30 research outputs found
Frontal lobe epilepsy associated with tuberous sclerosis: electroencephalographic-magnetic resonance image fusioning
No full textWe studied the topographic relationships between cortical and subcortical lesions shown on magnetic resonance images (MRI) and sources of epileptiform activity in a series of nine children with intractable epilepsy and tuberous sclerosis complex. Although video-electroencephalographic (EEG) monitoring was suggestive of a frontal seizure onset, interictal EEG was, in seven of nine cases, in the form of apparently bisynchronous discharges. In all cases, the use of a short time lag estimation procedure based on a nonlinear correlation function between surface recorded EEG signals allowed the detection of a lateralized onset of EEG paroxysmal activity. Furthermore, a computerized method based on a source localization EEG-MRI image fusioning procedure, has revealed a topographic concordance between well-defined frontal cortical lesions shown on MRI and site of onset of paroxysmal discharges. Lennox-like EEG patterns frequently reported in children with tuberous sclerosis complex could be the result of the tendency of frontal tubers to induce secondary bilateral synchrony, with implications in the medical and eventually surgical management of the often drug-resistant associated seizures
Cortical sensorimotor interactions during the expectancy of a go/no-go task: effects of painful stimuli
No full textEEG microstate duration and syntax in acute, medication-naïve, first-episode schizophrenia: A multi-center study
No full textIn young, first-episode, productive, medication-naive patients with schizophrenia, EEG microstates (building blocks of mentation) tend to be shortened. Koenig et al. [Koenig, T., Lehmann, D., Merlo, M., Kochi, K., Hell, D., Koukkou, M., 1999. A deviant EEG brain microstate in acute, neuroleptic-naive schizophrenics at rest. European Archives of Psychiatry and Clinical Neuroscience 249, 205-211] suggested that shortening concerned specific microstate classes. Sequence rules (microstate concatenations, syntax) conceivably might also be affected. In 27 patients of the above type and 27 controls, from three centers, multichannel resting EEG was analyzed into microstates using k-means clustering of momentary potential topographies into four microstate classes (A-D). In patients, microstates were shortened in classes B and D (from 80 to 70 ms and from 94 to 82 ms, respectively), occurred more frequently in classes A and C, and covered more time in A and less in B. Topography differed only in class B where LORETA tomography predominantly showed stronger left and anterior activity in patients. Microstate concatenation (syntax) generally were disturbed in patients; specifically, the class sequence A -> C -> D -> A predominated in controls, but was reversed in patients (A -> D -> C -> A). In schizophrenia, information processing in certain classes of mental operations might deviate because of precocious termination. The intermittent occurrence might account for Bleuler's "double bookkeeping." The disturbed microstate syntax opens a novel physiological comparison of mental operations between patients and controls
Donepezil effects on sources of cortical rhythms in mild Alzheimer's disease: Responders vs. Non-Responders.
No full textAcetylcholinesterase inhibitors (AChEI) such as donepezil act in
mild Alzheimer’s disease (AD) by increasing cholinergic tone.
Differences in the clinical response in patients who do or do not
benefit from therapy may be due to different functional features
of the central neural systems. We tested this hypothesis using
cortical electroencephalographic (EEG) rhythmicity. Resting eyesclosed
EEG data were recorded in 58 mild AD patients (Mini
Mental State Examination [MMSE] range 17– 24) before and
approximately 1 year after standard donepezil treatment. Based
on changes of MMSE scores between baseline and follow-up, 28
patients were classified as ‘‘Responders’’ (MMSEvar 0) and 30
patients as ‘‘Non-Responders’’ (MMSEvar <0). 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 sources were studied with low-resolution brain
electromagnetic tomography (LORETA). Before treatment, posterior
sources of delta, alpha 1 and alpha 2 frequencies were greater
in amplitude in Non-Responders. After treatment, a lesser
magnitude reduction of occipital and temporal alpha 1 sources
characterized Responders. These results suggest that Responders
and Non-Responders had different EEG cortical rhythms. Donepezil
could act by reactivating existing yet functionally silent
cortical synapses in Responders, restoring temporal and occipital
alpha rhythms
Donepezil effects on sources of cortical rhythms in mild Alzheimer's disease: Responders vs. Non-Responders.
No full textThe cross-frequency mediation mechanism of intracortical information transactions
No full text1. AbstractIn a seminal paper by von Stein and Sarnthein (2000), it was hypothesized that “bottom-up” information processing of “content” elicits local, high frequency (beta-gamma) oscillations, whereas “top-down” processing is “contextual”, characterized by large scale integration spanning distant cortical regions, and implemented by slower frequency (theta-alpha) oscillations. This corresponds to a mechanism of cortical information transactions, where synchronization of beta-gamma oscillations between distant cortical regions is mediated by widespread theta-alpha oscillations. It is the aim of this paper to express this hypothesis quantitatively, in terms of a model that will allow testing this type of information transaction mechanism. The basic methodology used here corresponds to statistical mediation analysis, originally developed by (Baron and Kenny 1986). We generalize the classical mediator model to the case of multivariate complex-valued data, consisting of the discrete Fourier transform coefficients of signals of electric neuronal activity, at different frequencies, and at different cortical locations. The “mediation effect” is quantified here in a novel way, as the product of “dual frequency RV-coupling coefficients”, that were introduced in (Pascual-Marqui et al 2016, http://arxiv.org/abs/1603.05343). Relevant statistical procedures are presented for testing the cross-frequency mediation mechanism in general, and in particular for testing the von Stein & Sarnthein hypothesis.</jats:p
Mapping distributed sources of cortical rhythms in mild Alzheimer’s disease. A Multi-Centric EEG Study.
No full textThe study aimed at mapping (i) the distributed electroencephalographic
(EEG) sources specific for mild Alzheimer’s disease (AD)
compared to vascular dementia (VaD) or normal elderly people (Nold)
and (ii) the distributed EEG sources sensitive to the mild AD at
different stages of severity. Resting EEG (10– 20 electrode montage)
was recorded from 48 mild AD, 20 VaD, and 38 Nold subjects. Both AD
and VaD patients had 24– 17 of mini mental state examination
(MMSE). EEG rhythms 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 sources were modeled by low resolution
brain electromagnetic tomography (LORETA). Regarding issue i, there
was a decline of central, parietal, temporal, and limbic alpha 1 (low
alpha) sources specific for mild AD group with respect to Nold and VaD
groups. Furthermore, occipital alpha 1 sources showed a strong decline
in mild AD compared to VaD group. Finally, distributed theta sources
were largely abnormal in VaD but not in mild AD group. Regarding
issue ii, there was a lower power of occipital alpha 1 sources in mild AD
subgroup having more severe disease. Compared to previous field
studies, this was the first investigation that illustrated the power
spectrum profiles at the level of cortical (macroregions) EEG sources in
mild AD patients having different severity of the disease with respect to
VaD and normal subjects. Future studies should evaluate the clinical
usefulness of this approach in early differential diagnosis, disease
staging, and therapy monitoring
Cortical sources of resting state EEG rhythms are sensitive to the progression of early stage Alzheimer's disease
No full textCortical sources of resting state electroencephalographic (EEG) rhythms are abnormal in subjects with Alzheimer's disease (AD). Here we tested the hypothesis that these sources are also sensitive to the progression of early stage AD over the course of one year. The resting state eyes-closed EEG data were recorded in 88 mild AD patients at baseline (Mini Mental State Evaluation, MMSE I = 21.7 ± 0.2 standard error, SE) and at approximately one-year follow up (13.3 months ± 0.5 SE; MMSE II = 20 ± 0.4 SE). All patients received standard therapy with acetylcholinesterase inhibitors. EEG recordings were also performed in 35 normal elderly (Nold) subjects as controls. 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), beta 2 (20-30 Hz), and gamma (30-40 Hz). Cortical EEG sources were estimated by low-resolution brain electromagnetic tomography (LORETA). Compared to the Nold subjects, the mild AD patients were characterized by a power increase of widespread delta sources and by a power decrease of posterior alpha sources. In the mild AD patients, the follow-up EEG recordings showed increased power of widespread delta sources as well as decreased power of widespread alpha and posterior beta 1 sources. These results suggest that the resting state EEG sources were sensitive, at least at group level, to the cognitive decline occurring in the mild AD group over a one-year period, and might represent cost-effective and non-invasive markers with which to enrich cohorts of AD patients that decline faster for clinical studies
Resting state cortical electroencephalographic rhythms in covert hepatic encephalopathy and Alzheimer's disease
No full textPatients suffering from prodromal (i.e., amnestic mild cognitive impairment, aMCI) and overt Alzheimer's disease (AD) show abnormal cortical sources of resting state electroencephalographic (EEG) rhythms. Here we tested the hypothesis that these sources show extensive abnormalities in liver cirrhosis (LC) patients with a cognitive impairment due to covert and diffuse hepatic encephalopathy (CHE). EEG activity was recorded in 64 LC (including 21 CHE), 21 aMCI, 21 AD, and 21 cognitively intact (Nold) subjects. EEG rhythms of interest were delta (2-4 Hz), theta (4-8 Hz), alpha 1 (8-10.5 Hz), alpha 2 (10.5-13 Hz), beta 1 (13-20 Hz), and beta 2 (20-30 Hz). EEG cortical sources were estimated by LORETA. Widespread sources of theta (all but frontal), alpha 1 (all but occipital), and alpha 2 (parietal, temporal) rhythms were higher in amplitude in all LC patients than in the Nold subjects. In these LC patients, the activity of central, parietal, and temporal theta sources correlated negatively, and parietal and temporal alpha 2 sources correlated positively with an index of global cognitive status. Finally, widespread theta (all but frontal) and alpha 1 (all but occipital) sources showed higher activity in the sub-group of LC patients with CHE than in the patients with aMCI or AD. These results unveiled the larger spatial-frequency abnormalities of the resting state EEG sources in the CHE compared to the AD condition
