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Summary: The present literature points to an alteration of the human K‐complex during non‐rapid eye movement sleep in Alzheimer's disease. Nevertheless, the few findings on the K‐complex changes in mild cognitive impairment and their possible predictive role on the Alzheimer's disease conversion show mixed findings, lack of replication, and a main interest for the frontal region. The aim of the present study was to assess K‐complex measures in amnesic mild cognitive impairment subsequently converted in Alzheimer's disease over different cortical regions, comparing them with healthy controls and stable amnesic mild cognitive impairment. We assessed baseline K‐complex density, amplitude, area under the curve and overnight changes in frontal, central and parietal midline derivations of 12 amnesic mild cognitive impairment subsequently converted in Alzheimer's disease, 12 stable amnesic mild cognitive impairment and 12 healthy controls. We also assessed delta electroencephalogram power, to determine if K‐complex alterations in amnesic mild cognitive impairment occur with modification of the electroencephalogram power in the frequency range of the slow‐wave activity. We found a reduced parietal K‐complex density in amnesic mild cognitive impairment subsequently converted in Alzheimer's disease compared with stable amnesic mild cognitive impairment and healthy controls, without changes in K‐complex morphology and overnight modulation. Both amnesic mild cognitive impairment groups showed decreased slow‐wave sleep percentage compared with healthy controls. No differences between groups were observed in slow‐wave activity power. Our findings suggest that K‐complex alterations in mild cognitive impairment may be observed earlier in parietal regions, likely mirroring the topographical progression of Alzheimer's disease‐related brain pathology, and express a frontal predominance only in a full‐blown phase of Alzheimer's disease. Consistently with previous results, such K‐complex modification occurs in the absence of significant electroencephalogram power changes in the slow oscillations range. [ABSTRACT FROM AUTHOR]

Aim: Congestive heart failure (CHF) is a very complex clinical syndrome that may lead to ischemic cerebral hypoxia condition. The aim of the present study is to analyze the effects of CHF on brain activity through electroencephalographic (EEG) complexity measures, like approximate entropy (ApEn). Methods: Twenty patients with CHF and 18 healthy elderly people were recruited. ApEn values were evaluated in the total spectrum (0.2–47 Hz) and main EEG frequency bands: delta (2–4 Hz), theta (4–8 Hz), alpha 1 (8–11 Hz), alpha 2 (11–13 Hz), beta 1 (13–20 Hz), beta 2 (20–30 Hz), and gamma (30–45 Hz) to identify differences between CHF group and control. Moreover, a correlation analysis was performed between ApEn parameters and clinical data (i.e., B‐type natriuretic peptides (BNP), New York Heart Association (NYHA), and systolic blood pressure (SBP)) within the CHF group. Results: Statistical topographic maps showed statistically significant differences between the two groups in the total spectrum and theta frequency band. Within the CHF group, significant negative correlations were found between total ApEn and BNP in O2 channel and between theta ApEn and NYHA scores in Fp1, Fp2, and Fz channels; instead, a significant positive correlation was found between theta ApEn and SBP in C3 channel and a nearly significant positive correlation was obtained between theta ApEn and SBP in F4 channel. Conclusion: EEG abnormalities in CHF are very similar to those observed in cognitive‐impaired patients, suggesting analogies between the effects of neurodegeneration and brain chronic hypovolaemia due to heart disorder and underlying high brain sensitivity to CHF. [ABSTRACT FROM AUTHOR]

Objective: Mild cognitive impairment (MCI) is a condition intermediate between physiological brain aging and dementia. Amnesic-MCI (aMCI) subjects progress to dementia (typically to Alzheimer-Dementia = AD) at an annual rate which is 20 times higher than that of cognitively intact elderly. The present study aims to investigate whether EEG network Small World properties (SW) combined with Apo-E genotyping, could reliably discriminate aMCI subjects who will convert to AD after approximately a year.Methods: 145 aMCI subjects were divided into two sub-groups and, according to the clinical follow-up, were classified as Converted to AD (C-MCI, 71) or Stable (S-MCI, 74).Results: Results showed significant differences in SW in delta, alpha1, alpha2, beta2, gamma bands, with C-MCI in the baseline similar to AD. Receiver Operating Characteristic(ROC) curve, based on a first-order polynomial regression of SW, showed 57% sensitivity, 66% specificity and 61% accuracy(area under the curve: AUC=0.64). In 97 out of 145 MCI, Apo-E allele testing was also available. Combining this genetic risk factor with Small Word EEG, results showed: 96.7% sensitivity, 86% specificity and 91.7% accuracy(AUC=0.97). Moreover, using only the Small World values in these 97 subjects, the ROC showed an AUC of 0.63; the resulting classifier presented 50% sensitivity, 69% specificity and 59.6% accuracy. When different types of EEG analysis (power density spectrum) were tested, the accuracy levels were lower (68.86%).Interpretation: Concluding, this innovative EEG analysis, in combination with a genetic test (both low-cost and widely available), could evaluate on an individual basis with great precision the risk of MCI progression. This evaluation could then be used to screen large populations and quickly identify aMCI in a prodromal stage of dementia. Ann Neurol 2018 Ann Neurol 2018;84:302-314. [ABSTRACT FROM AUTHOR]

Sleep onset is characterized by a specific and orchestrated pattern of frequency and topographical EEG changes. Conventional power analyses of electroencephalographic (EEG) and computational assessments of network dynamics have described an earlier synchronization of the centrofrontal areas rhythms and a spread of synchronizing signals from associative prefrontal to posterior areas. Here, we assess how 'small world' characteristics of the brain networks, as reflected in the EEG rhythms, are modified in the wakefulness-sleep transition comparing the pre- and post-sleep onset epochs. The results show that sleep onset is characterized by a less ordered brain network (as reflected by the higher value of small world) in the sigma band for the frontal lobes indicating stronger connectivity, and a more ordered brain network in the low frequency delta and theta bands indicating disconnection on the remaining brain areas. Our results depict the timing and topography of the specific mechanisms for the maintenance of functional connectivity of frontal brain regions at the sleep onset, also providing a possible explanation for the prevalence of the frontal-to-posterior information flow directionality previously observed after sleep onset. Hum Brain Mapp 38:5456-5464, 2017. © 2017 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Free water elimination (FWE) in brain diffusion MRI has been shown to improve tissue specificity in human white matter characterization both in health and in disease. Relative to the classical diffusion tensor imaging (DTI) model, FWE is also expected to increase sensitivity to microstructural changes in longitudinal studies. However, it is not clear if these two models differ in their test-retest reproducibility. This study compares a bi-tensor model for FWE with DTI by extending a previous longitudinal-reproducibility 3T multisite study (10 sites, 7 different scanner models) of 50 healthy elderly participants (55-80 years old) scanned in two sessions at least 1 week apart. We computed the reproducibility of commonly used DTI metrics (FA: fractional anisotropy, MD: mean diffusivity, RD: radial diffusivity, and AXD: axial diffusivity), derived either using a DTI model or a FWE model. The DTI metrics were evaluated over 48 white-matter regions of the JHU-ICBM-DTI-81 white-matter labels atlas, and reproducibility errors were assessed. We found that relative to the DTI model, FWE significantly reduced reproducibility errors in most areas tested. In particular, for the FA and MD metrics, there was an average reduction of approximately 1% in the reproducibility error. The reproducibility scores did not significantly differ across sites. This study shows that FWE improves sensitivity and is thus promising for clinical applications, with the potential to identify more subtle changes. The increased reproducibility allows for smaller sample size or shorter trials in studies evaluating biomarkers of disease progression or treatment effects. Hum Brain Mapp 38:12-26, 2017. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Several studies have shown that, in spite of the fact that motor symptoms manifest late in the course of Alzheimer's disease (AD), neuropathological progression in the motor cortex parallels that in other brain areas generally considered more specific targets of the neurodegenerative process. It has been suggested that motor cortex excitability is enhanced in AD from the early stages, and that this is related to disease's severity and progression. To investigate the neurophysiological hallmarks of motor cortex functionality in early AD we combined transcranial magnetic stimulation (TMS) with electroencephalography (EEG). We demonstrated that in mild AD the sensorimotor system is hyperexcitable, despite the lack of clinically evident motor manifestations. This phenomenon causes a stronger response to stimulation in a specific time window, possibly due to locally acting reinforcing circuits, while network activity and connectivity is reduced. These changes could be interpreted as a compensatory mechanism allowing for the preservation of sensorimotor programming and execution over a long period of time, regardless of the disease's progression. Hum Brain Mapp 37:2083-2096, 2016. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Although the inhibitory action that tactile stimuli can have on pain is well documented, the precise timing of the interaction between the painful and non-painful stimuli in the central nervous system is unclear. The aim of this study was to investigate this issue by measuring the timing of the amplitude modulation of laser evoked potentials ( LEPs) due to conditioning non-painful stimuli. LEPs were recorded from 31 scalp electrodes in 10 healthy subjects after painful stimulation of the right arm (C6-C7 dermatomes). Non-painful electrical stimuli were applied by ring electrodes on the second and third finger of the right hand. Electrical stimuli were delivered at +50, +150, +200 and +250 ms interstimulus intervals ( ISIs) after the laser pulses. LEPs obtained without any conditioning stimulation were used as a baseline. As compared to the baseline, non-painful electrical stimulation reduced the amplitude of the vertex N2/P2 LEP component and the laser pain rating when electrical stimuli followed the laser pulses only at +150 and +200 ms ISIs. As at these ISIs the collision between the non-painful and painful input is likely to take place at the cortical level, we can conclude that the late processing of painful (thermal) stimuli is partially inhibited by the processing of non-painful (cutaneous) stimuli within the cerebral cortex. Moreover, our results do not provide evidence that non-painful inputs can inhibit pain at a lower level, including the spinal cord. [ABSTRACT FROM AUTHOR]

ABSTRACT Introduction In this study we evaluated whether near-infrared spectroscopy (NIRS) can determine the metabolic patterns of dermatomyositis (DM), polymyositis (PM), and inclusion-body myositis (IBM). Methods We enrolled 10 consecutive patients affected by DM, 11 by PM, and 9 by IBM, and 3 groups of healthy controls. We measured changes in oxygenated and deoxygenated hemoglobin/myoglobin in the extensor digitorum communis during venous and arterial occlusion testing (VOT) and post-occlusion hyperemia. Results DM showed lower oxygen consumption ( P = 0.04) during VOT and reduced oxygen supply after VOT ( P = 0.04) compared with controls. IBM patients showed higher oxygen consumption ( P = 0.04) during VOT and higher oxygen supply after VOT ( P = 0.03) than controls. DM patients showed reduced oxidative metabolism compared with IBM ( P = 0.001), and an impaired ability to supply oxygen compared with PM ( P = 0.03) and IBM ( P = 0.001) patients. Conclusions NIRS differentiated samples of DM and IBM patients from controls, but it could not distinguish PM patients from a sample of healthy subjects. Muscle Nerve 51: 830-837, 2015 [ABSTRACT FROM AUTHOR]

Introduction: Familial amyloid polyneuropathy is a rare condition caused by mutations of the transthyretin gene (TTR). We assessed the pattern of nerve ultrasound (US) abnormalities in patients with TTR-related neuropathy. Methods: Seven patients with TTR-related neuropathy (TTR-N) and 5 asymptomatic TTR-mutation carriers (TTR-C) underwent neurological examination, nerve conduction studies, and US evaluation. Results: Multifocal US abnormalities were identified in 6 of 7 TTR-N patients. A single patient with only a mild sensory polyneuropathy had normal nerves on US evaluation. In the TTR-C, we only detected an enlarged ulnar nerve at the elbow. Interestingly, disease severity correlated with number of nerves affected on US evaluation. Conclusions: No specific pattern of US abnormalities was identified in this cohort. However, in TTR-related amyloid neuropathy, US may be a helpful tool in monitoring disease progression, and/or clinical response to pharmacological treatment. [ABSTRACT FROM AUTHOR]

Purpose Motor evoked potentials (MEPs) elicited by a train of consecutive, individual transcranial magnetic stimuli demonstrate fluctuations in amplitude with respect to time when recorded from a relaxed muscle. The influence of time-varying, instantaneous modifications of the electroencephalography (EEG) properties immediately preceding the transcranial magnetic stimulation (TMS) has rarely been explored. The aim of this study was to investigate the influence of the pre-TMS motor cortex and related areas EEG profile on time variants of the MEPs amplitude. Method MRI-navigated TMS and multichannel TMS-compatible EEG devices were used. For each experimental subject, post-hoc analysis of the MEPs amplitude that was based on the 50th percentile of the MEPs amplitude distribution provided two subgroups corresponding to 'high' (large amplitude) and 'low' (small amplitude). The pre-stimulus EEG characteristics (coherence and spectral profile) from the motor cortex and related areas were analyzed separately for the 'high' and 'low' MEPs and were then compared. Results On the stimulated hemisphere, EEG coupling was observed more often in the high compared to the low MEP trials. Moreover, a paradigmatic pattern in which TMS was able to lead to significantly larger MEPs was found when the EEG of the stimulated motor cortex was coupled in the beta 2 band with the ipsilateral prefrontal cortex and in the delta band with the bilateral centro-parietal-occipital cortices. Conclusion This data provide evidence for a statistically significant influence of time-varying and spatially patterned synchronization of EEG rhythms in determining cortical excitability, namely motor cortex excitability in response to TMS. Hum Brain Mapp 35:1969-1980, 2014. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Brain effective connectivity can be tracked by cerebral recruitments evoked by transcranial magnetic stimulation (TMS), as measured by simultaneous electroencephalography (TMS-EEG). When TMS is targeting the primary motor area, motor evoked potentials (MEPs) can be collected from the 'target' muscles. The aim of this study was to measure whether or not effective brain connectivity changes with the excitability level of the corticospinal motor pathway (CSMP) as parameterized by MEP amplitude. After averaging two subgroups of EEG-evoked responses corresponding to high and low MEP amplitudes, we calculated the individual differences between them and submitted the grand average to sLORETA algorithm obtaining localized regions of interest (RoIs). Statistical differences of RoI recruitment strength between low and high CSMP excitation was assessed in single subjects. Preceding the feedback arrival, neural recruitment for stronger CSMP activation were weaker at 6-10 ms of homotopic sensorimotor areas BA3/4/5 of the right nonstimulated hemisphere (trend), weaker at 18-25 ms of left parietal BA2/3/40, and stronger at 26-32 ms of bilateral frontal motor areas BA6/8. The proposed method enables the tracking of brain network connectivity during stimulation of one node by measuring the strength of the connected recruited node activations. Spontaneous increases of the excitation of the node originating the transmission within the hand control network gave rise to dynamic recruitment patterns with opposite behaviors, weaker in homotopic and parietal circuits, stronger in frontal ones. The effective connectivity within bilateral circuits orchestrating hand control appeared dynamically modulated in time even in resting state as probed by TMS. Hum Brain Mapp 35:1740-1749, 2014. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Objective Meta-analyses show that nonbound ceruloplasmin (non-Cp) copper (also known as free or labile copper) in serum is higher in patients with Alzheimer disease (AD). It differentiates subjects with mild cognitive impairment (MCI) from healthy controls. However, a longitudinal study on an MCI cohort has not yet been performed to assess the accuracy of non-Cp copper for the prediction of conversion from MCI to AD during a long-term follow-up. Methods The study included 42 MCI converters and 99 stable MCI subjects. We assessed levels of copper, ceruloplasmin, non-Cp copper, iron, transferrin, ferritin, and APOE genotype. A multiple Cox regression analysis-with age, sex, baseline Mini-Mental State Examination, APOE4, iron, non-Cp copper, transferrin, ferritin, hypercholesterolemia, and hypertension as covariates-was applied to predict the conversion from MCI to AD. Results Among the evaluated parameters, the only significant predictor of conversion to AD was non-Cp copper (hazard ratio = 1.23, 95% confidence interval = 1.03-1.47, p = 0.022); for each additional micromole per liter unit (μmol/l) of non-Cp copper, the hazard increased by ∼20%. Subjects with non-Cp copper levels >1.6μmol/l had a hazard conversion rate (50% of conversion in 4 years) that was ∼3× higher than those with values ≤1.6μmol/l (<20% in 4 years). The rate of conversion was similar between APOE4 carriers and noncarriers ( p = 0.321), indicating that the non-Cp copper association was independent of APOE4. Interpretation Non-Cp copper appears to predict conversion from MCI to AD. These results encourage healthy life style choices and dietary intervention to modify this risk. ANN NEUROL 2014;75:574-580 [ABSTRACT FROM AUTHOR]

Previous evidence has shown that resting eyes-closed cortical alpha rhythms are higher in amplitude in mild cognitive impairment (MCI) than Alzheimer's disease (AD) subjects (Babiloni et al. [2006a]: Human Brain Mapp 27:162-172; [2006b]: Clin Neurophysiol 117:252-268; [2006c]: Neuroimage 29:948-964; [2006d]: Ann Neurol 59:323-334; [2006e]: Clin Neurophysiol 117:1113-1129; [2006f]: Neuroimage 31:1650-1665). This study tested the hypothesis that, in amnesic MCI subjects, high amplitude of baseline cortical alpha rhythms is related to long-term stability of global cognition on clinical follow-up. Resting electroencephalographic (EEG) data were recorded in 100 amnesic MCI subjects during eyes-closed condition. 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 by low-resolution brain electromagnetic tomography (LORETA). Global cognition was indexed by mini mental state evaluation (MMSE) score at the time of EEG recordings (baseline) and about after 1 year. Based on the MMSE percentage difference between baseline and 1-year follow-up (MMSEvar), the MCI subjects were retrospectively divided into three arbitrary groups: DECREASED (MMSEvar ≤ −4%; N = 43), STABLE (MMSEvar ≈ 0; N = 27), and INCREASED (MMSEvar ≥ +4%; N = 30). Subjects' age, education, individual alpha frequency, gender, and MMSE scores were used as covariates for statistical analysis. Baseline posterior cortical sources of alpha 1 rhythms were higher in amplitude in the STABLE than in the DECREASED and INCREASED groups. These results suggest that preserved resting cortical neural synchronization at alpha frequency is related to a long-term (1 year) stable cognitive function in MCI subjects. Future studies should use serial MMSE measurements to confirm and refine the present results. Hum Brain Mapp, 2011. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

This study investigates cortical involvement during ankle passive mobilization in healthy subjects, and is part of a pilot study on stroke patient rehabilitation. Magnetoencephalographic signals from the primary sensorimotor areas devoted to the lower limb were collected together with simultaneous electromyographic activities from tibialis anterior (TA). This was done bilaterally, on seven healthy subjects (aged 29 ± 7), during rest, left and right passive ankle dorsiflexion (imparted through the SHADE orthosis, O-PM, or neuromuscular electrical stimulation, NMES-PM), and during active isometric contraction (IC-AM). The effects of focussing attention on ankle passive movements were considered. Primary sensory (FSS1) and motor (FSM1) area activities were discriminated by the Functional Source Separation algorithm. Only contralateral FSS1 was recruited by common peroneal nerve stimulation and only contralateral FSM1 displayed coherence with TA muscular activity. FSM1 showed higher power of gamma rhythms (33-90 Hz) than FSS1. Both sources displayed higher beta (14-32 Hz) and gamma powers in the left than in the right hemisphere. Both sources displayed a bilateral reduction of beta power during IC-AM with respect to rest. Only FSS1 beta band power reduced during O-PM. No beta band modulation was observed of either source during NMES-PM. Mutual FSS1-FSM1 coherence in gamma2 band (61-90 Hz) showed a slight trend towards an increase when focussing attention during O-PM. Somatosensory and motor counterparts of lower limb cortical representations were discriminated in both hemispheres. SHADE was effective in generating repeatable dorsiflexion and inducing primary sensory involvement similarly to voluntary movement. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Demyelination and axonal damage are pathologic hallmarks of multiple sclerosis (MS), leading to loss of neuronal synchronization, functional disconnection amongst brain relays, and clinical sequelae. To investigate these properties, the primary component of the sensorimotor network was analyzed in mildly disabled Relapsing-Remitting MS patients without sensory symptoms at the time of the investigation. By magnetoencephalography (MEG), the recruitment pattern within the primary sensory (S1) and motor (M1) areas was estimated through the morphology of the early components of somatosensory evoked magnetic fields (SEFs), after evaluating the S1 responsiveness to sensory inputs from the contralateral arm. In each hemisphere, network recruitment properties were correlated with ispilateral thalamus volume, estimated by morphometric techniques upon high-resolution 3D structural magnetic resonance images (MRI). S1 activation was preserved, whereas SEF morphology was strikingly distorted in MS patients, marking a disruption of primary somatosensory network patterning. An unbalance of S1-M1 dynamic recruitment was documented and correlated with the thalamic volume reduction in the left hemisphere. These findings support the model of MS as a disconnection syndrome, with major susceptibility to damage experienced by nodes belonging to more frequently recruited and highly specialized networks. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Is conscious perception of emotional face expression related to enhanced cortical responses? Electroencephalographic data (112 channels) were recorded in 15 normal adults during the presentation of cue stimuli with neutral, happy or sad schematic faces (duration: 'threshold time' inducing about 50% of correct recognitions), masking stimuli (2 s), and go stimuli with happy or sad schematic faces (0.5 s). The subjects clicked left (right) mouse button in response to go stimuli with happy (sad) faces. After the response, they said 'seen' or 'not seen' with reference to previous cue stimulus. Electroencephalographic data formed visual event-related potentials (ERPs). Cortical sources of ERPs were estimated by LORETA software. Reaction time to go stimuli was generally shorter during 'seen' than 'not seen' trials, possibly due to covert attention and awareness. The cue stimuli evoked four ERP components (posterior N100, N170, P200, and P300), which had similar peak latency in the 'not seen' and 'seen' ERPs. Only N170 amplitude showed differences in amplitude in the 'seen' versus 'not seen' ERPs. Compared to the 'not seen' ERPs, the 'seen' ones showed prefrontal, premotor, and posterior parietal sources of N170 higher in amplitude with the sad cue stimuli and lower in amplitude with the neutral and happy cue stimuli. These results suggest that nonconscious and conscious processing of schematic emotional facial expressions shares a similar temporal evolution of cortical activity, and conscious processing induces an early enhancement of bilateral cortical activity for the schematic sad facial expressions (N170). Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

A wide range of essential reasoning tasks rely on contradiction identification, a cornerstone of human rationality, communication and debate founded on the inversion of the logical operators 'Every' and 'Some.' A high-density electroencephalographic (EEG) study was performed in 11 normal young adults. The cerebral network involved in the identification of contradiction included the orbito-frontal and anterior-cingulate cortices and the temporo-polar cortices. The event-related dynamic of this network showed an early negative deflection lasting 500 ms after sentence presentation. This was followed by a positive deflection lasting 1.5 s, which was different for the two logical operators. A lesser degree of network activation (either in neuron number or their level of phase locking or both) occurred while processing statements with 'Some,' suggesting that this was a relatively simpler scenario with one example to be figured out, instead of the many examples or the absence of a counterexample searched for while processing statements with 'Every.' A self-generated reward system seemed to resonate the recruited circuitry when the contradictory task is successfully completed. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Does impairment of cholinergic systems represent an important factor in the development of amnesic mild cognitive impairment (aMCI), as a preclinical stage of Alzheimer's disease (AD)? Here we tested the hypothesis that electroencephalographic (EEG) rhythms, known to be modulated by the cholinergic system, may be particularly affected in aMCI patients with lesions along the cholinergic white-matter tracts. Eyes-closed resting EEG data were recorded in 28 healthy elderly (Nold) and 57 aMCI patients. Lesions along the cholinergic white-matter tracts were detected with fluid-attenuated inversion recovery sequences on magnetic resonance imaging. The estimation of the cholinergic lesion was performed with a validated semi-automatic algorithm pipeline after registration to a stereotactic template, image integration with stereotactic masks of the cholinergic tracts, and normalization to intracranial volume. The aMCI patients were divided into two groups of high (MCI Ch+; N = 29; MMSE = 26.2) and low cholinergic damage (MCI Ch−; N = 28; MMSE = 26.6). 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). Cortical EEG generators were estimated by LORETA software. As main results, (i) power of occipital, parietal, temporal, and limbic alpha 1 sources was maximum in Nold, intermediate in MCI Ch−, and low in MCI Ch+ patients; (ii) the same trend was true in theta sources. These results are consistent with the hypothesis that damage to the cholinergic system is associated with alterations of EEG sources in aMCI subjects. Hum Brain Mapp 2009. © 2008 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

What is the timing of cortical activation related to consciousness of visuo-spatial executive functions? Electroencephalographic data (128 channels) were recorded in 13 adults. Cue stimulus briefly appeared on right or left (equal probability) monitor side for a period, inducing about 50% of recognitions. It was then masked and followed (2 s) by a central visual go stimulus. Left (right) mouse button had to be clicked after right (left) cue stimulus. This 'inverted' response indexed executive processes. Afterward, subjects said 'seen' if they had detected the cue stimulus or 'not seen' when it was missed. Sources of event-related potentials (ERPs) were estimated by LORETA software. The inverted responses were about 95% in seen trials and about 60% in not seen trials. Cue stimulus evoked frontal-parietooccipital potentials, having the same peak latencies in the seen and not seen data. Maximal difference in amplitude of the seen and not seen ERPs was detected at about +300-ms post-stimulus (P3). P3 sources were higher in amplitude in the seen than not seen trials in dorsolateral prefrontal, premotor and parietooccipital areas. This was true in dorsolateral prefrontal and premotor cortex even when percentage of the inverted responses and reaction time were paired in the seen and not seen trials. These results suggest that, in normal subjects, the primary consciousness enhances the efficacy of visuo-spatial executive processes and is sub-served by a late (100- to 400-ms post-stimulus) enhancement of the neural synchronization in frontal areas. Hum Brain Mapp, 2009. © 2008 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

We propose a novel electroencephalographic application of a recently developed cerebral source extraction method (Functional Source Separation, FSS), which starts from extracranial signals and adds a functional constraint to the cost function of a basic independent component analysis model without requiring solutions to be independent. Five ad-hoc functional constraints were used to extract the activity reflecting the temporal sequence of sensory information processing along the somatosensory pathway in response to the separate left and right median nerve galvanic stimulation. Constraints required only the maximization of the responsiveness at specific latencies following sensory stimulation, without taking into account that any frequency or spatial information. After source extraction, the reliability of identified FS was assessed based on the position of single dipoles fitted on its retroprojected signals and on a discrepancy measure. The FS positions were consistent with previously reported data (two early subcortical sources localized in the brain stem and thalamus, the three later sources in cortical areas), leaving negligible residual activity at the corresponding latencies. The high-frequency component of the oscillatory activity (HFO) of the extracted component was analyzed. The integrity of the low amplitude HFOs was preserved for each FS. On the basis of our data, we suggest that FSS can be an effective tool to investigate the HFO behavior of the different neuronal pools, recruited at successive times after median nerve galvanic stimulation. As FSs are reconstructed along the entire experimental session, directional and dynamic HFO synchronization phenomena can be studied. Hum Brain Mapp, 2009. © 2008 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Brain atrophy (BA) is observed in 20–50% of patients with epilepsy. Hyper-total-homocysteinemia (hyper-tHcy), which occurs in 10–40% of patients, is considered to be a risk factor for cardiovascular diseases and BA. The present study was aimed at investigating the possible association of hyper-tHcy with BA in a population of patients with epilepsy. Fifty-eight patients (33 M/25 F, 43.5 ± 13.1 years of age) chronically treated with antiepileptic drugs (AEDs) and 60 controls matched for age and sex were enrolled. All participants underwent determination of plasma tHcy, folate, vitamin B12, and C677T methylene-tetrahydrofolate-reductase (MTHFR) polymorphism genotyping, and brain magnetic resonance imaging (MRI). Patients exhibited significantly higher tHcy and lower folate levels than controls; hyper-tHcy was significantly associated with the variables group (patients vs. controls), MTHFR genotype, and their interaction terms. BA was observed in 30.1% of patients and was significantly associated with hyper-tHcy (β = 0.45, p = 0.003) and polytherapy (β = 0.31, p < 0.001). Our investigation suggests that hyper-tHcy plays a role in the development of BA in patients with epilepsy. Although the real origin of this phenomenon is not yet fully elucidated, experimental data support the hypothesis of a link of the neuronal Hcy-mediated damage with oxidative stress and excitotoxicity. [ABSTRACT FROM AUTHOR]

What is the neural substrate of our capability to properly react to changes in the environment? It can be hypothesized that the anterior cingulate cortex (ACC) manages repetitive stimuli in routine conditions and alerts the dorsolateral prefrontal cortex (PFC) when stimulation unexpectedly changes. To provide evidence in favor of this hypothesis, intracerebral stereoelectroencephalographic (SEEG) data were recorded from the anterior cingulate and dorsolateral PFC of eight epileptic patients in a standard visual oddball task during presurgical monitoring. Two types of stimuli (200 ms duration) such as the letters O (frequent stimuli; 80% of probability) and X (rare stimuli) were presented in random order, with an interstimulus interval between 2 and 5 s. Subjects had to mentally count the rare (target) stimuli and to press a button with their dominant hand as quickly and accurately as possible. EEG frequency bands of interest were θ (4-8 Hz), α (8-12 Hz), β (14-30 Hz), and γ (30-45 Hz). The directionality of the information flux within the EEG rhythms was indexed by a directed transfer function (DTF). The results showed that compared with the frequent stimuli, the target stimuli induced a statistically significant increase of DTF values from the anterior cingulate to the dorsolateral PFC at the θ rhythms ( P < 0.01). These results provide support to the hypothesis that ACC directly or indirectly affects the oscillatory activity of dorsolateral PFC by a selective frequency code under typical oddball conditions. Hum Brain Mapp 2009. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Do cerebrovascular and Alzheimer's disease (AD) lesions represent additive factors in the development of mild cognitive impairment (MCI) as a putative preclinical stage of AD? Here we tested the hypothesis that directionality of fronto-parietal functional coupling of electroencephalographic (EEG) rhythms is relatively preserved in amnesic MCI subjects in whom the cognitive decline is mainly explained by white-matter vascular load. Resting EEG was recorded in 40 healthy elderly (Nold) and 78 amnesic MCI. In the MCI subjects, white-matter vascular load was quantified based on magnetic resonance images (0-30 visual rating scale). EEG rhythms of interest were δ (2-4 Hz), θ (4-8 Hz), α1 (8-10.5 Hz), α2 (10.5-13 Hz), β1 (13-20 Hz), and β2 (20-30 Hz). Directionality of fronto-parietal functional coupling of EEG rhythms was estimated by directed transfer function software. As main results, (i) fronto-parietal functional coupling of EEG rhythms was higher in magnitude in the Nold than in the MCI subjects; (ii) more interestingly, that coupling was higher at θ, α1, α2, and β1 in MCI V+ (high vascular load; N = 42; MMSE = 26) than in MCI V− group (low vascular load; N = 36; MMSE= 26.7). These results are interpreted as supporting the additive model according to which MCI state would result from the combination of cerebrovascular and neurodegenerative lesions. Hum Brain Mapp 2008. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Humans have an individual profile of the electroencephalographic power spectra at the 8 to 16Hz frequency during non-rapid eye movement sleep that is stable over time and resistant to experimental perturbations. We tested the hypothesis that this electroencephalographic 'fingerprint' is genetically determined, by recording 40 monozygotic and dizygotic twins during baseline and recovery sleep after prolonged wakefulness. We show a largely greater similarity within monozygotic than dizygotic pairs, resulting in a heritability estimate of 96%, not influenced by sleep need and intensity. If replicated, these results will establish the electroencephalographic profile during sleep as one of the most heritable traits of humans. Ann Neurol 2008 [ABSTRACT FROM AUTHOR]

Abstract: Background: In North America, the Alzheimer''s Disease Neuroimaging Initiative (ADNI) has established a platform to track the brain changes of Alzheimer''s disease. A pilot study has been carried out in Europe to test the feasibility of the adoption of the ADNI platform (pilot E-ADNI). Methods: Seven academic sites of the European Alzheimer''s Disease Consortium (EADC) enrolled 19 patients with mild cognitive impairment (MCI), 22 with AD, and 18 older healthy persons by using the ADNI clinical and neuropsychological battery. ADNI compliant magnetic resonance imaging (MRI) scans, cerebrospinal fluid, and blood samples were shipped to central repositories. Medial temporal atrophy (MTA) and white matter hyperintensities (WMH) were assessed by a single rater by using visual rating scales. Results: Recruitment rate was 3.5 subjects per month per site. The cognitive, behavioral, and neuropsychological features of the European subjects were very similar to their U.S. counterparts. Three-dimensional T1-weighted MRI sequences were successfully performed on all subjects, and cerebrospinal fluid samples were obtained from 77%, 68%, and 83% of AD patients, MCI patients, and controls, respectively. Mean MTA score showed a significant increase from controls (left, right: 0.4, 0.3) to MCI patients (0.9, 0.8) to AD patients (2.3, 2.0), whereas mean WMH score did not differ among the three diagnostic groups (between 0.7 and 0.9). The distribution of both MRI markers was comparable to matched US-ADNI subjects. Conclusions: Academic EADC centers can adopt the ADNI platform to enroll MCI and AD patients and older controls with global cognitive and structural imaging features remarkably similar to those of the US-ADNI. [Copyright &y& Elsevier]

Transcranial magnetic stimulation (TMS) can transiently modulate cortical excitability, with a net effect depending on the stimulation frequency (≤1 Hz inhibition vs. ≥5 Hz facilitation, at least for the motor cortex). This possibility has generated interest in experiments aiming to improve deficits in clinical settings, as well as deficits in the cognitive domain. The aim of the present study was to investigate the on-line effects of low frequency (1 Hz) TMS on the EEG oscillatory activity in the healthy human brain, focusing particularly on the outcome of these modulatory effects in relation to the duration of the TMS stimulation. To this end, we used the event-related desynchronization/synchronization (ERD/ERS) approach to determine the patterns of oscillatory activity during two consecutive trains of sham and real TMS. Each train of stimulation was delivered to the left primary motor cortex (MI) of healthy subjects over a period of 10 min, while EEG rhythms were simultaneously recorded. Results indicated that TMS induced an increase in the power of brain rhythms that was related to the period of the stimulation, i.e. the synchronization of the α band increased with the duration of the stimulation, and this increase was inversely correlated with motor-evoked potentials (MEPs) amplitude. In conclusion, low frequency TMS over primary motor cortex induces a synchronization of the background oscillatory activity on the stimulated region. This induced modulation in brain oscillations seems to increase coherently with the duration of stimulation, suggesting that TMS effects may involve short-term modification of the neural circuitry sustaining MEPs characteristics. Hum Brain Mapp 2008. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The present magnetoencephalography (MEG) study tested the hypothesis of a phase synchronization (functional coupling) of cortical alpha rhythms (about 6-12 Hz) within a 'speech' cortical neural network comprising bilateral primary auditory cortex and Wernicke's areas, during dichotic listening (DL) of consonant-vowel (CV) syllables. Dichotic stimulation was done with the CV-syllable pairs /da/-/ba/ (true DL, yielded by stimuli having high spectral overlap) and /da/-/ka/ (sham DL, obtained with stimuli having poor spectral overlap). Whole-head MEG activity (165 sensors) was recorded from 10 healthy right-handed non-musicians showing right ear advantage in a speech DL task. Functional coupling of alpha rhythms was defined as the spectral coherence at the following bands: alpha 1 (about 6-8 Hz), alpha 2 (about 8-10 Hz), and alpha 3 (about 10-12) with respect to the peak of individual alpha frequency. Results showed an inverse pattern of functional coupling: during DL of speech sounds, spectral coherence of the high-band alpha rhythms increased between left auditory and Wernicke's areas with respect to sham DL, whereas it decreased between left and right auditory areas. The increase of functional coupling within the left hemisphere would underlie the processing of the syllable presented to the right ear, which arrives to the left auditory cortex without the interference of the other syllable presented to the left ear. Conversely, the decrease of inter-hemispherical coupling of the high-band alpha might be due to the fact that the two auditory cortices do not receive the same information from the ears during DL. These results suggest that functional coupling of alpha rhythms can constitute a neural substrate for the lateralization of auditory stimuli during DL. Hum Brain Mapp 2008. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The functional source separation procedure (FSS) was applied to identify the activities of the primary sensorimotor areas (SM1) devoted to hand control. FSS adds a functional constraint to the cost function of the basic independent component analysis, and obtains source activity all along different processing states. Magnetoencephalographic signals from the left SM1 were recorded in 14 healthy subjects during a simple sensorimotor paradigm-galvanic right median nerve stimuli intermingled with submaximal isometric thumb opposition. Two functional sources related to the sensory flow in the primary cortex were extracted requiring maximal responsiveness to the nerve stimulation at around 20 and 30 ms (S1a, S1b). Maximal cortico-muscular coherence was required for the extraction of the motor source (M1). Sources were multiplied by the Euclidean norm of their corresponding weight vectors, allowing amplitude comparisons among sources in a fixed position. In all subjects, S1a, S1b, M1 were successfully obtained, positioned consistently with the SM1 organization, and behaved as physiologically expected during the movement and processing of the sensory stimuli. The M1 source reacted to the nerve stimulation with higher intensity at latencies around 30 ms than around 20 ms. The FSS method was demonstrated to be able to obtain the dynamics of different primary cortical network activities, two devoted mainly to sensory inflow, and the other to the motor control of the contralateral hand. It was possible to observe each source both during pure sensory processing and during motor tasks. In all conditions, a direct comparison of source intensities can be achieved. Hum Brain Mapp, 2008. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Previous findings have shown that the human somatosensory cortical systems that are activated by passive nonpainful electrical stimulation include the contralateral primary somatosensory area (SI), bilateral secondary somatosensory area (SII), and bilateral insula. The present study tested the hypothesis that these areas have different sensitivities to stimulation frequency in the condition of passive stimulation. Functional MRI (fMRI) was recorded in 24 normal volunteers during nonpainful electrical median nerve stimulations at 0.5, 1, 2, and 4 Hz repetition rates in separate recording blocks in pseudorandom order. Results of the blood oxygen level-dependent (BOLD) effect showed that the contralateral SI, the bilateral SII, and the bilateral insula were active during these stimulations. As a major finding, only the contralateral SI increased its activation with the increase of the stimulus frequency at the mentioned range. The fact that nonpainful median-nerve electrical stimuli at 4 Hz induces a larger BOLD response is of interest both for basic research and clinical applications in subjects unable to perform cognitive tasks in the fMRI scanner. Hum Brain Mapp 2006. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Previous evidence has shown that resting delta and alpha electroencephalographic (EEG) rhythms are abnormal in patients with Alzheimer's disease (AD) and its potential preclinical stage (mild cognitive impairment, MCI). Here, we tested the hypothesis that these EEG rhythms are correlated with memory and attention in the continuum across MCI and AD. Resting eyes-closed EEG data were recorded in 34 MCI and 53 AD 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 low-resolution brain electromagnetic tomography (LORETA). These sources were correlated with neuropsychological measures such as Rey list immediate recall (word short-term memory), Rey list delayed recall (word medium-term memory), Digit span forward (immediate memory for digits probing focused attention), and Corsi span forward (visuo-spatial immediate memory probing focused attention). A statistically significant negative correlation (Bonferroni corrected, P < 0.05) was observed between Corsi span forward score and amplitude of occipital or temporal delta sources across MCI and AD subjects. Furthermore, a positive correlation was shown between Digit span forward score and occipital alpha 1 sources (Bonferroni corrected, P < 0.05). These results suggest that cortical sources of resting delta and alpha rhythms correlate with neuropsychological measures of immediate memory based on focused attention in the continuum of MCI and AD subjects. [ABSTRACT FROM AUTHOR]

We tested the working hypothesis that electromagnetic fields from mobile phones (EMFs) affect interhemispheric synchronization of cerebral rhythms, an important physiological feature of information transfer into the brain. Ten subjects underwent two electroencephalographic (EEG) recordings, separated by 1 week, following a crossover double-blind paradigm in which they were exposed to a mobile phone signal (global system for mobile communications; GSM). The mobile phone was held on the left side of the subject head by a modified helmet, and orientated in the normal position for use over the ear. The microphone was orientated towards the corner of the mouth, and the antenna was near the head in the parietotemporal area. In addition, we positioned another similar phone (but without battery) on the right side of the helmet, to balance the weight and to prevent the subject localizing the side of GSM stimulation (and consequently lateralizing attention). In one session the exposure was real (GSM) while in the other it was Sham; both sessions lasted 45 min. Functional interhemispheric connectivity was modelled using the analysis of EEG spectral coherence between frontal, central and parietal electrode pairs. Individual EEG rhythms of interest were delta (about 2–4 Hz), theta (about 4–6 Hz), alpha 1 (about 6–8 Hz), alpha 2 (about 8–10 Hz) and alpha 3 (about 10–12 Hz). Results showed that, compared to Sham stimulation, GSM stimulation modulated the interhemispheric frontal and temporal coherence at alpha 2 and alpha 3 bands. The present results suggest that prolonged mobile phone emission affects not only the cortical activity but also the spread of neural synchronization conveyed by interhemispherical functional coupling of EEG rhythms. [ABSTRACT FROM AUTHOR]

We propose a novel cerebral source extraction method (functional source separation, FSS) starting from extra-cephalic magnetoencephalographic (MEG) signals in humans. It is obtained by adding a functional constraint to the cost function of a basic independent component analysis (ICA) model, defined according to the specific experiment under study, and removing the orthogonality constraint, (i.e., in a single-unit approach, skipping decorrelation of each new component from the subspace generated by the components already found). Source activity was obtained all along processing of a simple separate sensory stimulation of thumb, little finger, and median nerve. Being the sources obtained one by one in each stage applying different criteria, the a posteriori 'interesting sources selection' step is avoided. The obtained solutions were in agreement with the homuncular organization in all subjects, neurophysiologically reacting properly and with negligible residual activity. On this basis, the separated sources were interpreted as satisfactorily describing highly superimposed and interconnected neural networks devoted to cortical finger representation. The proposed procedure significantly improves the quality of the extraction with respect to a standard BSS algorithm. Moreover, it is very flexible in including different functional constraints, providing a promising tool to identify neuronal networks in very general cerebral processing. Hum Brain Mapp, 2006. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

This electroencephalographic (EEG) study tested whether cortical EEG rhythms (especially delta and alpha) show a progressive increasing or decreasing trend across physiological aging. To this aim, we analyzed the type of correlation (linear and nonlinear) between cortical EEG rhythms and age. Resting eyes-closed EEG data were recorded in 108 young (Nyoung; age range: 18-50 years, mean age 27.3 ± 7.3 SD) and 107 elderly (Nold; age range: 51-85 years, mean age 67.3 ± 9.2 SD) subjects. The 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 low-resolution brain electromagnetic tomography (LORETA). Statistical results showed that delta sources in the occipital area had significantly less magnitude in Nold compared to Nyoung subjects. Similarly, alpha 1 and alpha 2 sources in the parietal, occipital, temporal, and limbic areas had significantly less magnitude in Nold compared to Nyoung subjects. These nine EEG sources were given as input for evaluating the type (linear, exponential, logarithmic, and power) of correlation with age. When subjects were considered as a single group there was a significant linear correlation of age with the magnitude of delta sources in the occipital area and of alpha 1 sources in occipital and limbic areas. The same was true for alpha 2 sources in the parietal, occipital, temporal, and limbic areas. In general, the EEG sources showing significant linear correlation with age also supported a nonlinear correlation with age. These results suggest that the occipital delta and posterior cortical alpha rhythms decrease in magnitude during physiological aging with both linear and nonlinear trends. In conclusion, this new methodological approach holds promise for the prediction of dementia in mild cognitive impairment by regional source rather than surface EEG data and by both linear and nonlinear predictors. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Objectives Validation of an Italian version of the Telephone Interview for Cognitive Status (I-TICS). Methods Telephone administration of the I-TICS within 6 weeks of face-to-face testing with the Mini Mental State Examination (MMSE), in Probable Alzheimer's disease (AD) patients and healthy controls. Two hundred and seven consecutive outpatients with cognitive impairment were recruited from Dementia Clinic of University Campus BioMedico. Of these, 45 probable AD patients with complete data were analyzed. Other dementias, Mild Cognitive Impairment (MCI), and patients with incomplete data were excluded. The control sample consisted of 64 age- and sex-matched healthy subjects. For diagnosis, an extensive clinical evaluation, laboratory testing, brain imaging, EEG, neuropsychological battery and a depression scale were used. For I-TICS validation, telephone I-TICS and face-to-face MMSE were administered. Results The I-TICS correlated highly and linearly with the MMSE (Pearson's r = 0.904). Conversion equations are provided. Sensitivity and specificity were similar between tests (area under curve = 0.894 for the I-TICS; 0.966 for the MMSE). I-TICS sensitivity was 84% and specificity 86% at a cut-off score of 28. No significant difference in accuracy with the MMSE was present. Total agreement between I-TICS and MMSE was ‘substantial’ at 86% (Cohen's K = 0.717). Repeated testing in a subset of patients showed a disease progression related decrease of 4.2 points/year (t = 2.664; p = 0.018) in I-TICS scores. Conclusion The I-TICS is a valid instrument in clinical and research screening and monitoring of AD. Potential applications in other dementias and MCI are worth further studies. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Neuroimaging findings, including repetitive transcranial magnetic stimulation (rTMS) interference, point to an engagement of prefrontal cortex (PFC) in learning and memory. Whether parietal cortex (PC) activity is causally linked to successful episodic encoding and retrieval is still uncertain. We compared the effects of event-related active or sham rTMS (a rapid-rate train coincident to the very first phases of memoranda presentation) to the left or right intraparietal sulcus, during a standardized episodic memory task of visual scenes, with those obtained in a fully matched sample of subjects who received rTMS on left or right dorsolateral PFC during the same task. In these subjects, specific hemispheric effects of rTMS included interference with encoding after left stimulation and disruption of retrieval after right stimulation. The interference of PC-rTMS on encoding/retrieval performance was negligible, lacking specificity even when higher intensities of stimulation were applied. However, right PC-rTMS of the same intensity lengthened reaction times in the context of a purely attentive visuospatial task. These results suggest that the activity of intraparietal sulci shown in several funtional magnetic resonance studies on memory, unlike that of the dorsolateral PFC, is not causally engaged to a useful degree in memory encoding and retrieval of visual scenes. The parietal activations accompanying the memorization processes could reflect the engagement of a widespread brain attentional network, in which interference on a single ‘node’ is insufficient for an overt disruption of memory performance. [ABSTRACT FROM AUTHOR]

Objective The aim of this preliminary study was to investigate the physiologic substrate of executive function in anorexia nervosa (AN) by assessing the relation between brain perfusion and Stroop interference task (SIT). Method The classical SIT test and brain single-photon emission tomography (SPET) were evaluated in 16 AN females (mean age = 23.69 ± 8.68 years; mean body mass index [BMI] = 16.19 ± 1.53 kg/m2). The relation between the two examinations was searched by statistical parametric mapping (SPM 99) with a height threshold of p = .001. Results An abnormally low or a borderline SIT value was found in 25% of patients. A significant correlation between the SIT score and brain perfusion was found in the superior frontal gyrus of both hemispheres (Brodmann's area [BA] 6 in both hemispheres and BA 8 in the right hemisphere). No correlation was found in the anterior cingulate gyrus. Conclusion BA 6 and BA 8 and the anterior cingulate are believed to be the basis of both error detection and immediate correction. Activity of BA 6 and BA 8 reflects this executive task in AN patients as well, whereas the lack of correlation in the anterior cingulate may suggest its blunted activity in AN patients, similarly to what is shown in other conditions characterized by impaired executive function, such as patients with depression, patients with schizophrenia, and abstinent drug abusers. However, these findings should still be quoted as preliminary, given some limitations of the study design, such as the lack of a control group, and the unfeasibility of controlling some relevant confounding variables, such as psychiatric comorbidity, medication, and the time interval between examinations, mainly deriving from the relatively few patients studied. © 2005 by Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Magnetoencephalography (MEG) includes fast and comfortable recording procedures very suitable for the neurophysiological study of cognitive functions in aged people. In this exploratory MEG study in normal young adults, we tested whether very simple short-term memory (STM) demands induce visible changes in amplitude and latency of surface α rhythms. Two delayed response tasks were used. In the STM condition, a simple cue stimulus (one bit) was memorized along a brief delay period (3.5-5.5 s). In the control (no short-term memory; NSTM) condition, the cue stimulus remained available along the delay period. To make extremely simple the tasks, the explicit demand was visuospatial but the retention could be also based on phonological and somatomotor coding. Compared to the control condition, the amplitude of the α 1 (6-8 Hz) ERD decreased in the left hemisphere, whereas the amplitude of the α 2 (8-10 Hz) and α 3 (10-12 Hz) event-related desynchronization (ERD) increased in right and left parietal areas, respectively. Furthermore, the latency of the α ERD peak was slightly but significantly ( P < 0.05) later in STM compared to control condition. In conclusion, whole-head MEG technology and very simple STM demands revealed significant changes of human neuromagnetic α rhythms in normal young adults. Hum. Brain Mapp 24:184-192, 2005. © 2004 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The connectivity pattern of the neural network devoted to sensory processing depends on the timing of relay recruitment from receptors to cortical areas. The aim of the present work was to uncover and quantify the way the cortical relay recruitment is reflected in the shape of the brain-evoked responses. We recorded the magnetic somatosensory evoked fields (SEF) generated in 36 volunteers by separate bilateral electrical stimulation of median nerve, thumb, and little fingers. After defining an index that quantifies the shape similarity of two SEF traces, we studied the morphologic characteristics of the recorded SEFs within the 20-ms time window that followed the impulse arrival at the primary sensory cortex. Based on our similarity criterion, the shape of the SEFs obtained stimulating the median nerve was observed to be more similar to the one obtained from the thumb (same median nerve innervation) than to the one obtained from the little finger (ulnar nerve innervation). In addition, SEF shapes associated with different brain regions were more similar within an individual than between subjects. Because the SEF morphologic characteristics turned out to be quite diverse among subjects, we defined similarity levels that allowed us to identify three main classes of SEF shapes in normalcy. We show evidence that the morphology of the evoked response describes the anatomo-functional connectivity pattern in the primary sensory areas. Our findings suggest the possible existence of a thalamo-cortico-thalamic responsiveness loop related to the different classes. Hum Brain Mapp 24:99-108, 2005. © 2004 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the functional coupling between anterior and posterior areas as induced by the sleep onset process. The functional coupling was indexed by an analysis of spectral coherence and directed transfer function (DTF) from electroencephalographic (EEG) data. As it has been reported that more anterior areas first synchronize sleep EEG activity, we hypothesized a fronto-posterior direction of the cortical functional coupling during the sleep onset process. Ten normal right-handed male students slept for two-nights (one adaptation, one baseline) in the laboratory, with standard polysomnographic recordings. Spectral coherence and DTF were computed on data recorded by anterior (FzA1) and posterior (PzA1, OzA1) derivations. EEG coherence at the delta/theta band was higher during the presleep period than the sleep onset period, while EEG coherence at the alpha band was higher during the sleep onset period than the presleep period. The DTF findings indicated a prevalence of the occipital-to-frontal information flow at delta/theta and alpha bands during the presleep period and a prevalence of the frontal-to-parieto-occipital information flow at all bands during the sleep onset period. The coherent pattern of changes in EEG coherence and in DTF values at sleep onset lends further support to the notion of sleep as a local process, showing that the sleep onset process is subserved by the functional coordination of a cortical fronto-posterior network. In this network, prefrontal areas may play a leading role in the propagation of synchronizing signals conveyed at frequencies spanning delta to beta rhythms. [ABSTRACT FROM AUTHOR]

Intracortical facilitation and inhibition, as assessed by the paired-pulse transcranial magnetic stimulation technique with a subthreshold conditioning pulse followed by a suprathreshold test pulse, was studied upon awakening from REM and slow-wave sleep (SWS). Ten normal subjects were studied for four consecutive nights. Intracortical facilitation and inhibition were assessed upon awakening from SWS and REM sleep, and during a presleep baseline. Independently of sleep stage at awakening, intracortical inhibition was found at 1–3-ms interstimulus intervals and facilitation at 7–15-ms interstimulus intervals. Motor thresholds were higher in SWS awakenings, with no differences between REM awakenings and wakefulness, while motor evoked potential amplitude to unconditioned stimuli decreased upon REM awakening as compared to the other conditions. REM sleep awakenings showed a significant increase of intracortical facilitation at 10 and 15 ms, while intracortical inhibition was not affected by sleep stage at awakening. While the dissociation between motor thresholds and motor evoked potential amplitudes could be explained by the different excitability of the corticospinal system during SWS and REM sleep, the heightened cortical facilitation upon awakening from REM sleep points to a cortical motor activation during this stage. [ABSTRACT FROM AUTHOR]

Do recency processes associated with repetitive sensorimotor events modulate the magnitude and functional coupling of brain rhythmicity in human temporal cortex? Intracranial stereo electroencephalographic activity (SEEG; 256 Hz sampling rate) was recorded from hippocampus, and inferior (BA20) and middle (BA21) temporal cortex in four epilepsy patients. The repetitive events were represented by predicted imperative somatosensory stimuli (CNV paradigm) triggering hand movements (‘repetitive visuomotor’) or counting (‘repetitive counting’). The non-repetitive events were ‘rare’ (P3 paradigm) somatosensory stimuli triggering hand movements (‘non-repetitive visuomotor’) or counting (‘non-repetitive counting’). Brain rhythmicity was indexed by event-related desynchronization/synchronization (ERD/ERS) of SEEG data, whereas the functional coupling was evaluated by spectral SEEG coherence between pairs of the mentioned areas. The frequency bands of interest were theta (4–8 Hz), alpha (8–12 Hz), beta (14–30 Hz), and gamma (32–46 Hz). Compared to the non-repetitive events, the ‘repetitive visuomotor’ events showed a significant beta and gamma ERS in the hippocampus and a significant theta ERD in the inferior temporal cortex. Furthermore, the ‘repetitive visuomotor’ events induced a task-specific significant gamma coherence among the examined areas. These results suggest that recency processes do modulate the magnitude and functional coupling of brain rhythmicity (especially gamma) in the human temporal cortex. [ABSTRACT FROM AUTHOR]

Previous simulation studies have stressed the importance of the multimodal integration of electroencephalography (EEG) and magnetoencephalography (MEG) data in the estimation of cortical current density. In such studies, no systematic variations of the signal-to-noise ratio (SNR) and of the number of sensors were explicitly taken into account in the estimation process. We investigated effects of variable SNR and number of sensors on the accuracy of current density estimate by using multimodal EEG and MEG data. This was done by using as the dependent variable both the correlation coefficient (CC) and the relative error (RE) between imposed and estimated waveforms at the level of cortical region of interests (ROI). A realistic head and cortical surface model was used. Factors used in the simulations were: (1) the SNR of the simulated scalp data (with seven levels: infinite, 30, 20, 10, 5, 3, 1); (2) the particular inverse operator used to estimate the cortical source activity from the simulated scalp data (INVERSE, with two levels, including minimum norm and weighted minimum norm); and (3) the number of EEG or MEG sensors employed in the analysis (SENSORS, with three levels: 128, 61, 29 for EEG and 153, 61, or 38 in MEG). Analysis of variance demonstrated that all the considered factors significantly affect the CC and the RE indexes. Combined EEG-MEG data produced statistically significant lower RE and higher CC in source current density reconstructions compared to that estimated by the EEG and MEG data considered separately. These observations hold for the range of SNR values presented by the analyzed data. The superiority of current density estimation by multimodal integration of EEG and MEG was not due to differences in number of sensors between unimodal (EEG, MEG) and combined (EEG-MEG) inverse estimates. In fact, the current density estimate relative to the EEG-MEG multimodal integration involved 61 EEG plus 63 MEG sensors, whereas estimations carried out with the single modalities alone involved 128 sensors for EEG and 153 sensors for MEG. The results of the simulations also suggest that the use of simultaneous 29 EEG sensors during the MEG measurements carried out with full sensor arrangements (153 sensors) returned an accuracy of the cortical source estimate statistically similar to that obtained by combining 64 EEG and 153 MEG sensors. Hum. Brain Mapp. 22:54-64, 2004. © 2004 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]