Electrophysiological correlates of reading in children with attention deficit hyperactivity disorder. / Correlatos electrofisiologicos de la lectura en niños con trastorno por deficit de atencion/hiperactividad.

AIMS: To investigate whether or not the deficits in executive functions in the attention deficit hyperactivity disorder (ADHD) affect reading comprehension and identify a potential biological marker of this neuropsychological endophenotype through event-related potentials (ERP). The phenotypic association between reading comprehension and the specific functions of inhibition and working memory is studied. SUBJECTS AND METHODS: The sample consisted of 52 children with ADHD (8-13 years) divided in two groups according to the presence (TDAH-; n = 27; percentile < 30) or the absence (TDAH+; n = 25; percentile > 50) of reading comprehension deficits and a control group (n = 27). The executive functions were evaluated. The ERPs were assessed during a task in which anaphoric sentences of different lengths were presented, recording the ERP in the last adjective of the sentence that required a gender agreement. RESULTS: Working memory and inhibition were associated to reading comprehension performance. The ADHD+ group and the control group seem to detect the disagreement at 100 ms, while the ADHD- group does not activate its working memory until 250 ms. CONCLUSIONS: The delay in the implementation of the working memory mechanisms helps us to understand the deficits in reading comprehension of the ADHD- group.

TITLE: Correlatos electrofisiologicos de la lectura en niños con trastorno por deficit de atencion/hiperactividad.Objetivos. Investigar si los deficits en las funciones ejecutivas en el trastorno por deficit de atencion/hiperactividad (TDAH) afectan a su compresion lectora e identificar un potencial marcador biologico de este endofenotipo neuropsicologico a traves de potenciales relacionados con eventos. Especificamente, hipotetizar si las diferencias en memoria de trabajo e inhibicion mantienen una asociacion fenotipica con la comprension lectora en el TDAH. Sujetos y metodos. La muestra estuvo constituida por 52 niños con TDAH (8-13 años) divididos en dos grupos segun la presencia (TDAH­; n = 27; percentil < 30) o ausencia (TDAH+; n = 25; percentil > 50) de deficit en compresion lectora y un grupo control (n = 27). Se evaluaron las funciones ejecutivas y se realizo un experimento de potenciales relacionados con eventos en el que se presentaron oraciones anaforicas de diferentes longitudes, y se registraron los potenciales relacionados con eventos en el ultimo adjetivo de la oracion que requiere acuerdo de genero. Resultados. Se encontro una relacion entre memoria de trabajo e inhibicion con el rendimiento en compresion lectora. Mientras que los grupos de TDAH+ y control mostraron signos de deteccion de no concordancia sintactica a los 100 ms, el grupo de TDAH­ no activo la memoria de trabajo hasta los 250 ms. Conclusiones. La lentitud en la puesta en marcha de los mecanismos de memoria de trabajo nos ayuda a entender los deficits en comprension lectora del grupo de TDAH­.

[Neuropsychological assessment of memory in attention deficit hyperactivity disorder: the role of executive functions]. / Evaluación neuropsicológica de la memoria en el trastorno pordéficit de atención/hiperactividad: papel de las funciones ejecutivas.

INTRODUCTION: There is an important agreement on the consideration of attention deficit hyperactivity disorder (ADHD) as a condition characterized by neurodevelopmental dysfunction of fronto-striatal dopaminergic and noradrenergic circuits with resultant executive deficits in cognitive functioning. AIM: To assess the existence of memory deficits in children with ADHD associated with a poor performance executive. SUBJECTS AND METHODS: We assess 14 children diagnosed with ADHD combined type and 14 controls matched on intellectual coefficient, age and level of schooling, in a neuropsychological evaluation protocol designed to assess executive functions and memory skills using Auditory Verbal Learning Test, Memory for Stories Test -Test of Memory and Learning (TOMAL)-, Complex Figure Text, Visual Selective Reminding Test (TOMAL), Tower of Hanoi, Memory Phrases Test (Siegel and Ryan), Digit Span (Wechsler Intelligence Scale for Children-Revised) and Tapping Test (Wechsler Memory Scale III). RESULTS: The ADHD group showed deficits in the learning and free recall of verbal material, in procedural and working memory. No group differences were observed in the visual memory tasks. CONCLUSIONS: The results are analyzed in terms of difficulty in coding strategies, storage and search of information previously stored in the group with ADHD, at least for the kind of verbal information. These difficulties are associated with deficits in executive functioning.

Shift-back of right into left hemisphere language dominance after control of epileptic seizures: evidence for epilepsy driven functional cerebral organization.

Atypical, i.e. right hemisphere language dominance is frequently observed in early onset left hemisphere epilepsies. In left mesial temporal lobe epilepsy, where eloquent cortex is not directly involved, it is a matter of debate, to which degree atypical language dominance is driven not only by morphological lesions but also by epileptic dysfunction, and whether atypical dominance is hardwired or not. Taking this as the background this study evaluated the hypothesis that epilepsy driven atypical dominancy might be reversible when seizures are successfully controlled. This was evaluated in patients with left mesial temporal lobe epilepsy, who were atypically language dominant by means of language fMRI before surgery, and became seizure free after left selective amygdalo-hippocampectomy. Three out of 53 consecutive atypically dominant patients with chronic epilepsy fulfilled these criteria. Postoperative follow-up language fMRI indicated reversal of right into left dominance in one patient going along with unexpected losses in verbal memory performance. The two other patients experienced unchanged or even enhancement of the pre-existing dominance pattern, going along with consistent postoperative performance changes in cognition. The data thus provide supporting evidence that atypical language dominance can indeed be functionally driven and moreover that in at least some patients, right hemispheric language can shift-back to the left hemisphere when the driving factor, i.e. seizures, becomes successfully controlled. The results have clinical implications for outcome prediction after brain surgery in atypically dominant patients with epilepsy. However, further research in larger groups of atypically dominant patients is required to identify the conditions under which atypical dominance becomes hardwired and when not.