Improved peripheral nerve conduction, EEG and verbal IQ after bone marrow transplantation for adult metachromatic leukodystrophy

A 28-year-old woman with a 4 year history of slowly progressing 'frontal dementia' was diagnosed as having adult metachromatic leukodystrophy and was followed for 4 years after bone marrow transplantation (BMT). MRI, neurophysiological tests (EEG, ENeG, VEP, SEP and BAEP) and neuropsychological assessment were performed before, and repeatedly after BMT. MRI showed symmetrical white matter lesions in the frontal and parieto-occipital lobes and in the corpus callosum. EEG showed frontal and temporal slow wave abnormalities and nerve conduction was slow. Neuropsychological tests showed cognitive impairment in executive functions, decline in visuospatial-constructive and spatial memory tasks and disorganized thinking. IQ was low (52), with slightly better values for verbal IQ than for performance IQ. After BMT, the patient was followed for 4 years. Clear improvements were seen in EEG, in peripheral nerve conduction and in neuropsychological tests (especially in verbal IQ). MRI findings were unchanged. We believe that the improvement in our patient resulted from the bone marrow transplantation.     

Genetic and environmental influences on EEG coherence

EEG coherence measures the covariation in electrical brain activity between two locations on the scalp and is used to study connectivity between cortical regions. The aim of this study was to determine the heritability of EEG coherence. Coherence was measured in a group of 213 16-yr-old twin pairs. By including male and female twin pairs in the sample, sex differences in genetic architecture were systematically examined. The EEG was obtained during quiet supine resting. Coherence was estimated for short and long distance combinations of electrode pairs along the anterior-posterior axis within a hemisphere for four frequency bands (delta, theta, alpha and beta). Averaged over all electrode combinations about 60% of the variance was explained by genetic factors for coherence in the theta, alpha and beta bands. For the delta band, the heritability was somewhat lower. No systematic sex differences in genetic architecture were found. All environmental influences were nonshared, i.e., unique factors including measurement error. Environmental factors shared by twin siblings did not influence variation in EEG coherence. These results suggest that individual differences in coherence form a potential candidate for (molecular) genetic studies on brain function.     

Integrative visuomotor behavior is associated with interregionally coherent oscillations in the human brain

Coherent electrical brain activity has been demonstrated to be associated with perceptual events in mammals. It is unclear whether or not it is also a mechanism instrumental in the performance of sensorimotor tasks requiring the continuous processing of information between primarily executive and receptive brain areas. In particular it is unknown whether or not interregional coherent activity detectable in electroencephalographic (EEG) recordings on the scalp reflects interareal functional cooperativity in humans. We studied patterns of changes in EEG-coherence associated with a visuomotor force-tracking task in seven subjects. Interregional coherence of EEG signals recorded from scalp regions overlying the visual and the motor cortex increased in comparison to a resting condition when subjects tracked a visual target by producing an isometric force with their right index finger. Coherence between visual and motor cortex decreased when the subjects produced a similar motor output in the presence of a visual distractor and was unchanged in a purely visual and purely motor task. Increases and decreases of coherence were best differentiated in the low beta frequency range (13-21 Hz). This observation suggests a special functional significance of low frequency oscillations in information processing in large-scale networks. These findings substantiate the view that coherent brain activity underlies integrative sensorimotor behavior.     

Electrode discrimination and speech recognition in postlingually deafened adult cochlear implant subjects

This study investigated the relationship between electrode discrimination and speech recognition in 11 postlingually deafened adult cochlear implant subjects who were implanted with the Nucleus/Cochlear Corporation multichannel device. The discriminability of each electrode included in a subject's clinical map was measured using adaptive and fixed-level discrimination tasks. Considerable variability in electrode discriminability was observed across subjects. Two subjects could discriminate all electrodes, and discrimination performance by the remaining nine subjects varied from near perfect to very poor. In these nine subjects, the results obtained from the discrimination tasks were used to create a map that contained only discriminable electrodes, and subjects' performance on speech recognition tasks using this experimental map was measured. Four different speech recognition tests were administered: a nine-choice closed-set medial vowel recognition task, a 14-choice closed-set medial consonant recognition task, the NU6 Monosyllabic Words Test [T. W. Tillman and T. Carhart, Tech. Rep. No. SAM-TR-66-55, USAF School of Aerospace Medicine, Brooks Air Force Base, Texas (1966)] scored for both words and phonemes correct, and the Central Institute for the Deaf (CID) Everyday Sentences test [H. Davis and S. R. Silverman, Hearing and Deafness (Holt, Rinehart, and Winston, New York, 1978)]. Seven of the nine subjects tested with the experimental map showed significant improvement on at least one speech recognition measure, even though the experimental map contained fewer electrodes than the original map. Three subjects' scores improved significantly on the CID Everyday Sentences test, three subjects' scores improved significantly on the NU6 Monosyllabic Words test, and five subjects' scores improved significantly on the NU6 Monosyllabic Words test scored for phonemes correct. None of the subjects' scores improved significantly on either the vowel or consonant tests. No significant correlation was observed between electrode discrimination ability and speech recognition scores or between electrode discrimination ability and improvement in speech recognition scores when programmed with the experimental map. The results of this study suggest that electrode discrimination tasks may be used to improve speech recognition of some cochlear implant subjects, and that each electrode site does not necessarily provide perceptually distinct information.     

Regional changes in EEG power and coherence during cognition: Intensive study of two individuals.

Studied whether EEG power is relevant to cognitive performance by conducting weekly EEG recordings on 2 adult male volunteers who were living for several months in a controlled laboratory environment. Data from an 8-channel EEG during a resting period and during performance of 2 cognitive tasks (word fluency and mental imagery) were subjected to spectral analysis. Statistical analyses on power and coherence were conducted for each S separately. Although substantial individual differences were observed, particularly for the theta band, both Ss showed changes in the spectral information over the anterior left hemisphere during the word fluency task. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Automatic detection of left ventricular borders on electron beam CT sequential cardiac images using an adaptive algorithm

Differential cortical activation by cognitive processing was studied using dimensional complexity, a measure derived from nonlinear dynamics that indicates the degrees of freedom (complexity) of a dynamic system. We examined the EEG of 32 healthy subjects at rest, during a visually presented calculation task, and during a moving shape perception task. As a nonlinear measure of connectivity, the mutual dimension of selected electrode pairs was used. The first Lyapunov coefficient was also calculated. Data were tested for non-linearity using a surrogate data method and compared to spectral EEG measures (power, coherence). Surrogate data testing confirmed the presence of nonlinear structure in the data. Cognitive activation led to a highly significant rise in dimensional complexity. While both tasks activated central, parietal and temporal areas, mental arithmetic showed frontal activation and an activity maximum at T3, while the moving shape task led to occipital activation and a right parietal activity maximum. Analysis of mutual dimension showed activation of a bilateral temporal-right frontal network in calculation. The Lyapunov coefficient showed clear topographic variation, but was not significantly changed by mental tasks (p<.09). While dimensional complexity was almost unrelated to power values, nonlinear (mutual dimension) and linear (coherence) measures of connectivity shared up to 37% of variance. Data are interpreted in terms of increased cortical complexity as a result of recruitment of asynchronously active, distributed neuronal assemblies in cognition. The topography of nonlinear dynamics are related to neuropsychological and neuroimaging findings on mental calculation and moving shape perception.     

Spark-to-wave transition: saltatory transmission of calcium waves in cardiac myocytes

In order to investigate a possible regional specificity of activation asymmetries of different parts of the cortex and the stability of these asymmetries across time and conditions, EEG was recorded during rest and stimulation conditions in a large sample of right-handed university students (n = 60). Recordings were made in two sessions (interval between sessions 2-4 weeks). In the first session two rest periods were conducted (interval 30 min) and one under stimulation. In the second session EEG was again recorded at rest. Reliability analyses show that the long-term stability of orbitofrontal asymmetries is markedly lower than that of dorsolateral, temporal, and parietal scores. Intercorrelations of EEG asymmetries at different electrode positions suggest that anterior and posterior EEG asymmetries are largely independent measures of cortical laterality. Both this partial independence of activation asymmetries and the differences in temporal stability underscore the significance of the anterior-posterior dimension in laterality research and may be one reason for several contradictory observations in studies on brain laterality.     

Problem behaviors associated with deletion Prader-Willi, Smith-Magenis, and cri du chat syndromes

Many studies have failed to determine a systematic dose-response relationship across different cognitive tasks between caffeine and EEG power spectra. However, a nonlinear approach to EEG analysis, which reconstructs a multi-dimensional state space from each electrode recording, can be used to compute the number of active degrees of freedom in the signal (the correlation dimension, D2), and can be interpreted as a measure of signal complexity. This study attempted to determine a consistent dose-response relationship between caffeine and EEG D2, across six oral caffeine doses (100-600 mg), with each subject acting as their own control, to create a probabilistic bias against finding any consistent linear or nonlinear dose-response relationship across different cognitive tasks. The experiment (n = 10) was conducted with three within-subjects explanatory variables, 2 (experimental, placebo) x 8 (caffeine level) x 4 (type of cognitive task performed), with EEG D2 as the response variable, measured from Fz, F3, F4 and Cz. A significant three-way interaction was found [F(21,245.3) = 3.65, P = 0.001]. Regression analyses revealed a linear trend for the response variable across trials for the placebo condition (average R2 = 0.54), whereas linear+quadratic trends explained an average 30% of the variance for the experimental condition, compared to 0.01% for the linear fit, indicating a robust quadratic dose-response relationship between caffeine and EEG D2. Three conditions had positive quadratic co-efficients, and one condition had a negative quadratic co-efficient. These results are discussed in terms of the implications for brain dynamics, and with respect to recent criticisms of the computation of D2 from EEG.     

EEG-blocking before and during voluntary movements: differences between the eyes-closed and the eyes-open condition

Movement-related EEG periods of 1 s duration were analyzed by fast Fourier transformation in the Bereitschaftspotential (BP) paradigm in 21 healthy, right-handed normals. Spectra of the rest period and the BP period before the onset of the voluntary movement, and of the rest period and the movement period, were compared in order to describe blocking effects before and during movement execution (fast fist closure of the right hand). When comparing the rest period and the movement period with the eyes closed as well as with the eyes open, blocking was pronounced in both conditions within the total frequency range of the alpha-band, especially at positions contralateral to the movement over the motor cortex (C3') and the parietal cortex (P3) as well as at the parietal midline electrode (Pz). Moreover, when comparing the spectra of the rest and the BP periods in the eyes-closed condition, significant differences were again seen, with lower values during the BP period at C3' and P3. We were, however, able to observe over the parietal cortex an increase of alpha power in the 10 Hz range during the BP period with the eyes opened and fixated. This increase during the BP period in the eyes-open condition was not found when the eyes were closed. This paradoxical phenomenon of an increase of power with the eyes opened instead of blocking during the BP period, as observed in the eyes closed, may be due to an additional activation effect on the already activated (blocked) EEG in the eyes-open condition during fixation.     

Prolonged non-convulsive status epilepticus as an early clinical manifestation of epilepsy in connection with HIV infection--case report with EEG and MRI follow-up]

The non-convulsive status epilepticus (NCSE) is a complication of petit mal epilepsy or epilepsy with temporal lobe seizures. Very rarely it is the primary manifestation of a symptomatic epilepsy. This report is on a 30-year old female inpatient with NCSE as the primary manifestation of symptomatic epilepsy, occurring four years after HIV infection (stage B3 according to the CDC classification) through heterosexual contact. After an initial tonic-clonic seizure, the patient suffered from NCSE for four weeks with diminished consciousness and major cognitive deficits. During this whole time period the EEG showed bilateral synchrone 1-2 Hz spike-wave complexes. After several failed treatment attempts, the NCSE was successfully and permanently treated with a combination of valproic acid and ethosuximide. The cerebrospinal fluid, cranial CT and cranial MRI were completely uneventful with regard to a CNS infection by the HI-virus or other infectious agents. 20 days after the initial symptoms, MRI showed bilateral cortical-subcortical and bilateral hippocampal lesions which stood out as focal edema zones, gradually disappeared completely and occurred in combination with the development of a discrete brain and right sided hippocampal atrophy. The EEG continued to show signs of right-temporal epileptic discharges with tendencies to generalise after 3 months but normalised after 6 months. Epileptic seizures are rarely an initial clinical sign of an infection with the HI-Virus even if no signs of encephalitis is detectable in the cerebrospinal fluid or in the cerebral MRI.     

Topographic analysis of coherence and propagation of EEG activity during sleep and wakefulness

Overnight sleep EEG recorded from 21 derivations was studied in 8 healthy subjects. The vector autoregressive model was fitted to all 21 channels simultaneously. Ordinary, multiple and partial coherences and directed transfer functions were estimated for sleep stages and wakefulness. Ordinary coherences give rather trivial information that coherence decreases with distance. Partial coherences revealed specific structure that was well repeatable for the subjects studied. Differences in coherence patterns between sleep stages were found by means of statistical tests. An increase of coherence was found for sleep stages 2, 3 and 4. Directed transfer function made possible the identification of the main centers from which EEG activity is spreading during sleep and wakefulness. During sleep the influence of subcortical structures was manifested by propagation of activity from the fronto-central region. The range of this interaction was highest in sleep stages 3 and 4. An EEG analysis, based on the approach of treating time series as a realization of one process and on the simultaneous (not pair-wise) evaluation of signals offers new possibilities in the investigation of synchronization and functional relations in the brain.     

Cortical brain regions engaged by masked emotional faces in adolescents and adults: An fMRI study.

Face-emotion processing has shown signs of developmental change during adolescence. Functional magnetic resonance imaging (fMRI) was used on 10 adolescents and 10 adults to contrast brain regions engaged by a masked emotional-face task (viewing a fixation cross and a series of masked happy and masked fearful faces), while blood oxygen level dependent signal was monitored by a 1.5-T MRI scanner. Brain regions differentially engaged in the 2 age groups were mapped by using statistical parametric mapping. Summed across groups, the contrast of masked face versus fixation-cross viewing generated activations in occipital-temporal regions previously activated in passive face-viewing tasks. Adolescents showed higher maxima for activations in posterior association cortex for 3 of the 4 statistical contrasts. Adolescents and adults differed in the degree to which posterior hemisphere brain areas were engaged by viewing masked facial displays of emotion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cortical Networks Generating Movement-Related EEG Rhythms in Alzheimer's Disease: An EEG Coherence Study.

Patients with mild Alzheimer's disease (AD) present with abnormally strong values of frontal and ipsilateral central sensorimotor rhythms. The authors tested 2 working hypotheses of the related electroencephalographic (EEG) coherence: disconnection, defined as a sign of a reduced coordination within the frontoparietal and interhemispheric networks, and cooperation, defined as a reflection of the reorganization of the brain sensorimotor networks. Results showed that, compared with healthy controls, patients with mild AD had an unreactive and abnormally low interhemispheric EEG coherence and an unreactive and abnormally high frontoparietal EEG coherence. These findings support the hypothesis of an impaired mechanism of sensorimotor cortical coupling (disconnection) in mild AD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuroimage of voluntary movement: topography of the Bereitschaftspotential, a 64-channel DC current source density study

The Bereitschaftspotential (BP) was recorded at 56 scalp positions when 17 healthy subjects performed brisk extensions of the right index finger. Aim of the study was to contribute to our understanding of the physiology underlying the BP and, in particular, to specify the situation at BP onset. For this purpose, the spatial pattern of the BP was analyzed in short time intervals (35 and/or 70 ms) starting 2.51 s before movement onset. For each time segment a spherical model of the BP was calculated by using spline interpolation. Then the spatial distribution of the electric potential at the scalp surface was transformed into a spatial distribution of current source densities (CSD map). Onset times of the BP and onset times of initial CSD-activity ranged between 2.23 and 1.81 s before movement onset. We selected a time window between 1.6 and 1.5 s before movement onset in order to analyze the spatial CSD pattern in each subject. In 10 subjects there was a significant current sink in the scalp area located over medial-wall motor areas (pre-SMA, SMA proper and anterior cingulate cortex: electrode positions C1, C2, FCz, Cz) in the absence of a significant current sink over the primary motor cortex (MI: electrode positions C3, CP3, and CP5). In three subjects significant current sinks were present at both sites and in another three subjects a current sink only over the lateral motor cortex was observed. In one subject no significant current sinks were measured. It is concluded that there is a large group of subjects (13/17) in whom BP at onset is associated with a current sink over medial-wall motor areas. At a later time interval (0.6 to 0.5 s before movement onset), significant current sinks were found in 13 subjects in medial and in 10 subjects in lateral recordings. These data were considered to be consistent with the hypothesis that, at least in a majority of subjects, medial-wall motor areas are activated earlier than lateral motor areas when organizing the initiation of a simple self-paced movement. Surface-recordings of the EEG do not allow further specification of cortical areas, which contribute to the current sinks. But in context with the current literature of the electrophysiology of nonhuman primates and of brain imaging in humans it is suggested that SMA and anterior cingulate cortex contribute to the current sink, the fronto-central midline, and that the primary motor cortex (MI) contributes to the current sink in the scalp area, which is located above MI and closely posterior to it.     

"Willed action": a functional MRI study of the human prefrontal cortex during a sensorimotor task

Functional MRI (fMRI) was used to examine human brain activity within the dorsolateral prefrontal cortex during a sensorimotor task that had been proposed to require selection between several responses, a cognitive concept termed "willed action" in a positron emission tomography (PET) study by Frith et al. [Frith, C. D., Friston, K., Liddle, P. F. & Frackowiak, R. S. J. (1991) Proc. R. Soc. London Ser. B 244, 241-246]. We repeated their sensorimotor task, in which the subject chooses to move either of two fingers after a stimulus, by fMRI experiments in a 2.1-T imaging spectrometer. Echo-planar images were acquired from four coronal slices in the prefrontal cortex from nine healthy subjects. Slices were 5 mm thick, centers separated by 7 mm, with nominal in-plane spatial resolution of 9.6 x 5.0 mm2 for mean data. Our mean results are in agreement with the PET results in that we saw similar bilateral activations. The present results are compared with our previously published fMRI study of a verbal fluency task, which had also been proposed by Frith et al. to elicit a "willed action" response. We find a clear separation of activation foci in the left dorsolateral prefrontal cortex for the sensorimotor (Brodmann area 46) and verbal fluency (Brodmann area 45) tasks. Hence, assigning a particular activated region to "willed action" is not supported by the fMRI data when examined closely because identical regions are not activated with different modalities. Similar modality linked activations can be observed in the original PET study but the greater resolution of the fMRI data makes the modality linkages more definite.     

Paracrine mechanisms of ovarian follicle apoptosis

Early diagnosis of dementia can be difficult. Quantitative EEG (qEEG) in combination with cognitive tasks shows promise for improving diagnostic accuracy. The study of task induced qEEG changes in normal ageing is a prerequisite for differentiating these changes from those which are specific to dementia. Sixteen young adults (mean age 28.8+/-5.6 years) and 16 healthy cognitively normal older subjects (mean age 73.4+/-7.9 years) participated in the study. EEG recordings were made while subjects were in a relaxed (or resting) state, and also while they performed arithmetic and language tasks. From the resting to the arithmetic conditions, there was decreased alpha activity and increased delta and beta-3 activity for both subject groups. Changes in alpha and delta activity were found in almost all sites and could be associated with arousal. Increase in beta-3 activity was focal, appearing only in the posterior region of the brain and it could be assumed that this area is highly involved in arithmetic processes. In the young adult group, theta activity increased from the resting to the arithmetic conditions, while in the older group theta activity changes were in the opposite direction. From the resting to the language condition, there was increased delta activity and decreased alpha and beta-1 activity for both subject groups. Changes in alpha and delta activity were again found in almost all sites. The decrease in beta-1 activity was found in only four sites, but these were not specific to a region of the brain known to be involved in language processing. This consistency in qEEG changes during cognitive tasks suggests that the method can be applied to the investigation of cognitive deficits associated with a number of neurological syndromes.     

18F-labeled 2-deoxy-2-fluoro-D-glucose positron-emission tomography scans for the localization of the epileptogenic foci

The localization of epileptogenic foci that are amenable to curative epilepsy surgery may be accomplished by noninvasive surface electroencephalogram (EEG) recordings, clinical observations, computed tomography (CT), magnetic resonance imaging (MRI), and neuropsychologic tests. Other tests, such as invasive EEG, 18F-fluoro-deoxyglucose-positron-emission tomography (FDG-PET or PET) scans, and single-photon-emission computed tomography (SPECT) scans, have also been used at various epilepsy centers to help identify candidates who might benefit from such surgery. Interictal PET scans have demonstrated hypometabolism in areas concordant with the epileptogenic foci indicated by other diagnostic tests such as EEG and MRI. However, PET scans have also shown no abnormality in many patients with EEG-indicated epileptogenic foci; in others, the scans have shown abnormal metabolism in areas that were discordant with the epileptogenic foci. Although substitution of the noninvasive PET scan for the invasive EEG recordings would be desirable, the available data were insufficient to determine whether PET scans might serve as a reliable substitute for EEG. A positive PET scan might contribute independent information for identifying the epileptogenic site but could be noncontributory or confusing when hypometabolism is not seen or is seen in presumably normal brain areas. It is not evident from the data in the literature to what extent confirmatory PET scan findings might contribute to the management of patients with complex partial seizures.     

Effects of magnetic resonance imaging on cardiac pacemakers and electrodes

In phantom studies we investigated the effects of magnetic resonance imaging (MRI) on pacemakers and electrodes. Twenty-five electrodes were exposed to MRI in a 1.5T scanner with continuous registration of the temperature at the electrode tip. Eleven pacemakers (five single chamber and six dual chamber) were exposed to MRI. Pacemaker output was monitored to detect malfunction in VOO/DOO and VVI/DDD modes. A temperature increase at the electrode tip of up to 63.1 degrees C was observed during 90 seconds of scanning. In seven electrodes the temperature increase exceeded 15 degrees C. Although no pacemaker malfunctions were observed in asynchronous pacing mode (VOO/DOO), inhibition and rapid pacing were observed during spin-echo imaging if the pacemakers were set to VVI or DDD mode. Pacemaker function was not impaired during scanning with gradient-echo sequences. Next to pacemaker dysfunction, electrode heating has to be considered a possible adverse effect when exposing patients with pacemakers to MRI.