T. Harmony | Universidad Nacional Autónoma de México (original) (raw)

Papers by T. Harmony

Research paper thumbnail of Los padres como promotores del desarrollo de lenguaje de bebés prematuros: propuesta de intervención temprana

Actualidades en Psicología, May 15, 2018

Los padres como promotores del desarrollo de lenguaje de bebés prematuros: propuesta de intervenc... more Los padres como promotores del desarrollo de lenguaje de bebés prematuros: propuesta de intervención temprana Resumen. Cualquier programa de intervención puede beneficiarse de la participación de los padres, pero es necesario darles información de cómo pueden estimular el lenguaje de sus hijos. El objetivo fue entrenar a los padres acerca de lo que debían esperar del desarrollo del lenguaje de sus hijos y brindarles técnicas de estimulación de este para evitar secuelas. Se estudiaron 21 bebés prematuros mexicanos y se comprobó que, después del entrenamiento, los padres se sentían más capaces de estimular a sus hijos. A los bebés se les aplicó una prueba de lenguaje al año y a los tres años de edad; en ambas obtuvieron puntajes normales para su edad. Se concluye que los padres son buenos promotores del lenguaje en bebés prematuros. Palabras clave. Intervención temprana, lenguaje, prematurez, desarrollo del lenguaje, educación de padres.

Research paper thumbnail of Early detection and treatment of cognitive deficits in preterm infants

International Journal of Psychophysiology, Oct 1, 2016

Research paper thumbnail of Visuospatial Working Memory in Toddlers with a History of Periventricular Leukomalacia: An EEG Narrow-Band Power Analysis

PLoS ONE, 2013

Background: Periventricular Leukomalacia (PVL) affects white matter, but grey matter injuries hav... more Background: Periventricular Leukomalacia (PVL) affects white matter, but grey matter injuries have also been reported, particularly in the dorsomedial nucleus and the cortex. Both structures have been related to working memory (WM) processes. The aim of this study was to compare behavioral performances and EEG power spectra during a visuospatial working memory task (VSWMT) of toddlers with a history of PVL and healthy toddlers. Methodology/Principal Findings: A prospective, comparative study of WM was conducted in toddlers with a history of PVL and healthy toddlers. The task responses and the EEG narrow-band power spectra during a VSWMT were compared in both groups. The EEG absolute power was analyzed during the following three conditions: baseline, attention and WM retention. The number of correct responses was higher in the healthy group (20.565.0) compared to the PVL group (16.163.9) (p = 0.04). The healthy group had absolute power EEG increases (p#0.05) during WM compared to the attention condition in the bilateral frontal and right temporal, parietal and occipital regions in frequencies ranging from 1.17 to 2.34 Hz and in the right temporal, parietal and occipital regions in frequencies ranging from 14.06 to 15.23 Hz. In contrast, the PVL group had absolute power increases (p#0.05) in the bilateral fronto-parietal, left central and occipital regions in frequencies that ranged from 1.17 to 3.52 Hz and in the bilateral frontal and right temporal regions in frequencies ranging from 9.37 to 19.14 Hz. Conclusions/Significance: This study provides evidence that PVL toddlers have visuospatial WM deficits and a very different pattern of absolute power increases compared to a healthy group of toddlers, with greater absolute power in the low frequency range and widespread neuronal networks in the WM retention phase.

Research paper thumbnail of Exploratory EEG data analysis for neurophysiological experiments

Proceedings of the 25th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (IEEE Cat. No.03CH37439)

ABSTRACT A method for the exploratory analysis of (EEG) data for neurophysiological experiments i... more ABSTRACT A method for the exploratory analysis of (EEG) data for neurophysiological experiments is presented. It is based on a time-frequency decomposition of the EEG time series, which is measured at a number of electrodes in the skull surface, and includes: the computation of a statistic that measures the deviations of the log-power with respect to the pre-stimulus average; the computation of a significance index for these deviations, and the segmentation of the time-frequency plane into regions with uniform activation patterns. As particular example, an experiment to study EEG changes during figure and word categorization is analyzed in detail.

Research paper thumbnail of 3D Statistical Parametric Mapping of quiet sleep EEG in the first year of life

NeuroImage, 2012

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are

Research paper thumbnail of Do Specific EEG Frequencies Indicate Different Processes During Mental Calculation?

Neuroscience …, 1999

EEG recordings during mental calculation and a control task (with presentation of stimuli with si... more EEG recordings during mental calculation and a control task (with presentation of stimuli with similar physical characteristics to the arithmetic symbols) were obtained in 10 subjects. Narrow band analyses of the EEG and distributed sources for each EEG frequency were calculated using variable resolution electromagnetic tomography. Signi®cant differences between the sources for arithmetic and control tasks were observed at 3.9 Hz within Broca's and left parietotemporal cortices, suggesting that this frequency may be related with the production of internal speech, storage and rehearsal of verbal working memory. Differences at 5.46 Hz within the right dorsolateral prefrontal cortex were considered to be associated to sustained attention. The decrease at 12.46 Hz within the left parietal cortex was interpreted as a sign of retrieval of arithmetic facts from long term memory.

Research paper thumbnail of Changes In EEG Current Sources Induced by Neurofeedback In Learning Disabled Children. An Exploratory Study

Applied …, 2007

The objective of this work was to explore Neurofeedback (NFB) effects on EEG current sources in L... more The objective of this work was to explore Neurofeedback (NFB) effects on EEG current sources in Learning Disabled (LD) children, and to corroborate its beneficial consequences on behavioral and cognitive performance. NFB was given in twenty 30-min sessions to 11 LD children to reduce their abnormally high theta/alpha ratios (Experimental Group). Another five LD children with the same characteristics received a placebo treatment (Control Group). In the Control Group no changes in behavior or EEG current source were observed. In the Experimental Group, immediately after treatment children showed behavioral and cognitive improvements, but current source analysis showed few modifications; however, 2 months after treatment many changes occurred: a decrease in current of frequencies within the theta band, mainly in left frontal and cingulate regions, and enhancement in current of frequencies within the alpha band, principally in the right temporal lobe and right frontal regions, and of frequencies within the beta band, mainly in left temporal, right frontal and cingulate cortex regions. In conclusion, NFB is a possibly efficacious treatment for LD children with an abnormally high theta/alpha ratio in any lead. The changes observed in EEG current sources may reflect the neurophysiological bases of the improvement that children experienced in their behavioral and cognitive activities.

Research paper thumbnail of Delayed P300 During Sternberg and Color Discrimination Tasks In Poor Readers

International Journal of …, 2001

The P300 ERP component was studied in poor and normal readers, using Sternberg and color discrimi... more The P300 ERP component was studied in poor and normal readers, using Sternberg and color discrimination (Spaceships) tasks. During the first one, subjects must decide if a probe item belongs or not to a set of digits previously presented. In the second one, the participants must ...

Research paper thumbnail of Changes in EEG Current Sources Induced by Neurofeedback in Learning Disabled Children. An Exploratory Study

Applied Psychophysiology and Biofeedback, 2007

Research paper thumbnail of Neurofeedback in healthy elderly human subjects with electroencephalographic risk for cognitive disorder

Journal of Alzheimer's disease : JAD, 2012

In normal elderly subjects, the best electroencephalogram (EEG)-based predictor of cognitive impa... more In normal elderly subjects, the best electroencephalogram (EEG)-based predictor of cognitive impairment is theta EEG activity abnormally high for their age. The goal of this work was to explore the effectiveness of a neurofeedback (NFB) protocol in reducing theta EEG activity in normal elderly subjects who present abnormally high theta absolute power (AP). Fourteen subjects were randomly assigned to either the experimental group or the control group; the experimental group received a reward (tone of 1000 Hz) when the theta AP was reduced, and the control group received a placebo treatment, a random administration of the same tone. The results show that the experimental group exhibits greater improvement in EEG and behavioral measures. However, subjects of the control group also show improved EEG values and in memory, which may be attributed to a placebo effect. However, the effect of the NFB treatment was clear in the EG, although a placebo effect may also have been present.

Research paper thumbnail of 3D statistical parametric mapping of EEG source spectra by means of Variable Resolution Electromagnetic Tomography (VARETA)

This article describes a new method for 3D QEEG tomography in the frequency domain. A variant of ... more This article describes a new method for 3D QEEG tomography in the frequency domain. A variant of Statistical Parametric Mapping is presented for source log spectra. Sources are estimated by means of a Discrete Spline EEG inverse solution known as Variable Resolution Electromagnetic Tomography (VARETA). Anatomical constraints are incorporated by the use of the Montreal Neurological Institute (MNI) probabilistic brain atlas. Efficient methods are developed for frequency domain VARETA in order to estimate the source spectra for the set of 10(3)-10(5) voxels that comprise an EEG/MEG inverse solution. High resolution source Z spectra are then defined with respect to the age dependent mean and standard deviations of each voxel, which are summarized as regression equations calculated from the Cuban EEG normative database. The statistical issues involved are addressed by the use of extreme value statistics. Examples are shown that illustrate the potential clinical utility of the methods herein developed.

Research paper thumbnail of N400 and lexical decisions: automatic or controlled processing?

Clinical Neurophysiology, 1999

Objective: To investigate whether the N400 effect is sensitive to automatic or controlled process... more Objective: To investigate whether the N400 effect is sensitive to automatic or controlled processes.Methods: Two experiments were performed. In one experiment, directly related word pairs were used. In the other experiment, mediated-related word pairs were used. In order to reduce controlled processes, each experiment consisted of 3 tasks: Low- and high-proportion of related pairs, and single presentation lexical decision task.Results:

Research paper thumbnail of Sources of abnormal EEG activity in brain infarctions

Clinical EEG (electroencephalography), 2000

EEGs from 16 patients with stroke in three different stages of evolution were recorded. EEG sourc... more EEGs from 16 patients with stroke in three different stages of evolution were recorded. EEG sources were calculated every 0.39 Hz by frequency domain VARETA. The main source was within the delta band in 2 out of 4 chronic patients, and in 67% of the patients in the acute or subacute stages when edema (cytotoxic or vasogenic) was present. Moreover, all patients showed abnormal activity in the theta band. Sources of abnormal activity in cortical or corticosubcortical infarcts were located in the cortex, surrounding the lesion. At the site of the infarct, a decrease of EEG power was observed. Sources of abnormal theta power coincided with edema and/or ischemic penumbra.

Research paper thumbnail of Registration of brain MRI of patients with a tumor

... A. Gonzalez'i2, JL Marroquin', S. Botello', F. Calderon3, P. Valde... more ... A. Gonzalez'i2, JL Marroquin', S. Botello', F. Calderon3, P. Valdes4, E. Aubert4, J. Bosch4, A. Fernandez-Bouzas' ,T Harmony ... CA Cocosco, V. Kollokian, RK4. Kwan, AC Evans: “Brainweb: Online Interface to a 3D MRI Simulated Brain Database“ Neurolmage, vo1.5, no.4, part 214 ...

Research paper thumbnail of Longitudinal quantitative EEG study of children with different performances on a reading-writing test

Electroencephalography and Clinical Neurophysiology, 1995

In a previous paper, using the same test for the evaluation of reading-writing abilities, reporte... more In a previous paper, using the same test for the evaluation of reading-writing abilities, reported that children with severe difficulties had more delta in fronto-temporal regions, and this was interpreted as a sign of underlying cerebral dysfunction. Children with severe and minor difficulties in the test had more diffuse theta absolute and relative powers and less alpha relative power. As theta decreases with age, while alpha increases, these results suggested that children with minor and severe difficulties in reading had a maturational lag with respect to those with normal performance. We conducted this study in order to test this hypothesis. Two different EEG records were obtained with an interval of 2.58-3.15 years in 49 children classified in 3 groups according to their performance in a reading-writing test. Group 1: adequate performance for age and degree (control group); group 2: below level performance with minor difficulties; and group 3: below level performance, with severe difficulties. The mean age of the groups in the first study was 9 years. Absolute (AP) and relative powers (RP) in the delta, theta, alpha and beta bands were computed for each session. In general, groups 3 and 2 showed greater changes than group 1 from session to session. ANOVAs performed by session clearly demonstrate many significant differences between groups in the first study, while few significant differences in parieto-occipital regions in theta RP were observed in the second session. These results point toward a maturational spurt of children from groups 2 and 3.

Research paper thumbnail of EEG activation patterns during the performance of tasks involving different components of mental calculation

Electroencephalography and Clinical Neurophysiology, 1995

In this study we demonstrate the existence of different patterns of EEG activation during the per... more In this study we demonstrate the existence of different patterns of EEG activation during the performance of 4 different tasks involving different components of mental calculation in normal subjects. The EEG was recorded in all monopolar leads of the 10/20 system using linked ear lobes as reference. Absolute and relative power were calculated in the delta (1.5-3.5 Hz), theta (3.5-7.5 Hz), alpha (7.5-12.5 Hz) and beta (12.5-19 Hz) bands. The tasks were presented randomly and the EEG segments preceding presentation of the stimulus were considered as the rest corresponding to the task requested by the stimulus. Tasks were of 4 different types, involving number comprehension, recogaition of mathematical symbols, the calculation process and the spatial component. ANOVAs between the rest periods showed no differences in any band. Neither did ANOVAs between tasks. However, other variables (task minus rest), which were calculated as the differences in power between task and rest respectively, showed significant differences between tasks in the delta and beta bands in the frontal lobes. In addition, new variables were calculated as the difference between tasks, since many factors were common across several tasks. These variables correspond to the EEG change due to a specific component of mental calculation. Significant differences were obtained in delta and theta bands in fight posterior areas and in the beta band in frontal areas. We concluded that the EEG differences obse~:ved during different components of mental calculation suggest the participation of different networks.

Research paper thumbnail of Sources of Abnormal EEG Activity in Spontaneous Intracerebral Hemorrhage

Clinical EEG and Neuroscience, 2002

This report describes the results obtained with EEG source analysis in the frequency domain (FD-V... more This report describes the results obtained with EEG source analysis in the frequency domain (FD-VARETA), in 14 patients with brain hemorrhages; 6 hemorrhages were located in the putaminal region, 1 was mesencephalic and 7 were lobar cerebral hemorrhages. Our goal was to evaluate FD-VARETA accuracy for the localization of fast growth expansive brain lesions. FD-VARETA produces brain electromagnetic tomography images of EEG sources in every frequency. The location of the most abnormal or the maximum Z value across all frequencies was compared with the location of spontaneous hemorrhages in computed tomographies (CT). In all patients the main source was within delta or theta bands. The spatial extent of the sources, in the brain atlas, at these frequency values was almost the same as the volume of hematoma in CT. Putaminal lesions produced larger regions of cortical deafferentation than lobar hematomas, with higher abnormal Z values. FD-VARETA was more accurate in locating the lesions than traditional maps of absolute and relative power in delta, theta, alpha and beta bands. FD-VARETA is a valuable procedure for the functional evaluation of brain hemorrhages.

Research paper thumbnail of EEG Maturation on Children with Different Economic and Psychosocial Characteristics

International Journal of Neuroscience, 1988

It has been shown that EEG maturation can be described in terms of regression equations on age of... more It has been shown that EEG maturation can be described in terms of regression equations on age of broad band EEG frequency parameters. In the present paper six groups of children with different economic and psychosocial characteristics of three countries were studied. Regression equations on age of the EEG relative power (expressed in percentages of the total EEG activity) in the delta, theta, alpha and beta bands in 8 bipolar derivations were computed in each group of children and the slopes compared with those previously published by John et al. (1980). Those children who grew up with adequate nutritional, sanitary and cultural environmental conditions showed the same slopes as U.S. and Swedish children selected with strict criteria of normality. Children nourished in poor socioeconomic and sanitary environments and who frequently had pathological personal antecedents with risk factors associated with brain damage showed either a slow maturation of the EEG characterized by smaller slopes of theta relative power or a great variance of EEG parameters and no relation of these parameters to age.

Research paper thumbnail of Relationship of specific EEG frequencies at specific brain areas with performance

NeuroReport, 1998

THIS study shows that incorrect responses are preceded by different EEG characteristics than corr... more THIS study shows that incorrect responses are preceded by different EEG characteristics than correct responses, and that these differences appear in specific brain regions that participate in each particular task. EEGs were recorded in children during three different tasks: color discrimination (CDT), verbal working memory (VWM), and word categorization task (WCT). EEG segments previous to the presentation of the stimulus were analysed. Incorrect responses were preceded by lower EEG power values at 7. 8 Hz in posterior temporal and right parietal leads in CDT, 8.59 and 9.3 6 Hz in frontal areas in VWM, and 10.7 2 Hz in the left hemisphere in WCT. In the former task > 1.56 Hz power in frontal areas prior to an incorrect response was also observed. NeuroReport 9: 3681-3687

Research paper thumbnail of Specific EEG frequencies at specific brain areas and performance

NeuroReport, 2000

In this study it was shown that in adults, the frequency characteristics of EEG preceding stimuli... more In this study it was shown that in adults, the frequency characteristics of EEG preceding stimuli that were followed by incorrect responses were different from the characteristics of EEG preceding stimuli that were followed by correct responses. In the recording during three different tasks that explore different neuronal networks, higher values of current preceding incorrect performance in those areas directly related to the task were found in frequencies within the delta (1.56 and 3.12 Hz) and beta bands (13.26, 14.04, 14.82, 15.6, 17.16 and 17.94 Hz), suggesting that these frequencies signal inhibition. Frequencies within the alpha band (9.36 and 12.48 Hz) showed greater energy preceding correct responses in task-specific areas, supporting previous results observed in children.

Research paper thumbnail of Los padres como promotores del desarrollo de lenguaje de bebés prematuros: propuesta de intervención temprana

Actualidades en Psicología, May 15, 2018

Los padres como promotores del desarrollo de lenguaje de bebés prematuros: propuesta de intervenc... more Los padres como promotores del desarrollo de lenguaje de bebés prematuros: propuesta de intervención temprana Resumen. Cualquier programa de intervención puede beneficiarse de la participación de los padres, pero es necesario darles información de cómo pueden estimular el lenguaje de sus hijos. El objetivo fue entrenar a los padres acerca de lo que debían esperar del desarrollo del lenguaje de sus hijos y brindarles técnicas de estimulación de este para evitar secuelas. Se estudiaron 21 bebés prematuros mexicanos y se comprobó que, después del entrenamiento, los padres se sentían más capaces de estimular a sus hijos. A los bebés se les aplicó una prueba de lenguaje al año y a los tres años de edad; en ambas obtuvieron puntajes normales para su edad. Se concluye que los padres son buenos promotores del lenguaje en bebés prematuros. Palabras clave. Intervención temprana, lenguaje, prematurez, desarrollo del lenguaje, educación de padres.

Research paper thumbnail of Early detection and treatment of cognitive deficits in preterm infants

International Journal of Psychophysiology, Oct 1, 2016

Research paper thumbnail of Visuospatial Working Memory in Toddlers with a History of Periventricular Leukomalacia: An EEG Narrow-Band Power Analysis

PLoS ONE, 2013

Background: Periventricular Leukomalacia (PVL) affects white matter, but grey matter injuries hav... more Background: Periventricular Leukomalacia (PVL) affects white matter, but grey matter injuries have also been reported, particularly in the dorsomedial nucleus and the cortex. Both structures have been related to working memory (WM) processes. The aim of this study was to compare behavioral performances and EEG power spectra during a visuospatial working memory task (VSWMT) of toddlers with a history of PVL and healthy toddlers. Methodology/Principal Findings: A prospective, comparative study of WM was conducted in toddlers with a history of PVL and healthy toddlers. The task responses and the EEG narrow-band power spectra during a VSWMT were compared in both groups. The EEG absolute power was analyzed during the following three conditions: baseline, attention and WM retention. The number of correct responses was higher in the healthy group (20.565.0) compared to the PVL group (16.163.9) (p = 0.04). The healthy group had absolute power EEG increases (p#0.05) during WM compared to the attention condition in the bilateral frontal and right temporal, parietal and occipital regions in frequencies ranging from 1.17 to 2.34 Hz and in the right temporal, parietal and occipital regions in frequencies ranging from 14.06 to 15.23 Hz. In contrast, the PVL group had absolute power increases (p#0.05) in the bilateral fronto-parietal, left central and occipital regions in frequencies that ranged from 1.17 to 3.52 Hz and in the bilateral frontal and right temporal regions in frequencies ranging from 9.37 to 19.14 Hz. Conclusions/Significance: This study provides evidence that PVL toddlers have visuospatial WM deficits and a very different pattern of absolute power increases compared to a healthy group of toddlers, with greater absolute power in the low frequency range and widespread neuronal networks in the WM retention phase.

Research paper thumbnail of Exploratory EEG data analysis for neurophysiological experiments

Proceedings of the 25th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (IEEE Cat. No.03CH37439)

ABSTRACT A method for the exploratory analysis of (EEG) data for neurophysiological experiments i... more ABSTRACT A method for the exploratory analysis of (EEG) data for neurophysiological experiments is presented. It is based on a time-frequency decomposition of the EEG time series, which is measured at a number of electrodes in the skull surface, and includes: the computation of a statistic that measures the deviations of the log-power with respect to the pre-stimulus average; the computation of a significance index for these deviations, and the segmentation of the time-frequency plane into regions with uniform activation patterns. As particular example, an experiment to study EEG changes during figure and word categorization is analyzed in detail.

Research paper thumbnail of 3D Statistical Parametric Mapping of quiet sleep EEG in the first year of life

NeuroImage, 2012

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are

Research paper thumbnail of Do Specific EEG Frequencies Indicate Different Processes During Mental Calculation?

Neuroscience …, 1999

EEG recordings during mental calculation and a control task (with presentation of stimuli with si... more EEG recordings during mental calculation and a control task (with presentation of stimuli with similar physical characteristics to the arithmetic symbols) were obtained in 10 subjects. Narrow band analyses of the EEG and distributed sources for each EEG frequency were calculated using variable resolution electromagnetic tomography. Signi®cant differences between the sources for arithmetic and control tasks were observed at 3.9 Hz within Broca's and left parietotemporal cortices, suggesting that this frequency may be related with the production of internal speech, storage and rehearsal of verbal working memory. Differences at 5.46 Hz within the right dorsolateral prefrontal cortex were considered to be associated to sustained attention. The decrease at 12.46 Hz within the left parietal cortex was interpreted as a sign of retrieval of arithmetic facts from long term memory.

Research paper thumbnail of Changes In EEG Current Sources Induced by Neurofeedback In Learning Disabled Children. An Exploratory Study

Applied …, 2007

The objective of this work was to explore Neurofeedback (NFB) effects on EEG current sources in L... more The objective of this work was to explore Neurofeedback (NFB) effects on EEG current sources in Learning Disabled (LD) children, and to corroborate its beneficial consequences on behavioral and cognitive performance. NFB was given in twenty 30-min sessions to 11 LD children to reduce their abnormally high theta/alpha ratios (Experimental Group). Another five LD children with the same characteristics received a placebo treatment (Control Group). In the Control Group no changes in behavior or EEG current source were observed. In the Experimental Group, immediately after treatment children showed behavioral and cognitive improvements, but current source analysis showed few modifications; however, 2 months after treatment many changes occurred: a decrease in current of frequencies within the theta band, mainly in left frontal and cingulate regions, and enhancement in current of frequencies within the alpha band, principally in the right temporal lobe and right frontal regions, and of frequencies within the beta band, mainly in left temporal, right frontal and cingulate cortex regions. In conclusion, NFB is a possibly efficacious treatment for LD children with an abnormally high theta/alpha ratio in any lead. The changes observed in EEG current sources may reflect the neurophysiological bases of the improvement that children experienced in their behavioral and cognitive activities.

Research paper thumbnail of Delayed P300 During Sternberg and Color Discrimination Tasks In Poor Readers

International Journal of …, 2001

The P300 ERP component was studied in poor and normal readers, using Sternberg and color discrimi... more The P300 ERP component was studied in poor and normal readers, using Sternberg and color discrimination (Spaceships) tasks. During the first one, subjects must decide if a probe item belongs or not to a set of digits previously presented. In the second one, the participants must ...

Research paper thumbnail of Changes in EEG Current Sources Induced by Neurofeedback in Learning Disabled Children. An Exploratory Study

Applied Psychophysiology and Biofeedback, 2007

Research paper thumbnail of Neurofeedback in healthy elderly human subjects with electroencephalographic risk for cognitive disorder

Journal of Alzheimer's disease : JAD, 2012

In normal elderly subjects, the best electroencephalogram (EEG)-based predictor of cognitive impa... more In normal elderly subjects, the best electroencephalogram (EEG)-based predictor of cognitive impairment is theta EEG activity abnormally high for their age. The goal of this work was to explore the effectiveness of a neurofeedback (NFB) protocol in reducing theta EEG activity in normal elderly subjects who present abnormally high theta absolute power (AP). Fourteen subjects were randomly assigned to either the experimental group or the control group; the experimental group received a reward (tone of 1000 Hz) when the theta AP was reduced, and the control group received a placebo treatment, a random administration of the same tone. The results show that the experimental group exhibits greater improvement in EEG and behavioral measures. However, subjects of the control group also show improved EEG values and in memory, which may be attributed to a placebo effect. However, the effect of the NFB treatment was clear in the EG, although a placebo effect may also have been present.

Research paper thumbnail of 3D statistical parametric mapping of EEG source spectra by means of Variable Resolution Electromagnetic Tomography (VARETA)

This article describes a new method for 3D QEEG tomography in the frequency domain. A variant of ... more This article describes a new method for 3D QEEG tomography in the frequency domain. A variant of Statistical Parametric Mapping is presented for source log spectra. Sources are estimated by means of a Discrete Spline EEG inverse solution known as Variable Resolution Electromagnetic Tomography (VARETA). Anatomical constraints are incorporated by the use of the Montreal Neurological Institute (MNI) probabilistic brain atlas. Efficient methods are developed for frequency domain VARETA in order to estimate the source spectra for the set of 10(3)-10(5) voxels that comprise an EEG/MEG inverse solution. High resolution source Z spectra are then defined with respect to the age dependent mean and standard deviations of each voxel, which are summarized as regression equations calculated from the Cuban EEG normative database. The statistical issues involved are addressed by the use of extreme value statistics. Examples are shown that illustrate the potential clinical utility of the methods herein developed.

Research paper thumbnail of N400 and lexical decisions: automatic or controlled processing?

Clinical Neurophysiology, 1999

Objective: To investigate whether the N400 effect is sensitive to automatic or controlled process... more Objective: To investigate whether the N400 effect is sensitive to automatic or controlled processes.Methods: Two experiments were performed. In one experiment, directly related word pairs were used. In the other experiment, mediated-related word pairs were used. In order to reduce controlled processes, each experiment consisted of 3 tasks: Low- and high-proportion of related pairs, and single presentation lexical decision task.Results:

Research paper thumbnail of Sources of abnormal EEG activity in brain infarctions

Clinical EEG (electroencephalography), 2000

EEGs from 16 patients with stroke in three different stages of evolution were recorded. EEG sourc... more EEGs from 16 patients with stroke in three different stages of evolution were recorded. EEG sources were calculated every 0.39 Hz by frequency domain VARETA. The main source was within the delta band in 2 out of 4 chronic patients, and in 67% of the patients in the acute or subacute stages when edema (cytotoxic or vasogenic) was present. Moreover, all patients showed abnormal activity in the theta band. Sources of abnormal activity in cortical or corticosubcortical infarcts were located in the cortex, surrounding the lesion. At the site of the infarct, a decrease of EEG power was observed. Sources of abnormal theta power coincided with edema and/or ischemic penumbra.

Research paper thumbnail of Registration of brain MRI of patients with a tumor

... A. Gonzalez'i2, JL Marroquin', S. Botello', F. Calderon3, P. Valde... more ... A. Gonzalez'i2, JL Marroquin', S. Botello', F. Calderon3, P. Valdes4, E. Aubert4, J. Bosch4, A. Fernandez-Bouzas' ,T Harmony ... CA Cocosco, V. Kollokian, RK4. Kwan, AC Evans: “Brainweb: Online Interface to a 3D MRI Simulated Brain Database“ Neurolmage, vo1.5, no.4, part 214 ...

Research paper thumbnail of Longitudinal quantitative EEG study of children with different performances on a reading-writing test

Electroencephalography and Clinical Neurophysiology, 1995

In a previous paper, using the same test for the evaluation of reading-writing abilities, reporte... more In a previous paper, using the same test for the evaluation of reading-writing abilities, reported that children with severe difficulties had more delta in fronto-temporal regions, and this was interpreted as a sign of underlying cerebral dysfunction. Children with severe and minor difficulties in the test had more diffuse theta absolute and relative powers and less alpha relative power. As theta decreases with age, while alpha increases, these results suggested that children with minor and severe difficulties in reading had a maturational lag with respect to those with normal performance. We conducted this study in order to test this hypothesis. Two different EEG records were obtained with an interval of 2.58-3.15 years in 49 children classified in 3 groups according to their performance in a reading-writing test. Group 1: adequate performance for age and degree (control group); group 2: below level performance with minor difficulties; and group 3: below level performance, with severe difficulties. The mean age of the groups in the first study was 9 years. Absolute (AP) and relative powers (RP) in the delta, theta, alpha and beta bands were computed for each session. In general, groups 3 and 2 showed greater changes than group 1 from session to session. ANOVAs performed by session clearly demonstrate many significant differences between groups in the first study, while few significant differences in parieto-occipital regions in theta RP were observed in the second session. These results point toward a maturational spurt of children from groups 2 and 3.

Research paper thumbnail of EEG activation patterns during the performance of tasks involving different components of mental calculation

Electroencephalography and Clinical Neurophysiology, 1995

In this study we demonstrate the existence of different patterns of EEG activation during the per... more In this study we demonstrate the existence of different patterns of EEG activation during the performance of 4 different tasks involving different components of mental calculation in normal subjects. The EEG was recorded in all monopolar leads of the 10/20 system using linked ear lobes as reference. Absolute and relative power were calculated in the delta (1.5-3.5 Hz), theta (3.5-7.5 Hz), alpha (7.5-12.5 Hz) and beta (12.5-19 Hz) bands. The tasks were presented randomly and the EEG segments preceding presentation of the stimulus were considered as the rest corresponding to the task requested by the stimulus. Tasks were of 4 different types, involving number comprehension, recogaition of mathematical symbols, the calculation process and the spatial component. ANOVAs between the rest periods showed no differences in any band. Neither did ANOVAs between tasks. However, other variables (task minus rest), which were calculated as the differences in power between task and rest respectively, showed significant differences between tasks in the delta and beta bands in the frontal lobes. In addition, new variables were calculated as the difference between tasks, since many factors were common across several tasks. These variables correspond to the EEG change due to a specific component of mental calculation. Significant differences were obtained in delta and theta bands in fight posterior areas and in the beta band in frontal areas. We concluded that the EEG differences obse~:ved during different components of mental calculation suggest the participation of different networks.

Research paper thumbnail of Sources of Abnormal EEG Activity in Spontaneous Intracerebral Hemorrhage

Clinical EEG and Neuroscience, 2002

This report describes the results obtained with EEG source analysis in the frequency domain (FD-V... more This report describes the results obtained with EEG source analysis in the frequency domain (FD-VARETA), in 14 patients with brain hemorrhages; 6 hemorrhages were located in the putaminal region, 1 was mesencephalic and 7 were lobar cerebral hemorrhages. Our goal was to evaluate FD-VARETA accuracy for the localization of fast growth expansive brain lesions. FD-VARETA produces brain electromagnetic tomography images of EEG sources in every frequency. The location of the most abnormal or the maximum Z value across all frequencies was compared with the location of spontaneous hemorrhages in computed tomographies (CT). In all patients the main source was within delta or theta bands. The spatial extent of the sources, in the brain atlas, at these frequency values was almost the same as the volume of hematoma in CT. Putaminal lesions produced larger regions of cortical deafferentation than lobar hematomas, with higher abnormal Z values. FD-VARETA was more accurate in locating the lesions than traditional maps of absolute and relative power in delta, theta, alpha and beta bands. FD-VARETA is a valuable procedure for the functional evaluation of brain hemorrhages.

Research paper thumbnail of EEG Maturation on Children with Different Economic and Psychosocial Characteristics

International Journal of Neuroscience, 1988

It has been shown that EEG maturation can be described in terms of regression equations on age of... more It has been shown that EEG maturation can be described in terms of regression equations on age of broad band EEG frequency parameters. In the present paper six groups of children with different economic and psychosocial characteristics of three countries were studied. Regression equations on age of the EEG relative power (expressed in percentages of the total EEG activity) in the delta, theta, alpha and beta bands in 8 bipolar derivations were computed in each group of children and the slopes compared with those previously published by John et al. (1980). Those children who grew up with adequate nutritional, sanitary and cultural environmental conditions showed the same slopes as U.S. and Swedish children selected with strict criteria of normality. Children nourished in poor socioeconomic and sanitary environments and who frequently had pathological personal antecedents with risk factors associated with brain damage showed either a slow maturation of the EEG characterized by smaller slopes of theta relative power or a great variance of EEG parameters and no relation of these parameters to age.

Research paper thumbnail of Relationship of specific EEG frequencies at specific brain areas with performance

NeuroReport, 1998

THIS study shows that incorrect responses are preceded by different EEG characteristics than corr... more THIS study shows that incorrect responses are preceded by different EEG characteristics than correct responses, and that these differences appear in specific brain regions that participate in each particular task. EEGs were recorded in children during three different tasks: color discrimination (CDT), verbal working memory (VWM), and word categorization task (WCT). EEG segments previous to the presentation of the stimulus were analysed. Incorrect responses were preceded by lower EEG power values at 7. 8 Hz in posterior temporal and right parietal leads in CDT, 8.59 and 9.3 6 Hz in frontal areas in VWM, and 10.7 2 Hz in the left hemisphere in WCT. In the former task > 1.56 Hz power in frontal areas prior to an incorrect response was also observed. NeuroReport 9: 3681-3687

Research paper thumbnail of Specific EEG frequencies at specific brain areas and performance

NeuroReport, 2000

In this study it was shown that in adults, the frequency characteristics of EEG preceding stimuli... more In this study it was shown that in adults, the frequency characteristics of EEG preceding stimuli that were followed by incorrect responses were different from the characteristics of EEG preceding stimuli that were followed by correct responses. In the recording during three different tasks that explore different neuronal networks, higher values of current preceding incorrect performance in those areas directly related to the task were found in frequencies within the delta (1.56 and 3.12 Hz) and beta bands (13.26, 14.04, 14.82, 15.6, 17.16 and 17.94 Hz), suggesting that these frequencies signal inhibition. Frequencies within the alpha band (9.36 and 12.48 Hz) showed greater energy preceding correct responses in task-specific areas, supporting previous results observed in children.