Mirror visual feedback (MVF) technique consists in placing a mirror in a person's body midline to induce the illusion of bilateral synchronous movements of the limbs during actual unilateral ...movements. A recent electroencephalographical (EEG) study demonstrated that MVF‐induced illusion was related to the event‐related desynchronization (ERD) of alpha (8–12 Hz) rhythms (cortical activation) at the central and parietal scalp electrodes ipsilateral to the unilateral right finger movements. In the present study, we re‐analyzed those data to localize the cortical sources of alpha ERD during the anticipation and experience of the MVF‐induced illusion of index finger movements. To this aim, the exact Low‐Resolution Brain Electromagnetic Tomography freeware was used for the estimation of the cortical sources of the alpha ERD. Results showed that as compared to the condition without MVF, the MVF condition was characterized by greater (p < .01, uncorrected) alpha ERD sources in right frontopolar areas during the anticipation of the MVF‐induced illusion of left movements. The MVF condition was also characterized by greater (p < .05, corrected) alpha ERD sources in right premotor, primary somatomotor, and posterior inferior parietal areas during both the anticipation and experience of that MVF‐induced illusion. These findings suggest that the MVF‐induced illusory experience of left finger movements may be due to dynamic changes in alpha ERD in associative, premotor, somatomotor, and visuomotor frontal–parietal areas located in the hemisphere contralateral to the mirrored motor acts.
This study investigates the electroencephalographic (EEG) cortical sources during the Mirror Visual Feedback (MVF) illusory experience. The analysis of the EEG alpha desynchronization showed as the polar frontal cortex pre‐activates the somatomotor set (anticipation). The experience of the MVF is related to a strong activity of the premotor, somatomotor, and posterior parietal areas ipsilateral to the real movement (execution). These findings support the use of MVF‐based therapies and EEG‐based technologies for motor recovery.
Microglia, the brain's resident macrophages, actively contribute to the homeostasis of cerebral parenchyma by sensing neuronal activity and supporting synaptic remodeling and plasticity. While ...several studies demonstrated different roles for astrocytes in sleep, the contribution of microglia in the regulation of sleep/wake cycle and in the modulation of synaptic activity in the different day phases has not been deeply investigated. Using light as a zeitgeber cue, we studied the effects of microglial depletion with the colony stimulating factor‐1 receptor antagonist PLX5622 on the sleep/wake cycle and on hippocampal synaptic transmission in male mice. Our data demonstrate that almost complete microglial depletion increases the duration of NREM sleep and reduces the hippocampal excitatory neurotransmission. The fractalkine receptor CX3CR1 plays a relevant role in these effects, because cx3cr1GFP/GFP mice recapitulate what found in PLX5622‐treated mice. Furthermore, during the light phase, microglia express lower levels of cx3cr1 and a reduction of cx3cr1 expression is also observed when cultured microglial cells are stimulated by ATP, a purinergic molecule released during sleep. Our findings suggest that microglia participate in the regulation of sleep, adapting their cx3cr1 expression in response to the light/dark phase, and modulating synaptic activity in a phase‐dependent manner.
Main Points
Neuronal spontaneous activity and microglial CX3CR1 increase in the dark.
Microglia alterations affect sleep and synaptic transmission in a phase‐dependent manner.
CX3CR1 mediates microglial effects on neuronal activity in the light/dark cycle.
Abstract Occipital sources of resting-state electroencephalographic (EEG) alpha rhythms are abnormal, at the group level, in patients with amnesic mild cognitive impairment (MCI) and Alzheimer's ...disease (AD). Here, we evaluated the hypothesis that amplitude of these occipital sources is related to neurodegeneration in occipital lobe as measured by magnetic resonance imaging. Resting-state eyes-closed EEG rhythms were recorded in 45 healthy elderly (Nold), 100 MCI, and 90 AD subjects. Neurodegeneration of occipital lobe was indexed by weighted averages of gray matter density, estimated from structural MRIs. EEG rhythms of interest were alpha 1 (8–10.5 Hz) and alpha 2 (10.5–13 Hz). EEG cortical sources were estimated by low-resolution brain electromagnetic tomography. Results showed a positive correlation between occipital gray matter density and amplitude of occipital alpha 1 sources in Nold, MCI, and AD subjects as a whole group (r = 0.3, p = 0.000004, N = 235). Furthermore, there was a positive correlation between the amplitude of occipital alpha 1 sources and cognitive status as revealed by Mini Mental State Examination score across all subjects (r = 0.38, p = 0.000001, N = 235). Finally, amplitude of occipital alpha 1 sources allowed a moderate classification of individual Nold and AD subjects (sensitivity: 87.8%; specificity: 66.7%; area under the receiver operating characteristic curve: 0.81). These results suggest that the amplitude of occipital sources of resting-state alpha rhythms is related to AD neurodegeneration in occipital lobe along pathologic aging.
Alzheimer's disease (AD) is the most common type of neurodegenerative disorder, typically causing dementia along aging. AD is mainly characterized by a pathological extracellular accumulation of ...amyloid-beta peptides that affects excitatory and inhibitory synaptic transmission, inducing aberrant patterns in neuronal circuits. Growing evidence shows that AD targets cortical neuronal networks related to cognitive functions including episodic memory and visuospatial attention. This is partially reflected by the abnormal mechanisms of cortical neural synchronization and coupling that generate resting state electroencephalographic (EEG) rhythms. The cortical neural synchronization is typically indexed by EEG power density. The EEG coupling between electrode pairs probes functional (inter-relatedness of EEG signals) and effective (casual effect from one over the other electrode) connectivity. The former is typically indexed by synchronization likelihood (linear and nonlinear) or spectral coherence (linear), the latter by granger causality or information theory indexes. Here we reviewed literature concerning EEG studies in condition of resting state in AD and mild cognitive impairment (MCI) subjects as a window on abnormalities of the cortical neural synchronization and functional and effective connectivity. Results showed abnormalities of the EEG power density at specific frequency bands (<12Hz) in the MCI and AD populations, associated with an altered functional and effective EEG connectivity among long range cortical networks (i.e. fronto-parietal and fronto-temporal). These results suggest that resting state EEG rhythms reflect the abnormal cortical neural synchronization and coupling in the brain of prodromal and overt AD subjects, possibly reflecting dysfunctional neuroplasticity of the neural transmission in long range cortical networks.
Abstract Objective The “neural efficiency” hypothesis posits that neural activity is reduced in experts. Here we tested the hypothesis that compared with non-athletes, elite athletes are ...characterized by a reduced cortical activation during simple voluntary movement and that this is reflected by the modulation of dominant alpha rhythms (8–12 Hz). Methods EEG data (56 channels; EB-Neuro) were continuously recorded in the following right-handed subjects: 10 elite karate athletes and 12 non-athletes. During the EEG recordings, they performed brisk voluntary wrist extensions of the right or left hand (right movement and left movement). The EEG cortical sources were estimated by standardized low-resolution brain electromagnetic tomography (sLORETA) freeware. With reference to a baseline period, the power decrease of alpha rhythms during the motor preparation and execution indexed the cortical activation (event-related desynchronization, ERD). Results During both preparation and execution of the right movements, the low- (about 8–10 Hz) and high-frequency alpha ERD (about 10–12 Hz) was lower in amplitude in primary motor area, in lateral and medial premotor areas in the elite karate athletes than in the non-athletes. For the left movement, only the high-frequency alpha ERD during the motor execution was lower in the elite karate athletes than in the non-athletes. Conclusions These results confirmed that compared with non-athletes, elite athletes are characterized by a reduced cortical activation during simple voluntary movement. Significance Cortical alpha rhythms are implicated in the “neural efficiency” of athletes’ motor systems.
Using a mirror adequately oriented, the motion of just one hand induces the illusion of the movement with the other hand. Here, we tested the hypothesis that such a mirror phenomenon may be ...underpinned by an electroencephalographic (EEG) event‐related desynchronization/synchronization (ERD/ERS) of central alpha rhythms (around 10 Hz) as a neurophysiological measure of the interactions among cerebral cortex, basal ganglia, and thalamus during movement preparation and execution. Eighteen healthy right‐handed male participants performed standard auditory‐triggered unilateral (right) or bilateral finger movements in the No Mirror (M−) conditions. In the Mirror (M+) condition, the unilateral right finger movements were performed in front of a mirror oriented to induce the illusion of simultaneous left finger movements. EEG activity was recorded from 64 scalp electrodes, and the artifact‐free event‐related EEG epochs were used to compute alpha ERD. In the M− conditions, a bilateral prominent central alpha ERD was observed during the bilateral movements, while left central alpha ERD and right alpha ERS were seen during unilateral right movements. In contrast, the M+ condition showed significant bilateral and widespread alpha ERD during the unilateral right movements. These results suggest that the above illusion of the left movements may be related to alpha ERD measures reflecting excitatory desynchronizing signals in right lateral premotor and primary somatomotor areas possibly in relation to basal ganglia‐thalamic loops.
This researche aimed to unveil the cortical areas and neurophysiological mechanisms underlying the Mirror Visual Feedback illusory phenomenon. The analysis of the scalp EEG alpha ERD demonstrated a bilateral activity of the motor and posterior parietal cortex during unilateral mirrored finger movements, likely related to the ganglia‐thalamo‐cortical motor loop typically observed during actual movements. Enhancing our knowledge might be useful to developing therapies for those patients with motor diseases.
The present study tested the hypothesis that cortical electroencephalographic (EEG) rhythms. change across normal elderly (Nold), mild cognitive impairment (MCI), and Alzheimer's disease (AD) ...subjects as a function of the global cognitive level.
Resting eyes-closed EEG data were recorded in 155 MCI, 193 mild AD, and 126 age-matched Nold subjects. EEG rhythms of interest were delta (2–4
Hz), theta (4–8
Hz), alpha 1 (8–10.5
Hz), alpha 2 (10.5–13
Hz), beta 1 (13–20
Hz), and beta 2 (20–30
Hz). EEG cortical sources were estimated by LORETA.
Occipital delta and alpha 1 sources in parietal, occipital, temporal, and ‘limbic’ areas had an intermediate magnitude in MCI subjects compared to mild AD and Nold subjects. These five EEG sources presented both linear and nonlinear (linear, exponential, logarithmic, and power) correlations with the global cognitive level (as revealed by mini mental state examination score) across all subjects.
Cortical EEG rhythms change in pathological aging as a function of the global cognitive level.
The present functional data on large populations support the ‘transitional hypothesis’ of a shadow zone across normality, pre-clinical stage of dementia (MCI), and AD.
Highlights • ECoG activity was recorded in drug-resistant epileptic patients during movement execution and observation. • ECoG desynchronization and synchronization was lower during movement ...observation than movement execution. • This data support the existence of a mirror system in humans.
Highlights • New multivariate EEG connectivity markers were tested on Alzheimerians. • Alzheimer’s group showed decreased posterior-to-anterior EEG connectivity. • Promising results of classification ...between AD and control group: AUC = 86%.
Abstract Cortical sources of resting state electroencephalographic (EEG) rhythms are abnormal in subjects with mild cognitive impairment (MCI). Here, we tested the hypothesis that these sources in ...amnesic MCI subjects further deteriorate over 1 year. To this aim, the resting state eyes-closed EEG data were recorded in 54 MCI subjects at baseline (Mini Mental State Examination I = 26.9; standard error SE, 0.2) and at approximately 1-year follow-up (13.8 months; SE, 0.5; Mini Mental State Examination II = 25.8; SE, 0.2). As a control, EEG recordings were also performed in 45 normal elderly and in 50 mild Alzheimer's disease subjects. EEG rhythms of interest were delta (2–4 Hz), theta (4–8 Hz), alpha1 (8–10.5 Hz), alpha2 (10.5–13 Hz), beta1 (13–20 Hz), and beta2 (20–30 Hz). Cortical EEG sources were estimated using low-resolution brain electromagnetic tomography. Compared with the normal elderly and mild Alzheimer's disease subjects, the MCI subjects were characterized by an intermediate power of posterior alpha1 sources. In the MCI subjects, the follow-up EEG recordings showed a decreased power of posterior alpha1 and alpha2 sources. These results suggest that the resting state EEG alpha sources were sensitive—at least at the group level—to the cognitive decline occurring in the amnesic MCI group over 1 year, and might represent cost-effective, noninvasive and widely available markers to follow amnesic MCI populations in large clinical trials.
PDF
