ABSTRACT
Objective: Current treatment for borderline personality disorder (BPD) involves psychological and pharmacological interventions. However, neuromodulation techniques such as repetitive transcranial magnetic stimulation (rTMS) may positively affect BPD symptomatology. The objective of this study was to evaluate the clinical and neuropsychological effects of rTMS on the dorsomedial prefrontal cortex (DMPFC) in BPD patients. Methods: Fourteen patients with BPD were randomized into two groups (active vs. sham) for 15 sessions of rTMS on the DMPFC. Clinical effects were measured using the Borderline Symptoms List (BSL), Clinical Global Impression Scale for BPD (CGI-BPD), Borderline Evaluation of Severity over Time (BEST), Hamilton Depression Rating Scale (HDRS), Hamilton Anxiety Rating Scale (HARS), and Barratt's Impulsiveness Scale (BIS). Neuropsychological effects were determined by a Stop-Signal Task (SST), the Wisconsin Card-Sorting Test (WCST), and the Iowa Gambling Test (IGT). Results: Within-group comparison showed significant differences (p < 0.05) in CGI-BPD (total score and six of nine psychopathologic domains), BEST, HDRS, HARS, and IGT scores for active modality. Conclusion: The 5 Hz-DMPFC rTMS technique was well tolerated and lessened the severity of BPD symptomatology, especially abandonment, affective issues, interpersonal relationships, suicidal behavior, anger, and paranoid ideation. Cognitive improvement was seen in decision-making. Additional studies are needed to fully evaluate the effects of rTMS on BPD symptomatology. Clinical Trial Registration: NCT03832777.
Subject(s)
Humans , Borderline Personality Disorder/therapy , Transcranial Magnetic Stimulation , Anxiety , Anxiety Disorders , Treatment Outcome , Prefrontal CortexABSTRACT
Resumen El trastorno por atracón (TA) es una condición compleja en la que se han descrito diferentes aspectos clínicos y fallas neuropsicológicas en los sujetos que lo padecen. En este estudio se compararon variables clínicas (VC), neuropsicológicas (VNPS) y psicofisiológicas (VPFS) entre participantes sanos (n = 15) y con TA (n = 15) evaluados en la [Omitido por el editor]. Las VC incluyeron el inventario del anhelo por el consumo de alimentos (IACA), sintomatología depresiva (SD), ansiedad (SA) e impulsividad. Se utilizaron la Tarea de Cartas de Wisconsin para evaluar flexibilidad cognitiva (FC) y la Tarea de Señal de Alto para control inhibitorio (CI) dentro de las VNPS; en las VPFS se obtuvo la variabilidad de la frecuencia cardiaca (VFC) durante una prueba de exposición a imágenes de alimentos. Los resultados muestran que los participantes con TA obtuvieron puntuaciones mayores en los instrumentos IACA (p < .0001), SD (p < .0001) y SA (p < .0001); mientras que en las VNPS mostraron fallas en la FC con incremento en el porcentaje de errores totales (p = .01), errores perseverativos (p = .03) y CI (p = .004). Para las VPFS se encontró una reducción de la VFC (p < .0001) en aquellos participantes con TA.
Abstract Binge eating disorder (BED) is a complex condition in which different clinical aspects and neuropsychological faults have been treated in subjects who have it. In this study, clinical (VC), neuropsychological (VNPS) and psychophysiological (VPFS) variables were compared between healthy participants (n = 15) and with BED (n = 15) evaluated in the medicine school of the Autonomous University of Querétaro. The VC included the evaluation of the food craving scale (FCS), depressive symptomatology (DS), anxiety (AS) and impulsivity. It is used in the Wisconsin Cards Sorting Test for Cognitive Flexibility (CF) and the Stop Signal Task for Inhibitory Control (IC) within the VNPS; In the VPFS, the heart rate variability (HRV) was obtained during an exposure test to food images. The results showed that the participants obtained high scores in the evaluation instruments for FCS (p < .0001), SD (p < .0001) and SA (p < .0001); whereas in the VNPS it failed in the FC with an increase in the percentage of total errors (p = .01), perseverative errors (p = .03) and CI (p = .004). For the VPFS, a reduction in HRV (p < .0001) was found in those participants with AT.
ABSTRACT
Introducción: el estatus socioeconómico puede impactar sobre la cognición y la actividad eléctrica cerebral de los niños, por la influencia que tiene sobre el desarrollo durante etapas tempranas. Objetivo: evaluar la asociación de variables socioeconómicas, con alteraciones cognitivas y electroencefalográficas, en un grupo de niños escolares con riesgo de daño cerebral. Métodos: se estudiaron 42 niños mexicanos, de 6-7 años de edad. Se realizó un estudio socioeconómico a los padres y los niños fueron evaluados mediante la Evaluación Neuropsicológica Infantil (subpruebas de lectura-escritura y escala de signos neurológicos blandos), la Escala de Inteligencia de Wechsler para Niños, la Escala de Conners para Padres-Revisada y un electroencefalograma en diferentes edades. Resultados: con las variables socioeconómicas y, mediante un análisis de conglomerados, se encontraron 3 grupos que mostraban una adecuada diferenciación académica y económica entre sí. Por el método de clasificación basado en regresiones dispersas, se identificaron las variables que diferenciaban significativamente a los 3 grupos: problemas sociales, cognitivos, síntomas inatento, índice TDAH (Trastorno por Déficit de Atención e Hiperactividad, Escala de Conners para Padres-Revisada), lectura de palabras, comprensión en lectura de oraciones, dictado de sílabas, precisión de lectura en voz alta, lectura de sílabas, dictado de no palabras, movimiento de oposición digital, agarre de lápiz (Evaluación Neuropsicológica Infantil) y primer electroencefalograma normal. Conclusiones: el grupo con más desventajas socioeconómicas tuvo un peor desempeño en la lectoescritura y mayor prevalencia de actividad paroxística no epileptiforme; mientras que, el grupo con mayores ventajas socioeconómicas, mostró mejor desempeño en estas habilidades, mayor proporción de electroencefalogramas normales y una tendencia hacia problemas de atención(AU)
Introduction: the socioeconomic status can impact on the cognition and electrical brain activity of children due to the influence it has on the development during early stages. Objective: to evaluate the association of socioeconomic variables with cognitive and electroencephalographic alterations, in a group of school children at risk of brain damage. Methods: 42 Mexican children in the ages from 6 to 7 years old were studied. A socioeconomic study was conducted on the parents, and the children were evaluated through the Child Neuropsychological Assessment (reading-writing subtests and the scale of neurological soft signs), the Wechsler´s Intelligence Scale for Children, the Conners´ Scale for Parents-Revised and an electroencephalogram in different ages. Results: with the socioeconomic variables and by means of an analysis of conglomerate, 3 groups were found that showed an adequate academic and economic differentiation among themselves. By the classification method based on scattered regressions were identified variables that significantly differentiated the 3 groups: social and cognitive problems, inattentive symptoms, ADHD (Attention Deficit and Hyperactivity Disorder, Conners Scale for Parents-Revised), reading of words, comprehension in reading of sentences, dictation of syllables, accuracy of reading aloud, reading of syllables, dictation of non words, movement of digital opposition, pencil´s grip (Neuropsychological Evaluation of Children) and first normal electroencephalogram. Conclusions: the group with more socioeconomic disadvantages had a worse performance in reading and writing and a higher prevalence of non-epileptiform paroxysmal activity; whereas, the group with the greatest socioeconomic advantages showed a better performance in these skills, a greater proportion of normal electroencephalograms and a tendency towards attention problems(AU)
Subject(s)
Humans , Child , Brain Injuries, Diffuse , Social Class , Electroencephalography/methods , Mental Status and Dementia TestsABSTRACT
Resumen Objetivo: Comparar dos sistemas de puntuación para un test de fluidez verbal con el Modelo de Escalas de Calificación. Método: Se analizaron datos de 289 participantes, de los cuales 92 habían sido diagnosticados con Parkinson. Las puntuaciones se calcularon con dos sistemas de categorización: un procedimiento convencional y otro basado en percentiles. Resultados: Las puntuaciones Rasch procedentes de percentiles dan lugar a categorías adecuadas y medidas fiables; la correlación con las puntuaciones del test Minimental es evidencia de validez concurrente. Tras controlar estadísticamente el efecto de la edad, las medidas Rasch procedentes de percentiles discriminan entre ambos grupos, lo que evidencia validez predictiva. Conclusiones: El análisis de los dos procedimientos permite recomendar el uso de las categorías basadas en percentiles.
Abstract Objective: Two scoring systems for a verbal fluency test were compared using the Rasch Rating Scale Model. Method: The analysis was carried out on 289 participants, 92 of whom had had a Parkinson's disease diagnosis. Scores were calculated with two different category systems: a conventional procedure and a percentile-based one. Results: The percentile-based Rasch scores produce adequate categories and reliable measures, while the correlation with the Mini Mental State Examination evinces concurrent validity. After statistically controlling for age, percentile-based Rasch measures discriminated between both groups, demonstrating predictive validity. Conclusions: The analysis of the two procedures allows for the recommendation of the use of percentile-based categories.
Subject(s)
Humans , Male , Female , Infant, Newborn , Infant , Parents/psychology , Acoustic Stimulation/psychology , Infant, Premature/growth & development , Child Language , Early Intervention, Educational/trends , Language Development , Physical Stimulation , MexicoABSTRACT
Objective: Current treatment of borderline personality disorder (BPD) consists of psychotherapy and pharmacological interventions. However, the use of repetitive transcranial magnetic stimulation (rTMS) could be beneficial to improve some BPD symptoms. The objective of this study was to evaluate clinical improvement in patients with BPD after application of rTMS over the right or left dorsolateral prefrontal cortex (DLPFC). Method: Twenty-nine patients with BPD from the National Institute of Psychiatry, Mexico, were randomized in two groups to receive 15 sessions of rTMS applied over the right (1 Hz, n=15) or left (5 Hz, n=14) DLPFC. Improvement was measured by the Clinical Global Impression Scale for BPD (CGI-BPD), Borderline Evaluation of Severity Over Time (BEST), Beck Depression Inventory (BDI), Hamilton Anxiety Rating Scale (HAM-A), and Barratt Impulsiveness Scale (BIS). Results: Intragroup comparison showed significant (p < 0.05) reductions in every psychopathologic domain of the CGI-BPD and in the total scores of all scales in both groups. Conclusions: Both protocols produced global improvement in severity and symptoms of BPD, particularly in impulsiveness, affective instability, and anger. Further studies are warranted to explore the therapeutic effect of rTMS in BPD. Clinical trial registration: NCT02273674.
Subject(s)
Humans , Male , Female , Adolescent , Adult , Middle Aged , Young Adult , Borderline Personality Disorder/therapy , Transcranial Magnetic Stimulation/methods , Anxiety Disorders/psychology , Anxiety Disorders/therapy , Psychiatric Status Rating Scales , Severity of Illness Index , Borderline Personality Disorder/psychology , Treatment Outcome , Prefrontal Cortex , Depressive Disorder, Major/psychology , Depressive Disorder, Major/therapy , MexicoABSTRACT
En el presente trabajo se compararon dos grupos de niños mexicanos en edades comprendidas entre los 8 a 10 años, el primer grupo con trastorno específico en el aprendizaje (TEA), tanto en la precisión de la lectura como en el cálculo, y el otro con buen desempeño académico (BDA), por medio de Escala Wechsler de Inteligencia para Niños, en su cuarta versión (WISC-IV) y la batería de Evaluación Neuropsicológica Infantil (ENI), (subpruebas de Habilidades Académicas, Memoria, Atención y Habilidades Metalingüísticas), ambos instrumentos normados en población mexicana. Se encontraron diferencias significativas (p≤ 0.05) entre los niños BDA y TEA, mediante la U de Mann Whitney, en todas las subpruebas evaluadas a excepción del Índice Velocidad de Procesamiento (WISC), Conteo, Codificación/Evocación y Atención Auditiva, además de Atención visual (ENI). Mediante el Análisis de Componentes Principales se identificaron 5 subgrupos: 2 en los niños con BDA y 3 en los TEA. Las diferencias significativas (p≤ 0.05)entre las variables cognitivas y académicas fueron determinadas mediante la prueba de Kruskal-Wallis. Fue posible observar que los subgrupos TEA obtuvieron puntajes más bajos que los subgrupos BDA tanto en habilidades académicas como en otras variables cognitivas,siendo el Índice de Memoria de Trabajo en la escala Wechsler y las Habilidades Metalingüísticas de la ENI las que mejor diferenciaron a los subgrupos TEA de los BDA.Conclusión: La aplicación de instrumentos normados en la población bajo estudio resulta de gran utilidad para identificar subtipos neuropsicológicos tantoen niños con BDA como con TEA.
In this work two groups of Mexican children aged between 8 to 10 years old were compared, the first group with specific learningdisorder (SLD),in both reading accuracy as in the calculation, and the other compared to good performance academic (GPA) by Wechsler Intelligence Scale for Children, in its fourth version (WISC-IV) and battery Child Neuropsychological Assessment (ENI), (subtests Academic Skills, Memory, Attention and Metalinguistic Skills), both instruments normed in Mexican population. Significant differences (p ≤ 0.05) were found among SLD and GPA children, by Mann Whitney U Test, they were found in all subtests evaluated except Processing Speed Rate (WISC), Counting, Coding / Evocation and Auditory Attention, also Visual Attention (ENI). By the Principal Component Analysis were identified five subgroups: 2 children with GPA and 3 in the SLD. Significant differences (p ≤ 0.05) between cognitive and academic variables were determined by the Kruskal-Wallis Test. It was possible to observe that the TEA subgroups scored lower than the BDA subgroups in academic abilities as well as in other cognitive variables, with the Working Memory Index on the Wechsler scale as the subtests that evaluate the ENI Metalinguistic Skills the variables that give the best discrimination between the TEA and the BDA subgroups.Conclusion: The application of normed instruments in the population under study is useful to identify neuropsychological subtypes in children with GPA as SLD.
Subject(s)
Humans , Male , Female , Child , Linguistics , Memory, Short-Term , Specific Learning Disorder/diagnosis , Intelligence Tests , Mexico , Neuropsychological Tests , Principal Component AnalysisABSTRACT
This research assesses, in newborns, the hemodynamic response to acoustically modified syllables (pronounced in a prolonged manner), versus the response to unmodified syllables (pronounced at a normal rate). The aim was to assess which of these stimulation conditions produced better syllable discrimination in two groups of neonates: 13 preterm (mean gestational age 30 weeks, SD 3 weeks), and 13 full term newborns (mean age 38 weeks, SD 1 week). Syllable discrimination, in each condition, was assessed by using an oddball paradigm (equal syllable trials vs. different syllable trials). The statistical analysis was based on the comparison between the hemodynamic response [oxyHbO] obtained by Near Infrared Spectroscopy (NIRS) to different syllable trials vs. equal syllable trials, in each condition. The modified syllable condition was better in producing trial discrimination in both groups. The amplitude of the hemodynamic response to the different syllable trials was greater than the one to the equal syllable trials: for term infants, t = 2.59, p = 0.024, and for preterm t = 2.38, p = 0.035. This finding occurred in the left temporal lobe. These data suggest that the modified syllables facilitate processing of phonemes from birth.
Esta investigación evalúa, en neonatos, la respuesta hemodinámica ante sílabas modificadas acústicamente (pronunciadas de manera prolongada) en comparación con la respuesta a sílabas no modificadas (pronunciadas a una velocidad normal). El objetivo fue evaluar cuál de estas condiciones de estimulación producía una mejor discriminación silábica en dos grupos de neonatos: 13 prematuros (edad gestacional promedio de 30 semanas, DE 3 semanas) y 13 nacidos a término (edad gestacional promedio de 38 semanas, DE 1 semana). La discriminación de sílabas, en cada condición, se evaluó mediante un paradigma oddball (ensayos con sílabas iguales vs. ensayos con sílaba diferente). El análisis estadístico se basó en la comparación de la respuesta hemodinámica [oxyHb] obtenida por espectroscopia de infrarrojo cercano (NIRS) ante ensayos con sílabas iguales Vs. ensayos con una sílaba diferente en cada condición. Se encontró que la condición de sílabas modificadas obtuvo mejores resultados para la discriminación entre ensayos en ambos grupos. La amplitud de la respuesta hemodinámica ante el ensayo con una sílaba diferente fue significativamente mayor que ante el ensayo con sílabas iguales: en recién nacidos a término, t = 2,59, p = 0,024 y en los prematuros, t = 2,38, p = 0,035. Este hallazgo ocurrió en el lóbulo temporal izquierdo. Estos datos sugieren que las sílabas modificadas facilitan el procesamiento de fonemas desde el nacimiento.
Esta pesquisa avalia, em neonatos, a resposta hemodinâmica diante sílabas modificadas acusticamente (pronunciadas de maneira prolongada) em comparação com a resposta a sílabas não modificadas (pronunciadas a uma velocidade normal). O objetivo foi avaliar qual destas condições de estimulação produzia uma melhor discriminação silábica em dois grupos de neonatos: 13 prematuros (idade gestacional média de 30 semanas, DE 3 semanas) e 13 nascidos a termo (idade gestacional média de 38 semanas, DE 1 semana). A discriminação de sílabas, em cada condição, foi avaliada mediante um paradigma oddball (ensaios com sílabas iguais vs. ensaios com sílaba diferente). A análise estadística se baseou na comparação da resposta hemodinâmica [oxyHb] obtida por espectroscopia de infravermelho próximo (NIRS) ante ensaios com sílabas iguais Vs. ensaios com uma sílaba diferente em cada condição. Encontrou-se que a condição de sílabas modificadas obteve melhores resultados para a discriminação entre ensaios em ambos os grupos. A amplitude da resposta hemodinâmica ante o ensaio com uma sílaba diferente foi significativamente maior que perante o ensaio com sílabas iguais: em recém-nascidos a termo, t = 2,59, p = 0,024 e nos prematuros, t = 2,38, p = 0,035. Este descobrimento ocorreu no lóbulo temporal esquerdo. Estes dados sugerem que as sílabas modificadas facilitam o processamento de fonemas desde o nascimento.
Subject(s)
Humans , Male , Female , Infant, Newborn , Infant, Premature , Spectroscopy, Near-Infrared , Language DevelopmentABSTRACT
Transcranial Magnetic Stimulation (rTMS) is a technique that allows noninvasive electrical stimulation of the cortex with few side effects. An antidepressant effect has been proposed when rTMS is delivered over prefrontal dorsolateral cortex (DLPFC) ≥5Hz. Quantitative EEG studies have shown increases in alpha and theta power bands as well as frontal interhemispheric asymmetries in most recordings from depressed patients. rTMS over left DLPFC at 5Hz involve a safer and more tolerable procedure, and its neurophysiological correlates has not been explored using EEG source analysis. The aim of this research was to study changes in EEG sources using VARTERA method in a group of patients with major depressive disorder (MDD) treated with 5Hz rTMS over left DLPFC as single or combined treatment with escitalopram. Methods 18 patients with DSM-IV MDD diagnosis without treatment for the current episode were included. Subjects were randomly assigned to one of two groups: A) rTMS+escitalopram 10mg, n=9; B) rTMS+placebo, n=9. Subjects received 15 sessions of rTMS on a daily basis. In order to compare changes in EEG sources two recordings were obtained, prior and after treatment. HDRS, BDI and HARD were used for clinical assessments. Results All patients of group A and eight patients of group B showed response to treatment (considered as a reduction of 50% in HDRS score). An increase in absolute power at 9.37Hz and 10.17Hz in temporal and postcentral gyrus on the left hemisphere was found in group B. Absolute power in those frequencies was decreased in the same regions for group A. In addition, an increased power in beta band frequencies was observed in both hemispheres for group A. Conclusion Increases in alpha band could be the hallmark of the 5Hz rTMS, but it could be reduced by escitalopram. Besides, increases observed in beta band for group A could be related to escitalopram effect.
La estimulación magnética transcraneal repetitiva (EMTr) es una técnica que permite estimular eléctricamente la corteza cerebral de manera no invasiva y con pocos efectos secundarios. Se ha propuesto que la EMTr aplicada sobre la corteza prefrontal dorsolateral (CPFDL) izquierda con frecuencias ≥5Hz tiene efectos antidepresivos. Se ha encontrado que en el electroencefalograma cuantitativo (QEEG por sus siglas en inglés) la mayoría de pacientes deprimidos presentan incrementos en las bandas theta y alfa, así como asimetrías interhemisféricas en la actividad alfa en regiones anteriores. La EMTr sobre la CPFDL izquierda a 5Hz ofrece ventajas considerables en seguridad y tolerabilidad; sin embargo, sus correlatos neurofisiológicos no han sido explorados por el análisis de fuentes del EEG. Objetivo Estudiar los cambios en las fuentes del EEG según el método VARETA en un grupo de pacientes con trastorno depresivo mayor que recibieron EMTr a 5Hz sobre la corteza prefrontal dorsolateral izquierda como tratamiento único o en combinación con escitalopram. Material y métodos Se estudiaron 18 pacientes con diagnóstico de trastorno depresivo mayor de acuerdo con los criterios del DSM-IV sin tratamiento para el episodio en curso. Los sujetos habían sido aleatoriamente asignados a uno de los siguientes grupos de tratamiento: A) EMTr+escitalopram 10mg, n=9; B) EMTr+placebo, n=9. Se aplicó EMTr, a 5Hz en una sesión diaria durante 15 días. Se obtuvieron dos registros electroencefalográficos, uno basal y otro final, con el fin de comparar los cambios en las fuentes de actividad eléctrica cerebral, pretratamiento y post-tratamiento. Se realizaron evaluaciones clinimétricas con las escalas de Hamilton para Depresión y Ansiedad y el Inventario de Depresión de Beck. Resultados Todos los pacientes en el grupo A y ocho pacientes en el grupo B respondieron al tratamiento, con una reducción de 50% o más en la escala HDRS. En el análisis de fuentes se encontró un efecto en el grupo B caracterizado por incremento en la PA de 9.37 a 10.17Hz, en regiones temporales y giro poscentral izquierdos, mismo que se encontró disminuido en el grupo A, Además se encontró un incremento en fracuencias correspondientes a la banda beta en regiones frontales de ambos hemisferios en el grupo A. Conclusiones Podría considerarse que el incremento en la banda alfa es característico de la EMTr a 5Hz, mismo que se ve reducido por efecto del escitalopram. Por otro lado, se observó que el grupo A mostró incrementos en fuentes correspondientes a la banda beta como posible efecto relacionado del fármaco antidepresivo.
ABSTRACT
Drugs use at party contexts has increased in recent decades. Drugs dealing facilitates consumer access to substances, whose sales practices vary according to drugs use, places for the consumption and the drug social function. Drug dealing is socially constructed from a set of practices ranging from reasons to dealing and those related to the consolidation as a common practice. The aim of this research was to describe and analyze the drugs users' experience in party contexts, about their dealer's construction process. An interpretative multiple-case study with the snowball technique was carried out to get the participants. The information was obtained by a semi-structured interview and nonparticipant observation at the dealing places. The information obtained points out the group's participation on the selection of the dealer as the initiation of drugs dealing, the extroversion features and communication skills as an important profile to be a dealer; specially, the capability to satisfy the group's emotional request through the drugs. Also, benefits as acceptation, protection and the warmth from the group and the economical earning. The dealer/businessmen consolidation is socially constructed according to the new identity assumed, the group participation and the specific activities as a business.
El uso de drogas en contextos de fiesta se ha incrementado en las últimas décadas. El narcomenudeo facilita el acceso a sustancias de consumo, cuyas prácticas de venta varían conforme a la droga de uso, los espacios de consumo y la función de la droga en los grupos que la consumen. La venta de drogas implica una serie de prácticas que la construyen y que incluyen los motivos del inicio de venta, el proceso de desarrollo y las relacionadas con la consolidación de la venta como práctica habitual. El objetivo de esta investigación fue describir y analizar la experiencia de usuarios de drogas en contextos de fiesta respecto al proceso en que se construyen como dealers. Para lo anterior, se realizó un estudio interpretativo de casos múltiples, empleando la técnica de "bola de nieve" para captar a los participantes. La observación se obtuvo por medio de una entrevista semiestructurada y la observación no participante en escenarios de venta. Se obtuvo información relacionada con los elementos del salto del uso a la venta como la elección del dealer por el grupo, su perfil para ser elegido como la extroversión y habilidades de comunicación; y sobre todo su capacidad para satisfacer la demanda de emociones de los miembros de su grupo por medio de las drogas de venta. Además, de la aceptación, protección y afecto del grupo y las ganancias económicas. La consolidación como dealer/empresario se construye conforme se asumen una nueva identidad, la participación del grupo y las actividades específicas de la empresa.
ABSTRACT
Major Depressive Disorder (MDD) is a common psychiatric disorder that represents one of the main public health problems worldwide. It has been projected that for 2020 it will be the second cause of disability-adjusted life years just below ischemic heart disease. Quantitative electroencephalogram provides the opportunity to study cortical oscillatory activity across the different frequency bands. It constitutes an accessible tool to explore the clinical and neurophysiologic correlates underlying psychiatric disorders as well as the effect of diverse therapeutic options and the performance through cognitive tasks. Repetitive transcranial magnetic stimulation is a technique that allows the stimulation of the cerebral cortex noninvasively, relatively painlessly and with fairly few side effects. The vast majority of rTMS studies target left dorsolateral prefrontal cortex (DLPFC) based on imaging studies showing that left prefrontal cortex dysfunction is pathophysiologically linked to depression. However, there is some evidence implicating right PFC in the pathophysiology of depression. Comparison of antidepressant efficacy of diverse stimulation frequencies is relevant since a main concern around rTMS is its potential to induce seizures; hence we consider that frequency of stimulation is an important aspect to be studied. For this study we aimed to elucidate the clinical efficacy of rTMS comparing two groups of depressed patients stimulated over DLPFC, one over the left (at 5 Hz) and other over the right (at 1 Hz). We also meant to know if there were clinical and electroencephalographic differential long-term after-effects between those groups of treatment. We included twenty right-handed patients with a DSM-IVR diagnosis of MDD. They were assigned into two groups of treatment. Group 1 received 5Hz rTMS over the left DLPFC. Group 2 received 1Hz rTMS over the right DLPFC. We obtained two EEG measurements in order to analyze Z score of broad-band spectral parameters and cross-spectral. No statistical differences among groups were found in response to treatment after weekly comparisons of clinimetric scores and significant differences between baseline and final assessment by HDRS, MADRS, BDI and HARS. The major rTMS effect on EEG was observed in the group that received 1 Hz over the right DLPFC and no significant effects were observed for the group that received 5 Hz over the left DLPFC. Our results propose that administration of 15 sessions on either left (5 Hz) or right (1 Hz) rTMS over DLPFC is sufficient to reach response to treatment, assessed by HDRS, MADRS, BDI and HARS in subjects with MDD. Moreover, in both cases rTMS was able to induce an equivalent antidepressant effect. The major effect of rTMS on EEG was observed in the right 1 Hz rTMS group where changes were elicited mainly over frontal, central and temporal regions on alpha and particularly beta frequency bands. In a lesser extent for left 5 Hz rTMS group the main effect was observed on anterior regions for beta and particularly alpha frequency bands. We believe it is pertinent to continue exploring the therapeutic potential of lower stimulation frequencies, for what further research including larger samples is still necessary to confirm these trends.
El trastorno depresivo mayor es una entidad psiquiátrica que representa uno de los principales problemas de salud pública a nivel mundial. Se ha proyectado que para el año 2020 será la segunda causa de discapacidad únicamente por debajo de la cardiopatía isquémica. La utilización del electroencefalograma cuantitativo ofrece la oportunidad de estudiar la actividad oscilatoria cortical a través de las diferentes bandas de frecuencias. Éste constituye una herramienta para explorar las características clínicas y neurofisiológicas que subyacen a los trastornos psiquiátricos, así como un instrumento para evaluar el efecto de diversas opciones terapéuticas y el desempeño de los sujetos durante la realización de tareas cognitivas. La estimulación magnética transcraneal repetitiva (EMTr) es una técnica que permite la estimulación de la corteza cerebral de manera no invasiva, relativamente sin dolor y con pocos efectos secundarios. Con base en los estudios de neuroimagen que vinculan la fisiopatología de la depresión con disfunción en la corteza prefrontal dorsolateral (CPFDL), la mayoría de las investigaciones se han enfocado en estimular dicha corteza en el hemisferio izquierdo. No obstante, existen pruebas que implican a la corteza prefrontal derecha con la fisiopatología de la depresión. La relevancia de comparar la eficacia antidepresiva de diversas frecuencias radica en el hecho de que un tema de interés particular alrededor de la EMTr es su potencial para inducir convulsiones, por ello consideramos que la exploración de las diversas frecuencias de estimulación con efecto terapéutico constituye un aspecto importante de estudio. Para este trabajo nos propusimos determinar la eficacia antidepresiva de la EMTr comparando dos grupos de pacientes que fueron estimulados en la CPFDL derecha a 1 Hz o en la izquierda a 5 Hz. También buscamos dilucidar si existen diferencias clínicas y electroencefalográficas a largo plazo entre grupos de tratamiento. Para este estudio se incluyeron 20 pacientes con diagnóstico de trastorno depresivo mayor de acuerdo con los criterios del DSM-I V. Los sujetos fueron asignados aleatoriamente a uno de dos grupos de tratamiento. Un grupo recibió EMTr sobre la CPFDL izquierda a 5Hz; el otro recibió estimulación a 1 Hz sobre la corteza contralateral. Se obtuvieron dos registros electroencefalográficos, uno basal y otro final, con el fin de comparar las medidas espectrales de banda ancha y estrecha, pretratamiento y postratamiento. Se realizaron evaluaciones clinimétricas con las escalas de Hamilton para Depresión y Ansiedad, la escala de Depresión de Montgomery-Asberg y el Inventario de Beck. No encontramos diferencias significativas al comparar la respuesta a la EMTr entre ambos grupos. Los pacientes de ambos grupos presentaron respuesta a tratamiento (disminución de ≥50% de la sintomatología depresiva) medida por clinimetría. El efecto más importante de la EMTr sobre el EEG se observó en el grupo de estimulación derecha a 1 Hz donde encontramos disminución postratamiento en los valores Z de banda estrecha alfa y beta, principalmente en regiones fronto-centro-temporales. Aunque en menor proporción, en el grupo de estimulación izquierda a 5 Hz encontramos incrementos significativos post EMTr, predominantemente en las bandas beta y alfa sobre todo en regiones anteriores. No se encontraron resultados significativos en el análisis de banda ancha. Nuestros resultados sugieren que la administración de 15 sesiones de EMTr ya sea sobre la CPFDL derecha (1 Hz) o izquierda (5 Hz) es capaz de lograr respuesta antidepresiva. Nuestros hallazgos electrofisiológicos sugieren que uno de los efectos a largo plazo de la EMTr es la reorganización de los circuitos neuronales implicados en la depresión.
ABSTRACT
The DSM-IV-TR (Diagnostic and Statistical Manual of Mental Disorders, fourth Edition, text Revision) defines attention-deficit/hyperactivity disorder (ADHD) as a disorder usually first diagnosed during infancy. Its essential feature is a persistent pattern of inattention and/or hyperactivity-impulsivity that is more frequent and severe than typically observed in individuals at a comparable level of development. It produces a significant impairment in social, academic, or occupational functioning. The prevalence of ADHD among the general population is between 5-10% in children and adolescents, and 1.2% to 7.3% in adults. In clinical samples, the prevalence in adults is higher: 1 6.80%. Less than 10% of the children diagnosed with ADHD reached a total functional remission when they became adults. Subjects with ADHD have a higher risk of suffering personality disorders and substance abuse. This disorder has a genetic basis. About 80% of the variance is explained by genetics. Some of the genes implied in this disorder are the dopamine transporter, the dopamine receptor 4, the beta-hydroxilase enzyme, the adrenergic receptor α2, the serotonin transporter and the serotonin receptor 1B. Environmental factors such as parental nicotine consumption during pregnancy, low birth weight, perinatal problems, parental psychiatric disorders, social adversity, and low parental education are related to a higher risk for ADHD. Several studies have shown that there are morphological brain abnormalities in subjects with ADHD. Structures like frontal lobe, cerebellar hemispheres and vermis, callosum splenium, cingulate anterior cortex and right caudate, are smaller in subjects with ADHD compared with healthy subjects. On the other hand, regarding the response to stimulants, studies with positron emission tomography (PET), among other techniques, suggest that the dopamine and noradrenergic systems play a role in the pathophysiology of ADHD. From 1990 to date, there are 41 morphological studies in ADHD, published in English, reporting volumetric abnormalities. However, the results are contradictory, so definitive conclusions about the brain structures being involved in ADHD remain unclear. Objective This article reviews the general neurobiology of ADHD providing an updated and comprehensive overview of the brain structural findings. The methodologies of morphological studies using magnetic resonance imaging (MRI) are reviewed in detail so as to find the source of the contradictory findings reported in the published studies. Method A literature search and review of the relevant published articles in MEDLINE and PsycINFO sites was made using the following key words: attention deficit hyperactivity disorder, neurobiology, morphological alteration, and MRI. In general, the literature supports the genetic basis of the disorder as well as the involvement of dopaminergic and noradrenergic systems in the pathophysiology. Nevertheless, regarding the structural abnormalities reported in ADHD, there is an enormously heterogeneous methodology in MRI scan acquisition and processing. Almost every study used a different image analysis to measure brain structures. Some works chose a hand user definition of the region of interest (ROI), which is prone to a user's bias. Other papers used a semi-automated analysis combining a user-defined ROI and segmentation techniques based only in intensity. These methodologies are prone to bias and to a deficient separation of grey and white matter. Finally, the automated methods where there is no user intervention are preferred because they are not a biased in the selection of ROI and use tissue probability maps to improve the segmentation. Unfortunately, none of these methods has been validated against histological and anatomopatological data. So, there is not a measure of validity and reliability of these methods. On the other hand, female subjects are extremely underrepresented in these studies: only around 20% of the individuals studied were females and only 50% of the ADHD samples included female subjects, whereas 95% included males. The number of reports done in ADHD adults is very scarce. Discussion Despite the multiple inconsistencies found in each MRI study as a consequence of limitations such as small samples size, and methodological differences across the studies such as lack of consistency in the acquisition and the image analysis, the structures more frequently and consistently reported to be smaller in ADHD subjects, compared to healthy subjects, are regions of the frontal lobe, the callosum splenium, the anterior cingulate gyrus, the vermis, the cerebral hemispheres and the right caudate. However, these findings are applicable to the most frequently studied samples: male children. Considering the prevalence and lack of complete remission of ADHD symptoms during adulthood, there is a need for structural studies in adults as well as in women. Conclusion The findings and results of MRI studies represent clear but insufficient advances in the knowledge of the anatomical structures involved in ADHD. There is a lack of research on the age-related changes imposed by neurodevelopment. The brain abnormalities and their gender differences in ADHD individual are subjects of future research.
El trastorno por déficit de atención e hiperactividad (TDAH) se caracteriza por un patrón persistente de inatención y/o hiperactividad e impulsividad y produce un deterioro en diversas áreas del funcionamiento del individuo. La prevalencia del TDAH en niños y adolescentes en la población general es de 5-10% y en adultos es de 1.2 a 7.3%. Menos del 10% de los niños que fueron diagnosticados con TDAH alcanzan una remisión funcional total en la edad adulta. Estos sujetos presentan más riesgo de sufrir un trastorno grave de la personalidad así como de dependencia a substancias. Cerca del 80% de la varianza del TDAH se explica por factores genéticos. Los genes que han sido asociados al TDAH con más frecuencia son aquellos que codifican al transportador de dopamina, al receptor de dopamina D4, a la enzima beta-hidroxilasa, al receptor adrenérgico a2, al transportador de serotonina y al receptor de serotonina 1B. Existen variables medioambientales asociadas al TDAH; como el consumo materno de tabaco durante el embarazo, las complicaciones perinatales, la psicopatología de los padres, y la adversidad psicosocial. Por otra parte, la respuesta a los estimulantes así como los estudios hechos con tomografía por emisión de positrones, sugieren que la dopamina y los sistemas noradrenérgicos tienen un papel en la fisiopatología del TDAH. Desde 1990 a la fecha, se han realizado 41 estudios morfológicos del TDAH que han reportado anormalidades volumétricas. Sin embargo, los resultados son contradictorios, lo que no permite obtener conclusiones definitivas acerca de las estructuras involucradas en el trastorno. Objetivo El presente artículo presenta una revisión general de la neurobiología del TDAH y una actualización de las anomalías estructurales encefálicas en los sujetos con TDAH por medio del uso de imágenes por resonancia magnética (IRM). Se han revisado en detalle las metodologías usadas en los estudios estructurales con el fin de conocer el origen de los hallazgos contradictorios en los estudios publicados hasta la fecha. Métodos Se realizó una búsqueda en la bibliografía médica de los artículos publicados en las bases MEDLINE y PsycINFO, con las siguientes palabras clave: TDAH, neurobiología, alteraciones morfológicas e imágenes por resonancia magnética. Resultados Los estudios sobre las anormalidades estructurales en el TDAH muestran una enorme heterogeneidad en la metodología de la adquisición y del procesamiento de las IRM. Por otro lado, la mayoría de los estudios se han realizado en niños del sexo masculino. Existen pocos artículos realizados en sujetos del sexo femenino y en adultos. Discusión A pesar de las inconsistencias encontradas en cada estudio de IRM, las estructuras encefálicas que se reportan reducidas en los sujetos TDAH son: el lóbulo frontal, el esplenio calloso, el cíngulo anterior, el vermis cerebeloso, los hemisferios del cerebelo y el núcleo caudado derecho. Dada la alta prevalencia del TDAH y la falta de remisión de síntomas en la población adulta, es necesario realizar más estudios estructurales en sujetos adultos y femeninos. Conclusión Los resultados obtenidos en los estudios de IRM constituyen avances claros pero insuficientes en el conocimiento de las estructuras anatómicas involucradas en el TDAH. Las anormalidades encefálicas entre los sujetos TDAH y las diferencias de edad y género entre estos sujetos deben ser los objetivos de futuras investigaciones.
ABSTRACT
The obsessive compulsive disorder (OCD) is a diverse and multidimensional psychiatric syndrome, characterized by obsessions and compulsions, where anxiety is considered to be a key clinical component. Imaging studies have shown brain abnormalities in patients with OCD involving mainly the frontotemporal circuits, the orbitofrontal and the anterior cingulate cortex. These techniques have a high spatial resolution to identify brain alterations in this disorder but have less time resolution and are more expensive than electrophysiological studies. The electroencephalogram (EEG) and event-related potentials (ERPs) are the most common electrophysiological techniques used in the research of OCD. The EEG represents the electrical activity of the brain as recorded by electrodes placed on the scalp. The ERPs are voltage fluctuations that are temporarily linked to the presence of a physical or mental event. The best-known type of EEG is the <
El Trastorno Obsesivo Compulsivo (TOC) es un trastorno psiquiátrico crónico, clínicamente heterogéneo, multidimensional, caracterizado por la presencia de obsesiones y compulsiones, en el cual la ansiedad es un componente fundamental del cuadro clínico. Los estudios de imágenes tienen una gran resolución espacial que permite la identificación de las alteraciones presentes en esta entidad pero tienen menor resolución temporal y son de mayor costo que los estudios electrofisiológicos. Entre las técnicas electrofisiológicas más utilizadas para investigar el TOC se encuentran el electroencefalograma (EEG) y los potenciales relacionados con eventos (PREs). El EEG es el registro de la actividad eléctrica cerebral, es decir, de las diferencias de voltaje entre dos electrodos situados sobre el cuero cabelludo, en función del tiempo. Los PREs son las fluctuaciones de voltaje que están asociadas temporalmente a la presencia de un evento físico o mental. El tipo de EEG más conocido es aquél que se analiza por inspección visual (EEG tradicional: EEG-T) y que se describe mediante la presencia y distribución topográfica de cuatro tipos de actividades electroencefalográficas: delta (δ), theta (θ), alfa (α) y beta (β). Las bandas δ y θ se identifican como actividades lentas mientras que las bandas α y β se conocen como actividades rápidas. En el TOC se ha referido la actividad lenta como la anormalidad más común en el EEG-T, especialmente la actividad de tipo θ, aunque también se han descrito EEGs normales. Por otra parte, las medidas espectrales de banda ancha (MEBAs) han comprobado este exceso de actividad lenta además de anormalidades en las bandas rápidas, particularmente en la α. Entre las MEBAs más utilizadas se encuentran la potencia absoluta y la potencia relativa. Se ha demostrado, tanto con las MEBAs como con el análisis de generadores del EEG, que aquellos pacientes que tienen un exceso de a en regiones anteriores y medias responden mejor a los inhibidores de la recaptura de serotonina, lo cual es de gran utilidad clínica. Los PREs se dividen en dos tipos: exógenos y endógenos. En este trabajo se hará referencia a los endógenos o cognitivos. Entre los componentes de los PREs cognitivos más característicos están el N200 y el P300. En los pacientes con TOC se han descrito amplitudes mayores y latencias más cortas en los componentes P3b y N200, lo cual se ha atribuido a hiperalertamiento cortical y sobrefocalización de la atención. También se han observado correlaciones positivas entre la amplitud del componente N200 y la cronicidad del trastorno y entre la amplitud del componente P300 y la severidad de la sintomatología del TOC. Los pacientes con este trastorno tienen la sensación de que <
ABSTRACT
Attention deficit hyperactivity disorder (ADHD) is a neuro-developmental disorder clinically characterized by three core symptoms: deficits in attentional processes, failure in inhibitory control -usually expressed through behavioral and cognitive impulsiveness-, and motor and verbal restlessness. Deficit in attentional resources is the main alteration in patients with this disorder. Attention can be considered as a neurocognitive state of neural preparation that precedes both perception and action. Attention focalizes consciousness in order to filter the constant flux of sensorial information, solve competence between stimuli for parallel processing and recruit and activate cerebral regions necessary to accomplish appropriate responses. Event-related potentials (ERPs) are a technique that has proven useful in the gathering of valuable information in the study of ADHD. One of the most studied ERPs is the P300 component. The most robust finding in the P300 research in ADHD is a decrease in the amplitude of the component in patients when compared to normal controls. This finding is usually interpreted as an evidence for a deficit in attention. ADHD usually presents commorbidity with several disorders; research shows that up to 87% of the children with ADHD present commorbidity with another disorder, up to 60% has either a behavioral or affective disorder commorbid with ADHD. Due to the wide range of disorders that are usually associated with this entity, it is useful in the research of commorbidity to use dimensional diagnostics, that is, a patient with ADHD may have commorbidity with an externalized disorder (EXT) (i.e. oppositionist defiant disorder); an internalized (INT) disorder (i.e. anxiety or affective disorder); or both an externalized and an internalized disorder (MIX). Commorbidity may have important implications in the electrophysiology of ADHD since no homogeneous results have been evident in the scarce research on the subject. Taking into account these considerations, the following experiment was designed in order to answer the question: Patients with the same main diagnostic, ADHD, but different commorbidities (INT and MIX) show different psychophysiological patterns of activation, as measured by ERPs to a continuous performance task? Sixteen patients diagnosed with ADHD by a specialist were recruited. Diagnosis was corroborated by a semi-structured interview, K-SADS-PL-MX, eight of them with an externalized comorbid (EXT) disorder, and eight of them with at least two comorbid disorders, one externalized an one internalized (MIX). A control group (CON) of eight normal subjects with no psychiatric diagnostic and matched by sex was also recruited. All subjects were between 13-16 years old with no history of Central Nervous System damage and normal IQ in the Weschler Intelligence Scale for Children. Brain electrical activity was recorded in the 19 derivations of the 10-20 international system while subjects executed a continuous performance task (CPT). Comparisons of behavioral data between groups showed some significant differences. A one-way ANOVA found differences between groups in the mean reaction time to the first part of the CPT and in the number of false positives in the second part. Electrophysiological data was analyzed with a non-parametrical multivariate test of permutations. When comparing responses to the frequent stimulus with responses to the infrequent, statistically significant differences were found in every subject; such differences share the topography and latency characteristics of the P3b component. When comparing the amplitude of this component between the groups, only two statistically significant differences were found. First, the EXT group presented a greater amplitude of the component elicited by the first part of the task in a latency of 425 to 445 msec in the parietal region of the medial line than the CON group. Second, also in response to the first part of the task, the amplitude of the CON group was bigger than that of the MIX group in a latency between 355 and 420 msec in the left temporal anterior region. No other comparison yielded significant results. When comparing between groups, mean reaction time to the first part of the task was the only behavioral variable that adequately distinguished control and patients. Even though controls executed significantly faster, they maintained the same efficacy as no differences were found in the number of errors or correct responses. This result is not surprising due to the fact that long reaction times usually denote inattention and so the fact that both groups of patients execute slower than the controls may be interpreted as a sign that, in spite of having different commorbidities, inattention is still a common problem in every patient of the sample. On the second part of the task, only the number of false positives showed statistically significant differences. However, in a posterior analysis of the data, it was evident that such differences were only between the EXT and the CON groups, with the EXT group presenting significantly more errors. False positives, especially on the second part of the task, are a measure of behavioral inhibition. Failure in inhibitory control is one of the three main symptoms of ADHD. However, some have proposed it as the main characteristic of the disorder. Analysis of the electrophysiological response to the first part of the task showed characteristic profiles of execution for each group. First, the P300 component was smaller in amplitude in the MIX group than in the control group and, even though differences were significant only in one derivation (T3), several other electrode sites more typically associated with the P300 component (C3, C4, P3, P4 and Pz) showed similar tendencies that did not reach statistical significance. Second, EXT patients had greater amplitude of the same P300 component in Pz than CON subjects. This result may seem to contradict most of the research on ADHD and P300. Nevertheless, considering the behavioral data, specially that no differences in correct responses were found between patients an controls, it is posible to assert that the greater amplitude of the component represents an overactive compensation in attentional circuits, necessary in the EXT group in order to execute at the same level of non-ADHD subjects. The results of this study present with information on a poorly reasearched subject: comorbidity and electrophysiology on ADHD.
La principal función afectada en el trastorno por déficit de atención con hiperactividad (TDAH) es la atención, la cual puede considerarse como un estado neurocognoscitivo cerebral de preparación que precede tanto a la percepción como a la acción. Los potenciales relacionados con eventos (PREs), una técnica útil en el estudio de la atención en esta entidad, pueden definirse como los cambios en la actividad eléctrica cerebral asociados temporalmente con la aparición de un evento, ya sea un estímulo o un proceso cognitivo. Con esta técnica es posible explorar las representaciones eléctricas de los procesos sensoriales y congnoscitivos con una alta resolución temporal. Uno de los PREs más estudiados en el TDAH es el P300, un componente positivo que ocurre en una latencia de alrededor de los 300 mseg. El hallazgo más contundente en el estudio del P300 en pacientes con TDAH es un decremento en la amplitud al compararlos con sujetos controles, lo cual suele ser interpretado como expresión de una atención deficiente. Por otro lado, el TDAH suele presentarse en comorbilidad con diferentes trastornos y siendo la presentación más infrecuente del síndrome es el TDAH <
ABSTRACT
SUMMARY: Since the decade of the seventies, several neuropsychological abnormalities in very different cognitive domains have been described among patients with Obsessive-compulsive disorder (OCD). Due to the nature of these abnormalities, it was concluded that possibly the main dysfunction for this disorder was located in the right hemisphere, especially in the frontal cortex; nevertheless this particular brain region was found to be involved in other psychiatric disorders, so neuropsychological results were considered to be of limited precision and it was thought that the diversity in results was not due to the malfunction of one particular brain region. So it became evident that a new research methodology based in the information processing model with highly specific neuropsychological paradigms of frontal functioning was needed; as well as considering a subtypology based in the cognitive characteristics in patients with the same disorder and similar phenomenology. Regarding OCD it is well known that the dorsolateral prefrontal cortex is in charge of the regulation of complex actions, executive functions and the elaboration of logical strategies in a problem solving task; so its dysfunction causes a failure in the creation of response patterns and perseverations due to the inability to change a pattern when an alternative response is needed. On the other hand, obsessions are associated mainly with the anterior cingulated cortex and the basal region of the corpus striatum and its connections with the limbic system, giving place to incapacity to select the relevant information from the environment, which makes the individual perceive irrelevant stimuli as threatening for physical integrity. By the way, some clinical subtypes have also been identified: contamination/washing, aggressiveness/checking, hoarding, symmetry/ order. There is also some evidence of different patterns of brain activation to several visual stimuli related to the obsessive or compulsive object in the clinical subtypes, as shown by functional magnetic resonance image in some regions of the frontal lobe, either dorsolateral, medial or basal and its connections with the basal ganglia, and in some cases thalamus or limbic system. In the face of all this evidence, the goal of the present study was to find if within this disorder it was possible, through several neuropsychological paradigms of frontal functioning, to find different patterns of execution, considering the clinical subtype and the severity of obsessions and compulsions. Fifty-eight patients with a diagnosis of OCD were studied; all patients were under treatment at the OCD clinic of the National Institute of Psychiatry Ramón de la Fuente in Mexico City. Two neuropsychological tests were administered: 1) Trail Making Test (TMT) and 2) Wisconsin Card Sorting Test (WCST). From the Target Symptom List, the clinical subtype was obtained. After the statistical analysis, we found no differences between the severity of obsessions and the severity of compulsions as measured by the Yale-Brown Scale. Also, we observed three factors concerning the neuropsychological tests, and patients were grouped in four different groups, each one with a distinct cognitive performance. Through the interpretation of results it was concluded that in a sample of 58 patients with OCD, different groups of neuropsychological functioning where distinguished. In their own, these groups where associated with different clinical subtypes. These results are in accordance with the neurobiological modular organization model of OCD, which sustains the existence of independent systems of cognitive dysfunction that regulate different symptomatic expressions.
RESUMEN: La metodología de investigación, a partir del modelo del procesamiento de información con paradigmas neuropsicológicos de funcionamiento del lóbulo frontal, permite un estudio más específico de los trastornos psiquiátricos con fenomenología parecida, lo que a su vez permite crear modelos basados en una subtipología de índole cognoscitiva y, por ende, lleva al conocimiento de los circuitos neurales involucrados en la manifestación clínica de estos padecimientos. En el caso del trastorno obsesivo-compulsivo (TOC), la corteza prefrontal dorsolateral se encarga de regular las acciones complejas, las funciones ejecutivas y la elaboración de estrategias lógicas en la resolución de problemas, de tal manera que su mal funcionamiento ocasiona fallas en la creación de patrones de respuesta y perseveraciones por incapacidad de cambiar de patrón cuando se requiere otra alternativa de respuesta. Por otra parte, las obsesiones se relacionan predominantemente con el cíngulo anterior y la parte basal del cuerpo estriado y de sus conexiones con el sistema límbico, dando lugar a la incapacidad para seleccionar la información relevante del entorno. Esto genera que el individuo perciba los estímulos inocuos como "amenazantes" para la integridad física. También se han identificado subtipos clínicos de obsesiones y compulsiones, tales como contaminación, lavado, agresividad, comprobación, atesoramiento, simetría y de orden, entre otros, que se han relacionado con distintos patrones de transmisión genética, comorbilidad y respuesta a tratamiento. Además, se han documentado distintos patrones de aumento o disminución, ya sea de metabolismo cerebral o de flujo sanguíneo, en los circuitos fronto- estriados. Con la resonancia magnética funcional también se han encontrado distintos patrones de activación en los circuitos neuronales entre distintos subtipos clínicos, mediante la exposición de imágenes que se relacionan con el contenido de la obsesión o bien con la acción de la compulsión. Ante esta evidencia, se decidió averiguar si en pacientes con este trastorno era posible encontrar, mediante distintos paradigmas neuropsicológicos de funcionamiento frontal, dichos patrones diferenciales, considerando tanto el subtipo clínico como la gravedad de las obsesiones y compulsiones. En este estudio participaron 58 pacientes con este diagnóstico pertenecientes a la Clínica de TOC del Instituto Nacional de Psiquiatría Ramón de la Fuente, de los que 24 eran mujeres y 34, hombres. Una vez que los psiquiatras adscritos a dicha clínica confirmaban el diagnóstico obtenido en la cita de primera vez, referían a los pacientes al programa para computadora de Diagnóstico Neuropsicológico Automatizado (DIANA). Se aplicaron en una sola sesión las siguientes pruebas: 1) Trazado con Hitos (TH) y 2) Test de Categorización de Tarjetas de Wisconsin (TCTW). Con posterioridad a la aplicación de las pruebas a todos los pacientes, se revisó cada uno de los expedientes de la clínica de TOC para obtener el subtipo clínico. En el análisis estadístico de los datos se realizó primero un análisis factorial para disminuir el número de variables y luego un análisis de conglomerados para ver si se formaban grupos conforme a la ejecución de los sujetos en las pruebas aplicadas. De acuerdo con la ejecución de los pacientes se observó que los sujetos se agruparon en cuatro grupos distintos de desempeño cognoscitivo: el primero tuvo una ejecución muy deficiente en ambas pruebas. El segundo exhibió un desempeño regular en las dos pruebas pero fue mas rápido para terminar el TH. El tercero sólo estuvo constituido por dos pacientes que tuvieron un desempeño muy diferente al del resto, al presentar una ejecución sobresaliente en WCST pero con gran cantidad de errores en el TH. En tanto, en el cuarto de estos grupos, donde se concentraba la mayoría de la muestra, se consideró que su ejecución fue la más característica y su desempeño en ambas pruebas regular, pero más lento en TH. Cada uno de estos grupos de funcionamiento neuropsicológico se relacionó con los distintos subtipos de obsesiones y compulsiones, mas no con su gravedad. Encontrar subtipos neuropsicológicos de TOC asociados a sintomatología clínica distinta presta apoyo al modelo de organización modular de los diferentes circuitos neurales que intervienen en la manifestación sintomática de este padecimiento.
ABSTRACT
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Abstract: Introduction: An insight into the meaning of words is one of the central processes of semantic memory. To evalúate the access to the cognitive representation of the meaning of words, in the present study we used the lexical decision paradigm developed by Marcos. In this situation, the subject has to recognize if the presented stimulus corresponds to a word or a pseudo-word with the purpose of building a model of normal processing. Once such a model of normal processing is obtained, the findings can be contrasted with pathologies in which semantic memory is altered. Method: The sample consisted of 32 healthy subjects (7 men, 25 women), right-handed and with no personal or familial history of neurological or psychiatric conditions. The average age of the subjects was 34.4 (+ 9.56) years and they had an average educational level of 16.2 (+ 4.4) years. The lexical decision paradigm employed in this study is constituted by 408 stimuli, 240 words and 168 pseudo-words. The criteria for word selection were: frequency, length, grammatical category and morphology. Electroencephalogram (EEG) monopolar recording was obtained from 19 derivations (F3, F4, C3, C4, P3, P4, O1, O2, F7, F8, T3, T4, T5, T6, Fz, Cz and Pz), as well as event-related potentials (ERPs) for the word and pseudo-word sub-states. Results: In the first place, a chi-squared analysis was performed to establish whether significative differences existed between the rates of correct and incorrect answers for both sub-states. The value of chi-squared was 65.7 (gl=1) and significant for p<0.0001. A correlation value of 0.43 (p< 0.02) was found when the educational level and the percentage of correct answers in the sub-sate word were compared. On the other hand, for the pseudo-word sub-state, the value 0.24 was encountered for the same correlation, being statistically non-significant. Pearson's correlation coefficient was also calculated for the educational level variable compared to the mistakes committed when subjects were presented with frequent and infrequent words. In the case of infrequent words, a value of r = - 0.43 (p<0.02) was obtained when the educational level and the number of mistakes were correlated. No correlation was found when the educational level and the number of mistakes commited for frequent words were compared (r = - 0.06). A multivariate variance analysis for repeated measures was performed to determine significant differences between the reaction times when recognizing words or pseudo-words. The outcome showed that all effects were significant in the following cases: reaction times for words and pseudo-words, notwithstanding whether they were correct or incorrect; comparison between correct and incorrect answers, independently of their being words or pseudo-words, as well as the interactions between both effects. To determine differences between average ERPs for both sub-states, Student's T-test was applied with Bonferroni's correction and p<0.0002 as the significance level. Significant differences were encountered between the two sub-states, independently of the age or gender. In the 375-495 ms latency interval, a negative component was appreciated in the pseudo-words case, showing significant differences (p<0.0002) in the following derivations: F3, F4, C3, C4, P3, P4, O1, O2, T3, T5, T6, Fz, Cz and Pz. Amplitude differences between the two sub-states were more evident in Pz and P3 derivations followed by Cz. In addition, a positive component in the 700-795 ms latency interval was detected (mainly in 795 ms) when pseudo-words were presented. Here, the significant differences (p<0.0002) were manifest in the following derivations: F3, C3, P3, F7, T3, T5 and Pz. Amplitude differences between the two sub-states were mainly patent in Pz and P3 followed by C3. Discussion: When analyzing behavioral aspects, subjects made more mistakes when presented with words. However, individuals with less education were the ones committing more mistakes. From this we can infer that this variable may be associated with the range of lexical repertoire. A relation was encountered between educational level and word recognition. With regard to reaction times, significant differences were detected between both sub-states, since the recognition of both words and correct answers was achieved in shorter reaction times. Average reaction times for words and pseudo-words were 819.73 ms and 999.35 ms, respectively. Similarly, the latest potential component appeared in an interval of significant differences between 600 and 940 ms, though with a significance p<0.0005 between 690 and 805 ms. This means that positiveness occurred much sooner than the response, implying that the activity underlying ERPs is related to a cognitive processing of information due to the paradigm used. The analysis of ERPs primary components for both sub-states shows that significant differences arise until 270 ms. The negative component in this study was present between 270 and 580 ms, rendering it similar to N400 given its latency (around 400 ms). Although well-defined in centro-parietal regions, its distribution was generalized, which corresponds to the results of studies using the semantic incongruence paradigm. According to the data from previous research on ERPs, N400 has been associated with the integration process. If this were the case, this association would be equivalent to the semantic incongruence within a lexical integration process described in conventional literature as a "semantic facilitator", only that this time it would be limited to the process of access to the lexicon, which can be interpreted as a discrimination of the answer by assigning a meaning to a word, that is, to process information in the semantic module. This negative component may be related to the generalized response to brain activity when given a meaningless stimulus, i.e., a pseudo-word. Similarly, the wave amplitude may be related to the amount of activation necessary to gain access to the semantic representation of the stimulus in the memory. With regard to the positive component in this study, it is present between 600 and 940 ms and is interpreted as a late P300 (P3b), which has a latency in the 500-1400 ms interval. It is distributed over the centro-parietal region, making it a liable participant in the task categorization process, in which it is necessary to discriminate between the target from the non-target stimulus, and also reflects focalized attentional processes (voluntary) involved in the execution of the task. From the former, it is believed that this component may be related to attentional resources necessary to process the presentation of pseudo-words. Research dealing with the P600 component locate it within the context of statements and associate it with an anomaly in statement syntax. Therefore, even though the positive component lies within the P600 latency domain, this particular component was not considered as being present in this study, because a syntax incongruence paradigm was not used. Finally, the contribution of the present study lies in the finding of N400 and "P600" components, which have been reported when the "semantic facilitator" and the syntax incongruence paradigm were respectively used, but had not been observed when a lexical decision paradigm based on word recognition per se was utilized. Similarly, given that our results stem from a sample of healthy subjects, a comparison can be made with a patient population with semantic memory alterations.