Associations between EEG asymmetries and electrodermal lability in low vs. high depressive and anxious normal individuals

Operators' Load Monitoring and Management

Due to the introduction of highly automated vehicles and systems, the tasks of operators (drivers, pilots, air traffic controllers, production process managers) are in transition from "active control" to "passive monitoring" and "supervising". As a result of this transition, the roles of task load and workload are decreasing while the role of the mental load is increasing, thereby the new type of loads might be defined as information load and communication load. This paper deals with operators' load monitoring and management in highly automated systems. This research (i) introduces the changes in the role of operators and requirements in load management, (ii) defines the operators' models, (iii) describes the possible application of sensors and their integration into the working environment of operators, and (iv) develops the load observation and management concept. There are some examples of analyses of measurements and the concept of validation is discussed. This paper mainly deals with operators, particularly pilots and air traffic controllers (ATCOs).

Obimon: An open-source device enabling group measurement of electrodermal activity

Electrodermal activity (EDA) provides the means to gauge the activity of the sympathetic nervous system. Assessment of EDA for research purposes requires measurement systems that are sensitive to small changes in arousal in the full measurement range, collecting, storing, and monitoring data. The objective behind designing a new open-source device was to be able to measure EDA simultaneously on many subjects, monitoring their activity in real time remotely and collecting high precision data suitable for analyses. To assure feasibility of simultaneous measurements on multiple subjects, the devices must be compact and wearable, without compromising data quality. Experiments were carried out using synchronized devices in group and single subject environments. Validity of EDA measurements of Obimon was demonstrated compared to a reference system (Nexus) during a breathing exercise, a short movie, and while exposed to loud computer-generated tones, using Pearson correlation, Passing-Bablok regression, and Bland-Altman analysis. Seamless management of several Obimons and real-time visualization of EDA via Android phone/tablet application from a large number of participants was demonstrated. Based on analyses of the data collected, we conclude that the Obimon device presented here is a valid and feasible tool for collecting EDA in single or multisubject environments.

Neural substrates of trait impulsivity, anhedonia, and irritability: Mechanisms of heterotypic comorbidity between externalizing disorders and unipolar depression

Trait impulsivity, which is often defined as a strong preference for immediate over delayed rewards and results in behaviors that are socially inappropriate, maladaptive, and short-sighted, is a predisposing vulnerability to all externalizing spectrum disorders. In contrast, anhedonia is characterized by chronically low motivation and reduced capacity to experience pleasure, and is common to depressive disorders. Although externalizing and depressive disorders have virtually nonoverlapping diagnostic criteria in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, heterotypic comorbidity between them is common. Here, we review common neural substrates of trait impulsivity, anhedonia, and irritability, which include both low tonic mesolimbic dopamine activity and low phasic mesolimbic dopamine responding to incentives during reward anticipation and associative learning. We also consider how other neural networks, including bottom-up emotion generation systems and top-down emotion regulation systems, interact with mesolimbic dysfunction to result in alternative manifestations of psychiatric illness. Finally, we present a model that emphasizes a translational, transdiagnostic approach to understanding externalizing/depression comorbidity. This model should refine ways in which internalizing and externalizing disorders are studied, classified, and treated.

Stress-induced alterations of left-right electrodermal activity coupling indexed by pointwise transinformation

In this study, we tested the hypothesis that experimental stress induces a specific change of left-right electrodermal activity (EDA) coupling pattern, as indexed by pointwise transinformation (PTI). Further, we hypothesized that this change is associated with scores on psychometric measures of the chronic stress-related psychopathology. Ninety-nine university students underwent bilateral measurement of EDA during rest and stress-inducing Stroop test and completed a battery of self-report measures of chronic stress-related psychopathology. A significant decrease in the mean PTI value was the prevalent response to the stress conditions. No association between chronic stress and PTI was found. Raw scores of psychometric measures of stress-related psychopathology had no effect on either the resting levels of PTI or the amount of stress-induced PTI change. In summary, acute stress alters the level of coupling pattern of cortico-autonomic influences on the left and right sympathetic pathways to the palmar sweat glands. Different results obtained using the PTI, EDA laterality coefficient, and skin conductance level also show that the PTI algorithm represents a new analytical approach to EDA asymmetry description.

Differentiating adolescent self-injury from adolescent depression: possible implications for borderline personality development

Self-inflicted injury (SII) in adolescence marks heightened risk for suicide attempts, completed suicide, and adult psychopathology. Although several studies have revealed elevated rates of depression among adolescents who self injure, no one has compared adolescent self injury with adolescent depression on biological, self-, and informant-report markers of vulnerability and risk. Such a comparison may have important implications for treatment, prevention, and developmental models of self injury and borderline personality disorder. We used a multi-method, multi-informant approach to examine how adolescent SII differs from adolescent depression. Self-injuring, depressed, and typical adolescent females (n = 25 per group) and their mothers completed measures of psychopathology and emotion regulation, among others. In addition, we assessed electrodermal responding (EDR), a peripheral biomarker of trait impulsivity. Participants in the SII group (a) scored higher than depressed adolescents on measures of both externalizing psychopathology and emotion dysregulation, and (b) exhibited attenuated EDR, similar to patterns observed among impulsive, externalizing males. Self-injuring adolescents also scored higher on measures of borderline pathology. These findings reveal a coherent pattern of differences between self-injuring and depressed adolescent girls, consistent with theories that SII differs from depression in etiology and developmental course.

Respiratory sinus arrhythmia feedback in a stressed population exposed to a brief stressor demonstrated by quantitative EEG and sLORETA

Previous investigations of electroencephalograms during relaxation have identified increases in slow wave band power, correlations between increased levels of alpha activity with lower levels of anxiety, and autonomic changes characterized by otherwise documented decreased sympathetic activity. This study was carried out to determine the overall changes in quantitative electroencephalographic activity and the current source as a result of an acute session of respiratory sinus arrhythmia (RSA) biofeedback in a population of subjects experiencing stress. This study's findings provide physiological evidence of RSA feedback effect and suggest that RSA training may decrease arousal by promoting an increase of alpha band frequencies and decrease in beta frequencies overall and in areas critical to the regulation of stress. It was of interest that novices could achieve these objective alterations in EEG activity after minimal training and intervention periods considering that the previous literature on EEG and meditative states involve experienced meditators or participants who had been given extensive training. Additionally, these effects were present immediately following the training suggesting that the intervention may have effects beyond the actual practice.

Top-down and bottom-up mechanisms in mind-body medicine: development of an integrative framework for psychophysiological research

It has become increasingly evident that bidirectional ("top-down and bottom-up") interactions between the brain and peripheral tissues, including the cardiovascular and immune systems, contribute to both mental and physical health. Therapies directed toward addressing functional links between mind/brain and body may be particularly effective in treating the range of symptoms associated with many chronic diseases. In this paper, we describe the basic components of an integrative psychophysiological framework for research aimed at elucidating the underlying substrates of mind-body therapies. This framework recognizes the multiple levels of the neuraxis at which mind-body interactions occur. We emphasize the role of specific fronto-temporal cortical regions in the representation and control of adverse symptoms, which interact reciprocally with subcortical structures involved in bodily homeostasis and responses to stress. Bidirectional autonomic and neuroendocrine pathways transmit information between the central nervous system and the periphery and facilitate the expression of affective, autonomic, hormonal, and immune responses. We propose that heart rate variability (HRV) and markers of inflammation are important currently available indices of central-peripheral integration and homeostasis within this homeostatic network. Finally, we review current neuroimaging and psychophysiological research from diverse areas of mind-body medicine that supports the framework as a basis for future research on the specific biobehavioral mechanisms of mind-body therapies.

Identifying robust and sensitive frequency bands for interrogating neural oscillations

Recent years have seen an explosion of interest in using neural oscillations to characterize the mechanisms supporting cognition and emotion. Oftentimes, oscillatory activity is indexed by mean power density in predefined frequency bands. Some investigators use broad bands originally defined by prominent surface features of the spectrum. Others rely on narrower bands originally defined by spectral factor analysis (SFA). Presently, the robustness and sensitivity of these competing band definitions remains unclear. Here, a Monte Carlo-based SFA strategy was used to decompose the tonic ("resting" or "spontaneous") electroencephalogram (EEG) into five bands: delta (1-5Hz), alpha-low (6-9Hz), alpha-high (10-11Hz), beta (12-19Hz), and gamma (>21Hz). This pattern was consistent across SFA methods, artifact correction/rejection procedures, scalp regions, and samples. Subsequent analyses revealed that SFA failed to deliver enhanced sensitivity; narrow alpha sub-bands proved no more sensitive than the classical broadband to individual differences in temperament or mean differences in task-induced activation. Other analyses suggested that residual ocular and muscular artifact was the dominant source of activity during quiescence in the delta and gamma bands. This was observed following threshold-based artifact rejection or independent component analysis (ICA)-based artifact correction, indicating that such procedures do not necessarily confer adequate protection. Collectively, these findings highlight the limitations of several commonly used EEG procedures and underscore the necessity of routinely performing exploratory data analyses, particularly data visualization, prior to hypothesis testing. They also suggest the potential benefits of using techniques other than SFA for interrogating high-dimensional EEG datasets in the frequency or time-frequency (event-related spectral perturbation, event-related synchronization/desynchronization) domains.

Female menstrual phases modulate human prefrontal asymmetry: a magnetoencephalographic study

We previously reported that the trait/baseline prefrontal cortex (PFC) activity expresses a dynamic plasticity during female menstrual cycle. The shift of asymmetric lateralization of PFC baseline activity pinpoints a possible emotional regulation of negative affection. The current emotional Go/NoGo study aimed to investigate the state PFC responses of different menstrual phases during fear facial stimulation in fourteen healthy women. Our data disclosed that the menstrual cycle was coupled with a shift of asymmetric lateralization of frontal activation across different menstrual phases. Evoked magnetic field activity in the time window 200-300 ms (M1) and 300-450 ms (M2) after stimulus onset demonstrated significant interactions between hemispheric side and menstrual phase. The right hemispheric dominance in periovulatory phase (OV) changed to left hemispheric dominance in menstrual (MC) phase. Significant association between the anxiety score and the left PFC activation was particularly observed in MC phase. Our study revealed a plastic resilience of functional organization of human brain and a dynamic automaticity of inter-hemispheric synergism for possible adaptive regulation under the aversive confrontation in accordance with hormonal fluctuation during the menstrual cycle.

Long-term stability of frontal electroencephalographic asymmetry in adults with a history of depression and controls

We investigated the stability in resting EEG across a 1- to 3-year interval in 49 adults (33 female and 16 male) with a history of unipolar depression (first onset prior to the age of 14) and 50 controls (33 female and 17 male) with no history of major psychopathology. Current depressive symptoms were quantified by self-report at both assessments. For the entire sample, EEG asymmetry in the alpha range was moderately stable (intraclass correlations between 0.39 and 0.61). Sex, history of depression, depressive symptom severity at Time 2, and change in symptom severity between Time 1 and Time 2 were unrelated to stability of EEG asymmetry. These findings support the view that resting frontal EEG asymmetry reflects a moderately stable individual difference in adults, irrespective of sex and history of depression.

Frontal EEG asymmetry as a moderator and mediator of emotion

Frontal EEG asymmetry appears to serve as (1) an individual difference variable related to emotional responding and emotional disorders, and (2) a state-dependent concomitant of emotional responding. Such findings, highlighted in this review, suggest that frontal EEG asymmetry may serve as both a moderator and a mediator of emotion- and motivation-related constructs. Unequivocal evidence supporting frontal EEG asymmetry as a moderator and/or mediator of emotion is lacking, as insufficient attention has been given to analyzing the frontal EEG asymmetries in terms of moderators and mediators. The present report reviews the frontal EEG asymmetry literature from the framework of moderators and mediators, and overviews data analytic strategies that would support claims of moderation and mediation.

Manipulation of frontal brain asymmetry by cognitive tasks

The purpose of the present study was to evaluate whether verbal fluency tasks may specifically induce relatively greater left than right hemispheric activation in the dorsolateral prefrontal cortex. The effectiveness of the manipulation was evaluated by EEG, which was recorded during performance of the verbal fluency task and during two control conditions, i.e., a baseline condition without cognitive demands, and a mental arithmetic task, respectively. The results demonstrate that the desired effect can only be achieved in individuals with good performance on the verbal fluency task. Good and poor performers do not only differ in lateral asymmetry, but also in the most affected region within the prefrontal cortex. Whereas good performers show relatively increased activation in the cortical region and hemisphere putatively most specialized for this kind of task (i.e., the left dorsolateral frontal cortex), poor performers show a marked shift of frontopolar asymmetry to the right.

Theory, methods and new directions in the psychophysiology of the schizophrenic process and schizotypy

Theoretical and methodological issues in the psychophysiology of the schizophrenic process are reviewed. These include the importance of schizotypy with its compensatory abilities as well as deficits for elucidating the processes of development and prevention of schizophrenia. The importance of individual differences, syndromes and single case studies. The recognition that this is a dynamic and fluctuating illness and hence the relevance of functional neurophysiology, including the role of imbalances in hemispheric activation in ontogeny, developmental course, expression of symptoms, the effects of neuroleptics and recovery process, and the influence of stress a precipitant of breakdown. The role of thalamo-cortical activation systems. The particular value of electrocortical measures including the interrelations of electroencephalographic rhythms throughout the spectrum, and relations of gamma, dynamic core neuronal complexity, connectivity and sensory gating with experiences of unreality and disturbances of consciousness.

Hemispheric modulatory influences on skin resistance response latency: unilateral stimulation, bilateral recording

In order to evaluate the bilateral asymmetries in evoked electrodermal activity (EDA) and the use of EDA parameters as indices of relative hemispheric activation, skin resistance level (SRL), skin resistance response (SRR), and the SRR latency (L) were examined in 25 right-handed male subjects. We used bilateral recording with a unilateral stimulation (auditory click/patellar tendon tap) to assess the asymmetries of EDA variables related to the side of stimulation and to handedness. Although no significant asymmetry in C = SRRmax/SRL ratio was found, significant differences in latency were observed. Ipsilateral responses were 100 ms faster than contralateral responses for auditory stimulus, a result that can be explained in terms of contralateral delay of neuronal communication on EDA-l pathway. Response latency to reflex-motor activation was 60-100 ms shorter in the dominant hand, regardless of the stimulation site used. This result indicates that the reaction time of the EDA-2 pathway of the left hemisphere was shorter than the right for right-handed subjects. It is concluded that there is hemispheric asymmetry on EDA-2 pathway and that this asymmetry appears to be dependent on the preferred dexterity. These results have implications for the influence of both central and peripheral factors on EDA laterality and principally on laterality of response amplitude. Further, there is no single cortical mechanism modulating the asymmetries in the latency of this response.

Lateralization in human nasal chemoreception: differences in bilateral electrodermal responses related to olfactory and trigeminal stimuli

The study of olfactory lateralization in humans has given rise to many publications, but the findings have often been contradictory. There is growing evidence to suggest that the nature of the olfactory stimulus influences the processes of lateralization. An important factor could be the trigeminal component. Indeed, most odorants simultaneously stimulate both olfactory (CN I) and trigeminal (CN V) systems which differ in terms of their central projections, ipsilaterally for CN I and contralaterally for CN V. The aim of this study was to investigate variations in psychophysiological measurements between a nasal input with low (phenyl ethyl alcohol (PEA)) and high (allyl isothiocyanate (AIC)) intranal trigeminal stimulation. In a first experiment (20 subjects), the intensity, hedonicity and irritation levels of stimulus were tested with a psychophysical evaluation to study the possible influences of perceptual characteristics. A second experiment (37 subjects) used bilateral electrodermal recordings and compared the skin conductance responses (SCRs) for both nasal inputs on either monorhinal and birhinal stimulations. Firstly, the electrodermal activity (EDA) results showed no differences between the two nostrils for PEA as well as AIC, but differences in relation to the type of stimulus, e.g. higher amplitude in response to AIC versus PEA. Secondly, the results indicated bilateral differences in EDA recordings related to the nature of the stimulus and are discussed in terms of hemispheric asymmetric activation.

Dissociated autonomic regulation during stress and physical complaints

OBJECTIVE

In order to evaluate the relevance of individual differences in the regulation of autonomic subsystems to psychosomatic processes, reactivity of the autonomic nervous system to an emotional stressor was related to the occurrence of physical complaints. In contrast to most other studies, the measures were related to the degree of actually experienced stress.

METHODS

In a large sample (n=111), electrodermal activity (EDA) and heart rate variability (HRV) were obtained at rest and during emotional stress. Physical complaints were assessed by a standardized symptom checklist providing subscales for different physiological systems.

RESULTS

Subjects who were actually stressed by the stress induction procedure but showed only weak reactivity of EDA, and subjects who were only slightly stressed but showed a marked EDA response reported a high amount of gastrointestinal complaints. A greater decrease of high-frequency HRV from the rest to the stress condition was associated with reports of relatively more cardiovascular complaints.

CONCLUSION

Findings indicate that the link between regulation of EDA and gastrointestinal functions has to be localized in higher brain structures and support the hypothesis that minor autonomic dysregulation may represent one pathway linking negative affect and the development of physical disorders.