Estudio de rendimiento de las funciones ejecutivas en el trastorno por déficit de atención e hiperactividad (TDAH)implicación de la memoria de trabajo

Abstract

Introduction: The interest in studying the neuropsychological deficits that lie behind ADHD, among which the Working Memory (WM) stands out in its visuospatial and phonological dimensions, has been on increase. The aim of the current study was to explore the performance differences concerning the short-term memory and the visuospatial and phonological working memory among control and clinical groups acknowledging the clinical heterogeneity of the disorder. Additionally, our study aims to examine whether a deficiency in working memory, or any of its components, can be modulated by the different subtypes or by the severity of the basic characteristics of the disorder. Method: A group of 76 children with a prior diagnosis of ADHD was divided by the clinical subtype of the disorder: ADHD predominantly inattentive (n = 26, age M = 10,9, DT = 1,8; 66% male), and combined ADHD (n = 50, age M = 10.8, DT = 1.9; 61.5% male). Additionally, a control group of typically developing children was formed (n = 40, age M = 10.2, DT = 1.9; 57.5% male). Both groups completed a task battery to aimed to measure the short-term memory, as well as the visuospatial and phonological working memory. We calculated the Kolmogorov-Smirnov test in order to assess whether the data obtained had a normal distribution. Descriptive statistical analyzes were carried out and, subsequently, the Student&apos;s t test for the comparison of means for independent samples was applied. For the data that did not present a normal distribution (z <.05), it was necessary to resort to non-parametric tests: U-Mann-Whitney and H de Kruskal-Wallis. From a categorical perspective, we used an analysis of variance (unifactorial ANOVA) with the purpose of analyzing the differences of performance in the different cognitive tests between the subtypes. Likewise, the correlation between these clinical and performance variables in neuropsychological tasks was explored through the analysis of a Spearman correlation. The tasks that showed a significant correlation with the clinical scores, were standardized to Z scores, and included in multiple regression models with the clinical scores as dependent values. Results: The ADHD group showed a decreased performance at visuospatial (WMVS Task), as well as phonological (WISC Letter- Number Sequencing) working memory tasks. The decreased performance was consistent among the clinical subtypes and the control group. However, we did not find differences between clinical subtypes. The dimensions of ADHD and the performance output in the neuropsychological tasks used in the study were not related. Discussion: This study offers empirical evidence to the hypothesis that suggests that children with ADHD show a poor performance than controls at Working Memory tasks, including both visuospatial and phonological WM. Likewise, our study supports similar functioning in both dimensions of MT in clinical subtypes, suggesting that different nominal presentations of ADHD should be examined as the clinical expression of the disorder within a dimensional continuum rather than as two separable and separable qualitative disorders. In addition, the results of the study suggested that there is no correlation between the dimensions of the ADHD and the performance output in the Working Memory tasks.