the differences in emotional preference with age.

Probing ECG-based mental state monitoring on short time segments.

Electrocardiography is used to provide features for mental state monitoring systems. There is a need for quick mental state assessment in some applications such as attentive user interfaces. We analyzed how heart rate and heart rate variability features are influenced by working memory load (WKL) and time-on-task (TOT) on very short time segments (5s) with both statistical significance and classification performance results. It is shown that classification of such mental states can be performed on very short time segments and that heart rate is more predictive of TOT level than heart rate variability. However, both features are efficient for WKL level classification. What's more, interesting interaction effects are uncovered: TOT influences WKL level classification either favorably when based on HR, or adversely when based on HRV. Implications for mental state monitoring are discussed.

Mental fatigue and working memory load estimation: interaction and implications for EEG-based passive BCI.

Current mental state monitoring systems, a.k.a. passive brain-computer interfaces (pBCI), allow one to perform a real-time assessment of an operator's cognitive state. In EEG-based systems, typical measurements for workload level assessment are band power estimates in several frequency bands. Mental fatigue, arising from growing time-on-task (TOT), can significantly affect the distribution of these band power features. However, the impact of mental fatigue on workload (WKL) assessment has not yet been evaluated. With this paper we intend to help fill in this lack of knowledge by analyzing the influence of WKL and TOT on EEG band power features, as well as their interaction and its impact on classification performance. Twenty participants underwent an experiment that modulated both their WKL (low/high) and time spent on the task (short/long). Statistical analyses were performed on the EEG signals, behavioral and subjective data. They revealed opposite changes in alpha power distribution between WKL and TOT conditions, as well as a decrease in WKL level discriminability with increasing TOT in both number of statistical differences in band power and classification performance. Implications for pBCI systems and experimental protocol design are discussed.

Functional segregation of cortical language areas by sentence repetition.

The functional organization of the perisylvian language network was examined using a functional MRI (fMRI) adaptation paradigm with spoken sentences. In Experiment 1, a given sentence was presented every 14.4 s and repeated two, three, or four times in a row. The study of the temporal properties of the BOLD response revealed a temporal gradient along the dorsal-ventral and rostral-caudal directions: From Heschl's gyrus, where the fastest responses were recorded, responses became increasingly slower toward the posterior part of the superior temporal gyrus and toward the temporal poles and the left inferior frontal gyrus, where the slowest responses were observed. Repetition induced a decrease in amplitude and a speeding up of the BOLD response in the superior temporal sulcus (STS), while the most superior temporal regions were not affected. In Experiment 2, small blocks of six sentences were presented in which either the speaker voice or the linguistic content of the sentence, or both, were repeated. Data analyses revealed a clear asymmetry: While two clusters in the left superior temporal sulcus showed identical repetition suppression whether the sentences were produced by the same speaker or different speakers, the homologous right regions were sensitive to sentence repetition only when the speaker voice remained constant. Thus, hemispheric left regions encode linguistic content while homologous right regions encode more details about extralinguistic features like speaker voice. The results demonstrate the feasibility of using sentence-level adaptation to probe the functional organization of cortical language areas.