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.

Reading speed and efficiency are achieved through the automatic recognition of written words. Difficulties in learning and recognizing the orthography of words can arise despite reiterative exposure to texts. This study aimed to investigate, in native Spanish-speaking late adolescents, how different levels of orthographic knowledge might result in behavioral and event-related brain potential differences during the recognition of orthographic errors. Forty-five healthy high school students were selected and divided into 3 equal groups (High, Medium, Low) according to their performance on a 5-test battery of orthographic knowledge. All participants performed an orthographic recognition task consisting of the sequential presentation of a picture (object, fruit, or animal) followed by a correctly, or incorrectly, written word (orthographic mismatch) that named the picture just shown. Electroencephalogram (EEG) recording took place simultaneously. Behavioral results showed that the Low group had a significantly lower number of correct responses and increased reaction times while processing orthographical errors. Tests showed significant positive correlations between higher performance on the experimental task and faster and more accurate reading. The P150 and P450 components showed higher voltages in the High group when processing orthographic errors, whereas N170 seemed less lateralized to the left hemisphere in the lower orthographic performers. Also, trials with orthographic errors elicited a frontal P450 component that was only evident in the High group. The present results show that higher levels of orthographic knowledge correlate with high reading performance, likely because of faster and more accurate perceptual processing, better visual orthographic representations, and top-down supervision, as the event-related brain potential findings seem to suggest.

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.