In Attention Deficit Hyperactivity disorder (ADHD), fMRI studies show asymmetric alterations: widespread hypoactivation in anterior cortical areas and hyperactivation in some posterior regions, and the latter is considered to be related to compensatory processes. In Posner’s attentional networks, an important role is attributed to functional interhemispheric asymmetries. The psychophysiological Attention Network Test (ANT), which measures the efficiency of the alerting, orienting, and executive networks, seems particularly informative for ADHD. Potentials related to ANT stimuli (ANT-RPs) have revealed reduced cognitive potential P3 in ADHD. However, there are no studies associated with asymmetry of ANT-RPs. In the present study, conducted with 20 typically developing boys and 19 boys with ADHD, aged 11–13 years, the efficiency of the three Posner’s networks regarding performance and amplitude asymmetries in ANT-RPs was evaluated according to the arithmetic difference of these parameters between different cue and target presentation conditions. The results were correlated to Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) scores. Regarding accuracy and intraindividual variation in reaction time, ADHD subjects showed lower efficiency of executive and alerting network, and this effect was correlated with DSM. Regarding alerting network, ANT-RPs in ADHD did not have the right-side amplitude prevalence in the temporal regions, which was observed in controls. In all ANT conditions, significantly higher asymmetries were observed in ADHD than in controls in the occipital regions 40–200 ms after target onset. Their amplitude in ADHD subjects was inversely proportional to DSM scores of inattentiveness and directly proportional to accuracy and efficiency of the executive network. The results suggest impaired alerting and executive networks in ADHD and compensatory occipital mechanisms.

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Background: Various functional asymmetries detected by different neurophysiological and neuroimaging methods have been reported in the literature on the Attention Deficit Hyperactivity Disorder (ADHD), some of them pointing to the right hemisphere activity. In our attempt to discriminate the ADHD patients from normal subjects by hierarchical clustering of behavioural, psychological and event related potential (ERP) variables, the late P3 component of potentials from the right central region (C4) proved to be one of the most informative parameters (in preparation for publication). Here, we have studied the differences in ERPs between the left (C3) and right (C4) central leads and relation of this asymmetry to ADHD diagnosed using DSM. Methods: 16 typically developing (TD) boys and 16 boys diagnosed with ADHD according to DSM-IV-TR, aged 10-13 years, were examined by the Attentional Network Test (ANT), with simultaneous recording of the respective ERPs. The intergroup differences in the ERP amplitude parameters in the left (C3) and right (C4)central channels and in the difference in these parameters between the two channels ('C3 minus C4') were accessed. These characteristics were compared to the subjects' DSM scores and ANT performance. Results:The target-related potentials' late characteristics from the C4 showed significant difference between the groups, while no difference was observed for the C3. Only in the ADHD patients, both the left and right late target ERP characteristics correlated with the reaction time, while the DSM scores did not show any correlations in both groups. The difference between ERPs of the C3 and C4 channels inside the interval of 40-290 ms after target onset was positive in the ADHD group and negative in the control group. This asymmetry correlated with DSM scores, mainly to hyperactive and impulsive criteria. Conclusion:In ADHD patients, the results suggest ERP pattern of right-side functional predominance in the motor control, which correlates to DSM scores, mainly to hyperactive and impulsive criteria.

This article presents the results of a study to reduce the number of variables necessary to represent the Raman spectrum acquired from the artery tissue when irradiated by a low power infrared laser. The analyzed methods were: peak detection, genetic algorithm, wavelets and principal components. The reduced vectors generated by these methods were applied to an artificial neural network to classify the target artery tissue into a non-pathological tissue, atherosclerostic lesion or calcified tissue. For each method, the neural network was trained by a set of 15 reduced spectra of samples of the three types of tissues and validated by another set of 10 sample reduced spectra. Among the analyzed methods, the spectrum compression by wavelets and the variable number reduction by principal components presented the best results and they were selected for the next phase of the project.