Influence of Stimulant Medication and Response Speed on Lateralization of Movement-Related Potentials in Attention-Deficit/Hyperactivity Disorder

Hyperactivity is one of the core symptoms in attention deficit hyperactivity disorder (ADHD). However, it remains unclear in which way the motor system itself and its development are affected by the disorder. Movement-related potentials (MRP) can separate different stages of movement execution, from the programming of a movement to motor post-processing and memory traces. Pre-movement MRP are absent or positive during early childhood and display a developmental increase of negativity. We examined the influences of response-speed, an indicator of the level of attention, and stimulant medication on lateralized MRP in 16 children with combined type ADHD compared to 20 matched healthy controls. We detected a significantly diminished lateralisation of MRP over the pre-motor and primary motor cortex during movement execution (initial motor potential peak, iMP) in patients with ADHD. Fast reactions (indicating increased visuo-motor attention) led to increased lateralized negativity during movement execution only in healthy controls, while in children with ADHD faster reaction times were associated with more positive amplitudes. Even though stimulant medication had some effect on attenuating group differences in lateralized MRP, this effect was insufficient to normalize lateralized iMP amplitudes.A reduced focal (lateralized) motor cortex activation during the command to muscle contraction points towards an immature motor system and a maturation delay of the (pre-) motor cortex in children with ADHD. A delayed maturation of the neuronal circuitry, which involves primary motor cortex, may contribute to ADHD pathophysiology

Study of single sweep event related brain potentials in dyslexia

The study of event-related potentials in dyslexic children requires particular attention in the definition of the clinical and analysis protocols. The clinical protocol here described was studied for the analysis of the different functions involved in the reading process. The analysis procedure is aimed to the reduction of ocular artifact, to the extraction of single sweep responses, to the estimation of parameters for the characterization of the processes involved in the reading function. A group of normal and dyslexic children was studied, and different mechanisms were evidenced during the reading function, through the evaluation of the activation sequence of the involved cortical areas

Dynamic Time Warping in the study of ERPs in dyslexic children

Aim of this paper is to compute a normal ERP pattern (template) and to quantify the morphological characteristics of ERPs. ERPs were recorded from normal and dyslexic children in a passive and in an active condition. Dynamic Time Warping (DTW) was used to align the averaged ERPs of normal subjects. After the computation of the templates, individual averaged ERPs were aligned with the corresponding template, in order to automates the identification of the relevant ERPs components. The latencies of these components in normal and dyslexic subjects were compared in the two different conditions. ERPs components of dyslexic children were always delayed in respect to normal children. Statistically significant latency differences were noticed both in the short-latency waves, related to attention mechanisms, and in the long-latency waves, presumably related to memory processes. P1 latency in T4 differed in the two groups of children in both tasks, with p<0.05. Morphological differences between the ERPs of normal and dyslexic children were also noticed in the right hemisphere: N2 latency in T4 differed in the two groups of children with p<0.05. This result suggests that dyslexia is associated with more general disruptions of the cerebral functions than that confined to the classical linguistic areas