2018-04-06, Popova, Petia, Rockstroh, Brigitte, Miller, Gregory A, Wienbruch, Christian, Carolus, Almut, Popov, Tzvetan G.

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.

2015-05, Popov, Tzvetan G., Wienbruch, Christian, Meissner, Sarah, Miller, Gregory A., Rockstroh, Brigitte

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.

2009, Steffen, Astrid, Muller, Daniel, Wienbruch, Christian, Rockstroh, Brigitte

Reward processing is frequently examined in decision-making designs, as they involve essential components like evaluation of value and reward prediction. The present study examined magnetoencephalographic (MEG) correlates of such components in 20 volunteers: subjects had to decide, whether or not to gamble for 10 or 50 c (Eurocent), which they could win with 10%, 50% or 90% chance. MEG responses to the visually presented value (10 or 50 c) and chance (10, 50 or 90%) stimuli, analyzed using Minimum Norm Estimates (MNE), distinguished value evaluation and reward prediction in time windows between 150 and 350 ms after stimulus onset in different brain areas: righthemispheric temporo-parietal dipole activity 150 230 ms distinguished value evaluation (po .01), whereas the chance prediction varied with right-hemispheric temporo-parietal dipole activity at 215 255 ms (p o .05), bilateral fronto-temporal dipole activity at 235 275 ms (p o .01) and frontal dipole activity at 250 350 ms (p o .05). Frontal activity was larger and decision time was longer on risky trials (decision to gamble at 50% chance). Activation of the same region by both cues (value and chance) suggests that reward processing comprises the interaction of preferred value and expectancy of outcome, while the course of activity suggests a consecutively activated neuronal network of reward processing, including posterior temporal to prefrontal regions.

2006-10-15, Wienbruch, Christian, Paul, Isabella, Weisz, Nathan, Elbert, Thomas, Roberts, Larry E.

We used the 40-Hz auditory steady-state response (SSR) to compare for the first time tonotopic frequency representations in the region of primary auditory cortex (PAC) between subjects with chronic tinnitus and hearing impairment and normal hearing controls. Frequency representations were measured in normal hearing (n=17) and tinnitus (n=28) subjects using eight carrier frequencies between 384 and 6561 Hz, each amplitude modulated (AM) at 40-Hz on trials of 3 min duration under passive attention. In normal hearing subjects, frequency gradients were observed in the medial-lateral, anterior-posterior, and inferior-superior axes, which were consistent with the orientation of Heschl's gyrus and with functional organization revealed by fMRI investigations. The frequency representation in the right hemisphere was approximately 5 mm anterior and approximately 7 mm lateral to that in the left hemisphere, corroborating with MEG measurements hemispheric asymmetries reported by cytoarchitectonic studies of the PAC and by MRI morphometry. In the left hemisphere, frequency gradients were inflected near 2 kHz in normal hearing subjects. These SSR frequency gradients were attenuated in both hemispheres in tinnitus subjects. Dipole power was also elevated in tinnitus, suggesting that more neurons were entrained synchronously by the AM envelope. These findings are consistent with animal experiments reporting altered tonotopy and changes in the response properties of auditory cortical neurons after hearing loss induced by noise exposure. Degraded frequency representations in tinnitus may reflect a loss of intracortical inhibition in deafferented frequency regions of the PAC after hearing injury.

2017-08, Schalinski, Inga, Moran, James, Elbert, Thomas, Reindl, Vanessa, Wienbruch, Christian

Background
Individuals with trauma-related disorders are complex and heterogeneous; part of this complexity derives from additional psychopathology like dissociation as well as environmental adversities such as traumatic stress, experienced throughout the lifespan. Understanding the neurophysiological abnormalities in Post-traumatic stress disorder (PTSD) requires a simultaneous consideration of these factors.

Methods
Resting state magnetoencephalography (MEG) recordings were obtained from 41 women with PTSD and comorbid depressive symptoms, and 16 healthy women. Oscillatory brain activity was extracted for five frequency bands and 11 source locations, and analyzed in relation to shutdown dissociation and adversity-related measures.

Results
Dissociative symptoms were related to increased delta and lowered beta power. Adversity-related measures modulated theta and alpha oscillatory power (in particular childhood sexual abuse) and differed between patients and controls.

Limitations
Findings are based on women with comorbid depressive symptoms and therefore may not be applicable for men or groups with other clinical profiles. In respect to childhood adversities, we had no reliable source for the early infancy.

Conclusion
Trauma-related abnormalities in neural organization vary with both exposure to adversities as well as their potential to evoke ongoing shutdown responses.

2015, Mohamed, Wessam, Paul, Isabella, Wienbruch, Christian, Robert, Christina, Elbert, Thomas

The condition of dyslexia has been associated with problems in speech perception, particularly in the processing of speech signals (e.g., phonemes). Speech signals contain information on different time scales. For instance, while rapid spectral changes as formant transitions may occur on time scale (20-40ms), syllabic and prosodic information occur on a time scale of (150-300ms). Therefore, the segmentation of the auditory stream into discrete representations is a prerequisite for speech perception, According to Peoppel (2003); the input speech signal has a neural representation that is bilaterally symmetric at an early representational level; however it is elaborated asymmetrically in the time domain. Consequently, it has suggested that temporal integration in different windows is reflected as oscillatory neuronal activity in different frequency bands. In this study, we are testing if the temporal integration is reflected as oscillatory activity in different frequency bands by mapping focal slow waves in the delta (1.5-4Hz) frequency band. We used magnetoencephalographic (MEG) source imaging in a sample of 19 dyslexic children with poor categorical perception and 14 controls while listening passively to syllables /ba/ and /da/. Dyslexic children with poor categorical perception differ significantly in the density of magnetic slow waves produced by the two hemispheres. To illustrate, dyslexic children with poor categorical perception showed elevated production of focally generated slow waves (1-4Hz), predominately in the left hemisphere as compared to controls. The results suggest altered segmentation processes of speech sounds in a subset of children with dyslexia.

2008, Catani, Claudia, Neuner, Frank, Wienbruch, Christian, Elbert, Thomas

2016-12, Fiess, Johanna, Rockstroh, Brigitte, Schmidt, Roger, Wienbruch, Christian, Steffen, Astrid

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 110–330 ms following picture onset in source space for prior defined posterior and central regions of interest

Results

As early as 110 ms and across presentation interval, posterior neural activity modulation by picture category was similar in both groups, despite smaller initial (110–150 ms) 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.

2009, Jordanov, Todor, Popov, Tzvetan G., Wienbruch, Christian, Elbert, Thomas, Rockstroh, Brigitte

In a first step three different methods for dipole localization of M50 auditory sources evoked by the double click paradigm were compared in order to differentiate between 12 schizophrenic patients (1 female) and 10 controls (1 female). Dependent variables were sensory gating ratios (dipolemoment of themagnetic counterpart of click two divided by click one) and hemispheric asymmetry (left vs. right hemispheric dipole location). MEG was measured using a 148 channels magnetometer system. Dipoleswere fitted using (1) a spherical head model with 34 MEG channels over the left and right temporal lobe, respectively, (2) a spherical head model with 68MEGchannels over both temporal lobes, (3) a boundary element model (BEM) based on an averaged magnetic resonance imaging (MRI) dataset (using 68 MEG channels). Differentiation between patients and controls for both gating ratios and anterior-posterior asymmetry was most precise when dipole moments were calculated with the BEM model. Thus, in a second step, the BEM method was used to investigate changes across 4 weeks, during which patients completed a cognitive training program. In patients, gating ratios were decreased after training but no changes in the asymmetry were noticed. Stability of measures was confirmed in controls.

2007, Paul, Isabella, Bott, Christof, Heim, Sabine, Wienbruch, Christian, Elbert, Thomas