Vladimir V. Lazarev

EEG photic driving: right-hemisphere reactivity deficit in childhood autism. A pilot study.

In 14 autistic boys, aged 6-14 years, free of drug treatment, with relatively intact verbal functions and without severe or moderate mental retardation (I.Q. 91.4+/-22.8), intermittent photic stimulation at 11 fixed frequencies of 3-24 Hz revealed latent deficiency of the right hemisphere in the photic driving reactivity, predominantly at the fast alpha and beta frequencies of stimulation. The left-side prevalence was observed: 1) in the total number of driving peaks evaluated for the first four harmonics in the EEG spectra of 14 cortical areas and 2) in the driving amplitude in the spectra of the 2 occipital areas. As compared to 21 normally developing boys matched on age who did not show interhemispheric asymmetry in the driving reactivity, the autistic patients had significantly lower driving characteristics only in the right hemisphere. There were no significant differences between the autistic and control groups in the spontaneous EEG spectra of the occipital areas in the resting state.

Spectral F-Test power evaluation in the EEG during intermittent photic stimulaton

Intermittent photic stimulation (IPS) is an important functional test, which can induce the photic driving in the electroencephalogram (EEG). It is capable of enhancing latent oscillations manifestations not present in the resting EEG. However, for adequate quantitative evaluation of the photic driving, these changes should be assessed on a statistical basis. With this aim, the sampling distribution of spectral F test was investigated. On this basis, confidence limits of the SFT-estimate could be obtained for different practical situations, in which the signal-to-noise ratio and the number of epochs used in the estimation may vary. The technique was applied to the EEG of 10 normal subjects during IPS, and allowed detecting responses not only at the fundamental IPS frequency but also at higher harmonics. It also permitted to assess the strength of the photic driving responses and to compare them in different derivations and in different subjects.

Electrophysiological Correlates of Morphological Neuroplasticity in Human Callosal Dysgenesis

In search for the functional counterpart of the alternative Probst and sigmoid bundles, considered as morphological evidence of neuroplasticity in callosal dysgenesis, electroencephalographic (EEG) coherence analysis was combined with high resolution and diffusion tensor magnetic resonance imaging. Data of two patients with callosal agenesis, plus two with typical partial dysgenesis with a remnant genu, and one atypical patient with a substantially reduced genu were compared to those of fifteen neurotypic controls. The interhemispheric EEG coherence between homologous nontemporal brain regions corresponded to absence or partial presence of callosal connections. A generalized coherence reduction was observed in complete acallosal patients, as well as coherence preservation in the anterior areas of the two patients with a remnant genu. jThe sigmoid bundles found in three patients with partial dysgenesis correlated with augmented EEG coherence between anterior regions of one hemisphere and posterior regions of the other. These heterologous (crossed) interhemispheric connections were asymmetric in both imaging and EEG patterns, with predominance of the right-anterior-to-left-posterior connections over the mirror ones. The Probst bundles correlated with higher intrahemispheric long-distance coherence in all patients. The significant correlations observed for the delta, theta and alpha bands indicate that these alternative pathways are functional, although the neuropsychological nature of this function is still unknown.

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

Background Eye 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. Methods The 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. Results According 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. Conclusion The method is very simple and effective for VEOG attenuation without significant distortion of the EEG signal and embedded ERPs in all channels.

Auditory brainstem function in microcephaly related to Zika virus infection

Objective To study the effect of prenatal Zika virus (ZV) infection on brainstem function reflected in brainstem auditory evoked potentials (BAEPs). Methods In a cross-sectional study in 19 children (12 girls) with microcephaly related to ZV infection, aged between 12 and 62 weeks, the brainstem function was examined through BAEPs. The latencies of wave peaks I, III, and V of the left and right ears (n = 37) were standardized according to normative data, and compared between them by 2-tailed t test. The confounding variables (cephalic perimeter at the born and chronological age) were correlated with the normalized latencies using Pearson test. Results All patients showed, in general, clear waveforms, with latencies within 3 SDs of the normative values. However, statistically increased latencies of waves I and III (I > III, p = 0.031) were observed, relative to wave V (p < 0.001), the latter being closer to respective normative value. The latency of wave I was observed to increase with age (r = 0.45, p = 0.005). The waves, in turn, did not depend on cephalic perimeter. Conclusions These results are consistent with the functional normality of the brainstem structure and its lack of correlation with microcephaly, suggesting that the disruption produced by the ZV infection does not act in the cell proliferation phase, but mostly in the processes of neuronal migration and differentiation in the telencephalon.

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

Objective: To find objective evidence of accuracy of the Diagnostic and Statistical Manual of Mental Disorders (DSM) in the diagnosis of Attention Deficit Hyperactivity Disorder (ADHD), by comparing classifications of subjects based on behavioral (Attentional Network Test - ANT), psychological (Wechsler Intelligence Scale for Children - WISC-III), and neurophysiological (ANT-related potentials) data. Methods: Twenty typically developing (TD) boys and 19 boys diagnosed with ADHD according to DSM-IV-TR, aged 10-13 years, were examined using the ANT with simultaneous recording of the respective event-related potentials (ERPs). They also performed the Block Design, Digit Spam, Vocabulary and Arithmetic subtests of the WISC-III. A total of 815 variables of interest (VOI) obtained from the ANT, WISC-III scores, and ERP parameters were grouped by hierarchical clustering and integrated in 2 to 6 resultant vectors (RVs), from clusters at hierarchical levels 1 to 5. These RVs were used for the reclassification of subjects using the k-means method. Results: Regarding DSM-IV-TR diagnostics, the RVs from behavioral and psychological data and ERPs from the mid-frontal, mid-parietal plus right frontal, right central, and right temporal channels showed accuracy rates from 0.64 to 0.82 using the k-means reclassification. Among reclassifications with higher agreement (0.82), six subjects were reclassified (4 from the TD group, and 2 from the ADHD group). Assuming the reclassification of these six subjects, the estimated agreement between DSM and biological data was 84.61% with kappa index of 0.69. Conclusion: Results suggest biological validity and efficiency of DSM as a tool for ADHD diagnostics.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. Methods: Twenty 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) Results: From 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”. Discussion: Results 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.

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

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.