Gabriel Curio

Publications of Gabriel Curio

• Cross-frequency decomposition: A novel technique for studying interactions between neuronal oscillations with different frequencies.

  Authors: Vadim V Nikulin, Guido Nolte, Gabriel Curio

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology. 01/2012;

  OBJECTIVE: We present a novel method for the extraction of neuronal components showing cross-frequency phase synchronization. METHODS: In general the method can be applied for the detection of phaseOBJECTIVE: We present a novel method for the extraction of neuronal components showing cross-frequency phase synchronization. METHODS: In general the method can be applied for the detection of phase interactions between components with frequencies f1 and f2, where f2≈rf1 and r is some integer. We refer to the method as cross-frequency decomposition (CFD), which consists of the following steps: (a) extraction of f1-oscillations with the spatio-spectral decomposition algorithm (SSD); (b) frequency modification of the f1-oscillations obtained with SSD; and (c) finding f2-oscillations synchronous with f1-oscillations using least-squares estimation. RESULTS: Our simulations showed that CFD was capable of recovering interacting components even when the signal-to-noise ratio was as low as 0.01. An application of CFD to the real EEG data demonstrated that cross-frequency phase synchronization between alpha and beta oscillations can originate from the same or remote neuronal populations. CONCLUSIONS: CFD allows a compact representation of the sets of interacting components. The application of CFD to EEG data allows differentiating cross-frequency synchronization arising due to genuine neurophysiological interactions from interactions occurring due to quasi-sinusoidal waveform of neuronal oscillations. SIGNIFICANCE: CFD is a method capable of extracting cross-frequency coupled neuronal oscillations even in the presence of strong noise.

• Are brain currents detectable by means of low-field NMR? A phantom study.

  Authors: Nora Höfner, Hans-Helge Albrecht, Antonino Mario Cassará, Gabriel Curio, Stefan Hartwig, Jens Haueisen, Ingo Hilschenz, Rainer Körber, Sven Martens, Hans-Jürgen Scheer, Jens Voigt, Lutz Trahms, Martin Burghoff

  Magnetic resonance imaging. 09/2011; 29(10):1365-73.

  A number of different methods have been developed in order to detect the spreading of neuronal currents by means of noninvasive imaging techniques. However, all of these are subjected to limitationsA number of different methods have been developed in order to detect the spreading of neuronal currents by means of noninvasive imaging techniques. However, all of these are subjected to limitations in the temporal or spatial resolution. A new approach of neuronal current detection is based on the use of low-field nuclear magnetic resonance (LF-NMR) that records brain activity directly. In the following, we describe a phantom study in order to assess the feasibility of neuronal current detection using LF-NMR. In addition to that, necessary preliminary subject studies examining somatosensory evoked neuronal currents are presented. During the phantom study, the influences of two different neuronal time signals on (1)H-NMR signals were observed. The measurements were carried out by using a head phantom with an integrated current dipole to simulate neuronal activity. Two LF-NMR methods based on a DC and an AC (resonant) mechanism were utilized to study the feasibility of detecting both types of magnetic brain signals. Measurements were made inside an extremely magnetically shielded room by using a superconducting quantum interference device magnetometer system. The measurement principles were validated applying currents of higher intensity than those typical of the neuronal currents. Through stepwise reduction of the amplitude of the current dipole strength, the resolution limits of the two measuring procedures were found. The results indicate that it is necessary to improve the signal-to-noise ratio of the measurement system by at least a factor of 38 in order to detect typical human neuronal activity directly by means of LF-NMR. In addition to that, ways of achieving this factor are discussed.

• Enhanced performance by a hybrid NIRS-EEG brain computer interface.

  Authors: Siamac Fazli, Jan Mehnert, Jens Steinbrink, Gabriel Curio, Arno Villringer, Klaus-Robert Müller, Benjamin Blankertz

  NeuroImage. 08/2011; 59(1):519-29.

  Noninvasive Brain Computer Interfaces (BCI) have been promoted to be used for neuroprosthetics. However, reports on applications with electroencephalography (EEG) show a demand for a better accuracyNoninvasive Brain Computer Interfaces (BCI) have been promoted to be used for neuroprosthetics. However, reports on applications with electroencephalography (EEG) show a demand for a better accuracy and stability. Here we investigate whether near-infrared spectroscopy (NIRS) can be used to enhance the EEG approach. In our study both methods were applied simultaneously in a real-time Sensory Motor Rhythm (SMR)-based BCI paradigm, involving executed movements as well as motor imagery. We tested how the classification of NIRS data can complement ongoing real-time EEG classification. Our results show that simultaneous measurements of NIRS and EEG can significantly improve the classification accuracy of motor imagery in over 90% of considered subjects and increases performance by 5% on average (p<0:01). However, the long time delay of the hemodynamic response may hinder an overall increase of bit-rates. Furthermore we find that EEG and NIRS complement each other in terms of information content and are thus a viable multimodal imaging technique, suitable for BCI.

• Revealing the neural response to imperceptible peripheral flicker with machine learning.

  Authors: Anne K Porbadnigk, Simon Scholler, Benjamin Blankertz, Arnd Ritz, Matthias Born, Robert Scholl, Klaus-Robert Muller, Gabriel Curio, Matthias S Treder

  Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference. 08/2011; 2011:3692-5.

  Lighting in modern-day devices is often discrete. The sharp onsets and offsets of light are known to induce a steady-state visually evoked potential (SSVEP) in the electroencephalogram (EEG) at lowLighting in modern-day devices is often discrete. The sharp onsets and offsets of light are known to induce a steady-state visually evoked potential (SSVEP) in the electroencephalogram (EEG) at low frequencies. However, it is not well-known how the brain processes visual flicker at the threshold of conscious perception and beyond. To shed more light on this, we ran an EEG study in which we asked participants (N=6) to discriminate on a behavioral level between visual stimuli in which they perceived flicker and those that they perceived as constant wave light. We found that high frequency flicker which is not perceived consciously anymore still elicits a neural response in the corresponding frequency band of EEG, con-tralateral to the stimulated hemifield. The main contribution of this paper is to show the benefit of machine learning techniques for investigating this effect of subconscious processing: Common Spatial Pattern (CSP) filtering in combination with classification based on Linear Discriminant Analysis (LDA) could be used to reveal the effect for additional participants and stimuli, with high statistical significance. We conclude that machine learning techniques are a valuable extension of conventional neurophysiological analysis that can substantially boost the sensitivity to subconscious effects, such as the processing of imperceptible flicker.

• EEG potentials predict upcoming emergency brakings during simulated driving.

  Authors: Stefan Haufe, Matthias S Treder, Manfred F Gugler, Max Sagebaum, Gabriel Curio, Benjamin Blankertz

  Journal of neural engineering. 07/2011; 8(5):056001.

  Emergency braking assistance has the potential to prevent a large number of car crashes. State-of-the-art systems operate in two stages. Basic safety measures are adopted once external sensorsEmergency braking assistance has the potential to prevent a large number of car crashes. State-of-the-art systems operate in two stages. Basic safety measures are adopted once external sensors indicate a potential upcoming crash. If further activity at the brake pedal is detected, the system automatically performs emergency braking. Here, we present the results of a driving simulator study indicating that the driver's intention to perform emergency braking can be detected based on muscle activation and cerebral activity prior to the behavioural response. Identical levels of predictive accuracy were attained using electroencephalography (EEG), which worked more quickly than electromyography (EMG), and using EMG, which worked more quickly than pedal dynamics. A simulated assistance system using EEG and EMG was found to detect emergency brakings 130 ms earlier than a system relying only on pedal responses. At 100 km h(-1) driving speed, this amounts to reducing the braking distance by 3.66 m. This result motivates a neuroergonomic approach to driving assistance. Our EEG analysis yielded a characteristic event-related potential signature that comprised components related to the sensory registration of a critical traffic situation, mental evaluation of the sensory percept and motor preparation. While all these components should occur often during normal driving, we conjecture that it is their characteristic spatio-temporal superposition in emergency braking situations that leads to the considerable prediction performance we observed.

• Effect of complete stimulus predictability on P3 and N2 components: an electroencephalographic study.

  Authors: Katherina M B von Carlowitz-Ghori, Friederike U Hohlefeld, Zubeyir Bayraktaroglu, Gabriel Curio, Vadim V Nikulin

  Neuroreport. 06/2011; 22(9):459-63.

  In everyday life one may encounter both unpredictable and self-initiated, hence anticipated, events. Here, we analyzed the effects of self-initiated auditory stimulus presentation on P3 and N2In everyday life one may encounter both unpredictable and self-initiated, hence anticipated, events. Here, we analyzed the effects of self-initiated auditory stimulus presentation on P3 and N2 components in an oddball paradigm. If the stimulus sequence was fully self-determined, both components were attenuated in comparison with computer-controlled representation. In contrast, both components were increased when only the stimulus onset was self-initiated, yet the forthcoming stimulus type was unknown. We hypothesize that predictive forward models offer an unifying explanation for the modulation of both P3 and N2 through: (a) attenuation of neuronal responses to anticipated stimuli contingent on one's own motor action and (b) enhancement of responses in case of incongruity between an anticipated action effect and the actual perceptual consequences.

• High-frequency EEG covaries with spike burst patterns detected in cortical neurons.

  Authors: Bartosz Telenczuk, Stuart N Baker, Andreas V M Herz, Gabriel Curio

  Journal of neurophysiology. 06/2011; 105(6):2951-9.

  Invasive microelectrode recordings measure neuronal spikes, which are commonly considered inaccessible through standard surface electroencephalogram (EEG). Yet high-frequency EEG potentials (hf-EEG,Invasive microelectrode recordings measure neuronal spikes, which are commonly considered inaccessible through standard surface electroencephalogram (EEG). Yet high-frequency EEG potentials (hf-EEG, f > 400 Hz) found in somatosensory evoked potentials of primates may reflect the mean population spike responses of coactivated cortical neurons. Since cortical responses to electrical nerve stimulation vary strongly from trial to trial, we investigated whether the hf-EEG signal can also echo single-trial variability observed at the single-unit level. We recorded extracellular single-unit activity in the primary somatosensory cortex of behaving macaque monkeys and identified variable spike burst responses following peripheral stimulation. Each of these responses was classified according to the timing of its spike constituents, conforming to one of a discrete set of spike patterns. We here show that these spike patterns are accompanied by variations in the concomitant epidural hf-EEG. These variations cannot be explained by fluctuating stimulus efficacy, suggesting that they were generated within the thalamocortical network. As high-frequency EEG signals can also be reliably recorded from the scalp of human subjects, they may provide a noninvasive window on fluctuating cortical spike activity in humans.

• Optimal imaging of cortico-muscular coherence through a novel regression technique based on multi-channel EEG and un-rectified EMG.

  Authors: Zubeyir Bayraktaroglu, Katherina von Carlowitz-Ghori, Florian Losch, Guido Nolte, Gabriel Curio, Vadim V Nikulin

  NeuroImage. 05/2011; 57(3):1059-67.

  Cortico-muscular coherence (CMC) reflects interactions between muscular and cortical activities as detected with EMG and EEG recordings, respectively. Most previous studies utilized EMG rectificationCortico-muscular coherence (CMC) reflects interactions between muscular and cortical activities as detected with EMG and EEG recordings, respectively. Most previous studies utilized EMG rectification for CMC calculation. Yet, recent modeling studies predicted that EMG rectification might have disadvantages for CMC evaluation. In addition, previously the effect of rectification on CMC was estimated with single-channel EEG which might be suboptimal for detection of CMC. In order to optimally detect CMC with un-rectified EMG and resolve the issue of EMG rectification for CMC estimation, we introduce a novel method, Regression CMC (R-CMC), which maximizes the coherence between EEG and EMG. The core idea is to use multiple regression where narrowly filtered EEG signals serve as predictors and EMG is the dependent variable. We investigated CMC during isometric contraction of the abductor pollicis brevis muscle. In order to facilitate the comparison with previous studies, we estimated the effect of rectification with frequently used Laplacian filtering and C3/C4 vs. linked earlobes. For all three types of analysis, we detected CMC in the beta frequency range above the contralateral sensorimotor areas. The R-CMC approach was validated with simulations and real data and was found capable of recovering CMC even in case of high levels of background noise. When using single channel data, there were no changes in the strength of CMC estimated with rectified or un-rectified EMG--in agreement with the previous findings. Critically, for both Laplacian and R-CMC analyses EMG rectification resulted in significantly smaller CMC values compared to un-rectified EMG. Thus, the present results provide empirical evidence for the predictions from the earlier modeling studies that rectification of EMG can reduce CMC.

• Simultaneous measurements of somatosensory evoked AC and near-DC MEG signals.

  Authors: Rainer Körber, Gabriel Curio, Stefan Hartwig, Ingo Hilschenz, Nora Höfner, Hans-Jürgen Scheer, Lutz Trahms, Jens Voigt, Martin Burghoff

  Biomedizinische Technik. Biomedical engineering. 03/2011; 56(2):91-7.

  Magnetoencephalography measurements of somatosensory evoked brain activity taken inside an extremely magnetically shielded room are reported. The massive low frequency shielding in combination with aMagnetoencephalography measurements of somatosensory evoked brain activity taken inside an extremely magnetically shielded room are reported. The massive low frequency shielding in combination with a high sampling rate enabled the simultaneous observation of AC and near-DC effects. Neuronal activation was achieved by repetitive electrostimulation of the right median nerve above motor threshold using repetition rates from 3 Hz to 12 Hz. Stimulation sequences lasted for 10 s and were interspersed with periods of rest of equal length. The recorded magnetic fields, inferred for the N20m and a sustained near-DC component, revealed mainly dipolar patterns with mutually rotated orientations with angles of rotation of 30° and 75°. At the start of the stimulation we observed a fast rise within 100 ms in the evoked magnetic near-DC fields for which a maximum equivalent current dipole strength of 65 nAm was obtained. The sustained fields decayed by a factor of ∼4 to a lower DC-level B(γ) with a time constant τ of order of seconds. For 12 Hz repetition rate B(γ) was decreased. We suggest that the sustained neuronal activity evoked by repetitive electrostimulation could provide a suitable scheme to realize the direct detection of DC effects of neuronal currents via low field magnetic resonance.

• Covert movements trigger repetition suppression of electroencephalography in sensorimotor cortex.

  Authors: Friederike U Hohlefeld, Vadim V Nikulin, Gabriel Curio

  Neuroreport. 02/2011; 22(3):141-5.

  'Repetition suppression' (RS) denotes the decrease of neural responses to repeated external sensory stimuli. We showed that RS can be also triggered by internal processes alone. When individuals'Repetition suppression' (RS) denotes the decrease of neural responses to repeated external sensory stimuli. We showed that RS can be also triggered by internal processes alone. When individuals perform repetitive covert movements, that is, motor imagery or quasi-movements, both of which are associated with pericentral cortical activity without muscle activations, there was a significant recovery of electroencephalographic oscillations over sensorimotor cortices back to resting baseline level. After 58 s of task performance only 20% of α and 5% of β suppressions remained (overt movements: 34% remaining in α, complete recovery in β). This result suggests that various, possibly all, repeated cerebral activations are associated with RS, presumably reflecting the adaptation to stereotyped activation in neural networks.

• Non-invasive simultaneous recording of neuronal and vascular signals in subacute ischemic stroke.

  Authors: Stefanie Leistner, Tilmann Sander-Thoemmes, Heidrun Wabnitz, Michael Moeller, Michaela Wachs, Gabriel Curio, Rainer Macdonald, Lutz Trahms, Bruno-Marcel Mackert

  Biomedizinische Technik. Biomedical engineering. 02/2011; 56(2):85-90.

  In acute focal cerebral ischemia blood flow and neuronal activity change dramatically. A better understanding of the pathophysiological interactions of these two important parameters is limited owingIn acute focal cerebral ischemia blood flow and neuronal activity change dramatically. A better understanding of the pathophysiological interactions of these two important parameters is limited owing to the lack of noninvasive techniques to simultaneously measure these parameters in humans. In this feasibility study, we used DC-magnetoencephalography and near-infrared spectroscopy to find out whether blood flow and neuronal activity as well as neurovascular coupling can be analyzed in patients suffering from subacute ischemic stroke. In a simple motor test condition, six patients with subacute ischemic stroke performed self-paced finger movements (30-s periods of movement, separated by 30-s periods of rest; for a total of 15 min). Combined DC-magnetoencephalography and near-infrared spectroscopy were recorded over the affected and unaffected hemispheres. As a control group, four healthy subjects were investigated. In four out of six patients, the time courses of both signals closely followed the motor task cycles revealing significant differences between movement and rest periods. The vascular signal reached a maximum 1-5 s later than the neuronal signals. This proof-of-principle study demonstrates that it has become feasible to simultaneously and noninvasively monitor neuronal and vascular signal changes in patients in the subacute state of ischemic stroke.

• Towards the influence of vibration on evaluation of speech utterances in mobile devices.

  Authors: Henrik von Coler, Shiva Sundaram, Robert Schleicher, Gabriel Curio

  IEEE Workshop on Applications of Signal Processing to Audio and Acoustics, WASPAA 2011, New Paltz, NY, USA, October 16-19, 2011; 01/2011

• A novel method for reliable and fast extraction of neuronal EEG/MEG oscillations on the basis of spatio-spectral decomposition.

  Authors: Vadim V Nikulin, Guido Nolte, Gabriel Curio

  NeuroImage. 01/2011; 55(4):1528-35.

  Neuronal oscillations have been shown to underlie various cognitive, perceptual and motor functions in the brain. However, studying these oscillations is notoriously difficult with EEG/MEG recordingsNeuronal oscillations have been shown to underlie various cognitive, perceptual and motor functions in the brain. However, studying these oscillations is notoriously difficult with EEG/MEG recordings due to a massive overlap of activity from multiple sources and also due to the strong background noise. Here we present a novel method for the reliable and fast extraction of neuronal oscillations from multi-channel EEG/MEG/LFP recordings. The method is based on a linear decomposition of recordings: it maximizes the signal power at a peak frequency while simultaneously minimizing it at the neighboring, surrounding frequency bins. Such procedure leads to the optimization of signal-to-noise ratio and allows extraction of components with a characteristic "peaky" spectral profile, which is typical for oscillatory processes. We refer to this method as spatio-spectral decomposition (SSD). Our simulations demonstrate that the method allows extraction of oscillatory signals even with a signal-to-noise ratio as low as 1:10. The SSD also outperformed conventional approaches based on independent component analysis. Using real EEG data we also show that SSD allows extraction of neuronal oscillations (e.g., in alpha frequency range) with high signal-to-noise ratio and with the spatial patterns corresponding to central and occipito-parietal sources. Importantly, running time for SSD is only a few milliseconds, which clearly distinguishes it from other extraction techniques usually requiring minutes or even hours of computational time. Due to the high accuracy and speed, we suggest that SSD can be used as a reliable method for the extraction of neuronal oscillations from multi-channel electrophysiological recordings.

• Event-related desynchronization of sensorimotor EEG rhythms in hemiparetic patients with acute stroke.

  Authors: Magdalena Stępień, Jan Conradi, Gunnar Waterstraat, Friederike U Hohlefeld, Gabriel Curio, Vadim V Nikulin

  Neuroscience letters. 11/2010; 488(1):17-21.

  Previous neuroimaging studies based on neurovascular coupling have shown that stroke affects both, strength and spatial extent of brain activation during upper limb movements. Here, we investigatedPrevious neuroimaging studies based on neurovascular coupling have shown that stroke affects both, strength and spatial extent of brain activation during upper limb movements. Here, we investigated the sub-second amplitude dynamics of a direct neuronal measure, i.e., event-related desynchronization (ERD) of EEG oscillations during finger movements, in patients with acute cortical and subcortical stroke. Acute cortical strokes were found to decrease the ERD of alpha oscillations for the affected pericentral sensorimotor areas compared to a control group. Within the cortical stroke group, the affected hemisphere showed a smaller alpha-ERD compared to the unaffected hemisphere when each was contralateral to the acting hand. Furthermore, when cortical stroke patients moved their paretic hand, the ipsilateral (i.e., contralesional) alpha-ERD was stronger than the contralateral (ipsilesional) ERD. Interestingly, the alpha-ERD amplitude in a hemisphere with a cortical stroke was relatively well preserved for non-paretic hand movements compared to alpha-ERD amplitude for paretic hand movements. This finding provides a new perspective for assessing the rehabilitative potential, which could be utilized through training of the still responsive cortical network, e.g., via enforced use of the paretic hand.

• Visual stimuli evoke rapid activation (120 ms) of sensorimotor cortex for overt but not for covert movements.

  Authors: Friederike U Hohlefeld, Vadim V Nikulin, Gabriel Curio

  Brain research. 10/2010; 1368:185-95.

  Overt and covert movements (e.g., motor imagery) have been frequently demonstrated to engage common neuronal substrates in the motor system. However, it is an open question whether this similarity isOvert and covert movements (e.g., motor imagery) have been frequently demonstrated to engage common neuronal substrates in the motor system. However, it is an open question whether this similarity is also present during early stages of stimulus-processing. We utilized the high temporal resolution of multi-channel electroencephalography (EEG) in order to test whether the prior action intention (overt vs. covert movements) differentially modulates early stimulus-processing stages in the cortical sensorimotor system. The subjects performed overt or covert movements contingent upon an instructive visual stimulus (indicating left or right hand performance). We introduced a novel measure, LRPrect, calculated as Lateralized Readiness Potentials from rectified EEG signals. This measure overcomes a problem related to the EEG signal variability due to polarity differences in the spatial distribution of neuronal sources. The LRPrect showed an activation already at 120 ms after stimulus onset (latN120) focally over sensorimotor cortices contralateral to the upcoming hand movement, yet only for overt but not covert movements. Thus the prior action intention differentially routes early stimulus-processing into the sensorimotor system, which might contribute to significantly different behavioral outcomes, i.e., movement generation or inhibition. The present results have implications for studies of motor inhibition and action intention.

• Speed effects of deep brain stimulation for Parkinson's disease.

  Authors: Fabian Klostermann, Michael Wahl, Frank Marzinzik, Jan Vesper, Werner Sommer, Gabriel Curio

  Movement disorders : official journal of the Movement Disorder Society. 10/2010; 25(16):2762-8.

  Deep brain stimulation (DBS) of the subthalamic nucleus (STN) accelerates reaction time (RT) in patients with Parkinson's disease (PD), particularly in tasks in which decisions on the response sideDeep brain stimulation (DBS) of the subthalamic nucleus (STN) accelerates reaction time (RT) in patients with Parkinson's disease (PD), particularly in tasks in which decisions on the response side have to be made. This might indicate that DBS speeds up both motor and nonmotor operations. Therefore, we studied the extent to which modifications of different processing streams could explain changes of RT under subthalamic DBS. Ten PD patients on-DBS and off-DBS and 10 healthy subjects performed a choice-response task (CRT), requiring either right or left finger button presses. At the same time, EEG recordings were performed, so that RTs could be assessed together with lateralized readiness potentials (LRP), indicative of movement preparation. Additionally, an oddball task (OT) was run, in which right finger responses to target stimuli were recorded along with cognitive P300 responses. Generally, PD patients off-DBS had longer RTs than controls. Subthalamic DBS accelerated RT only in CRT. This could largely be explained by analog shortenings of LRP. No DBS-dependent changes were identified in OT, neither on the level of RT nor on the level of P300 latencies. It follows that RT accelerations under DBS of the STN are predominantly due to effects on the timing of motor instead of nonmotor processes. This starting point explains why DBS gains of response speed are low in tasks in which reactions are initiated from an advanced level of movement preparation (as in OT), and high whenever motor responses have to be raised from scratch (as in CRT).

• Role of neuronal synchrony in the generation of evoked EEG/MEG responses.

  Authors: Bartosz Telenczuk, Vadim V Nikulin, Gabriel Curio

  Journal of neurophysiology. 10/2010; 104(6):3557-67.

  Evoked EEG/MEG responses are a primary real-time measure of perceptual and cognitive activity in the human brain, but their neuronal generator mechanisms are not yet fully understood. Arguments haveEvoked EEG/MEG responses are a primary real-time measure of perceptual and cognitive activity in the human brain, but their neuronal generator mechanisms are not yet fully understood. Arguments have been put forward in favor of either "phase-reset" of ongoing oscillations or "added-energy" models. Instead of advocating for one or the other model, here we show theoretically that the differentiation between these two generation mechanisms might not be possible if based solely on macroscopic EEG/MEG recordings. Using mathematical modeling, we show that a simultaneous phase reset of multiple oscillating neuronal (microscopic) sources contributing to EEG/MEG can produce evoked responses in agreement with both, the "added-energy" and the "phase-reset" model. We observe a smooth transition between the two models by just varying the strength of synchronization between the multiple microscopic sources. Consequently, because precise knowledge about the strength of microscopic ensemble synchronization is commonly not available in noninvasive EEG/MEG studies, they cannot, in principle, differentiate between the two mechanisms for macroscopic-evoked responses.

• Non-zero mean of oscillations as a mechanism for the generation of evoked responses Reply to "Amplitude asymmetry as a mechanism for the generation of slow evoked responses"

  Authors: Vadim V Nikulin, Klaus Linkenkaer-Hansen, Guido Nolte, Matias J Palva, Gabriel Curio

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology. 04/2010;

• Miniaturized electroencephalographic scalp electrode for optimal wearing comfort.

  Authors: Vadim V Nikulin, Jewgeni Kegeles, Gabriel Curio

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology. 03/2010; 121(7):1007-14.

  Current mainstream EEG electrode setups permit efficient recordings, but are often bulky and uncomfortable for subjects. Here we introduce a novel type of EEG electrode, which is designed for anCurrent mainstream EEG electrode setups permit efficient recordings, but are often bulky and uncomfortable for subjects. Here we introduce a novel type of EEG electrode, which is designed for an optimal wearing comfort. The electrode is referred to as C-electrode where "C" stands for comfort. The C-electrode does not require any holder/cap for fixation on the head nor does it use traditional pads/lining of disposable electrodes - thus, it does not disturb subjects. Fixation of the C-electrode on the scalp is based entirely on the adhesive interaction between the very light C-electrode/wire construction (<35 mg) and a droplet of EEG paste/gel. Moreover, because of its miniaturization, both C-electrode (diameter 2-3mm) and a wire (diameter approximately 50 microm) are minimally (or not at all) visible to an external observer. EEG recordings with standard and C-electrodes were performed during rest condition, self-paced movements and median nerve stimulation. The quality of EEG recordings for all three types of experimental conditions was similar for standard and C-electrodes, i.e., for near-DC recordings (Bereitschaftspotential), standard rest EEG spectra (1-45 Hz) and very fast oscillations approximately 600 Hz (somatosensory evoked potentials). The tests showed also that once being placed on a subject's head, C-electrodes can be used for 9h without any loss in EEG recording quality. Furthermore, we showed that C-electrodes can be effectively utilized for Brain-Computer Interfacing. C-electrodes proved to posses a high stability of mechanical fixation (stayed attached with 2.5 g accelerations). Subjects also reported not having any tactile sensations associated with wearing of C-electrodes. C-electrodes provide optimal wearing comfort without any loss in the quality of EEG recordings. We anticipate that C-electrodes can be used in a wide range of clinical, research and emerging neuro-technological environments.

• Neurophysiological predictor of SMR-based BCI performance.

  Authors: Benjamin Blankertz, Claudia Sannelli, Sebastian Halder, Eva M Hammer, Andrea Kübler, Klaus-Robert Müller, Gabriel Curio, Thorsten Dickhaus

  NeuroImage. 03/2010; 51(4):1303-9.

  Brain-computer interfaces (BCIs) allow a user to control a computer application by brain activity as measured, e.g., by electroencephalography (EEG). After about 30years of BCI research, the successBrain-computer interfaces (BCIs) allow a user to control a computer application by brain activity as measured, e.g., by electroencephalography (EEG). After about 30years of BCI research, the success of control that is achieved by means of a BCI system still greatly varies between subjects. For about 20% of potential users the obtained accuracy does not reach the level criterion, meaning that BCI control is not accurate enough to control an application. The determination of factors that may serve to predict BCI performance, and the development of methods to quantify a predictor value from psychological and/or physiological data serve two purposes: a better understanding of the 'BCI-illiteracy phenomenon', and avoidance of a costly and eventually frustrating training procedure for participants who might not obtain BCI control. Furthermore, such predictors may lead to approaches to antagonize BCI illiteracy. Here, we propose a neurophysiological predictor of BCI performance which can be determined from a two minute recording of a 'relax with eyes open' condition using two Laplacian EEG channels. A correlation of r=0.53 between the proposed predictor and BCI feedback performance was obtained on a large data base with N=80 BCI-naive participants in their first session with the Berlin brain-computer interface (BBCI) system which operates on modulations of sensory motor rhythms (SMRs).