Event-related brain potentials in normal children during detection of inverse serial digits.

Three inverse serial digit detection tasks were evaluated with event-related brain potentials (ERPs) in 15 11-year-old children to determine how the increase of perceptual or memory demands could modify detection processing. Reaction times were significantly longer for the task that used visual blurring, compared to that with a greater memory demand. Difference-ERPs (target minus non-target conditions) showed three significant parietal components; one earlier positive peak at 162 ms interpreted as an index of working memory load; a same polarity 295 ms peak which probably represents a P3 analogous and a subsequent negative polarity component (520 ms) possibly involved with motor preparation. A fourth difference-component was a frontal positive peak at 680 ms, interpreted as related to task difficulty.

Event-related brain potentials during a continuous performance test (CPT) task in normal children.

BACKGROUND: Continuous Performance Test (CPT) is a commonly used paradigm to assess attention disorders that could involve working memory processes. METHODS: Event-related potentials (ERPs) during a CPT (X-AX) test were obtained in 16 healthy male students, with ages ranging from 9 to 11 years (X = 10.3). In grouped averaged ERPs, an endogenous slow positive potential was recorded in the first task (infrequent letter detection); maximum was at 460 msec with a slight lateralization tendency toward left parietal area. In the second task (target detection with an A as warning signal), an early (maximum at 330 msec) and more acute peak was detected without evidence of any lateralization. RESULTS: Reaction times were significantly shorter for the second task. Electrophysiologic differences between both target conditions showed an early, remarkable, and statistically significant component located at the parietal area at 340 msec. CONCLUSIONS: These ERPs findings could be interpreted as correlates with working memory processes in children.

Transitory cognitive impairment in epileptic children during a CPT task.

EEGs and behavioral responses were studied in two sex matched groups of 58 epileptic and 20 healthy children between 8 and 12 years of age, during the execution of a go-no go CPT (X; A-X) task to determine transitory cognitive impairment (TCI) incidence. Paroxysmal discharges were found on 87.9% and 5% of the EEGs in the epileptic and control groups respectively, with no differences related to sex. The predominant EEG findings with respect to paroxysmal discharges were the association of two or more types of paroxysms with frequency higher than 5/minute, an average duration less than 0.5 second and topographical distribution over temporal-parietal-occipital areas without significant interhemispheric differences. TCI was detected in 36.2% of epileptic children. The epileptic group showed significantly higher numbers of behavioral errors and longer reaction times (RTs) in relation to the control group. Analyzing RTs on the two blocks of the task, linear discriminant analysis showed an acceptable classification of TCI incidence between groups.

Activación Hemisférica Cerebral en Adultos Jóvenes Mientras Ejecutan Tareas Ortográficas Utilizando fMRI / Hemispheric Brain Activation in Young Adults While Performing Orthographic Tasks Using fMRI

Resumen El dominio del lenguaje escrito se basa en la consolidación de representaciones neurales complejas de los patrones ortográficos de las palabras. En virtud de explorar las características presentes en procesos neurales relacionados con la especialización ortográfica, se estudiaron con métodos de imagen por resonancia magnética funcional los niveles neurales de activación intrahemisférica de 27 jóvenes con alto y bajo rendimiento ortográfico mientras ejecutaban tareas ortográficas. Los resultados sugieren que, en participantes con alto rendimiento ortográfico, la intensidad de activación neural en el hemisferio izquierdo no difiere ante el estímulo de palabras o pseudohomófonos (palabras con error ortográfico); en cambio, difieren cuando se emiten respuestas correctas vs. incorrectas. En participantes con bajo rendimiento ortográfico no se encontró diferencia interhemisférica en ninguna tarea. Se encontró tendencia de que los participantes con bajo rendimiento ortográfico tienen mayor dispersión de la activación neural, respecto a los participantes con alto rendimiento, en el hemisferio derecho e izquierdo, además, en participantes con bajo rendimiento ortográfico se encontró tendencia de que la detección consciente aumenta la variación de la activación neural; sin embargo, no se encontró evidencia estadística concluyente. Este estudio ha abonado a la evidencia de la existencia de la especialización neural orientada a habilidades ortográficas.

Abstract The written language domain is based on the consolidation of complex neural representations of words' orthographic patterns. Here, we studied the characteristics and differences of the neural activation levels that occur in the neural processes related to orthographic specialization, with functional magnetic resonance imaging, in each hemisphere, of 27 young adults with low and high orthographic abilities when they performed orthographic tasks. The results suggest that in high-orthographic-performance participants' left hemispheric neural activation does not vary between words and pseudohomophones; otherwise, their neural activation variates in incorrect vs. correct responses. There were not found interhemispheric differences in low-orthographic-performance participants where they performed any type of task. There were some tendency in the low-orthographic-performance participants to have greater neural activation dispersion, regarding the high-orthographic-performance participants, in both hemispheres, also, there were found tendency in low-orthographic-performance participants to have greater neural activation variation in explicit tasks; nevertheless, there is not enough conclusive statistic evidence. This study increases the evidence of lateralized neural specialization of orthographic abilities.

Rapid automatized naming and lexical decision in children from an electrophysiological perspective.

Rapid Automatized Naming (RAN) deficits have been associated with less developed orthographic abilities that may affect lexical decisions. The effects of Spanish-speaking children's RAN performance on lexical decisions were evaluated by analyzing ERP and behavioral measures. Based upon their naming speed in four RAN tasks, 28 normal IQ, right-handed, 7-year-old children were selected and divided uniformly into two groups: average-naming (AN), and slow-naming (SN). ERPs were obtained during a lexical decision task consisting of 100 strings of four sequentially-presented letters that completed words (50 trials) or pseudowords (also 50 trials). The SN group showed major reading difficulties when compared to the AN group, as well as a significantly lower number of correct responses and slower reaction times in the lexical task. Two main ERP components were observed: parietal N320, interpreted as analogous to N170/N200; and a subsequent P3-like component (P500) with a higher amplitude for pseudowords, which probably reflects higher cognitive demands. Better reading comprehension and fewer misread pseudowords correlated with minor N320 latencies, while lower N320 amplitudes for words correlated with faster reading speeds, lower naming times and fewer errors while reading a text. The present results suggest that naming speed and ERP seem to be valuable in distinguishing early orthographic stored code retrieval abilities through a lexical decision task. Moreover, RAN and ERP emerge as accurate tools for evaluating reading processes in the early stages of reading acquisition.

[Methylphenidate and short-term memory in young females with attention deficit hyperactivity disorder. A study using functional magnetic resonance imaging]. / Metilfenidato y memoria a corto plazo en mujeres jovenes con trastorno por deficit de atencion/hiperactividad. Estudio de resonancia magnetica funcional.

INTRODUCTION: Attention deficit/hyperactivity disorder (ADHD) is a common behavioral disorder found mainly in males, thus current knowledge on its clinical expression in female adults is extremely limited. AIM. To evaluate the behavioral and neural substrates associated with the performance of a short-term memory task in female ADHD adults, with and without methylphenidate exposure, with respect to a control group. SUBJECTS AND METHODS: Two groups of eight young right-handed, female, university students with ADHD and healthy controls matched by age, gender, handedness and academic level, voluntarily participated. All subjects performed twice an easy auditory short-term memory task (ADHD group without, and 90 minutes post-intake of methylphenidate 0.4 mg/kg in a counterbalanced order). The BOLD-fMRI response was used as a measure of neural activity during task performance. RESULTS: ADHD subjects showed a tendency to improve their performances under medication, showing an increased widespread functional activation, especially relevant over left frontal and cerebellar areas, in comparison with control subjects. CONCLUSIONS: Methylphenidate slightly improves short-term memory task performance in adult female ADHD subjects by modifying underlying neural functioning patterns.

Time reproduction disturbances in ADHD children: an ERP study.

Sixteen ADHD children and a control group were asked to reproduce the varying time duration of successively presented visual stimuli. Time estimation was poorer in ADHD children, who showed more impulsive errors. ERPs exhibited similar grand-mean waveforms for both groups during the estimating period, but they were significantly different during the reproducing stage, when an early positive wave over frontal regions characterized the control group, interpreted as memory-guided motor output, followed by a slow negativity probably reflecting an inhibitory motor closure process, both probably involving central executive networks that seem to be improperly activated in ADHD children.