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Harmony T, Fernández T, Silva J, Bernal J, Díaz-Comas L, Reyes A, Marosi E, Rodríguez M, Rodríguez M. EEG delta activity: an indicator of attention to internal processing during performance of mental tasks. Int J Psychophysiol 1996; 24:161-71. [PMID: 8978441 DOI: 10.1016/s0167-8760(96)00053-0] [Citation(s) in RCA: 235] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
In previous papers we proposed that an increase in delta EEG activity during mental tasks might be related to an increase in subjects' attention to internal processing. In this paper we have made a narrow band analysis to detect those EEG frequencies that change selectively during the performance of a mental task that requires attention to internal processing. Two different experiments were performed: (1) a difficult mental calculation task and a control stimulus with the same physical characteristics as the arithmetical symbols were presented in random order; (2) the Sternberg paradigm for the analysis of short term memory using a memory set of 5 or 3 digits was also presented in random order. Referential recordings to linked ears were obtained in all leads of the 10/20 system. In the first experiment, the increase of power from 1.56 to 5.46 Hz was observed only during the performance of the task and not during the control condition. In the Sternberg paradigm, the increase of power from 1.56 to 3.90 Hz was greater during the difficult than during the easy condition. These results support our hypothesis that an increase in delta activity may be related to attention to internal processing during the performance of a mental task.
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Clinical Trial |
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John ER, Karmel BZ, Corning WC, Easton P, Brown D, Ahn H, John M, Harmony T, Prichep L, Toro A, Gerson I, Bartlett F, Thatcher F, Kaye H, Valdes P, Schwartz E. Neurometrics. Science 1977; 196:1393-410. [PMID: 867036 DOI: 10.1126/science.867036] [Citation(s) in RCA: 199] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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48 |
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Bosch-Bayard J, Valdés-Sosa P, Virues-Alba T, Aubert-Vázquez E, John ER, Harmony T, Riera-Díaz J, Trujillo-Barreto N. 3D Statistical Parametric Mapping of EEG Source Spectra by Means of Variable Resolution Electromagnetic Tomography (VARETA). ACTA ACUST UNITED AC 2016; 32:47-61. [PMID: 11360721 DOI: 10.1177/155005940103200203] [Citation(s) in RCA: 154] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
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 103–105 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.
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Fernández T, Harmony T, Rodríguez M, Bernal J, Silva J, Reyes A, Marosi E. EEG activation patterns during the performance of tasks involving different components of mental calculation. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1995; 94:175-82. [PMID: 7536152 DOI: 10.1016/0013-4694(94)00262-j] [Citation(s) in RCA: 112] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
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, recognition 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 right posterior areas and in the beta band in frontal areas. We concluded that the EEG differences observed during different components of mental calculation suggest the participation of different networks.
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Harmony T, Marosi E, Díaz de León AE, Becker J, Fernández T. Effect of sex, psychosocial disadvantages and biological risk factors on EEG maturation. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1990; 75:482-91. [PMID: 1693893 DOI: 10.1016/0013-4694(90)90135-7] [Citation(s) in RCA: 94] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Broad-band frequency analysis was performed on the EEGs of school-age children in order to study the effects of sex, socioeconomic status (SES) and biological risk factors on EEG maturation. Absolute power and relative power in delta, theta, alpha and beta frequency bands were computed in monopolar recordings from F3, F4, C3, C4, P3, P4, O1, O2, F7, F8, T3, T4, T5 and T6. Total absolute power and power in the delta and theta bands decreased with age, following a quadratic polynomial expression. Relative power followed a linear regression with age. Delta and theta decreased while alpha and beta increased. Sex differences in relative power were observed, possibly related to a pubertal spurt: slopes of regression equations were steeper in girls than in boys. Children from low SES (very low income and/or illiterate mother) had higher values of absolute power and a higher percentage of delta and lower of alpha than children with good SES, suggesting a maturational lag. A group of children with personal antecedents of risk factors associated with brain damage were compared with children without antecedents. The former group had higher values of absolute power. Depending on the severity of the risk, children with more severe antecedents had greater differences from children with no antecedents than children in whom antecedents were considered as slight. Risk antecedents had no effect on relative power.
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Harmony T, Fernández T, Silva J, Bosch J, Valdés P, Fernández-Bouzas A, Galán L, Aubert E, Rodríguez D. Do specific EEG frequencies indicate different processes during mental calculation? Neurosci Lett 1999; 266:25-8. [PMID: 10336175 DOI: 10.1016/s0304-3940(99)00244-x] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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. Significant 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.
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Clinical Trial |
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Marosi E, Harmony T, Sánchez L, Becker J, Bernal J, Reyes A, Díaz de León AE, Rodríguez M, Fernández T. Maturation of the coherence of EEG activity in normal and learning-disabled children. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1992; 83:350-7. [PMID: 1281080 DOI: 10.1016/0013-4694(92)90070-x] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The age effect on coherence has been studied in control (98) and learning-disabled (LD, 54) school-aged children (from 6.0 to 16.8 years old). The EEG recordings were made at rest in 15 leads, and 105 pairwise combinations for coherence were calculated (each lead was compared with all the rest) for delta, theta, alpha, beta and total frequency bands. A significant increase of coherence with age was found in both groups, with a different pattern of maturation. In the control group, a significant increase with age was found in the coherences between posterior regions and vertex (Cz). A significant decrease with age in the coherence between frontal areas was observed, especially in the theta band. The LD group showed a different pattern: no significant relation with age was found in the coherence between any lead and vertex. A high effect of age on coherence between temporal regions was observed with a predominance of the left side in comparison with the contralateral and the ipsilateral. No decrease in frontal coherence was found: in the same region where the control group showed negative values with age, the LD groups had no age effect. The results obtained are discussed as differences in brain organization, in myelogenesis and synaptogenesis and an explanation of the etiology of LD is proposed.
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Clinical Trial |
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Harmony T, Bernal J, Fernández T, Silva-Pereyra J, Fernández-Bouzas A, Marosi E, Rodríguez M, Reyes A. Primary task demands modulate P3a amplitude. BRAIN RESEARCH. COGNITIVE BRAIN RESEARCH 2000; 9:53-60. [PMID: 10666557 DOI: 10.1016/s0926-6410(99)00044-0] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Auditory event-related brain potentials (ERPs) were recorded from 10 subjects in two different conditions: (1) subjects were required to reorder five visually presented letters in order to form a word and provide a verbal response (task condition); (2) subjects were presented with a control stimulus with the same physical characteristics as the experimental stimulus, but containing just one type of letter (i.e., AAAAA). Subjects had to verbally respond to such stimuli by saying "A" (control condition). Tones of 1000 Hz (standard) and 1050 Hz (deviant) were also presented to the subjects in a 85%-15% probability paradigm 2 s before, during and 8 s after the presentation of the visual stimuli. Recordings were obtained from Fpz, Fz, Cz and Pz vs. linked ears. Auditory ERPs to the auditory stimuli after the presentation of the visual letter string and during the performance of the task were averaged for the standard and deviant tones in both conditions. Only correct responses were considered for the averages. The N100 was affected by stimulus type (standard vs. deviant) but not by condition (task vs. control); however, larger P3a waves were observed during the control than during the task condition. No significant differences between conditions were observed in the mismatch negativity (MMN) latency range. These results suggest that primary task demands modulate involuntary attention processing.
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Harmony T, Hinojosa G, Marosi E, Becker J, Rodriguez M, Reyes A, Rocha C. Correlation between EEG spectral parameters and an educational evaluation. Int J Neurosci 1990; 54:147-55. [PMID: 2265960 DOI: 10.3109/00207459008986630] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
EEG spectral parameters were computed in a group of children with different degrees of difficulty in learning to read and write. For statistical analyses, Z-transformed values according to normative age-regression equations were used to control the age effects. Canonical Correlation Analysis between absolute power in different bands and the categories of the educational evaluation (good, regular, poor and very poor) showed that more delta was probably related to a poor evaluation and more alpha in occipital areas to a good one. MONOVA also showed highly significant differences in the absolute power in many leads between children with different evaluations. As children with a poor evaluation very frequently had antecedents of risk factors related to brain damage and were from a low socioeconomic status, and both factors have been shown to affect absolute power, it may be that the differences observed were due to these causes. However, relative power correlated more with the learning problems. Children with minor difficulties, with no antecedents and with good socioeconomic status had more theta in almost all leads than children with a good evaluation and with the same characteristics. Children with a poor, or very poor, evaluation had more delta in left frontal and temporal areas (F3, F7 and T3) which may reflect underlying cerebral dysfunction of these regions directly involved in reading and writing processes.
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Fernández T, Herrera W, Harmony T, Díaz-Comas L, Santiago E, Sánchez L, Bosch J, Fernández-Bouzas A, Otero G, Ricardo-Garcell J, Barraza C, Aubert E, Galán L, Valdés R. EEG and behavioral changes following neurofeedback treatment in learning disabled children. ACTA ACUST UNITED AC 2004; 34:145-52. [PMID: 14521276 DOI: 10.1177/155005940303400308] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Neurofeedback (NFB) is an operant conditioning procedure, by which the subject learns to control his/her EEG activity. On one hand, Learning Disabled (LD) children have higher values of theta EEG absolute and relative power than normal children, and on the other hand, it has been shown that minimum alpha absolute power is necessary for adequate performance. Ten LD children were selected with higher than normal ratios of theta to alpha absolute power (theta/alpha). The Test Of Variables of Attention (TOVA) was applied. Children were divided into two groups in order to maintain similar IQ values, TOVA values, socioeconomical status, and gender for each group. In the experimental group, NFB was applied in the region with highest ratio, triggering a sound each time the ratio fell below a threshold value. Noncontingent reinforcement was given to the other group. Twenty half-hour sessions were applied, at a rate of 2 per week. At the end of the 20 sessions, TOVA, WISC and EEG were obtained. There was significant improvement in WISC performance in the experimental group that was not observed in the control group. EEG absolute power decreased in delta, theta, alpha and beta bands in the experimental group. Control children only showed a decrease in relative power in the delta band. All changes observed in the experimental group and not observed in the control group indicate better cognitive performance and the presence of greater EEG maturation in the experimental group, which suggests that changes were due not only to development but also to NFB treatment.
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Research Support, Non-U.S. Gov't |
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49 |
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Fernández-Bouzas A, Harmony T, Bosch J, Aubert E, Fernández T, Valdés P, Silva J, Marosi E, Martínez-López M, Casián G. Sources of abnormal EEG activity in the presence of brain lesions. CLINICAL EEG (ELECTROENCEPHALOGRAPHY) 1999; 30:46-52. [PMID: 10358783 DOI: 10.1177/155005949903000205] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In routine clinical EEG, a common origin is assumed for delta and theta rhythms produced by brain lesions. In previous papers, we have provided some experimental support, based on High Resolution qEEG and dipole fitting in the frequency domain, for the hypothesis that delta and theta spectral power have independent origins related to lesion and edema respectively. This paper describes the results obtained with Frequency Domain VARETA (FD-VARETA) in a group of 13 patients with cortical space-occupying lesions, in order to: 1) Test the accuracy of FD-VARETA for the localization of brain lesions, and 2) To provide further support for the independent origin of delta and theta components. FD VARETA is a distributed inverse solution, constrained by the Montreal Neurological Institute probabilistic atlas that estimates the spectra of EEG sources. In all patients, logarithmic transformed source spectra were compared with age-matched normative values, defining the Z source spectrum. Maximum Z values were found in 10 patients within the delta band (1.56 to 3.12 Hz); the spatial extent of these sources in the atlas corresponded with the location of the tumors in the CT. In 2 patients with small metastases and large volumes of edema and in a patient showing only edema, maximum Z values were found between 4.29 and 5.12 Hz. The spatial extent of the sources at these frequencies was within the volume of the edema in the CT. These results provided strong support to the hypothesis that both delta and theta abnormal EEG activities are the counterparts of two different pathophysiological processes.
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Becerra J, Fernández T, Harmony T, Caballero MI, García F, Fernández-Bouzas A, Santiago-Rodríguez E, Prado-Alcalá RA. Follow-up study of learning-disabled children treated with neurofeedback or placebo. Clin EEG Neurosci 2006; 37:198-203. [PMID: 16929704 DOI: 10.1177/155005940603700307] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This report is a 2-year follow-up to a previous study describing positive behavioral changes and a spurt of EEG maturation with theta/alpha neurofeedback (NFB) training in a group of Learning Disabled (LD) children. In a control paired group, treated with placebo, behavioral changes were not observed and the smaller maturational EEG changes observed were easily explained by increased age. Two years later, the EEG maturational lag in Control Group children increased, reaching abnormally high theta Relative Power values; the absence of positive behavioral changes continued and the neurological diagnosis remained LD. In contrast, after 2 years EEG maturation did continue in children who belonged to the Experimental Group with previous neurofeedback training; this was accompanied by positive behavioral changes, which were reflected in remission of LD symptoms.
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Controlled Clinical Trial |
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42 |
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Fernández T, Harmony T, Silva J, Galán L, Díaz-Comas L, Bosch J, Rodríguez M, Fernández-Bouzas A, Yáñez G, Otero G, Marosi E. Relationship of specific EEG frequencies at specific brain areas with performance. Neuroreport 1998; 9:3681-7. [PMID: 9858379 DOI: 10.1097/00001756-199811160-00021] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
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 9.36 Hz in frontal areas in VWM, and 10.72 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.
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Harmony T, Alvarez A, Pascual R, Ramos A, Marosi E, Díaz de León AE, Valdés P, Becker J. EEG maturation on children with different economic and psychosocial characteristics. Int J Neurosci 1988; 41:103-13. [PMID: 3410648 DOI: 10.3109/00207458808985747] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
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.
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Marosi E, Harmony T, Becker J, Reyes A, Bernal J, Fernández T, Rodríguez M, Silva J, Guerrero V. Electroencephalographic coherences discriminate between children with different pedagogical evaluation. Int J Psychophysiol 1995; 19:23-32. [PMID: 7790286 DOI: 10.1016/0167-8760(94)00059-n] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The relationship of reading-writing ability and EEG coherences was studied in 84 subjects from two age groups 7.0-8.9 and 9-11.2 years old. All children were divided into three groups according to their performance on a pedagogical test: ped1, normal children; ped2, children with mild problems; ped3, children with reading-writing disability. The following results were obtained: in general, children showed higher coherences in groups with poor performance in the delta, theta and beta bands. In the alpha band, higher coherence values were related to better performance. The exceptions to this general pattern were rare. Group ped2 had higher coherences in delta, theta and alpha bands than ped1 and ped3, in left temporal leads. In older children the same tendency was observed, but group differences in the theta, alpha and beta bands were few. In this age range, the significant group differences were almost all interhemispheric coherences. The discriminant analysis that classified subjects by their coherence values gave very good results, fact that demonstrates, that EEG coherence is a highly sensitive measurement indicating not only the existence of a reading-writing problem, but also the degree of its severity.
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Clinical Trial |
30 |
38 |
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Fernández T, Harmony T, Rodríguez M, Reyes A, Marosi E, Bernal J. Test-retest reliability of EEG spectral parameters during cognitive tasks: I. Absolute and relative power. Int J Neurosci 1993; 68:255-61. [PMID: 8063530 DOI: 10.3109/00207459308994280] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We analyzed test-retest reliability of Absolute (AP) and Relative Power (RP) during rest and during two cognitive tasks: one verbal, the search for a synonym, and the other consisting of mental arithmetic calculations. Under all conditions during the experiment the subjects had their eyes open. The experiment was performed twice, with a month's interval between each trial. Monopolar recordings were obtained in F3, F4, C3, C4, P3, P4, O1, O2, F7, F8, T3, T4, T5, T6 and Cz vs A1A2. Differences between sessions were observed mainly during rest with eyes open in the lapha band, with higher AP during the first session. During rest it is extremely difficult to control for the state of vigilance, anxiety and thinking. However, during cognitive tasks a more rigid control of the state of vigilance and thinking is obtained. Therefore, AP and RP are very reliable parameters for analyzing EEG during mental tasks. Comparisons between conditions were also made. The only significant differences observed were in delta AP in the second session, with more power during the cognitive tasks in C3 and O2. MANOVAs using the values of AP in the four bands showed significant differences between conditions in C3, C4, P3, O2 and T4. Several factors that may be involved in the origin of delta activity, including eye movements, slow potential shifts and the inhibition of cholinergic projections to the cortex, are discussed.
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Comparative Study |
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Harmony T, Marosi E, Becker J, Rodríguez M, Reyes A, Fernández T, Silva J, Bernal J. Longitudinal quantitative EEG study of children with different performances on a reading-writing test. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1995; 95:426-33. [PMID: 8536571 DOI: 10.1016/0013-4694(95)00135-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In a previous paper, using the same test for the evaluation of reading-writing abilities, Harmony et al. (1990b) 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.
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Harmony T, Ricardo J, Otero G, Fernandez G, Llorente S, Valdes P. Symmetry of the visual evoked potential in normal subjects. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1973; 35:237-40. [PMID: 4126173 DOI: 10.1016/0013-4694(73)90234-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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34 |
19
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Fernández-Bouzas A, Harmony T, Fernández T, Silva-Pereyra J, Valdés P, Bosch J, Aubert E, Casián G, Otero Ojeda G, Ricardo J, Hernández-Ballesteros A, Santiago E. Sources of abnormal EEG activity in brain infarctions. CLINICAL EEG (ELECTROENCEPHALOGRAPHY) 2000; 31:165-9. [PMID: 11056837 DOI: 10.1177/155005940003100403] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
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.
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20
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Silva-Pereyra J, Harmony T, Villanueva G, Fernández T, Rodríguez M, Galán L, Díaz-Comas L, Bernal J, Fernández-Bouzas A, Marosi E, Reyes A. N400 and lexical decisions: automatic or controlled processing? Clin Neurophysiol 1999; 110:813-24. [PMID: 10400194 DOI: 10.1016/s1388-2457(99)00009-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
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 In the first experiment, the amount of priming was equivalent for the 3 tasks. The N400 effect appeared in the high and low proportion of directly related words, but not in the single presentation task. In the second experiment, behavioral priming was also found in the 3 tasks. However, the N400 effect was observed only in the task with low proportion of related pairs. CONCLUSION These results suggest that the N400 effect may be related to controlled processes.
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Harmony T, Fernández-Bouzas A, Marosi E, Fernández T, Bernal J, Rodríguez M, Reyes A, Silva J, Alonso M, Casian G. Correlation between computed tomography and voltage and current source density spectral EEG parameters in patients with brain lesions. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1993; 87:196-205. [PMID: 7691550 DOI: 10.1016/0013-4694(93)90019-r] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In a group of patients with space-occupying brain lesions, CT measurements were correlated with absolute power (AP) and relative power (RP) of the delta, theta, alpha and beta EEG bands, calculated from the raw EEG potentials (EEGp) and from the Laplacian estimates also called "current source densities" (CSD). Rank correlations were calculated between the number of abnormal values in each band and the following CT measures: volume of the lesion and of the edema, density of the edema, percentage of ventricular collapse and midline shift. Abnormal spectral values are those which are significantly higher than the norm for the same age, in the delta and theta bands, and significantly lower in the alpha and beta bands. Spectral parameters obtained from the CSD showed higher correlations with CT measures than those calculated from the EEGp. In the Laplacian, all CT measures had a significant correlation with delta AP. Theta AP was significantly correlated with the volume and density of the edema, as well as with midline shift. Significant correlations were also observed with delta and alpha RP. However, changes in RP were considered to be a consequence of the increase in delta AP. Canonical correlation analyses between AP and RP calculated from EEGp or CSD and the first 3 CT measures showed that the volume of the lesion was only correlated with delta AP and RP. The volume and density of the edema showed a significant correlation with delta, theta and alpha AP calculated from EEGp and only with theta and alpha AP in the Laplacian. Since the EEGp tends to produce a more extensive and diffuse picture of abnormality, whereas the Laplacian acts as a spatial filter emphasizing local sources over distant sources, we concluded that edema is related not to delta activity, but to the theta and alpha power.
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Bernal J, Harmony T, Rodríguez M, Reyes A, Yáñez G, Fernández T, Galán L, Silva J, Fernández- Bouzas A, Rodríguez H, Guerrero V, Marosi E. Auditory event-related potentials in poor readers. Int J Psychophysiol 2000; 36:11-23. [PMID: 10700619 DOI: 10.1016/s0167-8760(99)00092-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Although poor readers (PR) are considered the major group among reading-disabled children, there are not event-related potentials (ERP) studies reported of PR on the subject. In this study, attentional and memory processes were studied in an auditory oddball task in PR and normal controls. ERP to auditory stimuli were recorded in 19 leads of the 10/20 system, using linked earlobes as references, in 20 normal children (10 female) and 20 PR (10 female) of the same age (10-12 years old). Two pure tones (1000 and 3000 Hz) were used in an oddball paradigm. No significant differences were observed in the amplitudes and latencies of N100 between the groups. However, N200 to frequent stimuli and P200 to both frequent and infrequent stimuli were of higher amplitude in poor readers than in normal children. There were no differences between groups in the latency and amplitude of P300. The results suggest that PR use more attentional resources in the components occurring before P300 to both frequent and infrequent stimuli than the normal children, and this finding is particularly marked for PR girls.
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Harmony T, Fernández T, Fernández-Bouzas A, Silva-Pereyra J, Bosch J, Díaz-Comas L, Galán L. EEG changes during word and figure categorization. Clin Neurophysiol 2001; 112:1486-98. [PMID: 11459689 DOI: 10.1016/s1388-2457(01)00582-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
OBJECTIVE To analyze whether the EEG changes observed during figure and word categorization are compatible with either the dual, the common amodal, or the alternative model (modality-specific codes for words and pictures, where meaning is represented for both in a higher-order amodal system) for semantic knowledge. METHODS EEG was recorded during word and figure categorization of animals or non-animals in a group of 28 children 8-10 years old. Computation of EEG sources in the frequency domain using variable resolution electrical tomography (VARETA) and their statistical evaluation by statistical parametric mapping were carried out. RESULTS At all frequencies, there were significant changes between EEG segments prior to the presentation of the stimuli and EEG segments recorded after the stimuli. Post-segments showed more power from 1.56 to 7.02 Hz, and less power than pre-segments from 8 to 12.48 Hz. EEG changes were only observed in the word task at: 3.9 (left occipital), 4.68, 5.46, and 6.24 Hz (temporo-occipital regions). These changes may be associated with visual encoding of words. Frequencies 7.8 and 17.94 Hz increased in prefrontal, anterior cingulate, and anterior temporal regions only during figure categorization. The prefrontal region may be related to object working memory. Thus, these frequencies might be related to figure codification. No significant differences between tasks were observed at 3.12 and 7.02 Hz in very wide brain areas (all lobes except occipital), suggesting that the amodal semantic system storage could be the model compatible with figure and word categorization. CONCLUSIONS Thus, our results support the modified amodal semantic hypothesis, which advocates that the meanings of both kinds of stimuli are represented in a conceptual memory that receives input from the logogen and iconogen systems.
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Marosi E, Rodríguez H, Harmony T, Yañez G, Rodrìguez M, Bernal J, Fernàndez T, Silva J, Reyes A, Guerrero V. Broad band spectral EEG parameters correlated with different IQ measurements. Int J Neurosci 1999; 97:17-27. [PMID: 10681115 DOI: 10.3109/00207459908994300] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The relationship of IQ (measured by WAIS and all its subscales) and EEG broad band spectral parameters were studied in 40 right-handed, male volunteers ranging in age from 20 to 25 years old. EEGs were recorded in 20 derivations during rest with eyes opened. The results obtained reveal positive and negative correlations with abundant frontal participation in all bands. Mean frequency data show a frequency shift in a very narrow range suggesting that more relations in narrow band could be achieved. These results highlight the need of psychological tests that measure more homogeneous abilities and finer measurement technique to reveal clearly explainable correlations and demonstrate that EEG recordings do reflect intellectual abilities.
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Harmony T, Urbá-Holmgren R, Urbay CM, Szava S. (Na-K)-ATPase activity in experimental epileptogenic foci. Brain Res 1968; 11:672-80. [PMID: 4237409 DOI: 10.1016/0006-8993(68)90155-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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