Sensorimotor EEG Rhythms Research Articles

Visual influences on sensorimotor EEG responses during observation of hand actions

There is growing interest within the field of social-cognitive neuroscience in the dynamics of sensorimotor EEG rhythms during the observation of actions performed by others. However, there remain important gaps in the literature regarding the effects of perceptual aspects of the observed hand movements. This study investigated two visual influences on the EEG response to hand actions. Specifically, the perspective of the action in relation to the participant (egocentric/allocentric) was varied and the effect of the hand used to carry out the action (left/right) was also assessed. While EEG was recorded, 28 undergraduate participants observed video clips showing an actor’s hand reaching for, grasping, and lifting a cylindrical object across four conditions (right-hand egocentric, left-hand egocentric, right-hand allocentric, and left-hand allocentric). For actions viewed from an egocentric perspective, significantly greater event-related desynchronization (ERD) was present in the 7–9Hz range over right mid-frontal, right central, and bilateral mid-parietal sites for right-handed actions compared to left-handed actions. In addition, greater ERD was observed within the 7–9Hz band during the observation of right-handed egocentric actions compared to actions viewed from the allocentric perspective. This finding was present at bilateral central and mid-parietal sites, and emerged as an anticipatory effect prior to the onset of the observed hand movements.

The effect of action experience on sensorimotor EEG rhythms during action observation

A recent line of inquiry has examined how an observer׳s experience with action changes the neural processing of similar actions when they are subsequently observed. The current study used electroencephalography (EEG) to test the hypothesis that giving participants different types and amounts of experience with specific objects would lead to differential patterns of sensorimotor rhythms during the observation of similar actions on those objects. While EEG was recorded, three groups of participants (n=20 in each group; mean age=22.0 years, SD=2.7) watched video clips of an actor reaching, grasping, and lifting two objects. Participants then received information about differences in weight between the two objects. One group gained this information through extended sensorimotor experience with the objects, a second group received much briefer sensorimotor experience with the objects, and the third group read written information about the objects׳ weights. Participants then viewed the action sequences again. For participants who had sensorimotor experience with the objects, the EEG response to viewing the actions was differentially sensitive to the anticipated weight of the objects. We conclude that this sensitivity was based on the participant׳s prior sensorimotor experience with the objects. The participants who only received semantic information about the objects showed no such effects. The primary conclusion is that even brief experience with actions affects sensorimotor cortex activity during the subsequent observation of similar actions.

Changes in cortical oscillations linked to multisensory modulation of nociception

Pain can be modulated by several contextual factors. For example, simply viewing one's own body can reduce pain, suggesting that the visual context may influence the processing of nociceptive stimuli. We studied changes in electroencephalographic (EEG) oscillatory activity related to visual modulation of nociception, comparing cortical oscillations during innocuous or noxious contact heat, while participants viewed either their own hand or a neutral object at the same location. Viewing the body compared with viewing the object reduced the intensity ratings of noxious stimuli, but not of innocuous heat. Time-frequency analysis of EEG data revealed that noxious, as opposed to warm, stimulation was associated with reduced beta (15-25Hz) power. Classically, such decreases in oscillatory power indicate increases in sensory cortical activation. These event-related oscillatory changes were moreover modulated by the visual context; viewing one's own body increased noxious stimulation-induced beta oscillatory activity bilaterally, relative to viewing a neutral object, possibly indicating inhibition of cortical nociceptive processing. These results demonstrate that visual-nociceptive interactions involve changes in sensorimotor EEG rhythms.

Level of participation in robotic-assisted treadmill walking modulates midline sensorimotor EEG rhythms in able-bodied subjects

In robot assisted gait training, a pattern of human locomotion is executed repetitively with the intention to restore the motor programs associated with walking. Several studies showed that active contribution to the movement is critical for the encoding of motor memory. We propose to use brain monitoring techniques during gait training to encourage active participation in the movement. We investigated the spectral patterns in the electroencephalogram (EEG) that are related to active and passive robot assisted gait. Fourteen healthy participants were considered. Infomax independent component analysis separated the EEG into independent components representing brain, muscle, and eye movement activity, as well as other artifacts. An equivalent current dipole was calculated for each independent component. Independent components were clustered across participants based on their anatomical position and frequency spectra. Four clusters were identified in the sensorimotor cortices that accounted for differences between active and passive walking or showed activity related to the gait cycle. We show that in central midline areas the mu (8-12 Hz) and beta (18-21 Hz) rhythms are suppressed during active compared to passive walking. These changes are statistically significant: mu (F(1, 13)=11.2 p ≤ 0.01) and beta (F(1, 13)=7.7, p ≤ 0.05). We also show that these differences depend on the gait cycle phases. We provide first evidence of modulations of the gamma rhythm in the band 25 to 40 Hz, localized in central midline areas related to the phases of the gait cycle. We observed a trend (F(1, 8)=11.03, p ≤ 0.06) for suppressed low gamma rhythm when comparing active and passive walking. Additionally we found significant suppressions of the mu (F(1, 11)=20.1 p ≤ 0.01), beta (F(1, 11)=11.3 p ≤ 0.05) and gamma (F(1, 11)=4.9 p ≤ 0.05) rhythms near C3 (in the right hand area of the primary motor cortex) during phases of active vs. passive robot assisted walking. To our knowledge this is the first study showing EEG analysis during robot assisted walking. We provide evidence for significant differences in cortical activation between active and passive robot assisted gait. Our findings may help to define appropriate features for single trial detection of active participation in gait training. This work is a further step toward the evaluation of brain monitoring techniques and brain-computer interface technologies for improving gait rehabilitation therapies in a top-down approach.

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

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 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.

Changes in EEG measurements in intractable epilepsy patients with neurofeedback training

To assess the effects of neurofeedback on brain electrophysiology and to determine how biofeedback works, power spectral density (PSD) and approximate entropy (ApEn) analyses are applied to the EEGs of six patients with intractable epilepsy who received neurofeedback training. After sessions of treatment, the EEG sensorimotor rhythm to theta PSD ratio calculated from the C4 electrode site becomes larger than that before the treatment, which is consistent with the biofeedback protocol. The ApEn over 16-channel EEG recordings all increase to different degrees. Larger increases occur in channels located near the training position (C4). All these results suggest that these EEG measurements are new criteria that can be used to evaluate the effect of neurofeedback.

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

Objective: To investigate the dynamics of EEG oscillations in patients with acute cortical or subcortical stroke during the performance of a sensorimotor task.

Motor imagery and action observation: Modulation of sensorimotor brain rhythms during mental control of a brain–computer interface

This study investigates the impact of a continuously presented visual feedback in the form of a grasping hand on the modulation of sensorimotor EEG rhythms during online control of a brain-computer interface (BCI). Two groups of participants were trained to use left or right hand motor imagery to control a specific output signal on a computer monitor: the experimental group controlled a moving hand performing an object-related grasp ('realistic feedback'), whereas the control group controlled a moving bar ('abstract feedback'). Continuous feedback was realized by using the outcome of a real-time classifier which was based on EEG signals recorded from left and right central sites. The classification results show no difference between the two feedback groups. For both groups, ERD/ERS analysis revealed a significant larger ERD during feedback presentation compared to an initial motor imagery screening session without feedback. Increased ERD during online BCI control was particularly found for the lower alpha (8-10 Hz) and for the beta bands (16-20, 20-24 Hz). The present study demonstrates that visual BCI feedback clearly modulates sensorimotor EEG rhythms. When the feedback provides equivalent information on both the continuous and final outcomes of mental actions, the presentation form (abstract versus realistic) does not influence the performance in a BCI, at least in initial training sessions. The present results are of practical interest for classifier development and BCI use in the field of motor restoration.

Sensorimotor EEG rhythms during execution, imagination and observation of movement

Sensorimotor EEG rhythms during execution, imagination and observation of movement

Non-invasive brain–computer interface system: Towards its application as assistive technology

The quality of life of people suffering from severe motor disabilities can benefit from the use of current assistive technology capable of ameliorating communication, house-environment management and mobility, according to the user's residual motor abilities. Brain–computer interfaces (BCIs) are systems that can translate brain activity into signals that control external devices. Thus they can represent the only technology for severely paralyzed patients to increase or maintain their communication and control options. Here we report on a pilot study in which a system was implemented and validated to allow disabled persons to improve or recover their mobility (directly or by emulation) and communication within the surrounding environment. The system is based on a software controller that offers to the user a communication interface that is matched with the individual's residual motor abilities. Patients ( n = 14) with severe motor disabilities due to progressive neurodegenerative disorders were trained to use the system prototype under a rehabilitation program carried out in a house-like furnished space. All users utilized regular assistive control options (e.g., microswitches or head trackers). In addition, four subjects learned to operate the system by means of a non-invasive EEG-based BCI. This system was controlled by the subjects’ voluntary modulations of EEG sensorimotor rhythms recorded on the scalp; this skill was learnt even though the subjects have not had control over their limbs for a long time. We conclude that such a prototype system, which integrates several different assistive technologies including a BCI system, can potentially facilitate the translation from pre-clinical demonstrations to a clinical useful BCI.

High-resolution EEG techniques for brain–computer interface applications

High-resolution electroencephalographic (HREEG) techniques allow estimation of cortical activity based on non-invasive scalp potential measurements, using appropriate models of volume conduction and of neuroelectrical sources. In this study we propose an application of this body of technologies, originally developed to obtain functional images of the brain's electrical activity, in the context of brain–computer interfaces (BCI). Our working hypothesis predicted that, since HREEG pre-processing removes spatial correlation introduced by current conduction in the head structures, by providing the BCI with waveforms that are mostly due to the unmixed activity of a small cortical region, a more reliable classification would be obtained, at least when the activity to detect has a limited generator, which is the case in motor related tasks. HREEG techniques employed in this study rely on (i) individual head models derived from anatomical magnetic resonance images, (ii) distributed source model, composed of a layer of current dipoles, geometrically constrained to the cortical mantle, (iii) depth-weighted minimum L 2-norm constraint and Tikhonov regularization for linear inverse problem solution and (iv) estimation of electrical activity in cortical regions of interest corresponding to relevant Brodmann areas. Six subjects were trained to learn self modulation of sensorimotor EEG rhythms, related to the imagination of limb movements. Off-line EEG data was used to estimate waveforms of cortical activity (cortical current density, CCD) on selected regions of interest. CCD waveforms were fed into the BCI computational pipeline as an alternative to raw EEG signals; spectral features are evaluated through statistical tests ( r 2 analysis), to quantify their reliability for BCI control. These results are compared, within subjects, to analogous results obtained without HREEG techniques. The processing procedure was designed in such a way that computations could be split into a setup phase (which includes most of the computational burden) and the actual EEG processing phase, which was limited to a single matrix multiplication. This separation allowed to make the procedure suitable for on-line utilization, and a pilot experiment was performed. Results show that lateralization of electrical activity, which is expected to be contralateral to the imagined movement, is more evident on the estimated CCDs than in the scalp potentials. CCDs produce a pattern of relevant spectral features that is more spatially focused, and has a higher statistical significance (EEG: 0.20 ± 0.114 S.D.; CCD: 0.55 ± 0.16 S.D.; p = 10 −5). A pilot experiment showed that a trained subject could utilize voluntary modulation of estimated CCDs for accurate (eight targets) on-line control of a cursor. This study showed that it is practically feasible to utilize HREEG techniques for on-line operation of a BCI system; off-line analysis suggests that accuracy of BCI control is enhanced by the proposed method.

Functional Brain Asymmetry and Individual Differences in Hand Preference in Early Ontogeny

This work was aimed at studying the brain mechanisms of hand preference in 10- to 11-month-old infants. According to the results of neuropsychological investigations, the preference for the right hand in children of this age (at the populational level) primarily arises in actions that demand involvement of the functions of planning and motor control of reaching (functions of the motor control of reaching: FMCR) for an object. The stage of development of the FMCR in each child was scored on the Diamond scale. Total numbers of movements performed by the right and left hands and a coefficient of the manual asymmetry (AC) were calculated. On the basis of quartile analysis of the AC distribution, groups of “right-handers,” “left-handers,” and “ambidextrals” were formed. The EEG was recorded in the state of visual focused attention, and the spectral absolute amplitude density (AAD) of the sensorimotor rhythm and other infant EEG rhythms in the α frequency band was analyzed. In order to estimate the statistical correlation of manual asymmetry, gender, and stage of development of the FMCR with functional asymmetry of the AAD of the α-band rhythms in different cortical derivations, analysis of variance with factors of repeated measurements and analysis of multiple regression were used. The main results showed that 10- to 11-month-old children with different types of manual asymmetry differed in interhemispheric asymmetry of the visual attention-related EEG α-band rhythms (including asymmetry of the sensorimotor rhythm). The maximum differences were observed in the lateral frontal and posterotemporal areas of the brain cortex. The leftward amplitude asymmetry was characteristic of right-handers; in left-handers and ambidextrals, the EEG amplitude was distributed over the brain hemispheres in a more symmetric way. The correlation between the brain and manual asymmetries was stronger in boys than in girls. There was a strict linear correlation between the degree of manual asymmetry and interhemispheric asymmetry of the EEG sensorimotor rhythm in the precentral and lateral frontal brain areas. On the whole, the close correlation of the manual asymmetry with functional asymmetry of the EEG sensorimotor rhythm suggests that it is determined by the formation of the brain FMCR lateralization.

Sensorimotor EEG rhythms and their connection to local/global neocortical dynamic theory

The EEG activity recorded from the human sensorimotor cortical area exhibits rhythmic activity covering a broad range of frequencies, including alpha, mu, beta, and gamma (40-Hz) rhythms. This commentary elaborates on connections between these sensorimotor rhythms and Nunez's neocortical dynamic theory.

The effects of external load on movement-related changes of the sensorimotor EEG rhythms

The effects of external load opposing brisk voluntary extension of the right index finger on the EEG rhythms in the left and right sensorimotor hand area were studied in 13 right-handed subjects. Four levels of external loads corresponding to the weights of 0 g (no load), 30 g, 80 g and 130 g were used. The effects of external load on EEG rhythms were the following: (i) prior to movement, the desynchronisation of beta-rhythms (18–25 Hz) over the contralateral sensorimotor area was greater under the two largest loads as compared to the 0 g load. However, beta-desynchronisation at ipsilateral electrodes was larger under the 80 g load than under the 130 g load, presumably due to a transcallosally mediated inhibition exerted by the highly excited contralateral motor area; (ii) the mu-rhythm desynchronisation continued over both hemispheres for about 0.3–0.4 s after movement and the largest load was accompanied by the longest mu-rhythm desynchronisation; (iii) the post-movement beta-synchronisation was also longer under the heaviest load (130 g) as compared to the no-load condition (0 g), especially in subjects who prolonged their total movement time under the heaviest load. The results show that (i) the movement-related desynchronisation and synchronisation of sensorimotor EEG rhythms is influenced by external load opposing finger movement, and (ii) the effects of external load differ for the mu- and beta-rhythms.

Composite Biofeedback Conditioning and Dangerous Offenders: III

Seventy-seven offenders, selected as subject to deep-brain complex seizures, were treated with varying amounts of a composite EEG-SMR and GSR-SCARS biofeedback conditioning procedure. Subjects were selected through successive screens, culminating in evidence of a perceptual-motor anomaly shown to predict to various types of dangerous criminal conduct. The lack of a recognizable prodrome that these subjects might use to cue voluntary selfregulation made it seem necessary to abandon the usual method of continuous analog biofeedback. An operant conditioning method was employed, which provided discontinuous and contingent reinforcing feedback during all occurrences of EEG sensorimotor rhythm (SMR) and for successive 1 K ohms increases in skin resistance (GSR). The mean duration of post-release follow-up was eighteen months. Criminal recidivism rates were shown to decrease roughly in proportion to the number of treatment sessions received. Recidivism rates varied from 65% for those receiving essentially no biofeedback treatment to 20% for those receiving more than 33 half-hour sessions. The results were interpreted as holding out hope for the identification and treatment modification of one subset of dangerous offenders.

A simple and a complex tic (Gilles de la Tourette's syndrome): Their response to EEG sensorimotor rhythm biofeedback training

This study presents a clinical treatment regime for the treatment of tic manifestation, both simple and complex. The response of a case of simple tic and a case of complex tic (Giles de la Tourette's syndrome) to EEG sensorimotor rhythm biofeedback training are presented. Specifically, the simple and the complex tic, both of long duration, were eliminated via this EEG biofeedback training procedure. It is hypothesized that this exercising of the sensorimotor cortex resulted in increased activation of this cerebrocortical subsystem and was reflected in increased voluntary muscle control and a heightened threshold for random motor discharge, resulting in the elimination of both tics as in the response of cases of epilepsy with motor involvement to EEG sensorimotor rhythm biofeedback training. The additional psychophysiologic sequelae of the complex tic—attention deficit disorder—remediated in the manner of the response of learning-disabled to EEG sensorimotor rhythm biofeedback training.

Brainwave signatures — An index reflective of the brain's functional neuroanatomy: Further findings on the effect of EEG sensorimotor rhythm biofeedback training on the neurologic precursors of learning disabilities

Eight boys, ages 7 years 11 months to 15 years 3 months, were provided withlong-term—symptom duration—sensorimotor rhythm biofeedback training for the remediation of their learning disabilities. Concurrently, the simultaneous recording of five frequency bands of brainwave activity (5 Hz, 7 Hz, 10 Hz, 12 Hz and 14 Hz), from one active electrode equidistant from reference and ground, was intended to provide a glimpse of the ‘brainwave signature’ reflective of the dynamic and synergistic processes involved in such cerebro-neural activation and the brain's global response to such an alteration in the sensorimotor subnetwork. Overall, the main effect of this procedure, for the biofeedback and subsequent conditioning of increased 14 Hz neural discharge patterns over the central Rolandic cortex in a clinical office setting, seems to be increase bilateral sensorimotor transactions resulting in substantive remediation of the learning disabilities of the recipients of such training—by way of internally exercising of, and/or recruitment of additional neural activation within, the sensorimotorsubnetwork/matrix. Observation of the changing brainwave signatures showed a tendency for decreased slow were activity concommitant with increases in fast wave activity, for cases with a Full Scale I.Q. within the range of 76 and 85; with those cases with a Full Scale I.Q. within the range of 102 and 116 exhibiting increased amplitudes over most of the monitored bands, but with the increases being much less at the slower frequencies. It is noteworthy that those four subjects with either a significant Verbal greater than Performance, or Performance greater than Verbal, I.Q. Score discrepancy exhibited no less than a 40% greater increase in the lower of the two I.Q. scores; indicating that this SMR training procedure also resulted in an increased symmetry in the interhemispheric interactions reflective of the higher cortical functions for these no longer learning disabled boys.

The response of a case of petit mal epilepsy to EEG sensorimotor rhythm biofeedback training

A 14-year-old girl, with a long history of absence seizures, sudden rages, spatial disorientation, and academic difficulties received long-term (33 sessions) EEG sensorimotor rhythm biofeedback training. Operantly conditioned increases in the average amplitude of the 14 Hz neural discharge rhythm, over the central Rolandic cortex and cerebrolongitudinal fissure, resulted in a total cessation of her absence seizures; which had, prior to the EEG sensorimotor rhythm biofeedback training, occurred at the rate of 4–5 absences per hour. Concurrently, her sudden rages, spatial disorientation, and academic functioning all evidenced significant remediation.

EEG sensorimotor rhythm biofeedback training: Some effects on the neurologic precursors of learning disabilities

This study presents a clinical treatment regime for pathological interhemispheric dysfunction with respect to a population of learning disabled boys. The results obtained replicate and extend earlier findings with respect to operantly conditioned increases in amplitude of sensorimotor transactions and its positive effect on learning disability. Specifically, the biofeedback, and subsequent conditioning, of increased 14 Hz neural discharge patterns (sensorimotor rhythm — SMR) over the central Rolandic cortex, appeared to increase bilateral sensorimotor transactions resulting in substantive reduction/remediation in the learning disabilities of the recipients of such EEG biofeedback training.

Correlations between CT scan and sensorimotor EEG rhythms in patients with cerebrovascular disorders

Fifty subjects with cerebrovascular disorders and motor deficits, all able to perform a voluntary hand movement and aged between 33 and 78 years, were involved in this study. CT scan and computerized analysis of sensorimotor rhytms (mu rhythm and central beta rhythm) were performed for all patients. From the mu rhythm, the hemispheric asymmetry in amplitude and ERD during movement (ERD = event-related desynchronization) was measured and referred to a group 38 neurologically normal subjects. Comparisons of CT scan data and EEG findings indicate a high correlation between morphological and functional findings. This correlation can be used to predict the localization of a lesion in the territory of the middle cerebral artery (MCA) based only on the amplitude and reactivity pattern of the mu rhythm. Thus, for example, an ipsilaterally enhanced mu rhythm in connection with a symmetric ERD indicates with a probability of 95% a deep, and with only 5%, a superficial lesion. Hemispheric mu amplitude symmetry and asymmetric ERD indicate a superficial cortical ischemia with a probability of 81%. An ipsilaterally attenuated mu rhythm accompanied by an asymmetric or abolished ERD indicates with 62% and 55%, respectively, a large extension of the infarct over the whole territory of the MCA.