Chakarov V, Naranjo JR, Schulte-Mö nting J, Omlor W, Huethe F, Kristeva R. Beta-range EEG-EMG coherence with isometric compensation for increasing modulated low-level forces. J Neurophysiol 102: 1115-1120, 2009. First published May 20, 2009 doi:10.1152/jn.91095.2008. Corticomuscular synchronization has been shown to occur in beta (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) and gamma range (30 -45 Hz) during isometric compensation of static and dynamic (periodically modulated) low-level forces, respectively. However, it is still unknown to what extent these synchronization processes in beta and gamma range are modified with increasing modulated force. We addressed this question by investigating the corticomuscular coherence (CMC) between the electroencephalogram (EEG) and electromyogram (EMG) from the first dorsal interosseus muscle (FDI) as well as the cortical and muscular spectral power during a visuomotor task where different levels of a dynamic (modulated) force were used. Seven healthy right-handed female subjects compensated dynamic forces at 8, 16, and 24% of the maximal voluntary contraction (MVC) isometrically with their right index finger. Under the three conditions investigated, we found a broad-band CMC comprising both beta and gamma range and peaking at ϳ22 Hz within the beta band. This broad-band coherence increased linearly with higher force level. A separate analysis of the gamma range CMC did not show significant modulation of the CMC by the force levels. EEG and EMG spectral power did not show any significant difference among the three force conditions. Our results favor the view that the function of beta range CMC is not specific for low-level static forces only. The sensorimotor system may resort to stronger and also broader beta-range CMC to generate stable corticospinal interaction during increased force level, as well as when compensating for dynamic modulated forces. This finding re-enforces the importance of the beta-range EEG-EMG coherence in sensorimotor integration. I N T R O D U C T I O NMuch attention has been given to the functional organization of the corticospinal system and the mechanisms of muscle control by the CNS and in particular to the universal mechanism of neuronal interaction via synchronization, which plays a relevant role in the effective coordination between the cortical motor areas and the muscles. This synchronization mechanism can be described by the coherence function for different frequency ranges. During maintained motor contraction the cortical motor areas and the muscles are synchronized in beta-range as shown in monkeys (Baker et al. 1997(Baker et al. , 1999 Fetz 1992, 1996) (Perez et al. 2006). Based on the finding that increased beta-range CMC and better performance are correlated, we suggested the betarange CMC as a mechanism for effective corticospinal interaction during static forces .Because one of the main functions of the motor cortex is to control force output (Ashe 1997), modulation of the beta-range CMC by different stati...

Background: There is growing scientific interest in assessing the biological correlates of non-pharmacological interventions such as mindfulness. Examinations of the beneficial effects of mindfulness on hypothalamus-pituitary-adrenocortical system activity (HPA SA) and sleep are sparse. The aim of the present study was to explore the impact of long- and short-term meditation experience on HPA SA and sleep. Method: There were 20 participants, 9 of whom had long-term experience in meditation (mean = 264 months) and 11 novices. Novices underwent an 8-week course in Mindfulness-Based Stress Reduction (MBSR), and cortisol samples were taken in the lab at the beginning and end of the course. To assess the cortisol awakening response, 4 morning cortisol samples were collected. Sleep and mindfulness were assessed by self-rating questionnaires. Results: Among participants with long-term meditation experience, morning cortisol decreased with length of experience. For novices, after an 8-week introductory MBSR course, morning cortisol levels had decreased, while both sleep and self-attribution of mindfulness significantly improved. Cortisol levels did not, however, change between the beginning and end of individual MBSR sessions. Conclusions: The pattern of results lends support to the view that MBSR/meditation has a favorable influence both on biomarkers of stress regulation, such as cortisol secretion, and on sleep.

ObjectivesSeveral recent studies report the presence of a specific EEG pattern named Thalamocortical Dysrhythmia (TCD) in patients with severe chronic neurogenic pain. This is of major interest since so far no neuroscientific indicator of chronic pain could be identified. We investigated whether a TCD-like pattern could be found in patients with moderate chronic back pain, and we compared patients with neuropathic and non-neuropathic pain components. We furthermore assessed the presence of psychopathology and the degree of psychological functioning and examined whether the strength of the TCD-related EEG markers is correlated with psychological symptoms and pain ratings.DesignControlled clinical trial with age and sex matched healthy controls.MethodsSpontaneous EEG was recorded in 37 back pain patients and 37 healthy controls.ResultsWe were not able to observe a statistically significant TCD effect in the EEG data of the whole patient group, but a subsample of patients with evidence for root damage showed a trend in this direction. Pain patients showed markedly increased psychopathology. In addition, patients' ratings of pain intensity within the last 1 to 12 months showed strong correlations with EEG power, while psychopathology was correlated to the peak frequency.ConclusionOut of several possible interpretations the most likely conclusion is that only patients with severe pain as well as root lesions with consecutive thalamic deafferentation develop the typical TCD pattern. Our primary method of defining ‘neuropathic pain’ could not reliably determine if such a deafferentation was present. Nevertheless the analysis of a specific subsample as well as correlations between pain ratings, psychopathology and EEG power and peak frequency give some support to the TCD concept.Trial RegistrationClinicalTrials.gov NCT00744575