A Tactile P300 Brain-Computer Interface

In this study, we investigated a Brain-Computer Interface (BCI) based on EEG responses to vibro-tactile stimuli around the waist. P300 BCIs based on tactile stimuli have the advantage of not taxing the visual or auditory system and of being potentially unnoticeable to other people. A tactile BCI could be especially suitable for patients whose vision or eye movements are impaired. In Experiment 1, we investigated its feasibility and the effect of the number of equally spaced tactors. Whereas a large number of tactors is expected to enhance the P300 amplitude since the target will be less frequent, it could also negatively affect the P300 since it will be difficult to identify the target when tactor density increases. Participants were asked to attend to the vibrations of a target tactor, embedded within a stream of distracters. The number of tactors was two, four or six. We demonstrated the feasibility of a tactile P300 BCI. We did not find a difference in SWLDA classification performance between the different numbers of tactors. In a second set of experiments we reduced the stimulus onset asynchrony (SOA) by shortening the on- and/or off-time of the tactors. The SOA for an optimum performance as measured in our experiments turned out to be close to conventional SOAs of visual P300 BCIs

Editorial: Using neurophysiological signals that reflect cognitive or affective state

The central question of this Frontiers Research Topic is: What can we learn from brain and other physiological signals about an individual's cognitive and affective state and how can we use this information? This question reflects three important issues which are addressed by the 22 articles in this volume: (1) the combination of central and peripheral neurophysiological measures; (2) the diversity of cognitive and affective processes reflected by these measures; and (3) how to apply these measures in real world applications

The Effects of Stimulus Duration and Group Size on Wearable Physiological Synchrony

Physiological synchrony refers to the degree to which physiological measures such as heart rate and electrodermal activity (EDA) across multiple individuals uniformly change. Physiological synchrony has shown to be informative of attention among individuals presented with a narrative stimulus: higher physiological synchrony is often related with better attention to the narrative. However, results are strongly dependent on basic factors such as group size and recording length. In the current work we explore what group size and recording length are needed for robust physiological synchrony results.<br/

Robustness of Physiological Synchrony in Wearable Electrodermal Activity and Heart Rate as a Measure of Attentional Engagement to Movie Clips

Individuals that pay attention to narrative stimuli show synchronized heart rate (HR) and electrodermal activity (EDA) responses. The degree to which this physiological synchrony occurs is related to attentional engagement. Factors that can influence attention, such as instructions, salience of the narrative stimulus and characteristics of the individual, affect physiological synchrony. The demonstrability of synchrony depends on the amount of data used in the analysis. We investigated how demonstrability of physiological synchrony varies with varying group size and stimulus duration. Thirty participants watched six 10 min movie clips while their HR and EDA were monitored using wearable sensors (Movisens EdaMove 4 and Wahoo Tickr, respectively). We calculated inter-subject correlations as a measure of synchrony. Group size and stimulus duration were varied by using data from subsets of the participants and movie clips in the analysis. We found that for HR, higher synchrony correlated significantly with the number of answers correct for questions about the movie, confirming that physiological synchrony is associated with attention. For both HR and EDA, with increasing amounts of data used, the percentage of participants with significant synchrony increased. Importantly, we found that it did not matter how the amount of data was increased. Increasing the group size or increasing the stimulus duration led to the same results. Initial comparisons with results from other studies suggest that our results do not only apply to our specific set of stimuli and participants. All in all, the current work can act as a guideline for future research, indicating the amount of data minimally needed for robust analysis of synchrony based on inter-subject correlations.</p

A usability study of physiological measurement in school using wearable sensors

Measuring psychophysiological signals of adolescents using unobtrusive wearable sensors may contribute to understanding the development of emotional disorders. This study investigated the feasibility of measuring high quality physiological data and examined the validity of signal processing in a school setting. Among 86 adolescents, a total of more than 410 h of electrodermal activity (EDA) data were recorded using a wrist-worn sensor with gelled electrodes and over 370 h of heart rate data were recorded using a chest-strap sensor. The results support the feasibility of monitoring physiological signals at school. We describe specific challenges and provide recommendations for signal analysis, including dealing with invalid signals due to loose sensors, and quantization noise that can be caused by limitations in analog-to-digital conversion in wearable devices and be mistaken as physiological responses. Importantly, our results show that using toolboxes for automatic signal preprocessing, decomposition, and artifact detection with default parameters while neglecting differences between devices and measurement contexts yield misleading results. Time courses of students' physiological signals throughout the course of a class were found to be clearer after applying our proposed preprocessing steps

Physiological synchrony in electrodermal activity predicts decreased vigilant attention induced by sleep deprivation

Introduction: When multiple individuals are presented with narrative movie oraudio clips, their electrodermal activity (EDA) and heart rate show significantsimilarities. Higher levels of such inter-subject physiological synchrony are relatedwith higher levels of attention toward the narrative, as for instance expressedby more correctly answered questions about the narrative. We here investigatewhether physiological synchrony in EDA and heart rate during watching ofmovie clips predicts performance on a subsequent vigilant attention task amongparticipants exposed to a night of total sleep deprivation.Methods: We recorded EDA and heart rate of 54 participants during a nightof total sleep deprivation. Every hour from 22:00 to 07:00 participants watcheda 10-min movie clip during which we computed inter-subject physiologicalsynchrony. Afterwards, they answered questions about the movie and performedthe psychomotor vigilance task (PVT) to capture attentional performance.Results: We replicated findings that inter-subject correlations in EDA and heartrate predicted the number of correct answers on questions about the movieclips. Furthermore, we found that inter-subject correlations in EDA, but not inheart rate, predicted PVT performance. Individuals’ mean EDA and heart rate alsopredicted their PVT performance. For EDA, inter-subject correlations explainedmore variance of PVT performance than individuals’ mean EDA.Discussion: Together, these findings confirm the association betweenphysiological synchrony and attention. Physiological synchrony in EDA doesnot only capture the attentional processing during the time that it is determined,but also proves valuable for capturing more general changes in the attentionalstate of monitored individuals.<br/