EEG Event-related Desynchronization Research Articles

Movement-Related EEG Oscillations of Contralesional Hemisphere Discloses Compensation Mechanisms of Severely Affected Motor Chronic Stroke Patients.

Conventional rehabilitation strategies for stroke survivors become difficult when voluntary movements are severely disturbed. Combining passive limb mobilization, robotic devices and EEG-based brain-computer interfaces (BCI) systems might improve treatment and clinical follow-up of these patients, but detailed knowledge of neurophysiological mechanisms involved in functional recovery, which might help for tailoring stroke treatment strategies, is lacking. Movement-related EEG changes (EEG event-related desynchronization (ERD) in [Formula: see text] and [Formula: see text] bands, an indicator of motor cortex activation traditionally used for BCI systems), were evaluated in a group of 23 paralyzed chronic stroke patients in two unilateral motor tasks alternating paretic and healthy hands ((i) passive movement, using a hand exoskeleton, and (ii) voluntary movement), and compared to nine healthy subjects. In tasks using unaffected hand, we observed an increase of contralesional hemisphere activation for stroke patients group. Unexpectedly, when using paralyzed hand, motor cortex activation was reduced or absent in severely affected group of patients, while patients with moderate motor deficit showed an activation greater than control group. Cortical activation was reduced or absent in damaged hemisphere of all the patients in both tasks. Significant differences related to severity of motor deficit were found in the time course of [Formula: see text]-[Formula: see text] bands power ratio in EEG of contralesional hemisphere while moving affected hand. These findings suggest the presence of different compensation mechanisms in contralesional hemisphere of stroke patients related to the grade of motor disability, that might turn quantitative EEG during a movement task, obtained from a BCI system controlling a robotic device included in a rehabilitation task, into a valuable tool for monitoring clinical progression, evaluating recovery, and tailoring treatment of stroke patients.

Associations between Task-Related Modulation of Motor-Evoked Potentials and EEG Event-Related Desynchronization in Children with ADHD.

Children with attention-deficit/hyperactivity disorder (ADHD) have previously shown a decreased magnitude of event-related desynchronization (ERD) during a finger-tapping task, with a large between-group effect. Because the neurobiology underlying several transcranial magnetic stimulation (TMS) measures have been studied in multiple contexts, we compared ERD and 3 TMS measures (resting motor threshold [RMT], short-interval cortical inhibition [SICI], and task-related up-modulation [TRUM]) within 14 participants with ADHD (ages 8-12years) and 17 control children. The typically developing (TD) group showed a correlation between greater RMT and greater magnitude of alpha (10-13Hz, here) ERD, and there was no diagnostic interaction effect, consistent with a rudimentary model of greater needed energy input to stimulate movement. Similarly, inhibition measured by SICI was also greater in the TD group when the magnitude of movement-related ERD was higher; there was a miniscule diagnostic interaction effect. Finally, TRUM during a response-inhibition task showed an unanticipated pattern: in TD children, the greater TMS task modulation (TRUM) was associated with a smaller magnitude of ERD during finger-tapping. The ADHD group showed the opposite direction of association: Greater TRUM was associated with larger magnitude of ERD. Prior EEG results have demonstrated specific alterations of task-related modulation of cortical physiology, and the current results provide a fulcrum for multimodal study.

FV 10. Motor imagery supported by neurofeedback: Age-related changes in EEG and fNIRS lateralization patterns

Motor imagery (MI) supported by neurofeedback has been suggested as a promising add-on therapy to facilitate motor recovery after stroke. Though the main target group for such an intervention are elderly patients, research so far is largely focused on young, healthy adults. We therefore examined in two experiments the influence of age on the neural correlates of motor imagery (MI) in a real-time electroencephalogram (EEG) neurofeedback framework. In a first experiment MI-induced activity was studied in MI and neurofeedback naive young ( N = 39; 18–30 years) and elderly ( N = 36; >55 years) healthy adults. MI was supported by EEG feedback, and feedback was based on features extracted from the mu and beta frequency bands. Electromyogram (EMG) data were recorded concurrently to control for executed movements. During MI the group of older participants was characterized by a significantly reduced lateralization of EEG event-related desynchronization (ERD), mainly due to stronger ipsilateral ERD, and, in consequence, reduced classification accuracies. EEG-based neurofeedback resulted in a task-related activity increase irrespective of age. Aim of the second experiment was to replicate and validate these results. To this end, EEG was combined with simultaneous functional near-infrared spectroscopy (fNIRS). MI-induced activity was studied in a new sample of MI and neurofeedback naive young ( N = 19; 18–30 years) and elderly ( N = 18; >55 years) healthy adults. As before, MI was supported by EEG feedback based on features extracted from mu and beta frequency bands and EMG data were recorded concurrently to control for executed movements. The observation of a reduced lateralization due to stronger ipsilateral ERD could be replicated. Furthermore, fNIRS deoxygenated haemoglobin concentration changes confirmed this less lateralized pattern in the elderly. For both age groups the EEG-based neurofeedback resulted in a task-related increase in ERD and fNIRS activity. The reduction of lateralized brain activity during MI in the elderly is in good agreement with previous research showing similar age-related changes during MI and other cognitive tasks. This finding is in line with the general view that compensatory processes are recruited to counteract neurodegenerative changes during healthy ageing. However, these age-related changes did not compromise the responsiveness to neurofeedback. We therefore conclude that the potential benefit of a neurofeedback supported modulation of brain activity is preserved in the elderly.

27. Modulation of motor cortex excitability and brain activation in professional pianists during music listening: A combined EEG and TMS study

Neuroimaging studies have reported mirroring motor activation to music listening in musicians. Actual corticospinal modulation remains to be clarified. We tested the motor cortex modulation in pianists while listening to well-known, predictable melodic sequences, using Transcranial Magnetic Stimulation (TMS) and electroencephalography (EEG). Two groups of subjects were studied: pianists (n = 10) and controls (n = 10). Participants listened to a melodic sequence containing the alternating repetition of a scale in two different octaves. Using a circular coil on the vertex, Motor Evoked Potentials (MEP) were recorded bilaterally on both hands at different time points, with 32 channels EEG monitoring. EEG event-related desynchronization (ERD) of the mu rhythm was assessed by comparing its spectral power during listening vs rest. Pianists, not controls, showed modulation of MEPs amplitude of right hand muscles according to the timing of their activation during actual performance. Left sensori-motor frontal mu ERD to the melodic sequence played with the right hand was present in 9 pianists vs 4 control. The dynamic auditory induced motor resonance to music listening observed in pianists suggests the presence of an audio-motor mirror system that can be related to the ability of musician to confer a gestural meaning to well-known melodies.

A Generalized Framework for Quantifying the Dynamics of EEG Event-Related Desynchronization

Brains were built by evolution to react swiftly to environmental challenges. Thus, sensory stimuli must be processed ad hoc, i.e., independent—to a large extent—from the momentary brain state incidentally prevailing during stimulus occurrence. Accordingly, computational neuroscience strives to model the robust processing of stimuli in the presence of dynamical cortical states. A pivotal feature of ongoing brain activity is the regional predominance of EEG eigenrhythms, such as the occipital alpha or the pericentral mu rhythm, both peaking spectrally at 10 Hz. Here, we establish a novel generalized concept to measure event-related desynchronization (ERD), which allows one to model neural oscillatory dynamics also in the presence of dynamical cortical states. Specifically, we demonstrate that a somatosensory stimulus causes a stereotypic sequence of first an ERD and then an ensuing amplitude overshoot (event-related synchronization), which at a dynamical cortical state becomes evident only if the natural relaxation dynamics of unperturbed EEG rhythms is utilized as reference dynamics. Moreover, this computational approach also encompasses the more general notion of a “conditional ERD,” through which candidate explanatory variables can be scrutinized with regard to their possible impact on a particular oscillatory dynamics under study. Thus, the generalized ERD represents a powerful novel analysis tool for extending our understanding of inter-trial variability of evoked responses and therefore the robust processing of environmental stimuli.

Abnormally high EEG alpha synchrony during working memory maintenance in twins discordant for schizophrenia

BackgroundThe present analyses aimed to test the prediction that schizophrenia patients and their non-schizophrenic co-twins would display reduced efficiency of the neurocognitive mechanisms subserving active maintenance of spatial information in working memory. MethodsUpper alpha frequency band EEG event-related desynchronization and synchronization (ERD/ERS) were calculated as percent changes in power relative to an inter-trial baseline across 4 memory loads in a spatial delayed-response task. ResultsDuring the delay, the diagnostic groups showed equivalent ERD/ERS activity over posterior scalp regions at the lowest memory load; however, as memory load increased, patients, and to an intermediate degree, their non-schizophrenic co-twins (monozygotic and dizygotic pairs collapsed together), showed significantly greater increases in ERD/ERS amplitude as compared with controls. ConclusionsThese findings demonstrate abnormally increased ERD/ERS amplitudes with increasing memory load in patients with schizophrenia and their co-twins, consistent with inefficiency of the neurocognitive mechanisms supporting active maintenance of information across a delay.

Brain oscillatory EEG event-related desynchronization (ERD) and -sychronization (ERS) responses during an auditory memory task are altered in children with epilepsy

Children with epilepsy are in risk for cognitive impairment, but reliable methods, other than neuropsychological testing, to verify such a decline are few. The purpose of this study was to assess the effect of infrequent seizures on cognitive skills in children with non-symptomatic focal epilepsy taking antiepileptic medication but still having infrequent seizures. EEG (electroencephalogram) brain electric oscillatory responses of the 4-6Hz, 6-8Hz, 8-10Hz and 10-12Hz EEG frequency bands were studied. These responses, assessed by means of the event-related desynchronization (ERD) and synchronization (ERS) method, were recorded in 6 children with epilepsy (mean age 11.3 years) and in 11 control children (mean age 12 years) while they performed an auditory memory task. All subjects also underwent a comprehensive neuropsychological test battery. The differences in the 4-6Hz ERD/ERS responses between encoding and recognition were smaller in the children with epilepsy as compared to those of the control children. In the 6-8Hz frequency band, the responses of the two groups dissociated most notably in the frontal electrodes. No statistically significant differences in the alpha frequency range (8-12Hz) were observed between the groups. Significant alterations in the lower EEG frequency (4-8Hz) ERD/ERS responses in children with epilepsy during auditory memory processing, as compared to age-matched, healthy children may suggest that seizures affect memory and underlying brain processes, indexed also by poorer performance particularly in neuropsychological subtests related to language functions.

Movement preparation is affected by tissue damage in multiple sclerosis: Evidence from EEG event-related desynchronization

Objective To investigate the impact of brain tissue damage in Multiple Sclerosis (MS) on the efficiency of programming of voluntary movement, assessed using event-related desynchronization of the EEG. Methods The onset latency of mu ERD (percent desyncronization of the mu rhythm preceding movement onset) to hand movement was studied in 34 MS patients. ERD onset was compared with normative data and correlated with T1 and T2 total lesion volume (TLV) at magnetic resonance imaging (MRI). Results ERD onset latency was significantly correlated with T1-TLV ( r=0.53, P=0.001) and T2 lesion load ( r=0.5, P=0.003), even after correcting for disability. Patients with higher T1-TLV had significantly delayed ERD onset compared with normal subjects and with patients with lower T1-TLV; patients with higher T2-TLV had significantly delayed ERD compared with normal subjects only. ERD onset latency was not correlated to clinical disability. Conclusions Our finding of delayed ERD onset in patients with more severe measures of brain damage, independently from clinical disability, suggests that functional cortico-cortical and cortico-subcortical connections underlying the expression of ERD during programming of voluntary movement are disrupted by the MS related pathological process. Further, studies are needed to evaluate the role of specific anatomical cortico-subcortical circuits in determining this abnormality. Significance The extent of brain lesion load in multiple sclerosis affects cortical changes related to motor preparation, detected by analysis of onset latency of event-related desynchronization (ERD) of the mu rhythm to self-paced movement.

Alcohol-induced alterations in ERD/ERS during an auditory memory task

The purpose of the present study was to examine the effects of alcohol on EEG event-related desynchronization (ERD) and event-related synchronization (ERS) of the 4–6, 6–8, 8–10, and 10–12 Hz frequency bands during an auditory memory task. Twenty subjects performed an auditory memory task during which the EEG was recorded. Half the subjects performed the task without the administration of alcohol and half under the influence of alcohol (∼0.7 g/l). The administration of alcohol itself did not alter the ERD/ERS responses . However, when the effects of alcohol were studied as a function of time and task (encoding vs. retrieval), we observed significant effects in the 4–6, 6–8, and 8–10 Hz frequency bands such that the administration of alcohol decreased the early-appearing ERS responses during auditory encoding and increased the later-appearing ERD responses during retrieval. Our results indicate that alcohol has disorganizing effects on brain electric oscillatory systems in the theta and lower alpha frequency range during cognitive processing.

A new method for quantifying EEG event-related desynchronization: amplitude evvelope analysis

Amplitude modulation (AM) analysis defines precisely the EEG signal envelope changes at sampling frequency. Heew we demonstrate mathematically that event-related desynchronization (ERD) corresponds to the integration of AM-EEG. We applied this new approach to a group of 12 healthy human volunteers hearing repeated auditory stimuli and statistically compared the results from ERD to those from AM-EEG. The results indicate that AM-EEG characterized more precisely a specific evoked EEG cortical activation event and may be a powerful method for studying the time-course of functional dynamic brain EEG mapping with improved time resolution.

Pharmacologically induced changes in arousal: effects on behavioral and electrophysiologic measures of alertness and attention

The relationships between the diffuse subcortical neurotransmitter systems and behavioral and physiologic measures of alertness and attention are not well understood. This study was designed to further understand these relationships. In this double-blind experiment, 23 subjects ingested methylphenidate, diphenhydramine or placebo on 3 different days and performed behavioral and cognitive tasks including covert orienting of spatial attention and visual search tasks. Subjective and physiologic measures of alertness included EEG frequency analysis, EEG event-related desynchronization, and amount of sleep and sleep onset time in the unstimulated eyes closed state. Performance on the cognitive tasks improved with MP and worsened with DPHA, but there were no specific attentional effects. The best measures of alertness were based on self-rated scales and on EEG recorded in the unstimulated eyes closed state. These observations suggest that methylphenidate and diphenhydramine primarily affected overall state and that healthy humans were able to partially compensate for the pharmacologically induced alertness changes during cognitive task performance.