Recent advances in diffusion weighted image acquisition and processing allow for the construction of anatomically highly precise structural connectomes. In this study, we introduce a method to compute high-resolution whole-brain structural connectome. Our method relies on cortical and subcortical triangulated surface models, and on a large number of fiber tracts generated using a probabilistic tractography algorithm. Each surface triangle is a node of the structural connectivity graph while edges are fiber tract densities across pairs of nodes. Surface-based registration and downsampling to a common surface space are introduced for group analysis whereas connectome surface smoothing aimed at improving whole-brain network estimate reliability. Based on 10 datasets acquired from a single healthy subject, we evaluated the effects of repeated probabilistic tractography, surface smoothing, surface registration and downsampling to the common surface space. We show that, provided enough fiber tracts and surface smoothing, good to excellent intra-acquisition reliability could be achieved. Surface registration and downsampling efficiently established triangle-to-triangle correspondence across acquisitions and high inter-acquisition reliability was obtained. Computational time and disk/memory usages were monitored throughout the steps. Although further testing on large cohort of subjects is required, our method presents the potential to accurately model whole-brain structural connectivity at high-resolution.
Objective: Patients with temporal lobe epilepsy (TLE) have impaired theory of mind (ToM). However, ToM involves a variety of processes, such as understanding a person's intentions ("cognitive" ToM) and emotional states ("affective" ToM). The objectives of the present study were to characterize ToM disorders in TLE patients, identify patients at risk of ToM disorders, and study the relationships between psychobehavioral and quality of life factors and ToM disorders. Method: Fifty TLE patients and 50 controls performed ToM tasks assessing their understanding of verbal clumsiness (faux pas), sarcastic remarks, and mentalistic actions. Demographic, cognitive, and psychobehavioral data, and (for TLE patients) clinical and quality of life factors, were recorded. Results: Compared with controls, TLE patients showed impairments in all ToM tasks: 84% misunderstood faux pas, and around 50% misunderstood sarcasm. A long duration of epilepsy and young age at onset were risk factors for ToM impairments. In TLE patients, ToM impairments were associated with impaired empathy and anhedonia. Their affective states were less positively and more negatively valenced than in controls. Low positive affectivity was predictive of greater cognitive and affective ToM impairments for the faux pas task, and high negative affectivity was predictive of greater cognitive ToM abilities for the sarcasm task. The lack of social support was correlated with impaired ToM but was not a predictive factor. Conclusions: Both cognitive and affective ToM processes are impaired in TLE patients. Impaired ToM has an impact on empathy abilities and is related to affective disturbances in TLE patients. (PsycINFO Database Record (c) 2014 APA, all rights reserved).
It is essential to detect and then treat factors that aggravate Alzheimer's disease (AD). Here, we sought to determine whether or not continuous positive airway pressure (CPAP) therapy for sleep apnoea syndrome (SAS) slows the rate of cognitive decline in mild-to-moderate AD patients.
The aim of this study was to evaluate the impact of two different therapeutic strategies in patients with partial seizures who were intractable to the first prescribed antiepileptic drug (AED); alternative monotherapy vs early add-on treatment.
Inhibition by a prepulse (prepulse inhibition, PPI) of the response to a startling acoustic pulse is modulated by attention. We sought to determine whether goal-directed and stimulus-driven attention differentially modulate (i) PPI of the N100 and P200 components of the auditory evoked potential (AEP) and (ii) the components' generators.
In view of freezing of gait's circumstances of occurrence in Parkinson's disease, attentional resources appear to be involved in step initiation failure. Anticipatory postural adjustments (APAs) are essential because they allow unloading of the stepping leg and so create the conditions required for progression. Our main objective was to establish whether or not a change in attentional load during step initiation modulates APAs differently in patients with vs. without freezing of gait.
The objective of the present study was to investigate the time course of long-interval intracortical inhibition (LICI) and late cortical disinhibition (LCD) as a function of the motor task (index abduction, thumb-index precision grip). Motor-evoked potentials were recorded from the first dorsal interosseus (FDI) muscle of the dominant limb in 13 healthy subjects. We used paired-pulse transcranial magnetic stimulation (TMS) paradigms in which a test pulse was preceded by a suprathreshold priming pulse (130% of the resting motor threshold) with varying interstimulus intervals (ISIs). In each task, double pulses were delivered with ISIs ranging from 30% of the corresponding silent period (SP; ~ 45 ms) to 220% of the SP (~ 330 ms). In both tasks, we found that LICI was followed by LCD (namely a period of increased cortical excitability lasting until ~ 200% of the SP). The time-dependent modulation of LICI and LCD differed in the two tasks; LICI was shorter (i.e. disinhibition occurred earlier) and LCD was more intense during precision grip than during index abduction. Long-interval intracortical inhibition disappeared well before the end of the SP in the precision grip task, suggesting that the mechanisms underlying these two inhibitory phenomena are distinct. Our data suggest that disinhibition might reflect adaptation of neural circuit excitability to the functional requirements of the motor task.
Simultaneous recording of electroencephalogram and functional MRI (EEG-fMRI) is a powerful tool for localizing epileptic networks via the detection of hemodynamic changes correlated with interictal epileptic discharges (IEDs). fMRI can be used to study the long-lasting effect of epileptic activity by assessing stationary functional connectivity during the resting-state period [especially, the connectivity of the default mode network (DMN)]. Temporal lobe epilepsy (TLE) and idiopathic generalized epilepsy (IGE) are associated with low responsiveness and disruption of DMN activity. A dynamic functional connectivity approach might enable us to determine the effect of IEDs on DMN connectivity and to better understand the correlation between DMN connectivity changes and altered consciousness.
Objective: Patients with idiopathic REM sleep behavior disorder (iRBD) often develop synucleinopathies (Parkinsons disease [PD], in particular). Cognitive disorders affecting different domains have been reported in patients with iRBD. Dysexecutive disorders seem to predominate, but there is no consensus on the nature of visuospatial disorders in iRBD. The objective is to identify and characterize visuospatial disorders in patients with REM sleep behavior disorder (RBD - either idiopathic or associated with PD). Methods: Fifteen patients with iRBD, 30 patients with PD (15 of whom had RBD), and 20 healthy control subjects underwent an extensive assessment of visuospatial functions. Two computerized tasks were used: a Biederman task (to assess the 3 levels of visuoperceptive processing) and a Posner paradigm (to assess visual attention). Results: The visual priming effects classically described for the Biederman task in healthy controls were not found in iRBD patients. Patients with iRBD were no quicker in naming objects with the same general structure as previously presented objects but did have a normal priming effect for strictly identical objects. Parkinsons disease patients with RBD had poorer visuoperceptive performance levels than PD patients without RBD. There were no significant differences between the 4 groups in the Posner attentional task. Conclusions: First, this study confirms the presence of visuoperceptive dysfunction in iRBD patients and revealed a selective defect in intermediate visuoperceptive processing (i.e., general object representation). Second, RBD in PD appeared to be associated with poorer visuoperceptive abilities. Third, this visuoperceptive dysfunction in RBD patients was not associated with impaired attention. (PsycINFO Database Record (c) 2013 APA, all rights reserved).
Rapid eye movement (REM) sleep behavior disorder (RBD) is a risk factor for dementia in Parkinson disease (PD) patients. The objectives of our study were to prospectively evaluate the frequency of RBD in a sample of treatment-naïve, newly diagnosed PD patients and compare sleep characteristics and cognition in RBD and non-RBD groups.
The purpose of this study was to determine whether task-dependent differences in corticospinal pathway excitability occur in going from isolated contractions of the index finger to its coordinated activity with the thumb. Focal transcranial magnetic stimulation (TMS) was used to measure input-output (I/O) curves--a measure of corticospinal pathway excitability--of the contralateral first dorsal interosseus (FDI) muscle in 21 healthy subjects performing two isometric motor tasks: index abduction and precision grip. The level of FDI electromyographic (EMG) activity was kept constant across tasks. The amplitude of the FDI motor evoked potentials (MEPs) and the duration of FDI silent period (SP) were plotted against TMS stimulus intensity and fitted, respectively, to a Boltzmann sigmoidal function. The plateau level of the FDI MEP amplitude I/O curve increased by an average of 40% during the precision grip compared with index abduction. Likewise, the steepness of the curve, as measured by the value of the maximum slope, increased by nearly 70%. By contrast, all I/O curve parameters [plateau, stimulus intensity required to obtain 50% of maximum response (S(50)), and slope] of SP duration were similar between the two tasks. Short- and long-latency intracortical inhibitions (SICI and LICI, respectively) were also measured in each task. Both measures of inhibition decreased during precision grip compared with the isolated contraction. The results demonstrate that the motor cortical circuits controlling index and thumb muscles become functionally coupled when the muscles are used synergistically and this may be due, at least in part, to a decrease of intracortical inhibition and an increase of recurrent excitation.
Focal cortical dysplasia is a malformation caused by abnormalities of cortical development. It is characterized by no dysmorphic or ballon cells (type I), dysmorphic neurons witout or with ballon cells (type II). It is the main cause of pharmacoresistant epilepsy. The combination of clinical and neurophysiological findings provided by VEEG and MRI had lead to an improvement in the diagnosis and outcome of FCD. This paper describes our experience in the form of a retrospective study conducted on the patients affected by FCD who were treated in the Clinical Neurophysiology Service at University Hospital of Lille in France.
Sensorimotor performance declines with normal aging. The present study explored age-related changes in sensorimotor integration by conditioning a supra-threshold transcranial magnetic stimulation pulse with a peripheral nerve shock at different interstimulus intervals. Cortical motor threshold of the abductor pollicis brevis muscle, intracortical inhibition and facilitation were measured. We also assessed the influence of median nerve stimulation on motor cortex excitability at intervals which evoked short- and long-latency afferent inhibition (SAI and LAI, respectively) and afferent-induced facilitation (AIF). We observed a marked decrease of the long latency influence of proprioceptive inputs on M1 excitability in the elderly, with the loss of AIF and LAI. The SAI, motor thresholds and intracortical inhibition and facilitation were not age-related. Decreased sensorimotor performance with aging appears to be associated with a decrease in the influence of proprioceptive inputs on motor cortex excitability at longer intervals (probably via higher order cortical areas).
Cognitive event-related potentials (especially P300) have long been used to explore attentional processes. The aim of this study was to identify the cortical areas involved in P300 generation during a selective attention task.
Paraclinical explorations in epilepsy depend on the clinical situation of the occurrence of seizure. Epileptic seizure is first a possible symptom of a progressive cerebral disease or a systemic origin (toxic, metabolic, iatrogenic). In this situation, the aim of urgent explorations is to find the etiology of the seizure. If epileptic seizure is related to an epilepsy onset, paraclinical explorations are aimed to characterize an epileptic syndrome (idiopathic or symptomatic). Then EEG and cerebral imaging are imperative, eventually completed by specialized investigations (genetics, metabolic, functional imaging).
Video-EEG monitoring (v-EEG) was originally restricted to the evaluation for epilepsy surgery. It is now widely available and often utilized to clarify the nature of paroxysmal events or to identify the epileptic syndrome. It is important to define carefully the diagnostic value of this high-cost and time-consuming procedure. Few data on children are available. In this study, we have evaluated the utility of this procedure and the factors leading to a successful recording in children. We retrospectively reviewed 380 v-EEG done in 320 children. The rate of event detection was 59%. The v-EEG recorded a seizure in 40% (n=150), a non-epileptic event in 19% (n=73), and both seizure and non-epileptic events in 3% (n=11). Only 9% remained without diagnosis after v-EEG. The frequency of the usual events was the only factor contributing to a successful recording. This procedure confirmed the diagnosis of epilepsy in 43% of patients but excluded it in 25% of them. In children with epilepsy, the v-EEG allowed to define a new syndrome (30% of patients) or to improve clinical description and to identify the origin of the seizures (30%). The treatments were modified in 66% of patients following the v-EEG. Continuous video-EEG monitoring is an efficient and valuable procedure in the diagnosis and management of epilepsy and paroxysmal disorders in children.
Seizures are frequent in the elderly, but their diagnosis can be challenging. The objective of this work was to develop and validate an expert-based algorithm for the diagnosis of seizures in elderly people. A multidisciplinary group of neurologists and geriatricians developed a diagnostic algorithm using a combination of selected clinical, electroencephalographical and radiological criteria. The algorithm was validated by multicentre retrospective analysis of data of patients referred for specific symptoms and classified by the experts as epileptic patients or not. The algorithm was applied to all the patients, and the diagnosis provided by the algorithm was compared to the clinical diagnosis of the experts. Twenty-nine clinical, electroencephalographical and radiological criteria were selected for the algorithm. According to criteria combination, seizures were classified in four levels of diagnosis: certain, highly probable, possible or improbable. To validate the algorithm, the medical records of 269 elderly patients were analyzed (138 with epileptic seizures, 131 with non-epileptic manifestations). Patients were mainly referred for a transient focal deficit (40%), confusion (38%), unconsciousness (27%). The algorithm best classified certain and probable seizures versus possible and improbable seizures, with 86.2% sensitivity and 67.2% specificity. Using logistical regression, 2 simplified models were developed, the first with 13 criteria (Se 85.5%, Sp 90.1%), and the second with 7 criteria only (Se 84.8%, Sp 88.6%). In conclusion, the present study validated the use of a revised diagnostic algorithm to help diagnosis epileptic seizures in the elderly. A prospective study is planned to further validate this algorithm.
Attention is often impaired in temporal lobe epilepsy (TLE). The P300 wave (an endogenous, event-related potential) is a correlate of attention which is usually recorded during an "oddball paradigm," where the subject is instructed to detect an infrequent target stimulus presented amongst frequent, standard stimuli. Modifications of the P300 waves latency and amplitude in TLE have been suggested, but it is still not known whether the source regions also differ. Our hypothesis was that temporal lobe dysfunction would modify the P3 source regions in TLE patients.
In idiopathic rapid eye movement sleep behaviour disorder (RBD), an association with visuoperceptive disorders has been described. However, such an association has not been clearly established in RBD secondary to Parkinsons disease (PD). We compared visuoperceptive function in four groups of non-demented patients (parkinsonian patients with or without RBD, patients with idiopathic RBD and control participants) via a procedure enabling the analysis of the various components of visual information processing and in order to answer the following question: is RBD associated with visuoperceptive and/or attentional disorders in PD and, if so, where is the dysfunction located along the visual pathway? Sensorial aspects of visual information were evaluated using a contrast sensitivity test, perceptual aspects were assessed using a contour-based object identification test and visual attention was measured in an attentional capture paradigm. The diagnosis of RBD was confirmed by polysomnography. We observed a higher object identification threshold (OIT) (1) in PD patients with RBD compared with PD patients without RBD and with controls and (2) in idiopathic RBD patients compared with controls. There were no significant OIT differences between PD patients with RBD and idiopathic RBD patients or between PD patients without RBD and controls. We did not find any significant inter-group differences in any of the other visuoperceptive tests. RBD, idiopathic or secondary to PD, is associated with perceptual closure dysfunction. Our results suggest that this perceptual dysfunction is specifically associated with RBD and may be related to a non-dopaminergic impairment.
A relationship between peripheral visual field loss and vigabatrin (VGB) has been reported in several studies but with inconsistent results. We investigated the level of visual processing at which the impairment occurs: attentional or cognitive (recognition) deficit. A simple reaction time task was used as a baseline condition. A spatial attention task measured the benefit and cost for the detection of a target appearing at a cued or at an uncued location. A rapid categorization task assessed object recognition. Performance was tested at eccentricities varying from 30 degrees to 60 degrees on a panoramic screen covering 180 degrees. Participants were patients with epilepsy treated with VGB, patients treated with other drugs and healthy controls. In the VGB group 9 patients exhibited a mild visual field constriction. We observed a general slowing down of response times in participants treated by VGB, especially at 60 degrees eccentricity but their performance remained above chance at large eccentricity in the most complex categorization task. The slowing down of visual processing at large eccentricity for flashed stimuli suggests that VGB treated patients might be impaired at detecting moving objects in the periphery and this may have consequences in behavioural tasks like driving.
Despite thorough investigation, approximately 15-20% of syncope cases remain unexplained. An underrecognized cause of syncope may occur when partial epileptic discharges profoundly disrupt normal cardiac rhythm, including cardiac asystole, the so-called arrhythmogenic epilepsy (AE).
Motor cortex stimulation therapy (MCS) is increasingly used to control refractory neuropathic pain. Post-movement beta synchronization (PMBS) is defined as a sharp increase in beta-frequency electroencephalographic power following movement offset and may reflect sensorimotor cortex inhibition induced, at least in part, by cortical processing of movement-related sensory afferent inputs. PMBS pattern is then often altered in case of neuropathic pain. The main objective of the present study was to test the hypothesis that implanted MCS modulates PMBS in patients presenting with neuropathic pain.
Acetylcholinesterase inhibitors (AChEIs) are the most widely used symptomatic treatment for mild to severe Alzheimers disease (AD) patients, while N-methyl-d-aspartic acid (NMDA) receptor antagonist memantine is licensed for use in moderate to severe AD patients. In this article, the effect of these compounds on resting state eyes-closed electroencephalographic (EEG) rhythms in AD patients is reviewed to form a knowledge platform for the European Innovative Medicine Initiative project "PharmaCog" (IMI Grant Agreement No. 115009) aimed at developing innovative translational models for drug testing in AD. Indeed, quite similar EEG experiments and the same kind of spectral data analysis can be performed in animal models of AD and in elderly individuals with prodromal or manifest AD. Several studies have shown that AChEIs affect both resting state EEG rhythms and cognitive functions in AD patients. After few weeks of successful treatment, delta (0-3 Hz) or theta (4-7 Hz) rhythms decrease, dominant alpha rhythms (8-10 Hz) increase, and cognitive functions slightly improve. Beneficial effects of these rhythms and cognitive functions were also found in AD responders to the long-term successful treatment (i.e. 6-12 months). In contrast, only one study has explored the long-term effects of memantine on EEG rhythms in AD patients, showing reduced theta rhythms. The present review enlightens the expected effects of AChEIs on resting state EEG rhythms in AD patients as promising EEG markers for the development of translational protocols both within the PharmaCog project and for wider use.
High-frequency (HF) repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex (M1) has been shown to reduce akinesia in Parkinsons disease (PD). Given that the processing of sensory afferents is deficient in PD and might be involved in akinesia, we sought to determine whether or not the application of very HF rTMS [intermittent theta-burst stimulation (iTBS) protocol] over the M1 affected sensorimotor integration (SMI) and akinesia. The experiments were carried out in: (i) 11 patients taking their usual dopaminergic treatment (on-drug); (ii) eight of the latter patients after withdrawal of dopaminergic treatment (off-drug); and (iii) 10 de novo (drug-naive) patients. Sham stimulation was applied in 11 other patients in the on-drug condition. SMI was investigated by conditioning a supra-threshold transcranial magnetic stimulation pulse in the motor region controlling the abductor pollicis brevis with a nerve shock over the median nerve at time intervals corresponding to short- and long-latency afferent inhibition (SAI and LAI) and afferent-induced facilitation (AIF). Akinesia was assessed with a pointing test. In on-drug, off-drug and de novo patients, akinesia in the contralateral arm was lower after iTBS. Sham stimulation had no effect. In on-drug patients (but not other groups), SMI was also influenced by iTBS, with an increase in AIF. No changes in SAI and LAI were observed. Our data suggest that iTBS might improve both akinesia and sensory processing in patients with PD taking levodopa.
The selection of task-relevant information requires both the focalization of attention on the task and resistance to interference from irrelevant stimuli. Both mechanisms rely on a dorsal frontoparietal network, while focalization additionally involves a ventral frontoparietal network. The role of subcortical structures in attention is less clear, despite the fact that the striatum interacts significantly with the frontal cortex via frontostriatal loops. One means of investigating the basal ganglias contributions to attention is to examine the features of P300 components (i.e. amplitude, latency, and generators) in patients with basal ganglia damage (such as in Parkinsons disease (PD), in which attention is often impaired). Three-stimulus oddball paradigms can be used to study distracter-elicited and target-elicited P300 subcomponents.
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