Increase in prefrontal cortex oxygenation during static muscular endurance performance is modulated by self-regulation strategies.

Enduring physical strain is an important ability and prototypically required in athletic activities. However, little is known about the psychological determinants of endurance performance and their underlying neural mechanisms. Here, we investigated self-regulation as one such factor. We recruited 60 participants who hold intertwined rings for as long as possible while avoiding contacts between them, either with a goal intention or an implementation intention to perform well. Performance was measured in terms of time-to-failure and contact errors. Additionally, we repeatedly assessed ratings of perceived exertion (RPE) and pain (RPP) and used functional near-infrared spectroscopy (fNIRS) to continuously monitor cerebral oxygenation in dorsal and ventral parts of the lateral prefrontal cortex (LPFC), brain regions associated with effortful attentional control and response inhibition, respectively. Performance, RPE and RPP were similar in the goal and the implementation intention condition. LPFC activity increased over time, but its activation level was generally lower in the implementation intention condition. Both effects were particularly pronounced in the dorsal LPFC. Moreover, the balance between effortful and more automatic regulation seems to differ between self-regulation strategies. Our results indicate that self-regulation plays an important role in endurance performance and that self-regulatory processes during endurance performance might be reflected in LPFC activation.

The impact of cognitive training on spontaneous gamma oscillations in schizophrenia.

Schizophrenia patients exhibit less gamma-frequency EEG/MEG activity (>30 Hz), a finding interpreted as evidence of poor temporal neural organization and functional network communication. Research has shown that neuroplasticity-oriented training can improve task-related oscillatory dynamics, indicating some reorganization capacity in schizophrenia. Demonstrating a generalization of such task training effects to spontaneous oscillations at rest would not only enrich understanding of this neuroplastic potential but inform the interpretation of spontaneous gamma oscillations in the service of normal cognitive function. In the present study, neuromagnetic resting-state oscillatory brain activity and cognitive performance were assessed before and after training in 61 schizophrenia patients, who were randomly assigned to 4 weeks of neuroplasticity-oriented targeted cognitive training or treatment as usual (TAU). Gamma power of 40-90 Hz increased after training, but not after TAU, in a frontoparietal network. Across two types of training, this increase was related to improved cognitive test performance. These results indicate that abnormal oscillatory dynamics in schizophrenia patients manifested in spontaneous gamma activity can be changed with neuroplasticity-oriented training parallel to cognitive performance.

The individual contribution of DSM 5 symptom clusters of PTSD, life events, and childhood adversity to frontal oscillatory brain asymmetry in a large sample of active combatants.

Post-Traumatic Stress Disorder (PTSD) has been linked to deviations in lateralized frontal functional oscillatory activity. This is possibly because left and right DLPFC have differential roles in regulating both memory and stress response, which are both dysfunctional in PTSD. However, previous results are heterogeneous, and could be attributable to individual symptom clusters, traumatic or aggressive life events, early life stress, or the interaction of these factors. In a large sample of active combatants (N=401), we regressed these factors on frontal electroencephalography (EEG) asymmetry across 5 frequency bands (delta: 2-4Hz; theta: 4-8Hz; alpha: 8-12Hz; beta: 12-24Hz; gamma: 24-48Hz). Negative cognition and mood was associated with stronger relative left delta and theta band power. Traumatic life events showed stronger right alpha and beta band power. Traumatic life events in interaction with hyperarousal predicted stronger relative right left-right imbalance (theta, alpha, and beta bands), whereas childhood adversity, in interaction with negative cognition and mood, predicted stronger relative left left-right imbalance (delta, theta, alpha and beta bands). The contribution of lateralized DLPFC dysfunction to PTSD is thus dependent on the individual complexities of subsymptom clusters and life history, and future studies need to take these factors into account.

Functional neurological symptoms modulate processing of emotionally salient stimuli.

OBJECTIVE: Dysfunctional emotion processing has been discussed as a contributing factor to functional neurological symptoms (FNS) in the context of conversion disorder, and refers to blunted recognition and the expression of one's own feelings. However, the emotion processing components characteristic for FNS and/or relevant for conversion remain to be specified. With this goal, the present study targeted the initial, automatic discrimination of emotionally salient stimuli. METHODS: The magnetoencephalogram (MEG) was monitored in 21 patients with functional weakness and/or sensory disturbance subtypes of FNS and 21 healthy comparison participants (HC) while they passively watched 600 emotionally arousing, pleasant, unpleasant or neutral stimuli in a rapid serial visual presentation (RSVP) design. Neuromagnetic activity was analyzed 110-330ms following picture onset in source space for prior defined posterior and central regions of interest. RESULTS: As early as 110ms and across presentation interval, posterior neural activity modulation by picture category was similar in both groups, despite smaller initial (110-150ms) overall and posterior power in patients with FNS. The initial activity modulation by picture category was also evident in the left sensorimotor area in patients with FNS, but not significant in HC. CONCLUSIONS: Similar activity modulation by emotional picture category in patients with FNS and HC suggests that the fast, automatic detection of emotional salience is unchanged in patients with FNS, but involves an emotion-processing network spanning posterior and sensorimotor areas.

A mechanism of deficient interregional neural communication in schizophrenia.

Cognitive interference control is disrupted in schizophrenia (SZ). Neuroimaging studies relate interference control to 4-7 Hz (theta) neural activity in a network spanning prefrontal, anterior cingulate (ACC), and parietal cortices. The mechanism of communication in this network and how it is disrupted in schizophrenia are unclear. Behavioral performance and EEG theta oscillations were examined in a Stroop color-word interference task in 17 healthy controls (HC) and 14 SZ patients. Color-word incongruence induced less theta power increase in SZ than in HC around 400 ms and 600-900 ms after word onset in ACC, left middle frontal gyrus (MFG), and inferior parietal regions. Coupling of ACC theta phase to MFG gamma amplitude, indexing interregional communication, was weaker in SZ than in HC. Results suggest ACC-MFG theta power modulation as a mechanism of interference control that supports executive function and is disrupted in schizophrenia.

Changing facial affect recognition in schizophrenia: effects of training on brain dynamics.

Deficits in social cognition including facial affect recognition and their detrimental effects on functional outcome are well established in schizophrenia. Structured training can have substantial effects on social cognitive measures including facial affect recognition. Elucidating training effects on cortical mechanisms involved in facial affect recognition may identify causes of dysfunctional facial affect recognition in schizophrenia and foster remediation strategies. In the present study, 57 schizophrenia patients were randomly assigned to (a) computer-based facial affect training that focused on affect discrimination and working memory in 20 daily 1-hour sessions, (b) similarly intense, targeted cognitive training on auditory-verbal discrimination and working memory, or (c) treatment as usual. Neuromagnetic activity was measured before and after training during a dynamic facial affect recognition task (5 s videos showing human faces gradually changing from neutral to fear or to happy expressions). Effects on 10-13 Hz (alpha) power during the transition from neutral to emotional expressions were assessed via MEG based on previous findings that alpha power increase is related to facial affect recognition and is smaller in schizophrenia than in healthy subjects. Targeted affect training improved overt performance on the training tasks. Moreover, alpha power increase during the dynamic facial affect recognition task was larger after affect training than after treatment-as-usual, though similar to that after targeted perceptual-cognitive training, indicating somewhat nonspecific benefits. Alpha power modulation was unrelated to general neuropsychological test performance, which improved in all groups. Results suggest that specific neural processes supporting facial affect recognition, evident in oscillatory phenomena, are modifiable. This should be considered when developing remediation strategies targeting social cognition in schizophrenia.

A neuronal network model for simulating the effects of repetitive transcranial magnetic stimulation on local field potential power spectra.

Repetitive transcranial magnetic stimulation (rTMS) holds promise as a non-invasive therapy for the treatment of neurological disorders such as depression, schizophrenia, tinnitus, and epilepsy. Complex interdependencies between stimulus duration, frequency and intensity obscure the exact effects of rTMS stimulation on neural activity in the cortex, making evaluation of and comparison between rTMS studies difficult. To explain the influence of rTMS on neural activity (e.g. in the motor cortex), we use a neuronal network model. The results demonstrate that the model adequately explains experimentally observed short term effects of rTMS on the band power in common frequency bands used in electroencephalography (EEG). We show that the equivalent local field potential (eLFP) band power depends on stimulation intensity rather than on stimulation frequency. Additionally, our model resolves contradictions in experiments.

Changes in cortical slow wave activity in healthy aging.

A number of studies have demonstrated enhanced slow wave activity associated with pathological brain function e.g. in stroke patients, schizophrenia, depression, Morbus Alzheimer, and post-traumatic stress disorder. However, the association between slow wave activity and healthy aging has remained largely unexplored. This study examined whether the frequency at which focal generators of delta waves appear in the healthy cerebral cortex changes with age and whether this measure relates to cognitive performance. We investigated 53 healthy individuals aged 18 to 89 years and assessed MEG during a resting condition. Generators of focal magnetic slow waves were localized. Results showed a significant influence of age: dipole density decreases with increasing age. The relationship between cognitive performance and delta dipole density was not significant. The results suggest that in healthy aging slow waves decrease with aging and emphasize the importance of age-matched control groups for further studies. Increased appearance of slow waves as a marker for pathological stages can only be detected in relation to a control group of the same age.

Distinct cognitive mechanisms in a gambling task share neural mechanisms.

Distinct psychological processes have been proposed to unfold in decision-making. The time course of neural mechanisms supporting these processes has not been fully identified. The present MEG study examined spatio-temporal activity related to components of decision-making proposed to support reward valuation, reward prediction, and outcome evaluation. Each trial presented information on reward value (10 or 50 cents) and reward probability (10%, 50%, or 90%). Brain activity related to those inputs and to outcome feedback was evaluated via electromagnetic responses in source space. Distributed dipole activity reflected reward value and reward probability 150-350 ms after information arrival. Neural responses to reward-value information peaked earlier than those to reward-probability information. Results suggest that valuation, prediction, and outcome evaluation share neural structures and mechanisms even on a relatively fine time scale.

Hippocampal activity during the transverse patterning task declines with cognitive competence but not with age.

BACKGROUND: The hippocampus is a brain region that is particularly affected by age-related morphological changes. It is generally assumed that a loss in hippocampal volume results in functional deficits that contribute to age-related cognitive decline. In a combined cross-sectional behavioural and magnetoencephalography (MEG) study we investigated whether hippocampal-associated neural current flow during a transverse patterning task - which requires learning relational associations between stimuli - correlates with age and whether it is modulated by cognitive competence. RESULTS: Better performance in several tests of verbal memory, verbal fluency and executive function was indeed associated with higher hippocampal neural activity. Age, however, was not related to the strength of hippocampal neural activity: elderly participants responded slower than younger individuals but on average produced the same neural mass activity. CONCLUSIONS: Our results suggest that in non-pathological aging, hippocampal neural activity does not decrease with age but is rather related to cognitive competence.

Local Heschl's Gyrus-based coordinate system for intersubject comparison of M50 auditory response modeled by single equivalent current dipole.

Allocating electromagnetic auditory responses to active regions in the human auditory cortex can be difficult because of high interindividual variability of the relevant structures. Location and orientation of the primary auditory cortex (Heschl's Gyrus) and the temporal plane vary with individual features such as age, gender, handedness, or between healthy subjects and patients with a psychiatric disorder (e.g., schizophrenia). Here, we propose a reference coordinate system that considers the individual MRI-based position, orientation and length of the primary auditory cortex to account for interindividual variability. Transformation of the M50 dipole localizations in this new HG-(Heschl's-Gyrus)-coordinate system, accomplished for 10 healthy subjects and 10 schizophrenia patients, confirmed group difference more precisely than other registration methods. We suggest to use the HG-coordinate system for localization of functional measures and evaluation of brain activity differences between groups or measurement conditions.

Localization of the magnetic equivalent of the ERN and induced oscillatory brain activity.

It has been found in numerous electroencephalographic (EEG) studies that a negative potential arises following an erroneous response (so-called Error-Related Negativity, ERN). This typical component of the EEG has, however, proven more difficult to identify when transferring analogous paradigms to magnetoencephalography (MEG). The aim of this study was to devise and apply a paradigm to elicit erroneous responses and using MEG to measure both the error-related evoked brain activity (mERN) as well as accompanying induced oscillatory activity. Results clearly demonstrate that it is possible to measure the mERN and to identify cortical sources associated with it. Using distributed source modeling, it is possible to identify the mERN in source space and corroborate EEG findings, with the mERN generated in the anterior cingulate cortex (ACC). This supports notions regarding the role of the ACC in error monitoring and cognitive control of motor behavior. Furthermore, changes in induced oscillatory activity were observed in the theta and beta bands. This extends previous studies, which show that evoked theta activity could underlie the generation of the ERN.

Adverse experiences in childhood influence brain responses to emotional stimuli in adult psychiatric patients.

Previous results suggest that early life stress (ELS) may be related to altered cortical responses to emotional stimuli. In a previous study, we found suppressed cortical responses to emotional pictures in psychiatric patients with high-ELS. The present study explored the stability of this effect across time and stimulation conditions. In addition, the relationship between ELS and current life stress was examined, and we probed whether this current life stress was related to the cortical responses. Fifteen patients with high, 16 patients with low-ELS and 15 psychiatrically healthy subjects with low-ELS participated in two sessions 8 months apart. Subjects monitored a rapid serial presentation of pleasant, neutral and unpleasant pictures during magnetoencephalographic recording. In both sessions, estimated neural activity in occipital-parietal-temporal regions between 70 and 250 ms after picture onset was smaller in patients, particularly in those with high-ELS, compared to healthy subjects. Modulation of activity by arousing (pleasant and unpleasant) compared to neutral stimuli around 200 ms post-stimulus did not differ between groups, whereas around 300 ms, patients did not show the pronounced cortical response to pleasant stimuli exhibited by healthy subjects. Results suggest that ELS and psychiatric disorder (1) diminish early perceptual processing (<200 ms) of emotional stimuli without substantially affecting activity modulation by stimulus arousal value, (2) diminish later attention allocation processes (>300 ms), and (3) are related to more recent life stress. High intraindividual correlations of activity patterns between sessions suggest lasting effects of ELS on processing modes.

Functional re-recruitment of dysfunctional brain areas predicts language recovery in chronic aphasia.

Functional recovery in response to a brain lesion, such as a stroke, can even occur years after the incident and may be accelerated by effective rehabilitation strategies. In eleven chronic aphasia patients, we administered a short-term intensive language training to improve language functions and to induce cortical reorganization under rigorously controlled conditions. Overt naming performance was assessed during functional magnetic resonance imaging (fMRI) prior to and immediately after the language training. Regions of interest (ROIs) for statistical analyses were constituted by areas with individually determined abnormally high densities of slow wave generators (identified by magnetoencephalography prior to the language intervention) that clustered mainly in left perilesional areas. Three additional individually defined regions served to control for the specificity of the results for the selected respective target region: the homologue area of the individual patient's lesion, the mirror image of the delta ROI in the right hemisphere and left hemispheric regions that did not produce a significant amount of slow wave activity. Treatment-induced changes of fMRI brain activation were highly correlated with improved naming of the trained pictures, but selectively within the pre-training dysfunctional perilesional brain areas. Our results suggest that remodeling of cortical functions is possible even years after a stroke. The behavioral gain seems to be mediated by brain regions that had been partially deprived from input after the initial stroke. We therefore provide first time direct evidence for the importance of treatment-induced functional reintegration of perilesional areas in a heterogeneous sample of chronic aphasia patients.

Altered oscillatory brain dynamics after repeated traumatic stress.

BACKGROUND: Repeated traumatic experiences, e.g. torture and war, lead to functional and structural cerebral changes, which should be detectable in cortical dynamics. Abnormal slow waves produced within circumscribed brain regions during a resting state have been associated with lesioned neural circuitry in neurological disorders and more recently also in mental illness. METHODS: Using magnetoencephalographic (MEG-based) source imaging, we mapped abnormal distributions of generators of slow waves in 97 survivors of torture and war with posttraumatic stress disorder (PTSD) in comparison to 97 controls. RESULTS: PTSD patients showed elevated production of focally generated slow waves (1-4 Hz), particularly in left temporal brain regions, with peak activities in the region of the insula. Furthermore, differential slow wave activity in right frontal areas was found in PTSD patients compared to controls. CONCLUSION: The insula, as a site of multimodal convergence, could play a key role in understanding the pathophysiology of PTSD, possibly accounting for what has been called posttraumatic alexithymia, i.e., reduced ability to identify, express and regulate emotional responses to reminders of traumatic events. Differences in activity in right frontal areas may indicate a dysfunctional PFC, which may lead to diminished extinction of conditioned fear and reduced inhibition of the amygdala.

Abnormal oscillatory brain dynamics in schizophrenia: a sign of deviant communication in neural network?

BACKGROUND: Slow waves in the delta (0.5-4 Hz) frequency range are indications of normal activity in sleep. In neurological disorders, focal electric and magnetic slow wave activity is generated in the vicinity of structural brain lesions. Initial studies, including our own, suggest that the distribution of the focal concentration of generators of slow waves (dipole density in the delta frequency band) also distinguishes patients with psychiatric disorders such as schizophrenia, affective disorders, and posttraumatic stress disorder. METHODS: The present study examined the distribution of focal slow wave activity (ASWA: abnormal slow wave activity) in 116 healthy subjects, 76 inpatients with schizophrenic or schizoaffective diagnoses and 42 inpatients with affective (ICD-10: F3) or neurotic/reactive (F4) diagnoses using a newly refined measure of dipole density. Based on 5-min resting magnetoencephalogram (MEG), sources of activity in the 1-4 Hz frequency band were determined by equivalent dipole fitting in anatomically defined cortical regions. RESULTS: Compared to healthy subjects the schizophrenia sample was characterized by significantly more intense slow wave activity, with maxima in frontal and central areas. In contrast, affective disorder patients exhibited less slow wave generators mainly in frontal and central regions when compared to healthy subjects and schizophrenia patients. In both samples, frontal ASWA were related to affective symptoms. CONCLUSION: In schizophrenic patients, the regions of ASWA correspond to those identified for gray matter loss. This suggests that ASWA might be evaluated as a measure of altered neuronal network architecture and communication, which may mediate psychopathological signs.

If-then planning modulates the P300 in children with attention deficit hyperactivity disorder.

Children with attention deficit hyperactivity disorder have difficulties with tasks that require response inhibition. We measured electroencephalographic data of nonmedicated children with attention deficit hyperactivity disorder and control children in two conditions: (a) a neutral condition without a self-regulation strategy and (b) a condition that involved the making of if-then plans (i.e. 'If situation X is encountered, then I will perform the goal-directed behavior Y'). If-then plans improved response inhibition and increased the P300 in children with attention deficit hyperactivity disorder compared with the neutral condition. The present results encourage the application of self-regulation using if-then plans in addition or as an alternative to common medical therapy.

Abnormal slow wave mapping (ASWAM)--A tool for the investigation of abnormal slow wave activity in the human brain.

Slow waves in the delta and theta frequency range, normal signs of deactivated networks in sleep stages, are considered 'abnormal' when prominent in the waking state and when generated in circumscribed brain areas. Structural cortical lesions, e.g. related to stroke, tumors, or scars, generate focal electric and magnetic slow wave activity in the penumbra. Focal concentrations of slow wave activity exceeding those of healthy subjects have also been found in individuals suffering from psychiatric disorders without obvious structural brain damage. Hence, identification and mapping of abnormal slow wave activity might contribute to the investigation of cortical indications of psychopathology. Here I propose a method for abnormal slow wave mapping (ASWAM), based on a 5 min resting magnetoencephalogramm (MEG) and equivalent current dipole fitting to sources in the 1-4 Hz frequency band (delta) in anatomically defined cortical regions. The method was tested in a sample of 116 healthy subjects (59 males), with the aim to provide a basis for later comparison with patient samples. As to be expected, delta dipole density was low in healthy subjects. However, its distribution differed between genders with fronto-central>posterior dipole density in male and posterior dominance in female participants, which was not significantly related to either age or head size. Results suggest that this method allows the identification of ASWA, so that comparison against Z-scores from a larger normal control group might assist diagnostic purposes in patient groups. As specific distributions seem to reflect differences between genders, this should be considered also in the analysis of patient samples.

Phonological but not auditory discrimination is impaired in dyslexia.

Deficient phonological skills are considered to be a core problem in developmental dyslexia. Children with dyslexia often demonstrate poorer performance than non-impaired readers when categorizing speech-sounds. Using the automatic mismatch response, we show that in contrast to this deficit at the behavioural level, neurophysiological responding in dyslexic children indicates their ability to automatically discriminate syllables. Therefore, the phonological deficit is unlikely to be caused by a temporal deficit or by a noisy functional organization in the respective representational cortex. We obtained measures of reading, spelling and categorical speech-perception from 58 dyslexic children and 21 control children. The children also participated in magnetoencephalographic measurements while being stimulated acoustically with the syllables /ba/ and /da/ in an oddball paradigm. Mismatch field (MMF) amplitudes between standard and deviant stimuli were obtained. Dyslexic children performed more poorly than control children on all test measures. However, the groups did not differ in MMF amplitude or latency. No correlations were found between MMF amplitudes and behavioural performance. These results were obtained with a large sample size and thus speak robustly against a general deficit in auditory discrimination in dyslexia. These results are compatible with the idea that decoding difficulties occur later in the processing stream where access to the phonological lexicon is attempted.

Decoupling neural networks from reality: dissociative experiences in torture victims are reflected in abnormal brain waves in left frontal cortex.

From a neuroscience perspective, little is known about the long-term effect of torture. Dissociative experiences and posttraumatic stress disorder are often the results of this experience. We examined psychological dissociation within a group of 23 torture victims and report its manifestations within neural networks in the human brain. In particular, we observed that dissociative experiences are associated with slow abnormal brain waves generated in left ventrolateral frontal cortex. Given that focal slow waves often result from depriving neural networks of major input, the present results may indicate decoupling of frontal affective processors from left cortical language areas. This interpretation is consistent with the fact that disturbed access to structured verbal memory concerning traumatic events is a core feature of the dissociative experience.