Tesis doctoral de Erika Proal Fernandez
Attention-deficit/hyperactivity disorder (adhd) is one of the most common neurodevelopmental disorders occurring in childhood. The main symptoms are developmentally excessive levels of inattention, impulsivity and hyperactivity. Adhd occurs in 8 to 12% of school age children worldwide; the majority (60%-85%) continues to meet criteria for the disorder during their teenage years. volumetric studies in children with attention-deficit/hyperactivity disorder (adhd) have consistently found global reductions of total brain volume with frontal-striatal regions, cerebellum and parieto-temporal regions particularly affected relative to typically developing subjects. The adult diagnosis of adhd requires onset in childhood, but persistence of adhd into adulthood is now well documented. This longitudinal course together with smaller brain volumes in children with adhd has raised questions about brain development into adulthood. the use of different neuroimaging techniques by independent groups is leading to an improved understanding of the neural substrates underlying the pathophysiology of adhd. Nowadays, researchers have begun to place more emphasis on the potential contributions of dysfunctional brain circuits, rather than isolated regional abnormalities. Therefore, the aim of this thesis is to examine the neural substrates of adhd by applying three different anatomic neuroimaging approaches. A secondary aim is to analyze whether these brain differences are related with the diagnosis of adhd in childhood or whether it is associated with the persistence of the diagnosis in adulthood. the results of the present dissertation are two-fold. First, in a large sample of children and adolescents with adhd, we found a striking volumetric reduction in the ventral striatum, a region critically involved in reward processes that is a key relay in cortical-striatal-thalamo-cortical circuits (reward circuit). Second, in adults diagnosed with adhd in childhood, we found reduced cortical thickness and voxel-based morphometry (vbm) gray matter volume in parietal and motor regions (dorsal attentional network). Most of these differences were independent of current adult diagnoses status. In other words, these differences were largely found in both individuals with persistent adhd and in those who were in remission. By contrast, reward-related regions were diminished in probands with persistent adhd compared to controls but not in those who were in remission. Thus differences in reward-related circuitry (ventral striatum in children, orbitofrontal cortex, parahippocampus, thalamus, and frontal pole in adults) were associated with the current diagnosis of adhd, whereas frontal-parietal motor cortex differences in adults with adhd seem to reflect the trait of having had adhd in childhood. our data allow us to suggest an overall integrative hypothesis that dysfunction in the reward circuit, which was particularly prominent in children and adolescents with adhd and in the adults with persistent adhd, reflects ongoing symptoms of adhd. By contrast, abnormalities in the top-down control dorsal attentional network seem to be related to the trait of having had adhd in childhood, as the abnormalities were comparable in adults who had remitted or who had persistent adhd. On the basis of our data, we propose a model of adhd physiopathology in which two main circuits interact. These are the dorsal attentional network, which seems to be anatomically abnormal in individuals with a history of adhd, whether or not they are currently affected. As such, we hypothesize that dorsal attentional network deficiencies may be related to the genetic factors associated with adhd. By contrast, anatomic abnormalities in the reward circuit appear to be related to current adhd symptoms. Based on our data, we cannot differentiate whether anatomic changes in the reward circuits are the basis for symptomatic remission, or whether such changes in brain circuits reflect brain remodeling secondary to behavioral effects, such as learning and selective reinforcement. This question will have to be addressed in the future through longitudinal brain imaging studies that can incorporate genetic factors and treatment tracking methods.
Datos académicos de la tesis doctoral «Brain anatomy of attention deficit/hyperactivity disorder in children and adults with childhood onset«
- Título de la tesis: Brain anatomy of attention deficit/hyperactivity disorder in children and adults with childhood onset
- Autor: Erika Proal Fernandez
- Universidad: Autónoma de barcelona
- Fecha de lectura de la tesis: 27/06/2011
Dirección y tribunal
- Director de la tesis
- Susana Carmona Cabañete
- Tribunal
- Presidente del tribunal: carmen Junque plaja
- diego Antonio Redolar ripoll (vocal)
- (vocal)
- (vocal)