Quantitative measures of the resting EEG in stroke: a systematic review on clinical correlation and prognostic value.

OBJECT: Quantitative electroencephalography (qEEG) has shown promising results as a predictor of clinical impairment in stroke. We systematically reviewed published papers that focus on qEEG metrics in the resting EEG of patients with mono-hemispheric stroke, to summarize current knowledge and pave the way for future research. METHODS: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we systematically searched the literature for papers that fitted our inclusion criteria. Rayyan QCRR was used to allow deduplication and collaborative blinded paper review. Due to multiple outcomes and non-homogeneous literature, a scoping review approach was used to address the topic. RESULTS: Or initial search (PubMed, Embase, Google scholar) yielded 3200 papers. After proper screening, we selected 71 papers that fitted our inclusion criteria and we developed a scoping review thar describes the current state of the art of qEEG in stroke. Notably, among selected papers 53 (74.3%) focused on spectral power; 11 (15.7%) focused on symmetry indexes, 17 (24.3%) on connectivity metrics, while 5 (7.1%) were about other metrics (e.g. detrended fluctuation analysis). Moreover, 42 (58.6%) studies were performed with standard 19 electrodes EEG caps and only a minority used high-definition EEG. CONCLUSIONS: We systematically assessed major findings on qEEG and stroke, evidencing strengths and potential pitfalls of this promising branch of research.

Early diagnosis of Alzheimer's disease: the role of biomarkers including advanced EEG signal analysis. Report from the IFCN-sponsored panel of experts.

Alzheimer's disease (AD) is the most common neurodegenerative disease among the elderly with a progressive decline in cognitive function significantly affecting quality of life. Both the prevalence and emotional and financial burdens of AD on patients, their families, and society are predicted to grow significantly in the near future, due to a prolongation of the lifespan. Several lines of evidence suggest that modifications of risk-enhancing life styles and initiation of pharmacological and non-pharmacological treatments in the early stage of disease, although not able to modify its course, helps to maintain personal autonomy in daily activities and significantly reduces the total costs of disease management. Moreover, many clinical trials with potentially disease-modifying drugs are devoted to prodromal stages of AD. Thus, the identification of markers of conversion from prodromal form to clinically AD may be crucial for developing strategies of early interventions. The current available markers, including volumetric magnetic resonance imaging (MRI), positron emission tomography (PET), and cerebral spinal fluid (CSF) analysis are expensive, poorly available in community health facilities, and relatively invasive. Taking into account its low cost, widespread availability and non-invasiveness, electroencephalography (EEG) would represent a candidate for tracking the prodromal phases of cognitive decline in routine clinical settings eventually in combination with other markers. In this scenario, the present paper provides an overview of epidemiology, genetic risk factors, neuropsychological, fluid and neuroimaging biomarkers in AD and describes the potential role of EEG in AD investigation, trying in particular to point out whether advanced analysis of EEG rhythms exploring brain function has sufficient specificity/sensitivity/accuracy for the early diagnosis of AD.

Personalizing the Electrode to Neuromodulate an Extended Cortical Region.

BACKGROUND: Among transcranial electric stimulation (tES) parameters, personalizing the electrode geometry might help overcome the individual variability of the induced effects. OBJECTIVE/HYPOTHESIS: To test the need for electrode personalization, instead of a universal electrode for everyone, to induce neuromodulation effects on the bilateral primary motor cortex (M1) devoted to upper and lower limb representation. METHODS: By an ad-hoc neuronavigation procedure, we shaped the personalized electrode and positioned it matching the projection on the scalp of the individual central sulcus by a 2 cm strip, with total area of 35 cm(2). The non-personalized electrode, i.e., equal for all subjects, was a 2 cm wide strip size-matched with the personalized electrode but shaped on a standard model fitting the curve passing through C3-CZ-C4 sites of the electroencephalographic (EEG) 10-20 International System. To test neuromodulation electrode-dependent efficacy, we induced a 20 Hz sinusoidal modulated current (transcranial alternating current stimulation, tACS) because it produces online effects. We simultaneously collected left and right hand and leg motor potentials (MEP) that were evoked by a rounded transcranial magnetic stimulation (TMS) coil. Through each electrode we delivered both real and sham stimulations. RESULTS: While cortical excitability during tACS increased during both the non-personalized and the personalized electrodes for the leg, the hand representation excitability enhancement was induced selectively when using the personalized electrode. The results were consistent bilaterally. CONCLUSIONS: We documented that by using a personalized electrode it is possible to induce the neuromodulation of a predetermined extended cortical target, which did not occur with a non-personalized electrode. Our findings can help in building neuromodulation methods that might compensate for individual alterations across specific brain networks.

Transcranial Direct Current Stimulation: Personalizing the neuromodulation.

The beneficial effects of transcranial direct current stimulation (tDCS) has been demonstrated, but the neuroscientific community is working to increase its efficiency. A promising line of advancement may be reducing the inter-individual variability of the response through the personalization of the stimulation, adapted to fit the structural and functional features of individual subjects. In this paper, we approach the personalization of stimulation parameters using modeling, a powerful tool to test montages enabling the optimization of brain's targeting.

Functional and structural balances of homologous sensorimotor regions in multiple sclerosis fatigue.

Fatigue in multiple sclerosis (MS) is a highly disabling symptom. Among the central mechanisms behind it, an involvement of sensorimotor networks is clearly evident from structural and functional studies. We aimed at assessing whether functional/structural balances of homologous sensorimotor regions-known to be crucial for sensorimotor networks effectiveness-decrease with MS fatigue increase. Functional connectivity measures at rest and during a simple motor task (weak handgrip of either the right or left hand) were derived from primary sensorimotor areas electroencephalographic recordings in 27 mildly disabled MS patients. Structural MRI-derived inter-hemispheric asymmetries included the cortical thickness of Rolandic regions and the volume of thalami. Fatigue symptoms increased together with the functional inter-hemispheric imbalance of sensorimotor homologous areas activities at rest and during movement, in absence of any appreciable parenchymal asymmetries. This finding supports the development of compensative interventions that may revert these neuronal activity imbalances to relieve fatigue in MS.

Inter-hemispheric functional connectivity changes with corpus callosum morphology in multiple sclerosis.

Multiple sclerosis (MS) affects myelin sheaths within the central nervous system, concurring to cause brain atrophy and neurodegeneration as well as gradual functional disconnections. To explore early signs of altered connectivity in MS from a structural and functional perspective, the morphology of corpus callosum (CC) was correlated with a dynamic inter-hemispheric connectivity index. Twenty mildly disabled patients affected by a relapsing-remitting (RR) form of MS (EDSS⩽3.5) and 15 healthy subjects underwent structural MRI to measure CC thickness over 100 sections and electroencephalography to assess a spectral coherence index between primary regions devoted to hand control, at rest and during an isometric handgrip. In patients, an overall CC atrophy was associated with increased lesion load. A less efficacious inter-hemispheric coherence (IHCoh) during movement was associated with CC atrophy in sections interconnecting homologous primary motor areas (anterior mid-body). In healthy controls, less efficacious IHCoh at rest was associated with a thinner CC splenium. Our data suggest that in mildly disabled RR-MS patients a covert impairment may be detected in the correlation between the structural (CC thickness) and functional (IHCoh) measures of homologous networks, whereas these two counterparts do not yet differ individually from controls.

Movement-induced uncoupling of primary sensory and motor areas in focal task-specific hand dystonia.

INTRODUCTION: Due to growing evidence of sensorimotor integration impairment in focal task-specific hand dystonia, we aimed at describing primary sensory (S1) and primary motor (M1) cortex source activities and their functional cross-talk during a non-dystonia-inducing sensorimotor task free of biases generated by the interfering with the occurrence of dystonic movements. METHOD: Magnetoencephalographic brain signals and opponens pollicis (OP) electromyographic activities were acquired at rest and during a simple isometric contraction performed either alone or in combination with median nerve stimulation. The task was performed separately with the right and left hand by eight patients suffering from focal task-specific hand dystonia and by eight healthy volunteers. Through an ad hoc procedure Functional Source Separation (FSS), distinct sources were identified in S1 (FSS1) and M1 (FSM1) devoted to hand control. Spectral properties and functional coupling (coherence) between the two sources were assessed in alpha [8,13]Hz, beta [14,32]Hz and gamma [33,45]Hz frequency bands. RESULTS: No differences were found between spectral properties of patients and controls for either FSM1 or FSS1 cerebral sources. Functional coupling between FSM1 and FSS1 (gamma band coherence), while comparable between dystonic patients and healthy controls at rest, was selectively reduced in patients during movement. All findings were present in both hemispheres. DISCUSSION: Because previous literature has shown that gamma-band sensory-motor synchronization reflects an efficiency index of sensory-motor integration, our data demonstrate that, in dystonic patients, uncoupling replaces the functional coupling required for efficient sensory-motor control during motor exertion. The presence of bi-hemispheric abnormalities in unilateral hand dystonia supports the presence of an endophenotypic trait.

Cortico-muscular coherence as an index of fatigue in multiple sclerosis.

BACKGROUND: Highly common in multiple sclerosis (MS), fatigue severely impacts patients' daily lives. Previous findings of altered connectivity patterns led to the hypothesis that the distortion of functional connections within the brain-muscle circuit plays a crucial pathogenic role. OBJECTIVE: The objective of this paper is to identify markers sensitive to fatigue in multiple sclerosis. METHODS: Structural (magnetic resonance imaging with assessment of thalamic volume and cortical thickness of the primary sensorimotor areas) and functional (cortico-muscular coherence (CMC) from simultaneous electroencephalo- and surface electromyographic recordings during a weak handgrip task) measures were used on 20 mildly disabled MS patients (relapsing-remitting course, Expanded Disability Status Scale score ≤ 2) who were recruited in two fatigue-dependent groups according to the Modified Fatigue Index Scale (MFIS) score. RESULTS: The two groups were similar in terms of demographic, clinical and imaging features, as well as task execution accuracy and weariness. In the absence of any fatigue-dependent brain and muscular oscillatory activity alterations, CMC worked at higher frequencies as fatigue increased, explaining 67% of MFIS variance (p=.002). CONCLUSION: Brain-muscle functional connectivity emerged as a sensitive marker of phenomena related to the origin of MS fatigue, impacting central-peripheral communication well before the appearance of any impairment in the communicating nodes.

A contralesional EEG power increase mediated by interhemispheric disconnection provides negative prognosis in acute stroke.

BACKGROUND AND PURPOSE: Despite similar clinical onset, recovery from stroke can be largely variable. We searched for electrophysiological prognostic indices, believing that they can guide future neuromodulation treatments boosting clinical recovery. METHODS: 19-channels resting electroencephalogram (EEG) was collected in 42 patients after 4-10 days (t0) from a unilateral ischemic stroke in the middle cerebral artery (MCA) territory and 20 controls. National Health Institute Stroke Scale (NIHSS) was collected at t0 and 6 months later (t1). Standard spectral band powers and interhemispheric coherences between homologous MCA regions were calculated in both hemispheres. RESULTS: Total spectral, delta and theta band powers were higher bilaterally in patients than in controls and directly correlated with NIHSSt0 in both hemispheres. A linear regression model including each EEG patient's variable differing from those of controls and correlating with effective recovery [ER = (NIHSSt0-NIHSSt1)/(NIHSSt0-NIHSS in healthy conditions)] showed contralesional delta power as the only valid predictor of ER. A further regression model including also NIHSSt0 confirmed that contralesional delta power can add prognostic information to acute clinical impairment. Contralesional delta activity increase was best explained, in addition to the increasing ipsilesional delta activity, by a reduction of interhemispheric functional coupling--which did not explain a significantly portion of effective recovery variability by itself. CONCLUSIONS: Contralesional EEG delta activity retains relevant negative prognostic information in acute stroke patients. Present results point to the interhemispheric interplay as a decisive target in setting up enriched rehabilitations.

Sensorimotor Cortex Reorganization in Alzheimer's Disease and Metal Dysfunction: A MEG Study.

Objective. To verify whether systemic biometals dysfunctions affect neurotransmission in living Alzheimer's disease (AD) patients. Methods. We performed a case-control study using magnetoencephalography to detect sensorimotor fields of AD patients, at rest and during median nerve stimulation. We analyzed position and amount of neurons synchronously activated by the stimulation in both hemispheres to investigate the capability of the primary somatosensory cortex to reorganize its circuitry disrupted by the disease. We also assessed systemic levels of copper, ceruloplasmin, non-Cp copper (i.e., copper not bound to ceruloplasmin), peroxides, transferrin, and total antioxidant capacity. Results. Patients' sensorimotor generators appeared spatially shifted, despite no change of latency and strength, while spontaneous activity sources appeared unchanged. Neuronal reorganization was greater in moderately ill patients, while delta activity increased in severe patients. Non-Cp copper was the only biological variable appearing to be associated with patient sensorimotor transmission. Conclusions. Our data strengthen the notion that non-Cp copper, not copper in general, affects neuronal activity in AD. Significance. High plasticity in the disease early stages in regions controlling more commonly used body parts strengthens the notion that physical and cognitive activities are protective factors against progression of dementia.

The myth of the 'unaffected' side after unilateral stroke: is reorganisation of the non-infarcted corticospinal system to re-establish balance the price for recovery?

BACKGROUND: Bilateral changes in the hemispheric reorganisation have been observed chronically after unilateral stroke. Our hypotheses were that activity dependent competition between the lesioned and non-lesioned corticospinal systems would result in persisting asymmetry and be associated with poor recovery. METHODS: Eleven subjects (medium 6.5 years after stroke) were compared to 9 age-matched controls. The power spectral density (PSD) of the sensorimotor electroencephalogram (SM1-EEG) and electromyogram (EMG) and corticomuscular coherence (CMC) were studied during rest and isometric contraction of right or left opponens pollicis (OP). Global recovery was assessed using NIH score. FINDINGS: There was bilateral loss of beta frequency activity in the SM1-EEGs and OP-EMGs in strokes compared to controls. There was no difference between strokes and controls in symmetry indices estimated between the two corticospinal systems for SM1-EEG, OP-EMG and CMC. Performance correlated with preservation of beta frequency power in OP-EMG in both hands. Symmetry indices for the SM1-EEG, OP-EMG and CMC correlated with recovery. INTERPRETATION: Significant changes occurred at both cortical and spinomuscular levels after stroke but to the same degree and in the same direction in both the lesioned and non-lesioned corticospinal systems. Global recovery correlated with the degree of symmetry between corticospinal systems at all three levels - cortical and spinomuscular levels and their connectivity (CMC), but not with the absolute degree of abnormality. Re-establishing balance between the corticospinal systems may be important for overall motor function, even if it is achieved at the expense of the non-lesioned system.

Inter-hemispheric coupling changes associate with motor improvements after robotic stroke rehabilitation.

PURPOSE: In the chronic phase of stroke brain plasticity plays a crucial role for further motor control improvements. This study aims to assess the brain plastic reorganizations and their association with clinical progresses induced by a robot-aided rehabilitation program in chronic stroke patients. METHODS: 7 stroke patients with an upper limb motor impairment in chronic phase underwent a multi-modal evaluation before starting and at the end of a 12-week upper-limb neurorehabilitation program. Fugl-Meyer Assessment (FMA) Scale scores and performance indices of hand movement performance (isometric pinch monitored through a visual feedback) were collected. Cerebral reorganizations were characterized by 32-channel electroencephalography (EEG) focusing on ipsilesional and contralesional resting state properties investigating both bipolar derivations overlying the middle cerebral artery territory and the primary somatosensory sources (S1) obtained through the Functional Source Separation (FSS) method. Power Spectral Density (PSD) and interhemispheric coherence (IHCoh) at rest were measured and correlated with clinical and hand control robot-induced improvements. RESULTS: After the robotic rehabilitation we found an improvement of FMAS scores and hand motor control performance and changes of brain connectivity in high frequency rhythms (24-90 Hz). In particular, the improvement of motor performance correlated with the modulation of the interhemispheric S1 coherence in the high beta band (24-33 Hz). CONCLUSIONS: Recently it has been shown that an upper limb robot-based rehabilitation improves motor performance in stroke patients. We confirm this potential and demonstrate that a robot-aided rehabilitation program induces brain reorganizations. Specifically, interhemispheric connectivity between primary somatosensory areas got closer to a 'physiological level' in parallel with the acquisition of more accurate hand control.

A neurally-interfaced hand prosthesis tuned inter-hemispheric communication.

PURPOSE: This work investigates how a direct bidirectional connection between brain and hand prosthesis modifies the bi-hemispheric sensorimotor system devoted to the movement control of the lost limb. Hand prostheses are often unable to satisfy users' expectations, mostly due to the poor performance of their interfacing system. Neural Interfaces implanted inside nerves of the stump offer the advantage of using the bidirectional neural pathways 'naturally' dispatching signals to control proper hand actions and feed-back sensations. Learning to control a neurally-interfaced hand prosthesis and decode sensory information was previously observed to reduce the inter-hemispheric asymmetry of cortical motor maps and the clinical symptoms of phantom limb syndrome. METHODS: Electroencephalographic (EEG) data was analysed using Functional Source Separation (FSS), a semi-blind method that incorporates prior knowledge about the signal of interest into data decomposition to give access to cortical patch activities. RESULTS: Bi-hemispheric cortices showed normalization of their activity (topographical and spectral patterns) and of functional connectivity between homologous hand controlling areas, during the delivery of the motor command to the cybernetic prosthesis. CONCLUSIONS: The re-establishment of central-peripheral communication with the lost limb induced by a neurally-interfaced hand prosthesis produces beneficial plastic reorganization, not only restructuring contralateral directly-connected control areas, but also their functional balance within the bi-hemispheric system necessary for motor control.

Sensorimotor integration in focal task-specific hand dystonia: a magnetoencephalographic assessment.

To obtain a direct sensorimotor integration assessment in primary hand cortical areas (M1) of patients suffering from focal task-specific hand dystonia, magnetoencephalographic (MEG) and opponens pollicis electromyographic (EMG) activities were acquired during a motor task expressly chosen not to induce dystonic movements in our patients, to disentangle abnormalities indicating a possible substrate on which dystonia develops. A simple isometric contraction was performed either alone or in combination with median nerve stimulation, i.e. when a non-physiological sensory inflow was overlapping with the physiological feedback. As control condition, median nerve stimulation was also performed at rest. The task was performed bilaterally both in eight patients and in 16 healthy volunteers. In comparison with results in controls we found that in dystonic patients: i) MEG-EMG coherence was higher; ii) it reduced much less during galvanic stimulation in the hemisphere contralateral to the dystonic arm, simultaneously with iii) stronger inhibition of the sensory areas responsiveness due to movement; iv) the cortical component including contributions from sensory inhibitory and motor structures was reduced and v) much more inhibited during movement. It is documented that a simultaneous cortico-muscular coherence increase occurs in presence of a reduced M1 responsiveness to the inflow from the sensory regions. This could indicate an unbalance of the fronto-parietal functional impact on M1, with a weakening of the parietal components. Concurrently, signs of a less differentiated sensory hand representation--possibly due to impaired inhibitory mechanisms efficiency--and signs of a reduced repertoire of voluntary motor control strategies were found.

Age dependence of primary motor cortex plasticity induced by paired associative stimulation.

OBJECTIVE: The increase of elderly population prompted growing research for the understanding of cerebral phenomena sustaining learning abilities, with inclusion of long-term potentiation (LTP)-like plasticity phenomena. Aim of the present study was to characterize LTP-like plasticity dependence on age and gender. METHODS: A LTP-like primary motor cortex plasticity inducing a potentiation of the motor evoked potential (MEP) to focal transcranial magnetic stimulation as a consequence of a paired associative stimulation (PAS) was induced in a 50 healthy subject cohort, equally distributed for gender and age groups (25 young subjects, mean age+/-SD=29.8+/-4.5 years; elderly 61.1+/-4.1 years). RESULTS: Resting motor thresholds' excitability level increased in the elderly group, the basal MEP did not depend on gender or age. The PAS-induced primary motor cortex (M1) plastic excitability modulation was similar in young females and males, while it decreased with age in females only. CONCLUSIONS: A reduction of the PAS-induced M1 plasticity in females after menopause was documented, possibly due to an impairment of intracortical excitatory network activity. SIGNIFICANCE: A LTP-like plasticity dependence on age was found in female only, suggesting caution in interpreting behavioural studies on learning abilities in dependence on age.

Neuroimaging experimental studies on brain plasticity in recovery from stroke.

Topographical cortical organization of sensorimotor area has been shown to be highly plastic, altering his configuration in response to training in different tasks in healthy controls and neurological patients. The term ''brain plasticity'' encompasses all possible mechanisms of neuronal reorganization: recruitment of pathways that are functionally homologous to, but anatomically distinct from, the damaged ones (eg, non-pyramidal corticospinal pathways), synaptogenesis, dendritic arborisation and reinforcement of existing but functionally silent synaptic connections (particularly at the periphery of core lesion). The study of neuroplasticity has clearly shown the ability of the developing brain--and of the adult and ageing brain--to be shaped by environmental inputs both under normal conditions (ie, learning) and after a lesion. Neuronal aggregates adjacent, or distant to a lesion in the sensorimotor area can progressively adopt the function of the injured area. Imaging studies indicate that recovery of motor function after a lesion (i.e. stroke) is associated with a progressive change of activation patterns in specific brain structures. Transcranial magnetic stimulation (TMS) and magnetoencephalography (MEG) can detect reshaping of sensorimotor areas; they have a high temporal resolution but have several limitations. TMS can only provide bidimensional scalp maps and MEG depicts three-dimensional spatial characteristics of virtual neural generators obtained by use of a mathematical model of the head and brain. However, the use of objective methods that assess brain reactivity to a physical stimulus (i.e., TMS) or to a sensory input (ie, electrical stimulation to hand and fingers) can integrate information from self-paced motor tasks, because the resolution of abnormal activation over time could be secondary to recovery. Functional MRI (fMRI) and positron emission tomography (PET), on their own, have insufficient time resolution to follow the hierarchical activation of relays within a neural network; however, because of their excellent spatial resolution, they can integrate the findings of TMS and MEG. An integrated approach constitutes, at present, the best way to assess the brain plasticity both under normal conditions and after a lesion.

Interhemispheric asymmetry of primary hand representation and recovery after stroke: a MEG study.

In patients affected by monohemispheric stroke in the middle cerebral artery territory, who do not regain a normal neurological function, a positive contribution to the clinical recovery seems to be made by the involvement of primary hand representation areas in the affected hemisphere (AH), excessively asymmetric to its homologous in the unaffected hemisphere (UH). We investigated primary sensory hand areas in 41 chronic patients who had improved their clinical status without reaching complete recovery. The location and strength of the first cerebral sources activated by a contralateral galvanic median nerve stimulation (M20 and M30) were evaluated in both hemispheres, together with their interhemispheric differences. The source displacement in the AH with respect to the UH was positively correlated with clinical recovery (Spearman's rho=0.584, p=0.003). The excessive interhemispheric asymmetry - as defined on the basis of reference ranges in the healthy population - could be interpreted as the involvement of neuronal pools in the AH outside the hand 'omega zone' of the Rolandic sulcus, revealing the presence of plasticity phenomena. The present data provide support to a positive role of cerebral plasticity phenomena, partially contributing to post-stroke recovery in patients unable to achieve normal neurological function.

Sensory-motor interaction in primary hand cortical areas: a magnetoencephalography assessment.

Movement control requires continuous and reciprocal exchange of information between activities of motor areas involved in the task program execution and those elaborating proprioceptive sensory information. Our aim was to investigate the sensorimotor interactions in the region dedicated to hand control in healthy humans, focusing onto primary sensory and motor cortices, by selecting the time window at very early latencies. Through magnetoencephalographic recordings, we obtained a simultaneous assessment of sensory cortex activity modulation due to movement and of motor cortex activity modulation due to sensory stimulation, by eliciting a galvanic stimulation to the nerve (the median nerve) innervating a muscle (the opponens pollicis), at rest or during voluntary contraction. The primary sensory and motor cortices activities were investigated respectively through excitability in response to sensory stimulation and the cortico-muscular coherence. The task was performed bilaterally. A clear reduction of the cortico-muscular coherence was found in the short time window following stimuli (between around 150-450 ms). In the same time period, the motor control of isometric contraction was preserved. This could suggest that cortical component of voluntary movement control was transiently mediated by neuronal firing rate tuning more than by cortico-muscular synchronization. In addition to the known primary sensory cortex inhibition due to movement, a more evident reduction was found for the component known to include a contribution from primary motor areas. Gating effects were lower in the dominant left hemisphere, suggesting that sensorimotor areas dominant for hand control benefit of narrowing down gating effects.

Long-term effects of stroke on neuronal rest activity in rolandic cortical areas.

To understand the relationship between neuronal function and clinical state in the framework of stroke, the long-term poststroke rolandic spontaneous neuronal activity was studied by means of magnetoencephalography. Fifty-six patients who had suffered a unilateral stroke within the middle cerebral artery were enrolled. Median time since stroke was 2.8 years. In association with lesion features and clinical picture, total and relative band powers and the spectral entropy were analyzed in the affected (AH) and unaffected (UH) hemispheres in comparison with an age-matched control group. An increase of absolute and relative slow band powers and a reduction of relative fast band powers were found in patients' AH with respect to both UH and control values. Absolute delta band was higher than in controls also in UH. New findings were the increase of rolandic rest activity power also in the alpha band and the decrease of spectral entropy in AH with respect to both UH and control values. Moreover, our results in chronic stroke patients indicate frequency-selective alterations related to specific dysfunctions: global clinical status was mostly impaired in patients with larger lesions and increased total and slow band activity powers, whereas hand functionality was mostly disrupted in patients with subcortical involvement and reduction of high-frequency rhythms and spectral entropy. Total power increase and spectral richness decrease are in agreement with a higher synchrony of local neuronal activity, a reduction of the intracortical inhibitory network's efficiency, and an increase of neuronal excitability.

[Exposure to traffic noise and effects on attention]. / Effetti sull'attenzione per esposizione a rumore da traffico urbano.

This study was aimed to evaluate if workers exposed to environmental stressors, including the urban traffic noise, might show significant differences compared to a control group in neuro-psychological and emotional profile as well as neurophysiological functions. In particular if these differences could be evidenced by the application of the "oddball paradigm" for event related potential P300 component. The study consisted of the following examinations: (1) exposed workers vs. controls under the odd-ball paradigm and the Stroop test in baseline condition; (2) amplitude and latency ofP300 (in baseline condition and after administration of acute urban traffic noise and Stroop test). The research was carried on a sample of 81 volunteers: 39 workers exposed to environmental stressors and 42 controls. The phonometric measurements showed mean levels of noise due urban traffic like 74 dBAeq. In baseline condition significative differences in exposed workers vs. control were found in Raven's Matrices PM 38 (p = 0.002) and Arithmetic reasoning from WAIS-R (p = 0.0024). Attention capacities as measured by Digit Span Forward and Visual Search, emotional functioning as measured by state- and trait-anxiety test and mood profile were not different in the two groups. Either in baseline condition or after acute stimuli no significant changes were found in two groups concerning the odd-ball paradigm. Exposed workers showed a higher execution time at Stroop test compared to controls (p = 0.047). No differences were found in the number of errors at the Stroop test. Before the acute stimulus, P300 amplitude was significant higher in the exposed workers than in controls (p = 0.002) while the latency was not different between two groups. Both noise (p = 0.001) and Stroop test (p = 0.002) stimulation increased the P300 latency of the whole sample, without significant differences between exposed workers and controls. A significative decrease of P300 amplitude due noise both in the exposed workers (p = 0.001) and in controls (p = 0.012) was found, without significant difference between the two groups. These results are interpreted as follows: (1) there are chronic effects on cognitive functioning in the exposed group vs. controls in baseline condition, like showed by significant differences in Raven PM38 and WAIS-R; (2) the exposed workers have a smaller cognitive flexibility, as shown by the Stroop test results; (3) in baseline condition the greater P300 amplitude in exposed workers reflect a greater division of attentive resources vs. controls, probably linked to the chronic stimulation by environmental stressors, especially noise, to which these workers are exposed; (4) the effects on P300 latency and amplitude can document the physiological response both in the exposed and not exposed to the acute stimulus and that the lack of significative differences in P300 latency and amplitude may be due to adaptative response to acute stimuli in exposed too. Our results allow us to consider that in workers exposed to urban stressor, such as noise, there are effects on cognitive functioning, especially on attention, without auditory damages. The valuation of P300 might represent a valid diagnostic instrument to evaluate the effects on cognitive functions especially on attention, in workers chronically and acutely exposed to urban stressors.