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SignificanceFunctional near-infrared spectroscopy (fNIRS) is a promising tool for neurofeedback (NFB) or brain–computer interfaces (BCIs). However, fNIRS signals are typically highly contaminated by systemic activity (SA) artifacts, and, if not properly corrected, NFB or BCIs run the risk of being based on noise instead of brain activity. This risk can likely be reduced by correcting for SA, in particular when short-distance channels (SDCs) are available. Literature comparing correction methods with and without SDCs is still sparse, specifically comparisons considering single trials are lacking.AimThis study aimed at comparing the performance of SA correction methods with and without SDCs.ApproachSemisimulated and real motor task data of healthy older adults were used. Correction methods without SDCs included a simple and a more advanced spatial filter. Correction methods with SDCs included a regression approach considering only the closest SDC and two GLM-based methods, one including all eight SDCs and one using only twoa prioriselected SDCs as regressors. All methods were compared with data uncorrected for SA and correction performance was assessed with quality measures quantifying signal improvement and spatial specificity at single trial level.ResultsAll correction methods were found to improve signal quality and enhance spatial specificity as compared with the uncorrected data. Methods with SDCs usually outperformed methods without SDCs. Correction methods without SDCs tended to overcorrect the data. However, the exact pattern of results and the degree of differences observable between correction methods varied between semisimulated and real data, and also between quality measures.ConclusionsOverall, results confirmed that both Δ[HbO] and Δ[HbR] are affected by SA and that correction methods with SDCs outperform methods without SDCs. Nonetheless, improvements in signal quality can also be achieved without SDCs and should therefore be given priority over not correcting for SA.

Neurofeedback (NF) is a versatile non-invasive neuromodulation technique. In combination with motor imagery (MI), NF has considerable potential for enhancing motor performance or supplementing motor rehabilitation. However, not all users achieve reliable NF control. While research has focused on various brain signal properties and the optimisation of signal processing to solve this issue, the impact of context, i.e. the conditions in which NF motor tasks occur, is comparatively unknown. We review current research on the impact of context on MI NF and related motor domains. We identify long-term factors that act at the level of the individual or of the intervention, and short-term factors, with levels before/after and during a session. The reviewed literature indicates that context plays a significant role. We propose considering context factors as well as within-level and across-level interactions when studying MI NF.

Compared to functional magnetic resonance imaging (fMRI), functional near infrared spectroscopy (fNIRS) has several advantages that make it particularly interesting for neurofeedback (NFB). A pre-requisite for NFB applications is that with fNIRS, signals from the brain region of interest can be measured. This study focused on the supplementary motor area (SMA). Healthy older participants (N = 16) completed separate continuous-wave (CW-) fNIRS and (f)MRI sessions. Data were collected for executed and imagined hand movements (motor imagery, MI), and for MI of whole body movements. Individual anatomical data were used to (i) define the regions of interest for fMRI analysis, to (ii) extract the fMRI BOLD response from the cortical regions corresponding to the fNIRS channels, and (iii) to select fNIRS channels. Concentration changes in oxygenated ([Formula: see text]) and deoxygenated ([Formula: see text]) hemoglobin were considered in the analyses. Results revealed subtle differences between the different MI tasks, indicating that for whole body MI movements as well as for MI of hand movements [Formula: see text] is the more specific signal. Selection of the fNIRS channel set based on individual anatomy did not improve the results. Overall, the study indicates that in terms of spatial specificity and task sensitivity SMA activation can be reliably measured with CW-fNIRS.

Motor imagery (MI) practice in combination with neurofeedback (NF) is a promising supplement to facilitate the acquisition of motor abilities and the recovery of impaired motor abilities following brain injuries. However, the ability to control MI NF is subject to a wide range of inter-individual variability. A substantial number of users experience difficulties in achieving good results, which compromises their chances to benefit from MI NF in a learning or rehabilitation context. It has been suggested that context factors, that is, factors outside the actual motor task, can explain individual differences in motor skill acquisition. Retrospective declarative interference and sleep have already been identified as critical factors for motor execution (ME) and MI based practice. Here, we investigate whether these findings generalize to MI NF practice.Three groups underwent three blocks of MI NF practice each on two subsequent days. In two of the groups, MI NF blocks were followed by either immediate or delayed declarative memory tasks. The control group performed only MI NF and no specific interference tasks. Two of the MI NF blocks were run on the first day of the experiment, the third in the morning of the second day. Significant within-block NF gains in mu and beta frequency event-related desynchronization (ERD) where evident for all groups. However, effects of sleep on MI NF ERD were not found. Data did also not indicate an impact of immediate or delayed declarative interference on MI NF ERD.Our results indicate that effects of sleep and declarative interference context on ME or MI practice cannot unconditionally be generalized to MI NF skill acquisition. The findings are discussed in the context of variable experimental task designs, inter-individual differences, and performance measures.

Neurofeedback is going through a renaissance. Advances in brain imaging and computing have renewed efforts to modify brain activity and behaviour using this technique. Here, over 80 neurofeedback researchers present a consensus-derived checklist – CRED-nf – for reporting and experimental design standards in the field., Neurofeedback has begun to attract the attention and scrutiny of the scientific and medical mainstream. Here, neurofeedback researchers present a consensus-derived checklist that aims to improve the reporting and experimental design standards in the field.

For motor imagery (MI) to be effective, an internal representation of the to-be-imagined movement may be required. A representation can be achieved through prior motor execution (ME), but the neural correlates of MI that are primed by ME practice are currently unknown. In this study, young healthy adults performed MI practice of a unimanual visuo-motor task (Group MI, n = 19) or ME practice combined with subsequent MI practice (Group ME&MI, n = 18) while electroencephalography (EEG) was recorded. Data analysis focused on the MI-induced event-related desynchronization (ERD). Specifically, changes in the ERD and movement times (MT) between a short familiarization block of ME (Block pre-ME), conducted before the MI or the ME combined with MI practice phase, and a short block of ME conducted after the practice phase (Block post-ME) were analyzed. Neither priming effects of ME practice on MI-induced ERD were found nor performance-enhancing effects of MI practice in general. We found enhancements of the ERD and MT in Block post-ME compared to Block pre-ME, but only for Group ME&MI. A comparison of ME performance measures before and after the MI phase indicated however that these changes could not be attributed to the combination of ME and MI practice. The mixed results of this study may be a consequence of the considerable intra- and inter-individual differences in the ERD, introduced by specifics of the experimental setup, in particular the individual and variable task duration, and suggest that task and experimental setup can affect the interplay of ME and MI.

This checklist is intended to encourage robust experimental design and clear reporting for clinical and cognitive-behavioural neurofeedback experiments.

Objective The study compared two channel-reduction approaches in order to investigate the effects of systematic motor imagery (MI) neurofeedback practice in an everyday environment using a very user-friendly EEG system consisting of individualized caps and highly portable hardware. Methods Sixteen BCI novices were trained over four consecutive days to imagine left and right hand movements while receiving feedback. The most informative bipolar channels for use on the subsequent days were identified on the first day for each individual based on a high-density online MI recording. Results Online classification accuracy on the first day was 85.1% on average (range: 64.7–97.7%). Offline an individually-selected bipolar channel pair based on common spatial patterns significantly outperformed a pair informed by independent component analysis and a standard 10–20 pair. From day 2 to day 4 online MI accuracy increased significantly (day 2: 69.1%; day 4: 73.3%), which was mostly caused by a reduction in ipsilateral event-related desynchronization of sensorimotor rhythms. Conclusion The present study demonstrates that systematic MI practice in an everyday environment with a user-friendly EEG system results in MI learning effects. Significance These findings help to bridge the gap between elaborate laboratory studies with healthy participants and efficient home or hospital based MI neurofeedback protocols.

The temporal properties of visual selective attention change with age as reflected in a longer and deeper impairment of identifying the second of two targets in a rapid stream of visual distracters. In younger adults, identification rates for both targets can be improved by a simultaneous, task irrelevant sound. Research in response time tasks has shown that older participants can benefit more from bimodal stimulation than younger subjects. Here we examine whether this facilitation in older participants can also be found in a setting in which relevant items need to be identified while competing rapid visual input needs to be ignored. The results of the first experiment indicated a trend in the predicted direction, but only for the first target. The second experiment tested whether increasing the probability of a sound to coincide with a target would modulate this trend. As before, the sound improved target identification rates, but an effect of age on the effectiveness of the sound was not evident. These results indicate that audiovisual integration can provide a useful means for improving visual temporal attention also in older adults, but that the gain is not larger in older than in younger adults.

Deficits in sustaining attention are common in various organic brain diseases. A recent study proposed self-alert training (SAT) as a technique to improve sustained attention. In the SAT, individuals learn to gain volitional control over their own state of arousal by means of electrodermal biofeedback.In this study, we investigated the behavioral, electrodermal, and electroencephalogram correlates of the SAT with a blinded, randomized, and active-controlled pre-post study design. Sustained attention capacity was assessed with the Sustained Attention to Response Task (SART).The SAT resulted in strong phasic increases in skin conductance response (SCR), but endogenous control of SCR without feedback was problematic. Electroencephalogram analysis revealed stronger alpha reduction during SART for the SAT than for the control group. Behaviorally, the SAT group performed more accurately and more slowly after intervention than the control group.The study provides further evidence that SAT helps to maintain SART accuracy over prolonged periods of time. Whether this accuracy is more related to sustained attention or response inhibition is discussed.

Motor imagery (MI) with neurofeedback has been suggested as promising for motor recovery after stroke. Evidence suggests that regular training facilitates compensatory plasticity, but frequent training is difficult to integrate into everyday life. Using a wireless electroencephalogram (EEG) system, we implemented a frequent and efficient neurofeedback training at the patients' home. Aiming to overcome maladaptive changes in cortical lateralization patterns we presented a visual feedback, representing the degree of contralateral sensorimotor cortical activity and the degree of sensorimotor cortex lateralization. Three stroke patients practiced every other day, over a period of 4 weeks. Training-related changes were evaluated on behavioral, functional, and structural levels. All 3 patients indicated that they enjoyed the training and were highly motivated throughout the entire training regime. EEG activity induced by MI of the affected hand became more lateralized over the course of training in all three patients. The patient with a significant functional change also showed increased white matter integrity as revealed by diffusion tensor imaging, and a substantial clinical improvement of upper limb motor functions. Our study provides evidence that regular, home-based practice of MI neurofeedback has the potential to facilitate cortical reorganization and may also increase associated improvements of upper limb motor function in chronic stroke patients.

The attentional blink (AB) occurs when the limits of temporal processing are reached. In a typical AB experiment, two targets (T1, T2) are presented within a stream of distracters, and detection of T2 is impaired when presented shortly after T1. Several theories focus on the mechanism underlying this deficit, among them proposals that see the similarity between distracters and targets as a crucial factor. The present study aimed to gain a better understanding of the effect of distracter stream properties on performance in the AB paradigm. A skeletal AB task was combined with a pretarget distracter stream. The presence and familiarity of the distracter stream and its similarityto the targets were manipulated in three separate experiments. The last distracter before T1 was sufficient to impair T1 detection in the standard rapid serial visual presentation (RSVP) paradigm. Second, T2|T1 performance was impaired by an RSVP stream with low target-distracter similarity but unfamiliar stimuli. Finally, a single mask before T1 was shown to impair T2|T1. The results suggest that it is the last distracter before T1, rather than the RSVP stream per se, that impairs T1 detection performance. T2|T1 performance is influenced by a combination of transient attentional capture mechanisms that include but are not limited to target-distracter similarity. Thus, the size of an AB is determined not only by target-distracter similarity but by the overall processing demands of the distracters.

Studying the brain in its natural state remains a major challenge for neuroscience. Solving this challenge would not only enable the refinement of cognitive theory, but also provide a better understanding of cognitive function in the type of complex and unpredictable situations that constitute daily life, and which are often disturbed in clinical populations. With mobile EEG, researchers now have access to a tool that can help address these issues. In this paper we present an overview of technical advancements in mobile EEG systems and associated analysis tools, and explore the benefits of this new technology. Using the example of motor imagery (MI) we will examine the translational potential of MI-based neurofeedback training for neurological rehabilitation and applied research.

The attentional blink phenomenon (AB) describes a transient deficit in temporally selective visual attention regarding the processing of the second of two target stimuli in a rapid serial visual presentation (RSVP) task. The AB is a very prominent paradigm in the Cognitive Neurosciences that has been extensively studied by diverse psychophysiological techniques such as EEG or fMRI. Association studies from molecular genetics are scarce although the high heritability of higher cognitive functioning is proven. Only one seminal study reported an association between AB magnitude and the dopamine receptor D2 (DRD2) C957T polymorphism (Colzato et al., 2011). This functional polymorphism influences striatal D2 receptor binding affinity and thereby the efficacy of dopaminergic neurotransmission which is important for working memory and attentional processes. Colzato et al. (2011) reported that DRD2 C957T T/T-carriers exhibit a significant smaller AB than C-allele carriers. In the present study this influence of the DRD2 SNP on the AB could not be replicated in N=211 healthy participants. However, a significantly larger lag 1 sparing was observed for homozygous T/T-carriers. Moreover, carriers of at least one T-allele showed a significantly poorer performance in the identification of T1. In general, these results support the notion of a role of the dopaminergic system on the AB. However, as our results do not parallel previous findings the exact nature of this influence and its dependence on task parameters will have to be examined in further genetic association studies.

A number of studies suggest that the clinical manifestation of neurological deficits in hepatic encephalopathy results from pathologically synchronized neuronal oscillations and altered oscillatory coupling. In the present study spontaneous and evoked oscillatory brain activities were analyzed jointly with established behavioral measures of altered visual oscillatory processing. Critical flicker and fusion frequencies (CFF, FUF) were measured in 25 patients diagnosed with liver cirrhosis and 30 healthy controls. Magnetoencephalography (MEG) data were collected at rest and during a visual task employing repetitive stimulation. Resting MEG and evoked fields were analyzed. CFF and FUF were found to be reduced in patients, providing behavioral evidence for deficits in visual oscillatory processing. These alterations were found to be related to resting brain activity in patients, namely that the lower the dominant MEG frequency at rest, the lower the CFF and FUF. An analysis of evoked fields at sensor level indicated that in comparison to normal controls, patients were not able to dynamically adapt to flickering visual stimulation. Evoked activity was also analyzed based on independent components (ICs) derived by independent component analysis. The similarity between the shape of each IC and an artificial sine function representing the stimulation frequency was tested via magnitude squared coherence. In controls, we observed a small number of components that correlated strongly with the sine function and a high number of ICs that did not correlate with the sine function. Interestingly, patient data were characterized by a high number of moderately correlating components. Taken together, these results indicate a fundamental divergence of the cerebral resonance activity in cirrhotic patients., Highlights • Cirrhotic patients show a fundamental divergence of cerebral resonance activity. • Patients show an impaired dynamical adaptation to visual flickering stimulation. • The MEG findings were significantly related to neuropsychological testing.

The perception of target events presented in a rapid stream of non-targets is impaired for early target positions, but then gradually improves, a phenomenon known as attentional awakening. This phenomenon has been associated with better resource allocation. It is unclear though whether improved resource allocation and attentional awakening are a consequence of the temporal context, that is, the position of the target event in the stimulus stream, or are due to a simple expectancy or foreperiod effect. Expectancy is an alternative explanation of attentional awakening because it depends on the a posteriori probabilities, which will increase with target position when all target positions are equally likely. To differentiate between the expectancy and the temporal context account the a priori (objective) probability of target position was defined such that the a posteriori probability would be high for early and late, and low for intermediate target positions. EEG was collected and the P3 ERP evoked by target events was derived as an indicator of resource allocation. A robust attentional awakening effect was observed. The relationships between measures of performance and P3 amplitude, and respectively target position, a priori, and a posteriori probability were analyzed. Results showed that in contrast to target position, a posteriori probability had little impact on performance and did not moderate the association between P3 amplitude and performance. Results also indicated that in spite of the evident role of target position on resource allocation and the perception of target events in rapid stimulus streams, target position is likely not the only variable these are affected by. Nevertheless, the findings of the present study suggest that whereas the temporal context of a rapid serial event is a key player for resource allocation to and perception of the event, expectancy seems of very little consequence.

Stroke frequently results in motor impairment. Motor imagery (MI), the mental practice of movements, has been suggested as a promising complement to other therapeutic approaches facilitating motor rehabilitation. Of particular potential is the combination of MI with neurofeedback (NF). However, MI NF protocols have been largely optimized only in younger healthy adults, although strokes occur more frequently in older adults. The present study examined the influence of age on the neural correlates of MI supported by electroencephalogram (EEG)-based NF and on the neural correlates of motor execution. We adopted a multimodal neuroimaging framework focusing on EEG-derived event-related desynchronization (ERD%) and oxygenated (HbO) and deoxygenated hemoglobin (HbR) concentrations simultaneously acquired using functional near-infrared spectroscopy (fNIRS). ERD%, HbO concentration and HbR concentration were compared between younger (mean age: 24.4 years) and older healthy adults (mean age: 62.6 years). During MI, ERD% and HbR concentration were less lateralized in older adults than in younger adults. The lateralization-by-age interaction was not significant for movement execution. Moreover, EEG-based NF was related to an increase in task-specific activity when compared to the absence of feedback in both older and younger adults. Finally, significant modulation correlations were found between ERD% and hemodynamic measures despite the absence of significant amplitude correlations. Overall, the findings suggest a complex relationship between age and movement-related activity in electrophysiological and hemodynamic measures. Our results emphasize that the age of the actual end-user should be taken into account when designing neurorehabilitation protocols.

Attentional awakening (AA) is an impairment in the identification of target stimuli that are presented early in a rapidly presented sequence of visual stimuli. Here we investigate whether AA is related to resource allocation, measured as amplitude of the P3 event-related potential and/or variance in the focus of temporal attention, measured as P3 phase distribution. We observed a relationship between P3 amplitude and AA that depended strongly on targets' a posteriori probabilities. Evidence was found for a link between performance and P3 phase distributions, but a relationship between AA and P3 phase distributions was not evident. These findings suggest that resource allocation is a relevant factor for AA whereas the variance in the focus of temporal attention contributes only little to AA.

The attentional blink (AB) is a deficit in reporting the second (T2) of two targets (T1, T2) when presented in close temporal succession and within a stream of distractor stimuli. The AB has received a great deal of attention in the past two decades because it allows to study the mechanisms that influence the rate and depth of information processing in various setups and therefore provides an elegant way to study correlates of conscious perception in supra-threshold stimuli. Recently evidence has accumulated suggesting that oscillatory signals play a significant role in temporally coordinating information between brain areas. This review focuses on studies looking into oscillatory brain activity in the AB. The results of these studies indicate that the AB is related to modulations in oscillatory brain activity in the theta, alpha, beta, and gamma frequency bands. These modulations are sometimes restricted to a circumscribed brain area but more frequently include several brain regions. They occur before targets are presented as well as after the presentation of the targets. We will argue that the complexity of the findings supports the idea that the AB is not the result of a processing impairment in one particular process or brain area, but the consequence of a dynamic interplay between several processes and/or parts of a neural network.

The functional cerebral asymmetry (FCA) in processing targets within rapid serial visual presentation (RSVP) streams has been reported to fluctuate across the menstrual cycle, with identification of the second of two closely spaced targets being impaired when both targets occur in the left or the right hemifield stream during the luteal phase, while during the menstrual phase identification of the second target is only impaired for target pairs presented in the right hemifield stream. This fluctuation has been proposed to result from variations in estradiol levels. The current study used EEG to investigated whether the cycle-related fluctuation in RSVP target identification FCA relates to changes in early, stimulus-driven, bottom-up or in later, top down-driven aspects of FCA. While the former would be expected to become evident in the early visual evoked potentials (VEPs) P1 or N1, the latter would be evident in later event-related potentials (ERPs) such as N2pc or P3. Women performed a dual-stream RSVP task once during the menstrual phase and once during the follicular phase. Estradiol levels were determined from saliva samples. In contrast to previous findings, FCA in RSVP target identification was not affected by cycle phase. However, the impairment in second-target identification when targets where closely spaced was generally smaller during the menstrual phase than during the follicular phase. This effect was matched by shorter peak latencies of P1 VEPs for the menstrual phase, and by a reduction in the latency of the second-target P3 ERP for closely spaced relative to widely spaced target pairs, again for the menstrual phase. Results suggest that in a dual-stream RSVP setup, target identification, early stage stimulus processing, and target consolidation are affected by cycle phase, but that the asymmetry of these effects does not differ between menstrual and follicular phase. The observed cycle-related modulations in neurophysiology and behavior could relate to the effects of estradiol on the locus ceruleus norepinephrine (LC-NE) system, which is known to play a major role in arousal, attention and stress response.

Since Hans Berger, a German psychiatrist, discovered in 1929 at Jena that brain activity can be recorded from the human scalp noninvasively, the electroencephalogram (EEG) has fascinated generations of neuroscientists. How complex mental functions such as attention, memory, language, or decision-making are implemented in the brain are fundamental questions in cognitive neuroscience, and the EEG technology provides information, which may be crucial in answering those questions. Indeed, understanding the neural underpinnings of cognitive functions would help developing effective treatments for patients suffering from various brain dysfunctions. We argue here that, among maybe a dozen or so technologies, the scalp-recorded EEG among the most informative ones when it comes to understanding the mind–brain relationship. Moreover, next generation EEG technology is unobtrusive, smartphone operated, and useable outside of the laboratory environment. This helps to advance applied fields such as brain–computer interfaces, neuroergonomics, and neurorehabilitation.

Objective Survivors of sepsis often develop long-term neuropsychological malfunctions, which can be reversible to a certain extent. The following study aimed to investigate whether this recovery is due to a loss in neural synchrony by regarding the response to a given frequency. Methods Magnetoencephalography measurements were conducted in 36 survivors of severe sepsis and septic shock three times within a time range of 12 months after discharge from intensive care unit. We analyzed steady state visual evoked responses using a set of familiar vs. unfamiliar pictures. Results Sepsis survivors exhibit oscillatory deficits in terms of an impaired response to periodic visual stimulation. Oscillatory deficits and neuropsychological impairments obtained by the DemTect questionnaire were strongly linked. Impaired responses were equally found during the presentation of familiar and unfamiliar stimuli. Compared to familiar stimuli however, the response to unfamiliar stimuli was significantly lower in the follow up but not in the post-acute stage. Conclusions We assume that the processing of unfamiliar pictures requires a higher amount of networking. In case of a disrupted network, complex networking might not be maintained. Significance Results indicate that neural synchrony might be restored to a certain level while more complex networking remains impaired.

Objective Survivors of severe sepsis and septic shock suffer from residual severe cognitive impairments, which persist even years after intensive care unit (ICU) discharge. As the awareness of long-term consequences gradually grows, research has focused on cognitive impairments via questionnaires, but only few have focused on structural or electrophysiological features, such as the peak resting frequency, which is commonly seen as a hallmark of brain function. Methods We aimed to analyze the long-term progression of the peak resting activity in terms of frequency and power in sepsis survivors. Healthy individuals with no history of ICU stay served as controls. Data were collected three times (shortly, 6 and 12 months after ICU discharge) in sepsis survivors and three times in controls. Participants also underwent behavioral neuropsychological assessment. Results Sepsis survivors exhibited significantly higher spectral power of the dominant peak, which was shifted towards lower frequencies. Within one year, resting frequency increased to the level of controls, but power did not decrease. We observed a close correlation between resting frequency and mental status. Conclusions Results support the assumption of a causal relationship between brain oscillations and behavioral performance. Significance We suggest that the postseptic frequency shift is due to abnormal thalamocortical dynamics.

Evidence is available that oscillatory activity in the gamma frequency range (>30 Hz) might be related to the attentional selection of target items. Rapid serial visual presentation (RSVP) paradigms are instrumental in addressing cognitive functions such as visual attention, and they are increasingly combined with the measurement of electrical brain activity. In the present study, gamma-band responses for target and standard stimuli were investigated in an RSVP oddball paradigm. In a first study, stimuli were presented at a frequency of 10 Hz, the stimulus sequence consisted of rare colored letters (targets) and frequent black letters (standards). In addition, stimulus size was varied across experimental blocks. Significant target modulations were observed for the P3 ERP and induced (i.e., not phase-locked) gamma-band responses. Besides this late activation, no further gamma-band responses were observed. A second study aimed at replicating these findings by employing a reduced stimulus presentation rate of 7.1 Hz. Again, besides the P3 ERP a late increase in induced gamma-band activity was observed. However, as compared to Study 1, this induced response was less pronounced. The induced gamma-band response observed in the present studies might reflect utilization of information derived from previous processing steps for behavioral performance or memory storage as suggested in the 'match-and-utilization-model' of gamma activity.

Objective: The effects of stimulus size, duration and eccentricity on the visual gamma-band response (GBR) in human EEG were investigated and compared to visual evoked potentials (VEPs) in order to differentiate in future (and past) experiments whether changes in GBRs are due to stimulus-related (exogenous) or cognitive effects. Methods: EEG was recorded from 23 subjects while they performed a simple choice reaction time task requiring discrimination of squares and circles. In separate blocks stimulus size, duration, and eccentricity were manipulated. EEG was recorded from 64 electrodes. A wavelet transform based on Morlet wavelets was employed for the analysis of gamma-band activity. Results: Amplitude of the GBR was diminished for small and peripheral stimuli. With short stimulus durations ON and OFF responses of the GBR merged into one peak. In comparison, VEP amplitudes were less susceptible to stimulus features. In contrast to VEP latencies, however, GBR latency did not show a lateralization for eccentric stimuli. Conclusions: In addition to previous experiments which have shown a modulation of the GBR by various cognitive processes, the present results demonstrate the susceptibility of the GBR in human EEG to exogenous factors, as numerous intracortical recordings in non-human primates have shown before. The results suggest that the human GBR resides in early visual areas. Significance: The demonstration of the susceptibility of the GBR to stimulus properties implies that studies aimed at exploring the involvement of the GBR in information processing have to be designed carefully. It also constrains the localization of the human GBR. q 2004 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

b Abstract An auditory novelty-oddball task, which is known to evoke a P3 event-related potential (ERP) in a target condition and a novelty-P3 ERP in response to task-irrelevant unique environmental sounds, was repeatedly applied to healthy participants (ns14) on two separate recording sessions, 7 days apart. Both target-P3 and novelty-P3 were internally consistent and test-retest reliable. Interestingly, novelty-P3 amplitude declined from the first to the second half of each recording session, whereas no systematic alteration between both sessions occurred. The target-P3 showed the opposite pattern, i.e. a reduced amplitude from the first to the second session, but no systematic change within each session. These findings suggest that novelty-P3 amplitude changes reflect habituation, whereas target-P3 session effects may indicate the adjusted amount of processing resources invested into the task. In general, the results support the interpretation of the novelty-P3 as indicating automatic, bottom-up related aspects of attention, whereas the target-P3, in the present paradigm, seems to reflect voluntary, top-down related aspects of attention. 2002 Elsevier Science B.V. All rights reserved.

Background Motor imagery (MI) training, in particular in combination with EEG-based neurofeedback (MI-NF), has been suggested as a potential add-on therapy for rehabilitation of upper limb motor impairments after stroke. Most MI-NF implementations are based on the event-related desynchronization (ERD) in the 8–30 Hz frequency range that is typically observed over sensorimotor areas during motor execution and imagination. The amplitude and consistency of the ERD depends, among other things, on brain structure and function during motor imagery (e.g., Halder et al., 2013 , Zich et al., 2015 ). Because the vast majority of the research on MI-NF has been conducted with young healthy individuals, it is unclear to what degree changes regarding the relationship between MI-induced ERD, MI-induced functional magnetic resonance imaging (fMRI) activation and brain structure in stroke patients are due to normal aging and the stroke, respectively. Objectives (1) to investigate in healthy older adults (>45 years) associations of MI-induced ERD, MI-induced fMRI activation and diffusion tensor imaging (DTI) measures, and (2) to investigate differences in these measures between chronic stroke patients and healthy older adults matched for age and gender. Methods We included 12 chronic stroke patients with residual upper limb motor impairment (mean age 61.5 years – range 49–75 years; 3 females) and 17 healthy older adults (mean age 60.4 years – range 48–77 years; 9 females). All participants completed a 3T MRI session and a 96-electrode EEG session. The MRI session included a high-resolution anatomical scan, DTI, and fMRI during rest, motor execution and kinesthetic MI of repeated hand opening and closing. The EEG session consisted of three blocks: motor execution, kinesthetic MI and kinesthetic MI with real-time EEG-based visual feedback, all with the same hand movement as during fMRI. Each patient also completed a motor assessment consisting of the upper limb section of the Fugl-Mayer Assessment and the Modified Ashworth Scale. Results We will present preliminary results regarding the correlations of ERD and fMRI activation related to motor execution and imagination. Moreover, we will present the results of a replication of the analysis of Halder et al. (2013) that for young healthy adults indicated a significant association between MI-induced ERD and white matter integrity (fractional anisotropy) in subcortical structures.

The mental practice of movements has been suggested as a promising add-on therapy to facilitate motor recovery after stroke. In the case of mentally practised movements, electroencephalogram (EEG) can be utilized to provide feedback about an otherwise covert act. The main target group for such an intervention are elderly patients, though research so far is largely focused on young populations (30 years). The present study therefore aimed to examine the influence of age on the neural correlates of covert movements (CMs) in a real-time EEG neurofeedback framework. CM-induced event-related desynchronization (ERD) was studied in young (mean age: 23.6 years) and elderly (mean age: 62.7 years) healthy adults. Participants performed covert and overt hand movements. CMs were based on kinesthetic motor imagery (MI) or quasi-movements (QM). Based on previous studies investigating QM in the mu frequency range (8-13Hz) QM were expected to result in more lateralized ERD% patterns and accordingly higher classification accuracies. Independent of CM strategy the elderly were characterized by a significantly reduced lateralization of ERD%, due to stronger ipsilateral ERD%, and in consequence, reduced classification accuracies. QM were generally perceived as more vivid, but no differences were evident between MI and QM in ERD% or classification accuracies. EEG feedback enhanced task-related activity independently of strategy and age. ERD% measures of overt and covert movements were strongly related in young adults, whereas in the elderly ERD% lateralization is dissociated. In summary, we did not find evidence in support of more pronounced ERD% lateralization patterns in QM. Our finding of a less lateralized activation pattern in the elderly is in accordance to previous research and with the idea that compensatory processes help to overcome neurodegenerative changes related to normal ageing. Importantly, it indicates that EEG neurofeedback studies should place more emphasis on the age of the potential end-users.