Simultaneous and independent electroencephalography and magnetic resonance imaging: A multimodal neuroimaging dataset.

We introduce an open access, multimodal neuroimaging dataset comprising simultaneously and independently collected Electroencephalography (EEG) and Magnetic Resonance Imaging (MRI) data from twenty healthy, young male individuals (mean age = 26 years; SD = 3.8 years). The dataset adheres to the BIDS standard specification and is structured into two components: 1) EEG data recorded outside the Magnetic Resonance (MR) environment, inside the MR scanner without image collection and during simultaneous functional MRI acquisition (EEG-fMRI) and 2) Functional MRI data acquired with and without simultaneous EEG recording and structural MRI data obtained with and without the participants wearing the EEG cap. EEG data were recorded with an MR-compatible EEG recording system (GES 400 MR, Electrical Geodesics Inc.) using a 32-channel sponge-based EEG cap (Geodesic Sensor Net). Eyes-closed resting-state EEG data were recorded for two minutes in both the outside and inside scanner conditions and for ten minutes during simultaneous EEG-fMRI. Eyes-open resting-state EEG data were recorded for two minutes under each condition. Participants also performed an eyes opening-eyes closure block-design task outside the scanner (two minutes) and during simultaneous EEG-fMRI (four minutes). The EEG data recorded outside the scanner provides a reference signal devoid of MR-related artifacts. The data collected inside the scanner without image acquisition captures the contribution of the ballistocardiographic (BCG) without the gradient artifact, making it suitable for testing and validating BCG artifact correction methods. The EEG-fMRI data is affected by both the gradient and BCG artifacts. Brain images were acquired using a 3T GE MR750-Discovery MR scanner equipped with a 32-channel head coil. Whole-brain functional images were obtained using a GRE-EPI T2* weighted sequence (TR = 2000 ms, TE = 40 ms, 35 interleaved axial slices with 4 mm isometric voxels). Structural images were acquired using an SPGR sequence (TR = 8.1 ms, TE = 3.2 ms, flip angle = 12°, 176 sagittal slices with 1 mm isometric voxels). This stands as one of the largest open access EEG-fMRI datasets available, which allows researchers to: 1) Assess the impact of gradient and BCG artifacts on EEG data, 2) Evaluate the effectiveness of novel artifact removal techniques to minimize artifact contribution and preserve EEG signal integrity, 3) Conduct hardware/setup comparison studies, 4) Evaluate the quality of structural and functional MRI data obtained with this particular EEG system, and 5) Implement and validate multimodal integrative analysis approaches on simultaneous EEG-fMRI data.

Preservation of EEG spectral power features during simultaneous EEG-fMRI.

Introduction: Electroencephalographic (EEG) data quality is severely compromised when recorded inside the magnetic resonance (MR) environment. Here we characterized the impact of the ballistocardiographic (BCG) artifact on resting-state EEG spectral properties and compared the effectiveness of seven common BCG correction methods to preserve EEG spectral features. We also assessed if these methods retained posterior alpha power reactivity to an eyes closure-opening (EC-EO) task and compared the results from EEG-informed fMRI analysis using different BCG correction approaches. Method: Electroencephalographic data from 20 healthy young adults were recorded outside the MR environment and during simultaneous fMRI acquisition. The gradient artifact was effectively removed from EEG-fMRI acquisitions using Average Artifact Subtraction (AAS). The BCG artifact was corrected with seven methods: AAS, Optimal Basis Set (OBS), Independent Component Analysis (ICA), OBS followed by ICA, AAS followed by ICA, PROJIC-AAS and PROJIC-OBS. EEG signal preservation was assessed by comparing the spectral power of traditional frequency bands from the corrected rs-EEG-fMRI data with the data recorded outside the scanner. We then assessed the preservation of posterior alpha functional reactivity by computing the ratio between the EC and EO conditions during the EC-EO task. EEG-informed fMRI analysis of the EC-EO task was performed using alpha power-derived BOLD signal predictors obtained from the EEG signals corrected with different methods. Results: The BCG artifact caused significant distortions (increased absolute power, altered relative power) across all frequency bands. Artifact residuals/signal losses were present after applying all correction methods. The EEG reactivity to the EC-EO task was better preserved with ICA-based correction approaches, particularly when using ICA feature extraction to isolate alpha power fluctuations, which allowed to accurately predict hemodynamic signal fluctuations during the EEG-informed fMRI analysis. Discussion: Current software solutions for the BCG artifact problem offer limited efficiency to preserve the EEG spectral power properties using this particular EEG setup. The state-of-the-art approaches tested here can be further refined and should be combined with hardware implementations to better preserve EEG signal properties during simultaneous EEG-fMRI. Existing and novel BCG artifact correction methods should be validated by evaluating signal preservation of both ERPs and spontaneous EEG spectral power.

Influencia del estatus socioeconómico sobre variables cognitivas y electroencefalográficas en escolares con riesgo de daño cerebral / Influence of socioeconomic status on cognitive and electroencephalographic variables school children at risk

Introducción: el estatus socioeconómico puede impactar sobre la cognición y la actividad eléctrica cerebral de los niños, por la influencia que tiene sobre el desarrollo durante etapas tempranas. Objetivo: evaluar la asociación de variables socioeconómicas, con alteraciones cognitivas y electroencefalográficas, en un grupo de niños escolares con riesgo de daño cerebral. Métodos: se estudiaron 42 niños mexicanos, de 6-7 años de edad. Se realizó un estudio socioeconómico a los padres y los niños fueron evaluados mediante la Evaluación Neuropsicológica Infantil (subpruebas de lectura-escritura y escala de signos neurológicos blandos), la Escala de Inteligencia de Wechsler para Niños, la Escala de Conners para Padres-Revisada y un electroencefalograma en diferentes edades. Resultados: con las variables socioeconómicas y, mediante un análisis de conglomerados, se encontraron 3 grupos que mostraban una adecuada diferenciación académica y económica entre sí. Por el método de clasificación basado en regresiones dispersas, se identificaron las variables que diferenciaban significativamente a los 3 grupos: problemas sociales, cognitivos, síntomas inatento, índice TDAH (Trastorno por Déficit de Atención e Hiperactividad, Escala de Conners para Padres-Revisada), lectura de palabras, comprensión en lectura de oraciones, dictado de sílabas, precisión de lectura en voz alta, lectura de sílabas, dictado de no palabras, movimiento de oposición digital, agarre de lápiz (Evaluación Neuropsicológica Infantil) y primer electroencefalograma normal. Conclusiones: el grupo con más desventajas socioeconómicas tuvo un peor desempeño en la lectoescritura y mayor prevalencia de actividad paroxística no epileptiforme; mientras que, el grupo con mayores ventajas socioeconómicas, mostró mejor desempeño en estas habilidades, mayor proporción de electroencefalogramas normales y una tendencia hacia problemas de atención(AU)

Introduction: the socioeconomic status can impact on the cognition and electrical brain activity of children due to the influence it has on the development during early stages. Objective: to evaluate the association of socioeconomic variables with cognitive and electroencephalographic alterations, in a group of school children at risk of brain damage. Methods: 42 Mexican children in the ages from 6 to 7 years old were studied. A socioeconomic study was conducted on the parents, and the children were evaluated through the Child Neuropsychological Assessment (reading-writing subtests and the scale of neurological soft signs), the Wechsler´s Intelligence Scale for Children, the Conners´ Scale for Parents-Revised and an electroencephalogram in different ages. Results: with the socioeconomic variables and by means of an analysis of conglomerate, 3 groups were found that showed an adequate academic and economic differentiation among themselves. By the classification method based on scattered regressions were identified variables that significantly differentiated the 3 groups: social and cognitive problems, inattentive symptoms, ADHD (Attention Deficit and Hyperactivity Disorder, Conners Scale for Parents-Revised), reading of words, comprehension in reading of sentences, dictation of syllables, accuracy of reading aloud, reading of syllables, dictation of non words, movement of digital opposition, pencil´s grip (Neuropsychological Evaluation of Children) and first normal electroencephalogram. Conclusions: the group with more socioeconomic disadvantages had a worse performance in reading and writing and a higher prevalence of non-epileptiform paroxysmal activity; whereas, the group with the greatest socioeconomic advantages showed a better performance in these skills, a greater proportion of normal electroencephalograms and a tendency towards attention problems(AU)

Effective connectivity during successful and unsuccessful recollection in young and old adults.

Aging effects on regional brain activation have been studied extensively to explain the gradual recollection failure that occurs with advancing age. However, little is known about the consequence of aging on the interaction among brain regions that support recollection. The purpose of this study was to examine effective connectivity at encoding and retrieval during successful and unsuccessful recollection in young and old adults. In particular, we analyzed a recollection network that is characterized by its susceptibility to aging effects by middle age or later, which is comprised of the occipital cortex, hippocampus and orbitofrontal cortex. Participants' brains were scanned using functional magnetic resonance imaging while they performed a spatial source memory task. Dynamic causal modeling and Bayesian model selection revealed that subsequent recollection during encoding and recollection during retrieval modulated the influence of the orbitofrontal cortex on the hippocampus in both age groups; this particular connectivity was not modulated by unsuccessful encoding in either group. Successful encoding and retrieval of item-source associations modulated all connections within the network in old adults. The findings revealed that the orbitofrontal cortex influences processes in the hippocampus to ensure successful recollection, and aging alters the recollection network by engaging non-specialized connections.

Brain activity during source memory retrieval in young, middle-aged and old adults.

We investigated neurofunctional changes associated with source memory decline across the adult life span using functional magnetic resonance imaging (fMRI). Young, middle-aged and old adults carried out a natural/artificial judgment of images of common objects that were randomly presented in one of the quadrants of the screen. At retrieval, the images were displayed at the center of the screen and the participants judged whether each image was new or old and, if old, they indicated in which quadrant of the screen the image had originally been presented. Comparing the items associated with correct versus incorrect source judgments revealed that no regions showed greater activity in young adults than in middle-aged adults; however, in young and middle-aged adults the activity in the left hippocampus and left anterior temporal cortex was of greater magnitude than in the older adults. Several regions also exhibited greater activity in young adults than in old adults. These results suggest that in middle age the recollection neural network, assessable by fMRI, is still preserved.

fMRI subsequent source memory effects in young, middle-aged and old adults.

The ability to remember the spatial context in which our experiences occur declines linearly across the adult lifespan. However, little is known about whether this source memory decline is associated with neural activity changes. In the present study, functional magnetic resonance imaging (fMRI) scans were recorded in young, middle-aged and old adults to investigate brain activity variations across the adult lifespan during encoding of subsequent spatial source memory retrieval. Twelve healthy individuals of both sexes were enrolled in each age group. During encoding, participants performed natural/artificial judgment of images of common objects that were randomly presented in one of the quadrants of the screen. During retrieval, the images presented at encoding were randomly mixed with new ones and displayed at the center of the screen. Participants judged whether each image was new or old and, if an image was old, they were instructed to indicate in which quadrant the image was presented in the encoding session. The contrast between study items that were later recognized and assigned a correct source judgment with those whose sources were subsequently forgotten revealed that positive subsequent memory effects disappear by middle age in the left medial orbitofrontal gyrus and appear in the left superior occipital gyrus. This under-recruitment and over-recruitment brain activity was also present in old adults. The results allowed us to identify the specific brain regions that first fail to encode spatial information into an episodic representation during the adult lifespan.

[Hydrogen magnetic resonance quantitative spectroscopy at 3 T in symptomatic and asymptomatic Huntington's disease patients]. / Espectroscopia cuantitativa de hidrógeno por resonancia magnética de 3 T en pacientes sintomáticos y asintomáticoscon enfermedad de Huntington.

INTRODUCTION: Huntington's disease is an hereditary autosomic-dominant neurodegenerative disorder, characterized by motor, cognitive and psychiatric symptoms. AIM: To quantify differences in N-acetylaspartate, creatine and choline in caudate nucleus, putamen and occipital cortex of patients with Huntington's disease, symptomatics and asymptomatics. SUBJECTS AND METHODS: Hydrogen magnetic resonance spectroscopy was performed with a 3 T scanner in 10 Huntington's disease gene-tested subjects, included in three groups: negative (control), positive symptomatics and positive asymptomatics. Data was quantified with LCModel and analyzed with ANOVA and Fisher tests. RESULTS: Symptomatic patients showed decreased creatine and N-acetylaspartate in the three regions, and decreased choline only in putamen (p < 0.05). Choline difference was found between symptomatics and asymptomatics in the caudate nucleus (p < 0.05). CONCLUSIONS: Results may reflect neuronal dysfunction and suggest that creatine and choline may serve as markers for Huntington's disease progression.