Biology subjects

Abramov, D. M.

Publications and source records attributed to Abramov, D. M..

3 recordsLinked to original sources

bioRxiv2018

Conservative method for attenuation of Vertical Electrooculogram based on local suppression of artifact templates from ongoing EEG

BackgroundEye movement during blinking can be a significant artifact in ERP analysis (mainly if ERP is blink-locked). Blinks produce a large positive potential in the vertical electrooculogram (VEOG), spreading towards posterior direction. Two methods are the most frequently used to suppress VEOGs: linear regression to subtract the VEOG signal from each EEG channel and Independent Component Analysis (ICA). However, both lose some EEG information.\n\nMethodsThe present algorithm (1) statistically identifies the time position of VEOGs in the frontopolar channels; (2) performs EEG averaging for each channel, which results in blink templates; (3) subtracts each template from the respective EEG at each VEOG position, only when the linear correlation index between the template and the segment is greater than a threshold L. The signals from twenty subjects were acquired using a behavioral test and were treated using FilterBlink for subsequent ERP analysis. A model was designed to test the method for each subject using twenty copies of the EEG signal from the mid-central channel of the subject (which has almost no VEOG) representing each one of the 20 EEG channels and their respective blink templates. At the same 200 equidistant time points (marks), a signal (2.5 sinusoidal cycles at 1050 ms to emulate an ERP) was mixed with each model channel, along with the respective blink template of that channel, between 500 to 1200 ms after each mark.\n\nResultsAccording to the model, VEOGs interfered with both ERPs and the ongoing EEG mainly on the anterior medial leads, and no significant effect was observed on the mid-central channel (Cz). FilterBlink recovered approximately 90% (at Fp1) to 98% (Fz) of the original ERP and EEG signals to L of 0.1. In the analysis of real signals, the method reduced drastically the VEOG effect on the EEG after ERP and blink-artifact averaging.\n\nConclusionThe method is very simple and effective for VEOG attenuation without significant distortion of the EEG signal and embedded ERPs in all channels.

bioinformatics↗

bioRxiv2017

Estimating DSM accuracy for Attention Deficit Hyperactivity Disorder Based on Neurophysiological, Psychological, and Behavioral Correlates

Background.Psychiatric nosology lacks objective biological foundation, as well as typical biomarkers for diagnoses, which raises questions about its validity. The problem is particularly evident concerning Attention Deficit/Hyperactivity Disorder (ADHD). The objective of this study is to estimate whether the \"Diagnostic and Statistical Manual of Mental Disorders\" (DSM) is biologically valid for ADHD diagnosis using a multivariate analysis for small samples from a large dataset concerning neurophysiological, behavioral, and psychological variables.\n\nMethodsTwenty typically developing boys and 19 boys diagnosed with ADHD, aged 10-13 years, were examined using the Attentional Network Test (ANT) with records of event-related potentials (ERPs). From 815 variables, a reduced number of latent variables (LVs) were extracted with a clustering method, for further reclassification of subjects using the k-means method. This approach allowed multivariate analysis to be applied to a significantly larger number of variables than the number of cases (E. Wigneau et al., 2003, 2015)\n\nResultsFrom datasets including ERPs from the mid-frontal, mid-parietal, right frontal, and central channels, only seven subjects were miss-reclassified by the LVs. An estimated specificity of 75.00% and sensitivity of 89.47% for DSM were found in the reclassification. The kappa index between DSM and behavioral/psychological/neurophysiological data was 0.75, which is regarded as a \"substantial level of agreement\".\n\nDiscussionResults showed that CLV is a useful method for diagnostic classification using a large dataset of small samples, suggesting the biological validity of DSM for ADHD diagnosis, in accordance to alterations in fronto-striatal networks previously related to ADHD.

neuroscience↗

bioRxiv2017

Functional Asymmetry In The Central Brain Regions In Boys With Attention Deficit Hyperactivity Disorder Detected By Event Related Potentials During Performance Of The Attentional Network Test

BackgroundVarious 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.\n\nMethods20 typically developing (TD) boys and 19 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.\n\nResultsThe target-related potentials late characteristics from the C4 and C3 did not shown significant difference between the groups. The difference between ERPs of the C3 and C4 channels inside the interval of 40-290 ms after target onset was larger in the ADHD group than in control, mainly for incongruent target condition. This asymmetry and right late component were correlated with DSM scores, mainly to hyperactive and impulsive criteria.\n\nConclusionIn 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.

neuroscience↗