The Significance of Impulsive Error in Children With ADHD.

A deficit of inhibition ability is a neuropsychological problem in children with attention deficit hyperactivity disorder (ADHD). We investigated whether in children who made impulsive error (IE), less error-related negativity (ERN) would correlate with poorer executive attention functions (EAFs). Ninety children (49 with ADHD and 41 without ADHD) were investigated by a 4-minute simple reaction time task and simultaneous electroencephalogram. When they made IE, the ERN in response-locked event-related potential (ERP) was defined as error awareness. The average area under curve of ERN in the control group with IEs was used as the proper criterion for regrouping the children with ADHD into 2 groups: ADHD children with enough ERN (ADHD-enough ERN) and those with less ERN (ADHD-less ERN). EAFs from Comprehensive Nonverbal Attention Test were used as objective indices, and behavioral questionnaires were used as subjective indices and statistically analyzed within ADHD groups. Forty-eight percent of the children made IEs. ADHD(n = 31, 63%) was significantly more than in the control group (n = 12, 29%; P < .001). The ADHD group had significantly less ERN than did the control group while making IE, especially at frontal and central electrodes ( P < .01). Both ADHD-less ERN and ADHD-enough ERN groups had poorer subjective EAFs on questionnaires. Only the ADHD-less ERN group had significant poorer objective EAFs on the Comprehensive Nonverbal Attention Test than did the ADHD without IE. We conclude that investigating the IE and ERN of IE in children with ADHD might help to differentiate subtypes of ADHD with different neuropsychological abilities, and the possibility that ADHD-less ERN children might be confirmed a meaningful subgroup that needs close follow-up, treatments different from standard, or both.

Electroencephalogram valid rate in simple reaction time task as an easy index of children's attention functions.

BACKGROUND: Electroencephalogram (EEG) signal artifacts occur often in children, but an EEG valid rate (VR), constructed by excluding the artifacts, might be meaningful to evaluate children's neuropsychological functions. The aim of this study was to develop an easy screening index, the EEGVR, and to investigate attention function in children using this index. METHODS: The EEG was carried out during a 4 min simple reaction time (SRT) task as standard procedure in 50 children, consisting of 26 with attention-deficit-hyperactivity disorder (ADHD; mean age, 9.8 years; range, 8-11.3 years) and 24 without (mean age, 10.1 years; range, 7.8-12 years). An easy index was derived from the valid rate (VR) of EEG using area under the receiver operating characteristic curve. The index was applied to regroup the 50 children into high VR (HVR) and low VR (LVR) groups, while the Comprehensive Non-verbal Attention Test (CNAT) and four behavioral questionnaires were compared between the two groups in order to investigate the validity of this index. RESULTS: The EEGVR at 75% was optimal to identify HVR and LVR (sensitivity, 0.769; specificity, 0.792). The LVR group had significantly lower scores on both CNAT and the behavioral questionnaires, although the demographic variables and full-scale intelligence quotient (FSIQ) were similar between the two groups. CONCLUSIONS: The EEGVR in an SRT task might be an easy and effective index to screen the attention function of children, and could consequently contribute to the early diagnosis of ADHD.

Selective modulation of motor cortical plasticity during voluntary contraction of the antagonist muscle.

A fundamental approach for resolving motor deficits in patients suffering from various neurological diseases is to improve the impaired cortical function through the modulation of plasticity. In order to advance clinical practice in this regard, it is necessary to better understand the interactions that occur between functional neuromuscular activity and the resulting cortical plasticity. This study tested whether the voluntary contraction of an antagonist muscle modulates the plasticity-like effect of continuous theta burst stimulation (cTBS) recorded from the agonist. The effects of various opposing torques produced by the antagonist were also measured. As a result, the suppressing effect of cTBS was enhanced by mild antagonist contraction, whereas effortful antagonist contraction suspended the plasticity caused by cTBS. In contrast, the antagonist contractions right after cTBS did not significantly influence the effect of cTBS. The results indicate that the antagonist activity alters the effect of cTBS, especially in protocols with synchronous magnetic stimulation and antagonist contraction. Such modulation on cTBS may be through a reciprocal mechanism within the motor cortex, although the spinal regulation of the motoneuronal pool cannot be fully excluded. The present findings are beneficial for elucidating the mechanism of neuromuscular control and for resolving related neurological disorders.