Specificity and sensitivity of visual evoked potentials in the diagnosis of schizophrenia: rethinking VEPs.

Alterations of the visual evoked potential (VEP) component P1 at the occipital region represent the most extended functional references of early visual dysfunctions in schizophrenia (SZ). However, P1 deficits are not reliable enough to be accepted as standard susceptibility markers for use in clinical psychiatry. We have previously reported a novel approach combining a standard checkerboard pattern-reversal stimulus, spectral resolution VEP, source detection techniques and statistical procedures which allowed the correct classification of all patients as SZ compared to controls. Here, we applied the same statistical approach but to a single surface VEP - in contrast to the complex EEG source analyses in our previous report. P1 and N1 amplitude differences among spectral resolution VEPs from a POz-F3 bipolar montage were computed for each component. The resulting F-values were then Z-transformed. Individual comparisons of each component of P1 and N1 showed that in 72% of patients, their individual Z-score deviated from the normal distribution of controls for at least one of the two components. Crossvalidation against the distribution in the SZ-group improved the detection rate to 93%. In all, six patients were misclassified. Clinical validation yielded striking positive (78.13%) and negative (92.69%) predictive values. The here presented procedure offers a potential clinical screening method for increased susceptibility to SZ which should then be followed by high density electrode array and source detection analyses. The most important aspect of this work is represented by the fact that this diagnostic technique is low-cost and involves equipment that is feasible to use in typical community clinics.

[Spectral analysis of the electroencephalogram in subjects with mild cognitive impairment]. / Análisis espectral del electroencefalogramaen sujetos con deterioro cognitivo leve.

INTRODUCTION: Mild cognitive impairment (MCI) is defined as a state of the ageing brain midway between normal cognition and dementia. Special attention has been paid to the electrophysiological substrate underlying Alzheimer's disease and MCI in order to identify as early as possible which subjects with MCI progress towards Alzheimer, which could be crucial for starting rehabilitation or pharmacological therapies. AIM: To perform a spectral characterisation of the electroencephalogram in subjects with MCI. PATIENTS AND METHODS: An electroencephalogram was carried out on 41 subjects with MCI in order to analyse the spectral measurements; apolipoprotein E genotype was also performed. RESULTS: In all, 94.8% of the sample displayed a significant increase in energy, and in 66.6% of them this was observed in the theta and delta bands, or both. Significant differences were found in the spectral measurements between carriers and non-carriers of the apolipoprotein E epsilon4 allele in the theta and alpha bands; there was also a statistically significant association between the years of schooling and being a carrier of this allele or not. An increase in the theta-alpha bands was observed in the left temporal region in subjects with a below-average number of years of schooling and carriers of the epsilon4 allele. CONCLUSIONS: In subjects with MCI and carriers of the epsilon4 allele, the alpha and theta cortical rhythms can be affected by similar pathological mechanisms and may be expressed earlier in subjects who have a lower level of schooling.

Análisis espectral del electroencefalogramaen sujetos con deterioro cognitivo leve / Spectral analysis of the electroencephalogram in subjects with mild cognitive impairment

Introducción. El deterioro cognitivo leve (DCL) se define como un estado del cerebro envejecido intermedio entrela cognición normal y la demencia; se ha prestado una especial atención al sustrato electrofisiológico de la enfermedad de Alzheimer y el DCL con la finalidad de identificar lo antes posible qué sujetos con DCL progresan a Alzheimer, lo cual podría ser crucial para el inicio de terapias de rehabilitación o farmacológicas. Objetivo. Caracterización espectral del electroencefalograma en sujetos con DCL. Pacientes y métodos. Se estudió a 41 sujetos con DCL a los cuales se les realizó electroencefalograma para el análisis de las medidas espectrales; además se realizó genotipo de apolipoproteína E. Resultados. El94,8por ciento de la muestra reveló un incremento significativo de energía; en el 66,6 por ciento de ellos se observó en las bandas theta y delta,o ambas. Se encontraron diferencias significativas en las medidas espectrales entre portadores y no portadores del alelo epsilon4 de la apolipoproteína E en las bandas theta y alfa, y además existió una asociación estadísticamente significativa entrelos años de escolaridad y ser portador o no de dicho alelo. Se observó un incremento en las bandas theta-alfa en la región temporal izquierda en los sujetos por debajo de la media de años de escolaridad y portadores del alelo epsilon4. Conclusiones. En los sujetos con DCL y portadores del alelo epsilon4, los ritmos corticales alfa y theta pueden verse afectados por mecanismospatológicos similares, y puede expresarse de forma más precoz en los sujetos que presentan un nivel de escolaridad bajo(AU)

INTRODUCTION: Mild cognitive impairment (MCI) is defined as a state of the ageing brain midway between normal cognition and dementia. Special attention has been paid to the electrophysiological substrate underlying Alzheimer's disease and MCI in order to identify as early as possible which subjects with MCI progress towards Alzheimer, which could be crucial for starting rehabilitation or pharmacological therapies. AIM: To perform a spectral characterisation of the electroencephalogram in subjects with MCI. PATIENTS AND METHODS: An electroencephalogram was carried out on 41 subjects with MCI in order to analyse the spectral measurements; apolipoprotein E genotype was also performed. RESULTS: In all, 94.8percent of the sample displayed a significant increase in energy, and in 66.6 percent of them this was observed in the theta and delta bands, or both. Significant differences were found in the spectral measurements between carriers and non-carriers of the apolipoprotein E epsilon4 allele in the theta and alpha bands; there was also a statistically significant association between the years of schooling and being a carrier of this allele or not. An increase in the theta-alpha bands was observed in the left temporal region in subjects with a below-average number of years of schooling and carriers of the epsilon4 allele. CONCLUSIONS: In subjects with MCI and carriers of the epsilon4 allele, the alpha and theta cortical rhythms can be affected by similar pathological mechanisms and may be expressed earlier in subjects who have a lower level of schooling(AU)

Análisis espectral del electroencefalograma en sujetos con deterioro cognitivo leve / Spectral analysis of the electroencephalogram in subjects with mild cognitive impairment

El deterioro cognitivo leve (DCL) se define como un estado del cerebro envejecido intermedio entrela cognición normal y la demencia; se ha prestado una especial atención al sustrato electrofisiológico de la enfermedad de Alzheimer y el DCL con la finalidad de identificar lo antes posible qué sujetos con DCL progresan a Alzheimer, lo cual podríaser crucial para el inicio de terapias de rehabilitación o farmacológicas. Objetivo. Caracterización espectral del electroencefalograma en sujetos con DCL. Pacientes y métodos. Se estudió a 41 sujetos con DCL a los cuales se les realizó electroencefalograma para el análisis de las medidas espectrales; además se realizó genotipo de apolipoproteína E. Resultados. El 94,8% de la muestra reveló un incremento significativo de energía; en el 66,6% de ellos se observó en las bandas theta y delta,o ambas. Se encontraron diferencias significativas en las medidas espectrales entre portadores y no portadores del alelo epsilon4 de la apolipoproteína E en las bandas theta y alfa, y además existió una asociación estadísticamente significativa entre los años de escolaridad y ser portador o no de dicho alelo. Se observó un incremento en las bandas theta-alfa en la región temporal izquierda en los sujetos por debajo de la media de años de escolaridad y portadores del alelo epsilon4. Conclusiones. En los sujetos con DCL y portadores del alelo epsilon4, los ritmos corticales alfa y theta pueden verse afectados por mecanismospatológicos similares, y puede expresarse de forma más precoz en los sujetos que presentan un nivel de escolaridad bajo

Mild cognitive impairment (MCI) is defined as a state of the ageing brain midway between normalcognition and dementia. Special attention has been paid to the electrophysiological substrate underlying Alzheimer’s disease and MCI in order to identify as early as possible which subjects with MCI progress towards Alzheimer, which could be crucial forstarting rehabilitation or pharmacological therapies. Aim. To perform a spectral characterisation of the electroencephalogram in subjects with MCI. Patients and methods. An electroencephalogram was carried out on 41 subjects with MCI in order to analyse the spectral measurements; apolipoprotein E genotype was also performed. Results. In all, 94.8% of the sampledisplayed a significant increase in energy, and in 66.6% of them this was observed in the theta and delta bands, or both. Significant differences were found in the spectral measurements between carriers and non-carriers of the apolipoprotein E epsilon4 allele in the theta and alpha bands; there was also a statistically significant association between the years of schoolingand being a carrier of this allele or not. An increase in the theta-alpha bands was observed in the left temporal region in subjects with a below-average number of years of schooling and carriers of the epsilon4 allele. Conclusions. In subjects withMCI and carriers of the epsilon4 allele, the alpha and theta cortical rhythms can be affected by similar pathological mechanisms and may be expressed earlier in subjects who have a lower level of schooling

Estudio de la negatividad de discrepancia auditiva en dos subtipos de niños con dislexia del desarrollo / The Mismatch Negativity ERP in two subtypes of children with developmental dyslexia

La caracterización neuropsicológica de subtipos en la dislexia del desarrollo contradice la idea de la existencia de un mecanismo cognitivo único que se encuentra dañado en esta entidad. Los potenciales relacionados con eventos permiten ubicar la disfunción subyacente dentro de la secuencia temporal de etapas de procesamiento implicadas en la lectura. El objetivo de este trabajo fue evaluar mediante la negatividad de discrepancia auditiva (MMN) el procesamiento perceptual auditivo de tonos puros en dos subtipos de dislexia del desarrollo. Se estudiaron 14 niños disléxicos y siete controles sanos. Mediante una tarea de lectura de palabras y seudopalabras, se pudo dividir el grupo de disléxicos en los subtipos fonológico y superficial. Se registró la MMN en los sujetos estudiados, utilizando el paradigma clásico de discriminación auditiva entre tonos puros de 1.000 y 1.200 Hz presentados secuencialmente con una probabilidad relativa de 0,15 y 0,85 respectivamente. Se obtuvo MMN para el grupo control y el de disléxicos superficiales. En el grupo de disléxicos fonológicos no aparece este potencial. Las diferencias encontradas en los perfiles electrofisiológicos de los dos subtipos de dislexia del desarrollo, contradicen la idea de un mecanismo cognitivo único dañado como base de este trastorno. La mayor afectación en la amplitud del componente MMN encontrada en los disléxicos fonológicos sugiere una dificultad subyacente más generalizada del procesamiento auditivo central

Neuropsychological characterization of subtypes in developmental dyslexia contradicts the idea of the existence of a unique cognitive mechanism damaged in this entity. The linguistic components of evoked related potentials (ERP) provide a functional window to find the underlying dysfunction within a temporal sequence of processing stages related with reading. The aim of this study was to evaluate with the mismatch negativity (MMN) in two subtypes of developmental dyslexia. Fourteen dyslexic children and seven siblings were examined. Using a words and pseudowords reading task, the dyslexic group was divided into two subtypes, phonologic or surface dyslexics respectively. A mismatch negativity (MMN) was measured in all this subjects, using the classical paradigm of auditory discrimination of pure tones (1.000 and 1.200 Hz) presented sequentially with a relative probability of 0.15 y 0.85 and 600 ms of interstimulus interval. An MMN was obtained to both, control subjects and the surface deficit group. Dyslexics with phonological deficit haven�t got this component. Differences in electrophysiological patterns of these two subtypes of developmental dyslexia, contradict the idea of a unique cognitive mechanism damaged in this impairment. The highest differences in the amplitude in MMN found in the phonologic dyslexics suggest a more generalized underlying difficulty in central auditory processing

[Video-EEG evaluation complemented by spectral and EEG source analysis in patients with medication-resistant medial temporal lobe epilepsy]. / Evaluación videoelectroencefalográfica complementada con análisis espectral y de las fuentes generadoras del electroencefalograma en pacientes con epilepsia del lóbulo temporal medial resistente a los fármacos.

AIM: To evaluate the value of prolonged video-electroencephalographic (video-EEG) monitoring complemented with spectral and EEG source analysis in identifying the epileptogenic area in patients with medial temporal lobe epilepsy who are candidates for non-lesional resective surgery. PATIENTS AND METHODS: The electrographic patterns during the onset of seizures were evaluated in over 667 seizures from 41 patients with a clinical diagnosis of medication-resistant partial epilepsy. Analyses were performed using Harmonie software and variable resolution electrical tomography (VARETA). RESULTS: Video-EEG was used to determine that 53.6% of the patients evaluated suffered complex partial seizures of a temporal origin; these were characterised by having an average frequency of 5.56 +/- 1.56 Hz, while the non-temporal seizures displayed a frequency within the range 9.17 +/- 3.32 Hz. The topographic location of the dominant ictal frequency during the period of maximum spectral energy in patients with temporal lobe epilepsy enabled us to draw a distinction between a group of patients with mesial seizures and those with non-mesial seizures that exceeded the number that was determined by visual inspection of the EEG, that is, 78.9 versus 47.3%, respectively. There was a 100% coincidence between the area where the seizures began as defined by surface EEG complemented with spectral analysis, the generator of this activity as defined by VARETA and the epileptogenic region. CONCLUSIONS: The localising information provided by video-EEG complemented with spectral and EEG source analysis allows for non-invasive location of the epileptogenic region in patients with medial temporal lobe epilepsy even when structural imaging studies show an absence or bilaterality of abnormalities.

Evaluación videoelectroencefalográfica complementada con análisis espectral y de las fuentes generadoras del electroencefalograma en pacientes con epilepsia del lóbulo temporal medial resistente a los fármacos / Video-EEG evaluation complemented by spectral and EEG source analysis in patients with medication-resistant medial temporal lobe epilepsy

Objetivo. Evaluar la contribución de la monitorización prolongada videoelectroencefalográfica (video EEG) complementada con análisis espectral y de las fuentes generadoras del electroencefalograma (EEG) en la identificación de la zona epileptogénica de pacientes con epilepsia del lóbulo temporal medial candidatos a cirugía resectiva no lesional. Pacientesy métodos. Se evaluaron los patrones electrográficos del inicio ictal en más de 667 crisis correspondientes a 41 pacientes con diagnóstico clínico de epilepsia parcial resistente a fármacos. Para el análisis se utilizaron el software Harmonie y la tomografía eléctrica de resolución variable (VARETA). Resultados. Mediante video-EEG se determinó que el 53,6por ciento de lospacientes evaluados presentaba crisis parciales complejas de origen temporal; éstas se caracterizaron por una frecuencia media de 5,56 ± 1,56 Hz, mientras que las no temporales presentaron una frecuencia en el rango de 9,17 ± 3,32 Hz. La localizacióntopográfica de la frecuencia ictal dominante durante el período de energía espectral máxima en los pacientes conepilepsia del lóbulo temporal permitió distinguir a un grupo de pacientes con crisis mesiales y otros no mesiales que superaron el número determinado por la inspección visual del EEG: un 78,9 frente a un 47,3por ciento, respectivamente. Se evidenció unacoincidencia del 100por ciento entre la zona de inicio ictal definida por EEG de superficie complementada con análisis espectral, el generador de esta actividad definido por VARETA y la zona epileptogénica. Conclusiones. La información localizadora aportadapor el video-EEG complementada con el análisis espectral y de las fuentes del EEG permite localizar de forma no invasiva la zona epileptogénica en pacientes con epilepsia del lóbulo temporal medial aun cuando los estudios imaginológicos estructurales evidencian ausencia o bilateralidad de anomalías(AU)

Summary. Aim. To evaluate the value of prolonged video electroencephalographic (video-EEG) monitoring complemented with spectral and EEG source analysis in identifying the epileptogenic area in patients with medial temporal lobe epilepsy who are candidates for non-lesional resective surgery. Patients and methods. The electrographic patterns during the onset of seizures were evaluated in over 667 seizures from 41 patients with a clinical diagnosis of medication-resistant partial epilepsy. Analyses were performed using Harmonie software and variable resolution electrical tomography (VARETA). Results. Video- EEG was used to determine that 53.6percent of the patients evaluated suffered complex partial seizures of a temporal origin; these were characterised by having an average frequency of 5.56 ± 1.56 Hz, while the non-temporal seizures displayed a frequency within the range 9.17 ± 3.32 Hz. The topographic location of the dominant ictal frequency during the period of maximum spectral energy in patients with temporal lobe epilepsy enabled us to draw a distinction between a group of patients withmesial seizures and those with non-mesial seizures that exceeded the number that was determined by visual inspection of the EEG, that is, 78.9 versus 47.3percent, respectively. There was a 100percent coincidence between the area where the seizures began asdefined by surface EEG complemented with spectral analysis, the generator of this activity as defined by VARETA and the epileptogenic region. Conclusions. The localising information provided by video-EEG complemented with spectral and EEG source analysis allows for non-invasive location of the epileptogenic region in patients with medial temporal lobe epilepsy even when structural imaging studies show an absence or bilaterality of abnormalities(AU)

Evaluación videoelectroencefalográfica complementada con análisis espectral y de las fuentes generadoras del electroencefalograma en pacientes con epilepsia del lóbulo temporal medial resistente a los fármacos / Video-EEG evaluation complemented by spectral and EEG source analysis in patients with medication-resistant medal temporal lobe epilepsy

Objetivo. Evaluar la contribución de la monitorización prolongada videoelectroencefalográfica (video-EEG) complementada con análisis espectral y de las fuentes generadoras del electroencefalograma (EEG) en la identificación de la zona epileptogénica de pacientes con epilepsia del lóbulo temporal medial candidatos a cirugía resectiva no lesional. Pacientes y métodos. Se evaluaron los patrones electrográficos del inicio ictal en más de 667 crisis correspondientes a 41 pacientes con diagnóstico clínico de epilepsia parcial resistente a fármacos. Para el análisis se utilizaron el software Harmonie y la tomografía eléctrica de resolución variable (VARETA). Resultados. Mediante video-EEG se determinó que el 53,6% de los pacientes evaluados presentaba crisis parciales complejas de origen temporal; éstas se caracterizaron por una frecuencia media de 5,56 ± 1,56 Hz, mientras que las no temporales presentaron una frecuencia en el rango de 9,17 ± 3,32 Hz. La localización topográfica de la frecuencia ictal dominante durante el período de energía espectral máxima en los pacientes con epilepsia del lóbulo temporal permitió distinguir a un grupo de pacientes con crisis mesiales y otros no mesiales que superaron el número determinado por la inspección visual del EEG: un 78,9 frente a un 47,3%, respectivamente. Se evidenció una coincidencia del 100% entre la zona de inicio ictal definida por EEG de superficie complementada con análisis espectral, el generador de esta actividad definido por VARETA y la zona epileptogénica. Conclusiones. La información localizadora aportada por el video-EEG complementada con el análisis espectral y de las fuentes del EEG permite localizar de forma no invasiva la zona epileptogénica en pacientes con epilepsia del lóbulo temporal medial aun cuando los estudios imaginológicos estructurales evidencian ausencia o bilateralidad de anomalías

Aim. To evaluate the value of prolonged video-electroencephalographic (video-EEG) monitoring complemented with spectral and EEG source analysis in identifying the epileptogenic area in patients with medial temporal lobe epilepsy who are candidates for non-lesional resective surgery. Patients and methods. The electrographic patterns during the onset of seizures were evaluated in over 667 seizures from 41 patients with a clinical diagnosis of medication-resistant partial epilepsy. Analyses were performed using Harmonie software and variable resolution electrical tomography (VARETA). Results. Video- EEG was used to determine that 53.6% of the patients evaluated suffered complex partial seizures of a temporal origin; these were characterised by having an average frequency of 5.56 ± 1.56 Hz, while the non-temporal seizures displayed a frequency within the range 9.17 ± 3.32 Hz. The topographic location of the dominant ictal frequency during the period of maximum spectral energy in patients with temporal lobe epilepsy enabled us to draw a distinction between a group of patients with mesial seizures and those with non-mesial seizures that exceeded the number that was determined by visual inspection of the EEG, that is, 78.9 versus 47.3%, respectively. There was a 100% coincidence between the area where the seizures began as defined by surface EEG complemented with spectral analysis, the generator of this activity as defined by VARETA and the epileptogenic region. Conclusions. The localising information provided by video-EEG complemented with spectral and EEG source analysis allows for non-invasive location of the epileptogenic region in patients with medial temporal lobe epilepsy even when structural imaging studies show an absence or bilaterality of abnormalities

[Selective attention disorders associated with a history of occupational exposure to organic solvents]. / Alteraciones de la atención selectiva asociadas a la historia de exposición ocupacional a solventes orgánicos.

INTRODUCTION: The cognitive effects of long-term exposure to organic solvents could be similar to those triggered by certain neurodegenerative diseases. AIMS: The purpose of this study was to evaluate the effects exerted by accumulated exposure on the cognitive functions. PATIENTS AND METHODS: 105 subjects with an average history of exposure of 19.3 years were evaluated using seven computerised cognitive tasks (CPT, digit-symbol substitution, Stroop, memory span, word learning and recognition, and TRD) and results were later compared with the performance of a non-exposure group and with a normative reference. A study was made of the association between the length of exposure and performance in the variables in which the exposed subjects displayed significantly lower values than control subjects. In order to evaluate the effect exerted by age, regression functions between performance and age were calculated for each group. RESULTS: Only the indicators from the Stroop and digit-symbol tasks correlated with the length of exposure. The regression functions between performance and age for each group showed that the former decreased significantly faster among exposed subjects than among controls. CONCLUSIONS: Findings suggest that, while recent exposure seems to have an effect on a wide range of functions, chronic exposure exerts a selective influence on a smaller group. In this case, only selective attention appears to deteriorate. Similar deficits have been observed in the early stages of patients with Alzheimer's and Parkinson's.

Alteraciones de la atención selectiva asociadas a la historia de exposición ocupacional a solventes orgánicos / Selective attention disorders associated with a history of occupational exposure to organic solvents

Introducción. Los efectos cognitivos de la exposición a largo plazo a solventes orgánicos podrían ser similares a los provocados por ciertas enfermedades neurodegenerativas. Objetivo. Evaluar los efectos de la exposición acumulada en las funciones cognitivas. Pacientes y métodos. Se evaluaron 105 sujetos con historia de exposición, con un promedio de 19,3 años, mediante siete tareas cognitivas computarizadas (CPT, dígito-símbolo, Stroop, amplitud de memoria, aprendizaje y reconocimiento de palabras, y TRD) y se comparó su desempeño con el de un grupo no expuesto y con una referencia normativa. Se evaluó la asociación entre la duración de la exposición y el desempeño en aquellas variables en las que los expuestos mostraron valores significativamente inferiores a los controles. Para evaluar el efecto de la edad, se calcularon funciones de regresión entre el desempeño y la edad en cada grupo. Resultados. Sólo los indicadores de las tareas de Stroop y de dígito-símbolo mostraron correlación con la duración de la exposición. Las funciones de regresión entre la edad y el desempeño para cada grupo mostraron que éste declinó significativamente más rápido entre los expuestos que entre los controles. Conclusiones. Los resultados sugieren que, mientras que la exposición reciente parece influir sobre un amplio conjunto de funciones, la exposición crónica ejerce una influencia selectiva sobre un grupo más reducido. En este caso, sólo parece deteriorarse la atención selectiva. Déficit similares se han observado en los estadios tempranos de enfermos de Alzheimer y Parkinson (AU)

Introduction. The cognitive effects of long-term exposure to organic solvents could be similar to those triggered by certain neurodegenerative diseases. Aims. The purpose of this study was to evaluate the effects exerted by accumulated exposure on the cognitive functions. Patients and methods. 105 subjects with an average history of exposure of 19.3 years were evaluated using seven computerized cognitive tasks (CPT, digit-symbol substitution, Stroop, memory span, word learning and recognition, and TRD) and results were later compared with the performance of a non-exposure group and with a normative reference. A study was made of the association between the length of exposure and performance in the variables in which the exposed subjects displayed significantly lower values than control subjects. In order to evaluate the effect exerted by age, regression functions between performance and age were calculated for each group. Results. Only the indicators from the Stroop and digit-symbol tasks correlated with the length of exposure. The regression functions between performance and age for each group showed that the former decreased significantly faster among exposed subjects than among controls. Conclusions. Findings suggest that, while recent exposure seems to have an effect on a wide range of functions, chronic exposure exerts a selective influence on a smaller group. In this case, only selective attention appears to deteriorate. Similar deficits have been observed in the early stages of patients with Alzheimer and Parkinson (AU)

Localization error in biomedical imaging.

Measures of false positive (FP) and false negative (FN) localization error are defined to assess the accuracy of diagnostic imaging procedures. These measures involve the weighting of FP and FN pixels in accordance to their distances from the true localization of the lesion and the region detected as abnormal by the classifier. The distance-based localization receiver operating characteristic (DL-ROC) curve is defined to describe the dependence of the FP and FN localization measures on the classifier's decision threshold. A computer system is presented for the analysis of localization experiments according to these concepts. As an illustration, the accuracy of two types of brain electric topographic montage is studied in the localization of brain tumors and sites of stroke.

On the structure of EEG development.

Two different descriptions of EEG maturation are compared: a broad-band spectral parameters (BBSPs) model and a recently developed xi-alpha (xi alpha) model. 'Developmental equations' were obtained for both parameter sets using 1 min, eyes closed EEG sample from 165 normal children (5-12 years old). At each age, the xi alpha parameter set described the average spectrum more closely than the BBSP developmental equations. Furthermore, a more detailed picture of changes of spectral shape with age is possible with the xi alpha model. A computer simulation illustrates the possible appearance of fixed frequency bands as a byproduct of inadequate statistical models.

Multivariate Box-Cox transformations with applications to neurometric data.

The Box-Cox power transform methodology for achieving Gaussianity is developed for a variety of models useful in neurometric statistical analysis. Algorithms are proposed for estimating the optimal transformations in the univariate and multivariate cases. Their use is briefly illustrated with neurometric data.