P1 Peak Research Articles

Temperature damping capacity and microstructure evolution of Mg–Al–Zn–Sn alloy

The temperature damping capacities of Mg–3Al–1Zn-xSn (x=3, 6, 9) alloys were investigated using a Dynamic Mechanical Thermal Analyzer (DMA) under varied loading frequencies and Sn concentrations. The addition of Sn resulted in a leftward shift of the P1 dislocation damping peak around 80 °C and a rightward shift of the P3 peak around 220 °C, which were attributed to the second phases in the vicinity of grain boundaries. By combining the Granato-Lücke model and the Peguin model, the damping curves were analyzed, and the temperature damping mechanism of Mg–3Al–1Zn-xSn alloy was summarized. Before 220 °C, the addition of Sn significantly enhanced the damping capacity at different frequencies, which was attributed to the increased of point defects and precipitates. The damping mechanism was dominated by microplastic internal friction in the later part of the test. There is a negative correlation between frequency and damping. The observation of microstructures suggested that the dynamic recrystallization, the twining, and the non-basal slipping systems were the sources of the microplastic damping capacity. The dynamic recrystallization mechanism owing to cyclic loading was identified.

Conflict and control in cortical responses to inconsistent emotional signals in a face-word Stroop.

Social communication is fraught with ambiguity. Negotiating the social world requires interpreting the affective signals we receive and often selecting between channels of conflicting affective information. The affective face-word Stroop (AFWS) provides an experimental paradigm which may identify cognitive-affective control mechanisms underpinning essential social-affective skills. Initial functional magnetic resonance imaging (fMRI) study of the AFWS identified right amygdala as driving this affective conflict and left rostral anterior cingulate cortex (rACC) as the locus of conflict control. We employed electroencephalogram (EEG) and eLORETA source localization to investigate the timing, location, and sequence of control processes when responding to affective conflict generated during the AFWS. However we designated affective word as the response target and affective face as the distractor to maximize conflict and control effects. Reaction times showed slowed responses in high vs. low control conditions, corresponding to a Rabbitt type control effect rather than the previously observed Grattan effect. Control related activation occurred in right rACC 96-118 ms post-stimulus, corresponding to the resolution of the P1 peak in the Visual Evoked Potential (VEP). Face distractors elicit right hemisphere control, while word distractors elicit left hemisphere control. Low control trials require rapid "booting up" control resources observable through VEPs. Incongruent trial activity in right fusiform face area is suppressed 118-156 ms post stimulus corresponding to onset and development of the N170 VEP component. Results are consistent with a predicted sequence of rapid early amygdala activation by affective conflict, then rACC inhibition of amygdala decreasing facilitation of affective face processing (however, amygdala activity is not observable with EEG).

A feasibility study for objective evaluation of visual acuity based on pattern-reversal visual evoked potentials and other related visual parameters with machine learning algorithm

BackgroundTo develop machine learning models for objectively evaluating visual acuity (VA) based on pattern-reversal visual evoked potentials (PRVEPs) and other related visual parameters.MethodsTwenty-four volunteers were recruited and forty-eight eyes were divided into four groups of 1.0, 0.8, 0.6, and 0.4 (decimal vision). The relationship between VA, peak time, or amplitude of P100 recorded at 5.7°, 2.6°, 1°, 34′, 15′, and 7′ check sizes were analyzed using repeated-measures analysis of variance. Correlations between VA and P100, contrast sensitivity (CS), refractive error, wavefront aberrations, and visual field were analyzed by rank correlation. Based on meaningful P100 peak time, P100 amplitude, and other related visual parameters, four machine learning algorithms and an ensemble classification algorithm were used to construct objective assessment models for VA. Receiver operating characteristic (ROC) curves were used to compare the efficacy of different models by repeated sampling comparisons and ten-fold cross-validation.ResultsThe main effects of P100 peak time and amplitude between different VA and check sizes were statistically significant (all P < 0.05). Except amplitude at 2.6° and 5.7°, VA was negatively correlated with peak time and positively correlated with amplitude. The peak time initially shortened with increasing check size and gradually lengthened after the minimum value was reached at 1°. At the 1° check size, there were statistically significant differences when comparing the peak times between the vision groups with each other (all P < 0.05), and the amplitudes of the vision reduction groups were significantly lower than that of the 1.0 vision group (all P < 0.01). The correlations between peak time, amplitude, and visual acuity were all highest at 1° (rs = − 0.740, 0.438). VA positively correlated with CS and spherical equivalent (all P < 0.001). There was a negative correlation between VA and coma aberrations (P < 0.05). For different binarization classifications of VA, the classifier models with the best assessment efficacy all had the mean area under the ROC curves (AUC) above 0.95 for 500 replicate samples and above 0.84 for ten-fold cross-validation.ConclusionsMachine learning models established by meaning visual parameters related to visual acuity can assist in the objective evaluation of VA.

Processing of attentional and emotional stimuli depends on retrospective response of foot pressure: Conceptualizing neuron-cognitive distribution in human brain

Cognitive function of human brain requires temporal execution of emotional or attentional tasks, or their inter-dependence influences. Smooth execution of such tasks requires spontaneous distribution of cognitive load at specific regions of brain based on its classification. A strong connectivity between peripheral sensors and central nervous system is thought to assist the cognitive load distribution effectively. Novelty of current study evaluates the modulation of foot pressure and its mapping with distributed cognitive load while executing attentional biased emotional tasks. Emotional stimulus in form of happy and sad faces with attentional paradigm drawn on them were used in the study. Behavioral results were measured with respect to the analysis of response time (RT) and response accuracy (%). Neurological signals were acquired using 10-channel EEG data acquisition system, whereas, another 6 channels were used to measure foot pressure in the left and right feet at three different locations of foot. Acquired signals were further analyzed in time and frequency domains to interpret the cognitive load distribution, and the influence of foot pressure on distribution of cognitive loads. We found that the foot pressure accelerated the response accuracy rate in attending the local scope of attention, which was not in the case of global scope of attention. This means that the global attention does not require any pressure from peripheral sensory neurons. Our event related potential (ERP) results revealed that the early sensory negative N100 characterized the processing of global scope of attention coupled with high-foot pressure. However, the late positive peak of P300 and P600 associated with local scope of attention along with high-foot pressure. The global scope of attention with low-foot pressure modulates delta and theta oscillations. These results largely contribute to the literature on cognitive neuroscience of attention and it corelation with the peripheral sensory foot pressure.

Analysis of relaxation peaks during continuous heating of cold rolled Al–Mg–Si alloy

ABSTRACT In this study the effect of plastic deformation on internal friction peaks in Al based alloy is discussed. For that, an Al–Mg–Si alloy (AA6060) is subjected to cold rolling with a ratio ϵ = 80%. For both samples (water quenched and water quenched then cold rolled), the results revealed the appearance of a peak P1 at medium temperature (∼463 K), which is related to the dragging of Mg or Mg-Si clouds in the strain field of dislocations firmly pinned by metastable precipitates. Moreover, cold rolled sample exhibits a second peak PR at high temperature that is interpreted as a transition from high IF background to low IF one due to a recrystallisation process. Besides to dynamical mechanical analysis, DSC, dilatometry and Vickers microhardness are used to follow the structural evolution of the alloy.

Electroencephalogram-based objective assessment of cognitive function level associated with age-related hearing loss.

Age-Related Hearing Loss (ARHL) is a common problem in aging. Numerous longitudinal cohort studies have revealed that ARHL is closely related to cognitive function, leading to a significant risk of cognitive decline and dementia. This risk gradually increases with the severity of hearing loss. We designed dual auditory Oddball and cognitive task paradigms for the ARHL subjects, then obtained the Montreal Cognitive Assessment (MoCA) scale evaluation results for all the subjects. Multi-dimensional EEG characteristics helped explore potential biomarkers to evaluate the cognitive level of the ARHL group, having a significantly lower P300 peak amplitude coupled with a prolonged latency. Moreover, visual memory, auditory memory, and logical calculation were investigated during the cognitive task paradigm. In the ARHL groups, the alpha-to-beta rhythm energy ratio in the visual and auditory memory retention period and the wavelet packet entropy value within the logical calculation period were significantly reduced. Correlation analysis between the above specificity indicators and the subjective scale results of the ARHL group revealed that the auditory P300 component characteristics could assess attention resources and information processing speed. The alpha and beta rhythm energy ratio and wavelet packet entropy can become potential indicators to determine working memory and logical cognitive computation-related cognitive ability.

Analysis of the slope between P50 and N95 waves of the large field pattern electroretinogram as an additional indicator of ganglion cell dysfunction.

Dysfunction of the retinal ganglion cells (RGC) can be detected by the pattern electroretinogram (PERG) as a reduction of the N95 amplitude, a decrease of the ratio between N95 and P50 amplitude and/or a shortening of P50 peak time. Additionally, the slope from the top of the P50 towards the N95 (P50-N95 slope) is less steep than in control subjects. The aim of the study was to quantitatively evaluate this slope in large field PERGs in controls and patients with RGC dysfunction due to optic neuropathy. Large field (21.6°X27.8°) PERGs and optical coherence tomography (OCT) data from 30 eyes of the 30 patients with different types of clinically confirmed optic neuropathies, and with P50 amplitudes within normal limits and abnormal PERG N95 were retrospectively analysed and compared to 30 healthy eyes of 30 control subjects. The P50-N95 slope was analysed with a linear regression from 50 to 80ms after the stimulus reversal. The patients with optic neuropathy exhibited a significant reduction of the N95 amplitude (p < 0.001) and N95/P50 ratio (p < 0.001), the P50 peak time was mildly shorter (p = 0.03). The P50-N95 slope was significantly less steep in eyes with optic neuropathies (-0.089 ± 0.029 vs. -0.220 ± 0.041, p < 0.001). Thickness of temporal RNFL and the P50-N95 slope appeared to be the most sensitive and specific parameters for detecting RGC dysfunction (AUC = 1.0). The slope between the P50 and N95 waves of a large field PERG is considerably less steep in patients with RGC dysfunction and could thus be an efficient biomarker, particularly in the diagnosis of early or borderline cases.

Quality evaluation of Eucommiae Folium extracts and discovery of efficacy-associated quality markers based on spectrum-effect relationship

ABSTRACT The spectrum-effect relationship between chemical fingerprints and antioxidant activities was established to evaluate the quality of Eucommiae Folium (EF) extracts and discover potential efficacy-associated quality markers. Characteristic fingerprints of different batches of EF extracts were generated by high-performance liquid chromatography (HPLC), and a similarity analysis was performed by hierarchical cluster analysis (HCA). Then the total antioxidant capacity assay kit with ferric reducing antioxidant assay (FRAP) method was used to determine antioxidant activity. The spectrum-effect relationship was established to identify the chemical constituents that impart antioxidant activities of Eucommiae Folium (EF) extracts using partial least squares regression (PLSR). HPLC fingerprints of EF extracts were established with the optimized chromatographic conditions: the mobile phase consisted 0.1% phosphoric acid -water (A) and acetonitrile (B), the detection wavelength was 326 nm, the column temperature was 30°C, and the flow rate was 0.8 mL/min. The correlation coefficient of similarity between 12 batches of extracts was ≥0.995. Compounds corresponding peaks P1, P2, P6 (chlorogenic acid), and P8 were closely related to the stable antioxidant activities of EF extracts, and could be selected as potential quality markers. An agile and efficient method that can ensure the intra-assay stability of biological activity of EF extracts and discover efficacy-associated quality markers was successfully built based on spectrum-effect relationship.

Electrophysiological evidence for the characteristics of implicit self-schema and other-schema in patients with major depressive disorder: An event-related potential study.

The significance of implicit self-schema and other-schema in major depressive disorder (MDD) is highlighted by both cognitive theory and attachment theory. The purpose of the current study was to investigate the behavioral and event-related potential (ERP) characteristics of implicit schemas in MDD patients. The current study recruited 40 patients with MDD and 33 healthy controls (HCs). The participants were screened for mental disorders using the Mini-International Neuropsychiatric Interview. Hamilton Depression Rating Scale-17 and Hamilton Anxiety Rating Scale-14 were employed to assess the clinical symptoms. Extrinsic Affective Simon Task (EAST) was conducted to measure the characteristics of implicit schemas. Meanwhile, reaction time and electroencephalogram data were recorded. Behavioral indexes showed that HCs responded faster to positive self and positive others than negative self (t = -3.304, p = 0.002, Cohen's d = 0.575) and negative others (t = -3.155, p = 0.003, Cohen's d = 0.549), respectively. However, MDD did not show this pattern (p > 0.05). The difference in other-EAST effect between HCs and MDD was significant (t = 2.937, p = 0.004, Cohen's d = 0.691). The ERP indicators of self-schema showed that under the condition of positive self, the mean amplitude of LPP in MDD was significantly smaller than that in HCs (t = -2.180, p = 0.034, Cohen's d = 0.902). The ERP indexes of other-schema showed that HCs had a larger absolute value of N200 peak amplitude for negative others (t = 2.950, p = 0.005, Cohen's d = 0.584) and a larger P300 peak amplitude for positive others (t = 2.185, p = 0.033, Cohen's d = 0.433). The above patterns were not shown in MDD (p > 0.05). The comparison between groups found that under the condition of negative others, the absolute value of N200 peak amplitude in HCs was larger than that in MDD (t = 2.833, p = 0.006, Cohen's d = 1.404); under the condition of positive others, the P300 peak amplitude (t = -2.906, p = 0.005, Cohen's d = 1.602) and LPP amplitude (t = -2.367, p = 0.022, Cohen's d = 1.100) in MDD were smaller than that in HCs. Patients with MDD lack positive self-schema and positive other-schema. Implicit other-schema might be related to abnormalities in both the early automatic processing stage and the late elaborate processing stage, while the implicit self-schema might be related only to the abnormality in the late elaborate processing stage.

Electrophysiological correlates of response time outliers: Outlier related potentials.

In response time (RT) research, RTs which largely deviate from the RT distribution are considered "outliers". Outliers are typically excluded from RT analysis building upon the implicit assumption that cognitive processing is distorted in outlier trials. The present study aims to test this assumption by comparing cognitive processing indexed by event-related potentials (ERP) of trials with outliers and valid trials in two different tasks. To this end, we compared stimulus- and response-locked ERPs for outliers identified by nine different methods with valid trials, using cluster-based permutation tests. Consistently across outlier exclusion methods and tasks, the late positive complex (P3) associated with response-related processes was reduced in outliers. Analyses of response-locked ERPs related this P3 attenuation to a slower and temporally more extended increase of the P3, possibly indexing reduced evidence accumulation speed in outliers. P3 peak amplitude in response-locked ERPs was similar between outliers and valid trials, suggesting that the absolute amount of evidence required for a response remained comparable. Furthermore, in addition to these more general ERP correlates of outliers, the contingent negative variation (CNV) ERP component was reduced in outliers as a function of preparatory demands of the task. Hence, electrophysiological correlates, and thus cognitive processing, are altered in outliers compared to valid trials. In order to avoid distortion of observed ERP differences between conditions, the RT outlier distribution should be considered for the analysis of ERPs in combined ERP and RT studies.

The integrity of psychophysical visual function in non-immunocompromised PLHIV (NIPLHIV) without retinitis on antiretroviral therapy (ART).

The present study investigated the integrity of contrast sensitivity (CS), colour vision, and pattern evoked vision potentials (VEP) in non-immunocompromised people living with HIV (NIPLHIV) without retinitis. All participants were visually asymptomatic and no history of ocular disorders, with CD4 counts above 350 cells/mm3, low viral loads and on ART. Thirty NIPLHIV and 30 age-matched HIV negative control groups underwent F100 hue colour assessment, Pelli-Robson contrast sensitivity assessment and pattern-reversal VEP. The median F100 total error scores for NIPLHIV and controls was 33 (IQR: 28;41) and 28 (IQR: 26;48.50) respectively, this was statistically different (p= 0.020). The median P100 amplitude for NIPLHIV was 5.75 µV (IQR: 4.4;8.85) and 4.05 µV (IQR: 3.2;5.8) for controls, this was statistically different (p=0.045). The mean LogCS score 1.83±0.14 and the median P100 peak latency was 105.45 msec (IQR: 102.98;108.98) for NIPLHIV. Higher CD4+ counts were significantly associated with having higher F100 total error scores (OR=0.995; p=0.018), lower P100 amplitudes (OR=1.007; p=0.010) and higher P100 latencies (OR=0.994; p=0.011). Contrast sensitivity function, colour vision, and VEP were uncompromised in NIPLHIV. Associations between CD4 counts with F100 total error scores and P100 latency may aid in the surveillance of vision of NIPLHIV.

A key role of the hippocampal P3 in the attentional blink

The attentional blink (AB) refers to an impaired identification of target stimuli (T2), which are presented shortly after a prior target (T1) within a rapid serial visual presentation (RSVP) stream. It has been suggested that the AB is related to a failed transfer of T2 into working memory and that hippocampus (HC) and entorhinal cortex (EC) are regions crucial for this transfer. Since the event-related P3 component has been linked to inhibitory processes, we hypothesized that the hippocampal P3 elicited by T1 may impact on T2 processing within HC and EC. To test this hypothesis, we reanalyzed microwire data from 21 patients, who performed an RSVP task, during intracranial recordings for epilepsy surgery assessment (Reber et al., 2017). We identified T1-related hippocampal P3 components in the local field potentials (LFPs) and determined the temporal onset of T2 processing in HC/EC based on single-unit response onset activity. In accordance with our hypothesis, T1-related single-trial P3 amplitudes at the onset of T2 processing were clearly larger for unseen compared to seen T2-stimuli. Moreover, increased T1-related single-trial P3 peak latencies were found for T2[unseen] versus T2[seen] trials in case of lags 1 to 3, which was in line with our predictions. In conclusion, our findings support inhibition models of the AB and indicate that the hippocampal P3 elicited by T1 plays a central role in the AB.

Neuroprotective influence of macular xanthophylls and retinal integrity on cognitive function among persons with multiple sclerosis

BackgroundNo studies to date have examined if macular xanthophyll accumulation and retinal integrity are independently associated with cognitive function in individuals with multiple sclerosis (MS). This study explored whether macular xanthophyll accumulation and structural morphometry in the retina were associated with behavioral performance and neuroelectric function during a computerized cognitive task among persons with MS and healthy controls (HCs). Methods42 HCs and 42 individuals with MS aged 18–64 years were enrolled. Macular pigment optical density (MPOD) was measured using heterochromatic flicker photometry. Optic disc retinal nerve fiber layer (odRNFL), macular retinal nerve fiber layer, and total macular volume were assessed via optical coherence tomography. Attentional inhibition was assessed using an Eriksen flanker task while underlying neuroelectric function was recorded using event-related potentials. ResultsPersons with MS had a slower reaction time, lower accuracy, and delayed P3 peak latency time during both congruent and incongruent trials compared with HCs. Within the MS group, MPOD explained variance in incongruent P3 peak latency, and odRNFL explained variance in congruent reaction time and congruent P3 peak latency. ConclusionsPersons with MS exhibited poorer attentional inhibition and slower processing speed, yet higher MPOD and odRNFL levels were independently associated with greater attentional inhibition and faster processing speed among persons with MS. Future interventions are necessary to determine if improvements in these metrics may promote cognitive function among persons with MS.

Automatic detection of nasalization in speech via cue-based analysis

Modern speech recognition systems are powerful, but it is not simple to understand the mechanisms by which they model speech, or precisely how they make use of acoustic cues. Moreover, a system for the explicit detection of individual acoustic cues may be useful not only for speech recognition but for understanding the principles that govern sub-phonemic patterns of surface-phonetic variation, and how specific cue patterns may reflect speech disorders. This report describes a transparent, acoustic cue-based nasalization detection module, that can be used to find not only nasal consonants but also nasalization wherever it appears, e.g., within a vocalic region. We lay out a framework for extracting measurements that are key to detecting nasalization, in particular, the nasality-related spectral peaks P0 and P1, and confirm the utility of these measurements for nasality detection in spoken words. In particular, we present a pre-processing and cue-value extraction framework, and propose a Gaussian Mixture Model-based approach to detect the regions of nasalization in a speech signal. This work on a detection module for nasalization is part of a larger effort to develop a speech recognition system that is based on landmarks and other acoustic cues.

The role of single trial variability in event related potentials in children with attention deficit hyperactivity disorder

ObjectiveChildren with attention deficit hyperactivity disorder (ADHD) show attenuated mean P3 component amplitudes compared to typically developing (TD) children. This finding may be the result of individual differences in P3 amplitudes, P3 latencies, and/or greater single trial variability (STV) in amplitude or latency, suggesting neural “noise.” MethodsEvent related potentials (ERPs) from 75 children with ADHD and 29 TD children were recorded with electroencephalography (EEG). Caregivers provided ratings on child ADHD symptoms. Single-trial ERP amplitudes and latencies were extracted from the P3 component time window during a visual oddball task. Additionally, we computed individual-centered and trial-centered P3 amplitudes to account for inter-individual and inter-trial variability in the timing of the P3 peak. ResultsIn line with prior research, greater ADHD symptom severity was associated with reduced mean P3 amplitude. This correlation was no longer significant after correcting for inter-trial differences in P3 latency. In contrast, greater ADHD symptom severity was associated with reduced STV in P3 amplitude. ConclusionsOur results suggest that attenuated average P3 amplitude in ADHD samples is due to a consistent reduction in strength of the neurophysiological signal at the single trial level, as well as increased inter-trial variability in the timing of P3 peak amplitudes. The traditional method of extracting P3 amplitudes based on a single time window for all trials may not adequately capture variability in P3 latencies associated with ADHD. SignificanceInter- and intra-individual differences in brain signatures should be considered in models of neurobiological differences in neurodevelopmental samples.

Frequency-domain analysis of transient visual evoked potentials in schizophrenia.

Frequency-domain measures were applied to characterize neural deficits in individuals with schizophrenia using transient visual evoked potentials (tVEP). These measures were compared with conventional time-domain measures to elucidate underlying neurophysiological mechanisms and examine the value of frequency analysis. Four frequency bands of activity identified in previous work were explored with respect to magnitude (spectral power), timing (phase), a combined measure, magnitude-squared coherence (MSC), and compared to amplitudes and times of prominent deflections in the response. Band 2 power/MSC (14-28Hz) captured the major deflections in the waveform and its power predicted N75-P100 amplitude for patients and controls. Band 3 power/MSC (30-40Hz) correlated highly with the earliest deflection (P60-N75), reflecting input to primary visual cortex (V1) and produced the largest magnitude effect. Phase of the 24th harmonic component predicted P100 peak time for patients and controls and yielded the largest group difference. Cluster analyses including time- and frequency-domain measures identified subgroups of patients with differential neurophysiological effects. A small but significant difference in visual acuity was found between groups that appears to be neurally based: Acuity (range 0.63-1.6) was not correlated with any tVEP measures in controls nor with input timing to V1 (P60 peak time) in patients, but was correlated with later tVEP measures in patients. All but two of the patients were on antipsychotic medication: Medication level (chlorpromazine equivalents) was correlated negatively with tVEP time measures and positively with certain magnitude measures yielding responses similar to controls at high levels. Overall, frequency-domain measures were shown to be objective and recommended as an alternative to conventional, subjective time-domain measures for analyzing tVEPs and in distinguishing between groups (patients vs. controls and patient subgroups). The findings implicated a loss of excitatory input to V1 in schizophrenia. Acuity as measured in the current study reflected disease status, and medication level was associated with improved tVEP responses. These novel tVEP techniques may be useful in revealing neurophysiological processes affected in schizophrenia and as a clinical tool.

Visual pathway function in untreated individuals with major depression.

Major depression (MD) is the one of the most debilitating diseases, affecting millions of people all around the world. To establish visual pathway function in untreated individuals with MD. In 29 untreated, newly diagnosed, ophthalmologically asymptomatic individuals (58 eyes) with MD (mean age: 47.3 years) and in 29 (58 eyes) of age-, sexand refractive error-matched healthy controls (mean age: 46.8 years), the following examinations were performed: 1) best corrected distance visual acuity (BCDVA); 2) intraocular pressure (IOP); 3) and 4) biomicroscopy of anterior and posterior segment of eye; 5) macular structure (SD-OCT-Zeiss); and 6) pattern visual evoked potentials (PVEPs) measurements according to the International Society for Clinical Electrophysiology of Vision (ISCEV) standard (ISCEV-standard PVEPs). An analysis of correlation between the parameters of PVEPs and the depression severity (Hamilton Depression Rating Scale (HAMD)) was performed. To estimate the diagnostic power of PVEPs test, a receiver operating characteristics (ROC) curve was used. Data were analyzed with the significance level of p < 0.05. In the study group and in healthy control, the clinical results and macular structure were normal and not different. In the MD group, in PVEPs test (check size: 1°4'and 0°16'), a significant decrease of amplitudes of P100 (AP100), associated with prolonged P100 peak time (PTP100; check size: 0°16', p < 0.004) were detected. The most frequent abnormality in PVEPs examination in the MD group was AP100 reduction (in 69% of individuals) detected using stimulation check size 0°16'. The statistically significant positive correlation between PTP100 (check size: 0°16') and HAMD score was found in severe MD (p = 0.03). The analysis of ROC curve revealed the highest sensitivity of 0.759 and specificity of 1.0 for AP100 (0°16'). The area under the curve (AUC) was 0.841 (p < 0.001). In individuals with newly diagnosed, ophthalmologically asymptomatic and untreated MD, a dysfunction of visual pathway is present without other signs of ocular pathology. The visual pathway dysfunction measured with ISCEV PVEPs has a potential value to be an objective biomarker of MD.

Characterization of Samples with Minor P3 Peak Elevations in a High Pressure Liquid Chromatography System for HbA1c: Contributions of Hemoglobin Variants and Storage Conditions.

In the Bio-Rad D-100TM (Bio-Rad, Hercules, CA) HPLC system for hemoglobin A1c (HbA1c) measurement, 7 peaks elute: HbA1a, HbA1b, HbF, LA1c, HbA1c, P3, and HbA0. HbA1c is calculated from the ratio of the HbA1c peak area to the total area, excluding HbF and peaks after HbA0, if present. A P3 peak >10% flags for potential interferences. We investigated 26 samples with elevated P3 peaks to determine the presence of hemoglobin variants, the effect of prolonged specimen storage in the P3 peak. The relationship between the P3 peak and the HbA1c concentration were also investigated. No hemoglobin variants were identified when the P3 peak was <14% (n = 14). Hemoglobin variants were detected in 7 of 12 with a P3 peak between 17.0% and 28.2%. Sample storage at room temperature had minimum impact on the P3 peak area (n = 20); the average P3 bias was -0.5 (-8.1% bias) after 3 days and 0.6 (12.2% bias) after 5 days. P3 increased with increasing HbA1c concentrations in samples with P3 < 10%. Most samples with P3 above 10 and up to 14% had marked HbA1c elevations. Minor elevations of the P3 peak were due only in part to hemoglobin variants, particularly in samples with P3 above 17% (below 28.2%). These elevations caused a decrease in HbA1c, whether hemoglobin variants are detected or not. Prolonged storage at room temperature did not cause P3 peaks to increase above 10%.

Characteristics and dynamics of pathological changes in visual evoked potentials in multiple sclerosis

Clarification of the characteristics and dynamics of changes in the main indicators of visual evoked potentials (VEP) for a reverse chess pattern in patients with multiple sclerosis (MS) at various stages of the disease and severity of disability. The study of VEP was carried out on 477 subjects, 120 of which were healthy volunteers and 357 patients with MS, including those with clinically isolated syndrome (CIS; 22.7%), remitting course (RT; 55.7%), primary progressive course (PPT; 8.4%), secondary progressive course (VPT; 13.2%). Disability was assessed using the Expanded Disability Status Scale (EDSS). A high sensitivity of VEP in the detection of demyelinating damage to the visual pathways, including subclinical, was noted already at the initial stages of MS, which increases with the progression of the disease from 77.8 to 97.8%. There was a significant increase in latency (r=0.42, p<0.05) and a decrease in amplitude (r= -0.26, p<0.05) of the P100 peak as the EDSS score increased. In patients with MS, 5 patterns of VEP were identified depending on the level and severity of damage to the visual pathways, where pattern 1 is normative VEP, pattern 5 is the absence of VEP recording in case of a pronounced axonal-demyelinating lesion of the visual pathways (prechiasmal/postchiasmal levels). Patterns 1 and 2 are most typical for CIS (22.2 and 53.1%) or RT (20.1 and 26.6%). Patterns 3 and 4 are typical for APT (70 and 20%) and VPT (48.9 and 21.3%), pattern 5 - for VPT (19.1%). Patterns 3-5 predominated in patients with higher EDSS (r=0.54, p<0.05). The classification of VEP changes into patterns makes it possible to identify the dissemination of a focal lesion in the projections of the visual pathways, which increases the diagnostic efficiency of the study and makes it possible to assess the severity of MS.

Evaluation of Diurnal Changes of Mental Fatigue Using a New Portable Device for Visual Cognitive Evoked Potentials.

In the age homogenous group of 13 healthy volunteers, we examined visual evoked potentials (VEP) visually evoked cognitive potentials (event-related potentials - ERP) and choice reaction time (CRT) five times during the day (from 10.00 a.m. up to midnight) to verify whether there are significant changes of the measured parameters of the cortical evoked potentials and CRT which might reflect the level of the mental fatigue. The electrophysiological testing was done with the use of a new portable VEP device named "VEPpeak" enabling to perform the examination outside standard labs in almost any conditions. It was found that the latency of ERP (P300 peak time) and CRT displayed significant prolongation toward midnight while VEP latency and all amplitudes did not change significantly. This pilot study supports our idea that the portable VEP device possibly might be used for the objective examination of mental fatigue that is needed in many situations. This should be confirmed in a larger study also including a comparison with non-electrophysiological fatigue testing.