P1 Peak Research Articles

Reconsidering electrophysiological markers of response inhibition in light of trigger failures in the stop-signal task.

This study investigates the neural correlates underpinning response inhibition using a parametric ex-Gaussian model of stop-signal task performance, fit with hierarchical Bayesian methods, in a large healthy sample (N=156). The parametric model accounted for both stop-signal reaction time (SSRT) and trigger failure (i.e., failures to initiate the inhibition process). The returned SSRT estimate (SSRTEXG3 ) was attenuated by ≈65ms compared to traditional nonparametric SSRT estimates (SSRTint ). The amplitude and latency of the N1 and P3 event-related potential components were derived for both stop-success and stop-failure trials and compared to behavioral estimates derived from traditional (SSRTint ) and parametric (SSRTEXG3 , trigger failure) models. Both the fronto-central N1 and P3 peaked earlier and were larger for stop-success than stop-failure trials. For stop-failure trials only, N1 peak latency correlated with both SSRT estimates as well as trigger failure and temporally coincided with SSRTEXG3 , but not SSRTint . In contrast, P3 peak and onset latency were not associated with any behavioral estimates of inhibition for either trial type. While the N1 peaked earlier for stop-success than stop-failure trials, this effect was not found in poor task performers (i.e., high trigger failure/slow SSRT). These findings are consistent with attentional modulation of both the speed and reliability of the inhibition process, but not for poor performers. Together with the absence of any P3 onset latency effect, our findings suggest that attentional mechanisms are important in supporting speeded and reliable inhibition processes required in the stop-signal task.

Effects of ignition location, obstacles, and vent location on the vented hydrogen-air deflagrations with low vent burst pressure in a 20-foot container

A series of experiments on vented lean hydrogen-air deflagrations with low vent burst pressure was performed in a 20-foot container. The effects of hydrogen concentration, ignition position, vent location, and obstacles were studied, and all tests were performed at about 290 K and 101 kPa. For the cases with end vent, three overpressure peaks of P1, P2, and P3 were recorded, resulting from the vent rupture, flame propagation to the vent, and the Helmholtz oscillation, respectively. Moreover, at the middle and later stages of the vented explosion, the acoustic oscillations with high-frequency were observed due to the thermo-acoustic-vibration coupling caused by the instability of lean hydrogen combustion. The peak overpressure for the case with the obstacle is lower than that without the obstacle. Vent rupture occurs quickly for front ignition and low hydrogen concentrations. For the tests with high hydrogen concentration such as 24 vol% and 28 vol%, since the polyethylene film can reach its static activation pressure and rupture, the peak overpressure is much larger. For the cases with the ceiling vents, only one overpressure peak P1, corresponding to the rupture of the vent cover, was recorded and its value increases with the hydrogen concentration. The obstacle causes the propagation direction of the flame to change, and resultantly the flame spreads upward and burns the polyethylene film, which decreases the internal overpressure rise time. This phenomenon is particularly evident for the tests with high hydrogen concentrations. Except for 16 vol%, the obstacle reduces the peak overpressure.

Effect of the Strain Rate on the Damping and Mechanical Properties of a ZK60 Magnesium Alloy.

High strain rate rolling (HRSS) of a ZK60 magnesium alloy at 300 °C with a strain rate from 5 s−1 to 25 s−1 was used to research the effect of the rate on the mechanical properties and damping capacity of the ZK60 alloy. The results show that as the strain rate increases, the tensile strength decreases from 355 MPa at 25 s−1 to 310 MPa at 5 s−1. Two damping peaks (P1 and P2) are detected in the high strain rate rolled ZK60 alloys at different strain rates. The P1 peak appears at low temperatures and is caused by grain boundaries sliding. The P2 peak appears at high temperatures and is caused by recrystallization. As the strain rate increases from 5 to 20 s−1, the dynamic recrystallization (DRX) volume percent rises and the dislocation density decreases, both of which cause the P1 peak to become more and more obvious, and activation energy rises. At the same time, the dislocation density decreases and leads to a decrease in the storage energy, which reduces the recrystallization driving force and shifts the P2 peak to high temperatures. When the strain rate reaches 20 and 25 s−1, DRX occurs fully in the sheet, so the activation energy of the P1 peak and the temperature where the P2 peak appears are basically equal.

Study of Neurocognitive Function in Type 2 Diabetes Mellitus Patients Using P300 Event-Related Potential

Background:Diabetes mellitus is the most prevailing metabolic disease. It causes structural and functional alterations in several organs, including the central nervous system. Altered glucose metabolism, atherosclerosis, and inflammation of blood vessels are seen in diabetes. This may lead to neuronal degeneration and decline in cognition. Event-related potential P300 can detect cognitive decline before the emergence of obvious neurological manifestations.Objective:The aim of this study is to assess and compare the P300 latencies in subjects with type 2 diabetes mellitus and in nondiabetic subjects and to determine the influence of type 2 diabetes mellitus on cognitive functions.Materials and Methods:In this study our sample size was 248 subjects, with type 2 diabetes mellitus patients (n = 124) and healthy controls (n = 124) between the age group of 31 and 60 years. This cross-sectional comparative study was conducted at SRM Medical College Hospital and Research Centre. The subjects were evaluated by a structured interview and they were assessed with a general health questionnaire to rule out any subpsychiatric illness. Fasting and postprandial blood glucose, HbA1c level, lipid profile, and creatinine were estimated. P300 amplitude and peak latencies were recorded using the standard auditory oddball paradigm.Results:The latencies of P300 were significantly increased and the amplitude of P300 was significantly reduced in the diabetic group when compared to the control group (P < .001). P300 latency has a positive correlation with the HbA1c levels (r = 0.136) and the duration of diabetes (r = 0.231).Conclusion:Prolongation of P300 latencies and the decreased amplitude in diabetic subjects may suggest the existence of a cognitive decline in individuals with type 2 diabetes compared to healthy individuals.

The relationship between aquaporin-4 antibody status and visual tract integrity in neuromyelitis optica spectrum disorders: A visual evoked potential study

BackgroundOptic neuritis (ON) is one of the hallmark symptomatic features of neuromyelitis optica spectrum disorders (NMOSD). The majority of patients with NMOSD present highly specific autoantibodies against aquaporin-4 (AQP4). A number of studies have reported poor visual acuity outcomes in individuals with AQP4 seropositive NMOSD, but no such relationship has been found with regard to visual evoked potentials (VEP) parameters such as the amplitude and latency of the P100 component. In this paper, we aimed (i) to describe VEP responses in patients with NMOSD; (ii) to analyze those results based on a scoring system; and (iii) to investigate the association between the VEPs and AQP4 antibody status. MethodsWe retrospectively analysed the VEP responses of 40 patients with a diagnosis of NMOSD (according to the 2015 IPND criteria), including 16 with AQP4-postive status (AQP4[+]) and 24 with AQP4-negative status (AQP4[-]). In the first step, we measured the P100 peak latency and P100-N2 peak-to-peak amplitude in each patient. In the second, we converted these measures to the VEP score (0–10) using the scoring proposed by Jung et al. (2008). All recordings were performed using the same VEP device and testing protocol. ResultsAbnormal VEPs were recorded in 25 of 40 patients (62.6%). Of these, 17 (42.5%) had prolonged P100 latency, and 8 (20%) had no response detected in at least one eye. The patients with ON as the initial relapse symptom had significantly higher median VEP scores than those who experienced the longitudinally extensive transverse myelitis (LETM) at the disease onset (7.0 [in­terquar­tile range (IQR), 2.0–8.0] vs. 0.0 [IQR, 0.0–4.0], p<0.001). A lack of VEP response in at least one eye was detected more frequently in the AQP4[+] group than the AQP4[-] group (7/16 vs. 1/24, p<0.005). Logistic regression model controlling for age, gender, disease duration, and the type of relapse at onset showed an independent impact of AQP4[+] status (OR=35.45, p = 0.018) on the higher rate of absent VEP responses. In the entire group of patients (n = 40), those with AQP4[+] showed a small tendency towards a higher median VEP score (4.0 [IQR, 0.0–7.8] vs. 1.0 [IQR, 0.0–4.0], p = 0.304). Among individuals with abnormal responses (n = 25), the patients with AQP4[+] had significantly higher median VEP scores (7.0 [IQR, 4.0–8.5] vs. 3.0 [IQR, 1.0–7.0], p = 0.034) and more common bilateral involvement of the optic tracts (80% vs. 40%, p = 0.048) than those who were seronegative for anti-AQP4 antibody. A median regression analysis model controlling for age, gender, disease duration, type of onset, and number of relapses in last 12 months showed an independent association between the AQP4-positive status and a higher VEP score in patients with NMOSD (t = 2.882, df=2, p = 0.007). ConclusionVEP study remains a useful tool in the assessment of NMOSD patients. Due to the high prevalence of absent VEPs in NMOSD patients, the scoring system appears to be more applicable for the precise analysis of VEP recordings. There is a positive association between the AQP-positive serostatus and the poorer outcome in VEP responses, especially in patients with severe impairment of the optic nerve(s).

Computer simulations of transapical mitral valve repair with neochordae implantation: Clinical implications.

ObjectivesTransapical beating heart neochordae implantation is an innovative mitral valve repair technique that has demonstrated promising clinical results in patients with primary mitral regurgitation. However, as clinical experience continues to increase, neochordae implantation criteria have not been fully standardized. The aim of this study was to investigate the biomechanical effects of selecting an antero-lateral apical access site compared with a postero-lateral site, and suboptimal neochordae length compared with optimal suture length, on restoring physiologic left heart dynamics.MethodsTransapical neochordae implantation using 3 and 4 sutures was computer simulated under 3 posterior mitral leaflet prolapse conditions: isolated P2, multiscallop P2/P3 and multiscallop P2/P1. Physiologic, pre- and postrepair left heart dynamics were evaluated using a fluid-structure interaction modeling framework.ResultsDespite the absence of residual mitral regurgitation in all postrepair models with optimal neochordae length, selecting an antero-lateral apical entry site for the treatment of P2/P3 prolapse generated a significant increase (>80%) in neochordae tension and P2 peak stress, with respect to a postero-lateral entry site. During isolated P2 prolapse repair, although neochordae overtension by 5% led to minimal hemodynamic changes in the regurgitant volume compared with using an optimal suture length, a significant increase in systolic and diastolic neochordae tension (>300%) and posterior leaflet average stress (70%-460%) was quantified. On the other hand, neochordae undertension by 5% led to worsening of regurgitation severity.ConclusionsThis parametric computer study represents a further step toward an improved understanding of the biomechanical outcomes of transapical neochordae technologies.

Neural Dynamics of Cognitive Control in Various Types of Incongruence.

Conflict-control is a core function of cognitive control. Although numerous studies have considered cognitive control to be domain-general, the shared and distinct brain responses to different types of incongruence or conflict remain unclear. Using a hybrid flanker task, the present study explored the temporal dynamics of brain activation to three types of incongruence: flanker interference, rule-based response switch (rule-switch), and action-based response switch (response-alternation). The results showed that: (1) all three types of incongruence evoked larger N2 amplitudes than the congruent condition in the frontal region, with the N2 amplitudes and topographical distribution of the N2 effect differing between the different types of incongruence; and (2) in the P300 time window, the flanker interference condition yielded the most delayed P300 latency, whereas the rule-switch and response-alternation conditions yielded smaller P300 amplitudes with a longer interval from P300 peak to a keypress. These findings suggest that different types of incongruence are first monitored similarly by the cognitive control system and then resolved differently.

Modulation of a multi-band tunable metamaterial with metal disk array

A multi-band metamaterial with vanadium dioxide (VO2) layer is proposed, manufactured, and measured in the terahertz (THz) band. Two absorption peaks (P1 and P2) are excited at 33.88 THz (60% amplitude, and 0.7 THz full width at half maximum (FWHM)) and 37.94 THz (76% amplitude, and 1.62 THz FWHM) at room temperature. The P1 peak is achieved based on the local surface plasmon (LSP) modes resonance, while the P2 peak is revealed by the LSP modes and the Ohmic loss of the bottom metal layer. Both P1 and P2 can be enhanced through increasing structural parameter D or reducing structural parameter P during experiments. As the temperature rises to T = 340k, the peaks P3 and P4 are obtained at 11.9 THz (80.1% amplitude, and 2.24 THz FWHM) and 23.52 THz (85.2% amplitude, and 3.83 THz FWHM). The resonance properties of P1 and P2 peaks are insensitive to temperature. The P3 peak is obtained based on the Fabry-Perot resonance between the metal disk and the lower VO2 layer, while the P4 peak is revealed by the ultra-thin Fabry-Perot resonance between the metal disk and the upper VO2 layer. The original resonance properties of the proposed metamaterial absorber can be kept stable, while the new absorption performances can be controlled through changing temperature.

Investigation of oxygen impurity in different growth zones of GaN crystal grown by Na-flux method

We investigated the dark zone and transparent zone in GaN crystal grown by Na-flux method. The impurity concentration was detected by secondary-ion mass spectroscopy, and a higher concentration of O impurity was observed in the dark zone of GaN. As photoluminescence spectra were measured, the contrast between the yellow luminescence of transparent zone and green luminescence of dark zone was obtained, indicating the optical property of Na-flux grown GaN would be strongly influenced by the O impurity. Meanwhile, from the detail Raman measurements, the vacancy-related mode of peak P1 at ~420 cm−1 and peak P3 at ~670 cm−1 were observed. As a positive correlation between the carrier concentrations and the vacancy-related defects was found, the O impurity and the accompanying VGa was suggested to be the primary factor responsible for the above vacancy-related Raman modes which have been widely observed in the Na-flux grown GaN crystal.

Action Real-Time Strategy Gaming Experience Related to Increased Attentional Resources: An Attentional Blink Study.

Action real-time strategy gaming (ARSG) is a cognitively demanding task which requires attention, sensorimotor skills, team cooperation, and strategy-making abilities. A recent study found that ARSG experts had superior visual selective attention (VSA) for detecting the location of a moving object that could appear in one of 24 different peripheral locations (Qiu et al., 2018), suggesting that ARSG experience is related to improvements in the spatial component of VSA. However, the influence of ARSG experience on the temporal component of VSA—the detection of an item among a sequence of items presented consecutively and quickly at a single location—still remains understudied. Using behavioral and electrophysiological measures, this study examined whether ARSG experts had superior temporal VSA performance compared to non-experts in an attentional blink (AB) task, which is typically used to examine temporal VSA. The results showed that the experts outperformed the non-experts in their detection rates of targets. Furthermore, compared to the non-experts, the experts had faster information processing as indicated by earlier P3 peak latencies in an AB period, more attentional resources distributed to targets as indicated by stronger P3 amplitudes, and a more flexible deployment of attentional resources. These findings suggest that experts were less prone to the AB effect. Thus, long-term ARSG experience is related to improvements in temporal VSA. The current findings support the benefit of video gaming experience on the development of VSA.

Electrophysiological and Structural Changes in Chinese Patients with LHON.

Objective To review retrospectively the electrophysiological and structural changes in 13 Chinese patients with Leber hereditary optic neuropathy (LHON). Methods 26 eyes of 13 patients with a genetically confirmed diagnosis of LHON were categorized into two groups according to the duration of the disease: group 1 (duration less than 3 months) and group 2 (duration between 3 months and 18 years). Clinical history, comprehensive visual electrophysiology, optical coherence tomography (OCT), and color fundus photography were performed. Results Fundoscopy showed optic disc hyperemia in group 1 and optic atrophy in group 2. OCT measures of retinal nerve fiber layer (RNFL) thickness around the optic disc and surrounding macula were normal in group 1 but reduced in group 2 (10 of 10 eyes). The thickness of the retinal ganglion cell layer (GCL) plus inner plexiform layer (IPL) surrounding the macula reduced significantly in group 1 and group 2 compared with a healthy control group. Pattern ERG (PERG) P50 amplitude was normal, but the N95/P50 ratio reduced in most of group 1 (4 of 5 eyes) and in all of group 2 (11 eyes). PERG P50 peak time was abnormally short in group 2. Multifocal electroretinography (mfERG) showed subnormal responses associated with ring 1 (the central area) and ring 2 in group 1 and reductions in rings 1, 2, and 3 in group 2. Conclusion The study highlights differences in retinal structure and function between the acute and chronic stages of LHON in a group of Chinese patients. There is PERG evidence of retinal ganglion cell dysfunction and OCT evidence of GCL + IPL thinning in both groups, but there is additional peripapillary RNFL loss in the chronic stage, associated with more severe RGC dysfunction. There is multifocal ERG evidence of localized macular dysfunction in both acute and chronic groups. The study highlights the importance of comprehensive electrophysiological and structural assessments of the retina in LHON and is pertinent to studies that aim to monitor disease progression or the effects of future therapeutic interventions.

Motor output matters: Evidence of a continuous relationship between Stop/No-go P300 amplitude and peak force on failed inhibitions at the trial-level.

Motor actions can be suppressed with varying degrees of success, but this variability is not often captured as responses are typically represented as binary (response vs. no-response). Although the Stop/No-go P300 has been implicated as an index of inhibitory-control, it is unclear how the range of motor outputs relates to the P300. We examined the nature of this association in two experiments using an Anticipatory Timing and a Go/No-go Task, while measuring peak force, movement onset time, and P300. In both experiments, our results showed that trial-by-trial P300 amplitude on Failed Inhibitions were continuously related to peak force, where higher force (reflecting a greater degree of error) was associated with smaller P300 amplitude. Compared to Successful Inhibitions, P300 amplitude and onset latency on Failed Inhibitions were significantly reduced and delayed. Although the binary categorization of inhibition-success (Successful vs. Failed) accounts for significant variance in the P300, it misses a reliable linear relationship that can be captured by continuous measures of motor output. Overall, the results provide evidence that P300 may reflect the continuously varying engagement of inhibitory-control. We present an activation model to visualize the P300-force association and to illustrate how motor output might be modeled in the context of inhibitory-control. Our results highlight the relevance of P300 amplitude and the importance of studying the spectrum of motor output and the need for future models to account for motor output.

Theoretical Analysis of Fe K-Edge XANES on Iron Pentacarbonyl.

Iron pentacarbonyl (Fe(CO)5) is a versatile material that is utilized as an inhibitor of flame, shows soot suppressibility, and is used as a precursor for focused electron-beam-induced deposition (FEBID). X-ray absorption near-edge structure (XANES) of the K edge, which is a powerful technique for monitoring the oxidation states and coordination environment of metal sites, can be used to gain insight into Fe(CO)5-related reaction mechanisms in in situ experiments. We use a finite difference method (FDM) and molecular-orbital-based time-dependent density functional theory (TDDFT) calculations to clarify the Fe K-edge XANES features of Fe(CO)5. The two pre-edge peaks P1 and P2 are mainly the Fe(1s) → Fe–C(σ*) and Fe(1s) → Fe–C(π*) transitions, respectively. When the geometry transformed from D3h to C4v symmetry, a ∼30% decrease of the pre-edge P2 intensity was observed in the simulated spectra. This implies that the π bonding of Fe and CO is sensitive to changes in geometry. The following rising edge and white line regions are assigned to the Fe(1s) → Fe(4p)(mixing C(2p)) transitions. Our results may provide useful information to interpret XANES spectra variations of in situ reactions of metal–CO or similar compounds with π acceptor ligandlike metal–CN complexes.

A randomized clinical trial on the acute therapeutic effect of TRPA1 and TRPM8 agonists in patients with oropharyngeal dysphagia.

Oropharyngeal dysphagia (OD) treatment is moving away from compensatory strategies toward active treatments that improve swallowing function. The aim of this study was to assess the acute therapeutic effect of TRPA1/M8 agonists in improving swallowing function in OD patients. Fifty-eight patients with OD caused by aging, stroke, or neurodegenerative disease were included in a three-arm, quadruple-blind, randomized clinical trial (NCT02193438). Swallowing safety and efficacy and the kinematics of the swallow response were assessed by videofluoroscopy (VFS) during the swallow of 182±2mPa·s viscosity (nectar) boluses of a xanthan gum thickener supplemented with (a) 756.6μmol/L cinnamaldehyde and 70μmol/L zinc (CIN-Zn) (TRPA1 agonists), (b) 1.6mmol/L citral (CIT) (TRPA1 agonist), or (c) 1.6mmol/L citral and 1.3mmol/L isopulegol (CIT-ISO) (TRPA1 and TRPM8 agonists). The effects on pharyngeal event-related potentials (ERP) were assessed by electroencephalography. TRPA1 stimulation with either CIN-Zn or CIT reduced time to laryngeal vestibule closure (CIN-Zn P=.002, CIT P=.023) and upper esophageal sphincter opening (CIN-Zn P=.007, CIT P=.035). In addition, CIN-Zn reduced the penetration-aspiration scale score (P=.009), increased the prevalence of safe swallows (P=.041), and reduced the latency of the P2 peak of the ERP. CIT-ISO had no positive effect on biomechanics or neurophysiology. No significant adverse events were observed. TRPA1 stimulation with CIN-Zn or CIT improves the swallow response which, in the case of CIN-Zn, is associated with a significant improvement in cortical activation and safety of swallow. These results provide the basis for the development of new active treatments for OD using TRPA1 agonists.

Emotional face prediction in rejection sensitive individuals: Evidence from event-related potentials

Human beings live in an uncertain world, but they continuously generate top-down predictions about emotional face information of other people around them. Although the prediction processing has repeatedly been investigated in the literature of prediction, little is known about the impact of rejection sensitive (RS) on individuals' emotional face prediction. To this end, high and low RS participants were asked to perform an identification task of emotional faces in which target faces were shown in either an angry or happy expression while their brain responses were recorded using an event-related potential (ERP) technique. The behavioral results suggested an effect of emotional face prediction. For the P100 component, low RS participants showed longer P100 peak latencies in the left than right hemisphere when they viewed predictable emotional faces. In addition, low RS participants showed larger N170 mean amplitudes for angry compared to happy faces when they perceived unpredictable faces, but not when these faces were predictable. This presumably reflected a sensibility to angry faces in the unpredictable trails. Interestingly, high RS participants did not demonstrate such a N170 difference, suggesting that high RS participants showed a reduced sensitivity to unpredictable angry faces. Furthermore, angry faces triggered increased LPP mean amplitudes compared to happy faces, which was consistent with the results of other ERP studies examining the processing of emotional faces. Finally, we observed significant negative correlations between behavioral and ERP prediction effect, indicating one consistency between the behavioral and electrophysiological data.

The Effect of Meditation on Comprehension of Statements About One-Self and Others: A Pilot ERP and Behavioral Study.

The main goal of this study was to examine the effect of long-term meditation practice on behavioral indicators and ERP peak characteristics during an error-recognition task, where participants were presented with emotionally negative (evoking anxiety or aggression) written sentences describing self-related or non-self-related emotional state and personality traits. In total, 200 sentences written in Russian with varying emotional coloring were presented during the task, with half of the sentences containing a grammatical error that the participants were asked to identify. The EEG was recorded in age-matched control individuals (n = 17) and two groups of Samatha meditators with relatively short- (3–5 years’ experience, n = 18) and long-term (10–30 years’ experience, n = 18) practice experience. Task performance time (TPT) and accuracy of error detection (AED) were chosen as behavioral values. Amplitude, time latency and cortical distribution of P300 and P600 peaks of ERP were used as a value of speech-related brain activity. All statistical effects of meditation were estimated, controlling for age and sex. No behavioral differences between two groups of meditators were found. General TPT was shorter for both groups of meditators compared to the control group. Non-meditators reacted significantly slower to sentences about aggression than to sentences about anxiety or non-emotional sentences, whereas no significance was found between meditator groups. Non-meditators had better AED for the sentences about one-self than for the sentences about other people, whereas the meditators did not show any significant difference. The amplitude of P300 peak in frontal and left temporal scalp regions was higher for long-term meditators in comparison with both intermediate and control groups. The latency of P300 and P600 in left frontal and temporal regions positively correlated with TPT, whereas the amplitude of P300 in these regions had a negative correlation with TPT. We demonstrate that long-term meditation practice increases the ability of an individual to process negative emotional stimuli. The differences in behavioral reactions after onset of negative information that was self-related and non-self-related, which is typical for non-meditators, disappeared due to the influence of meditation. ERP results could be interpreted as a value of increase in voluntary control over emotional state during meditational practice.

Effects of Age and Type of Stimulus on the Cortical Auditory Evoked Potential in Healthy Malaysian Children.

Background and ObjectivesThe cortical auditory evoked potential (CAEP) is a useful objective test for diagnosing hearing loss and auditory disorders. Prior to its clinical applications in the pediatric population, the possible influences of fundamental variables on the CAEP should be studied. The aim of the present study was to determine the effects of age and type of stimulus on the CAEP waveforms.Subjects and MethodsThirty-five healthy Malaysian children aged 4 to 12 years participated in this repeated-measures study. The CAEP waveforms were recorded from each child using a 1 kHz tone burst and the speech syllable /ba/. Latencies and amplitudes of P1, N1, and P2 peaks were analyzed accordingly. ResultsSignificant negative correlations were found between age and speech-evoked CAEP latency for each peak (p< 0.05). However, no significant correlations were found between age and tone-evoked CAEP amplitudes and latencies (p>0.05). The speech syllable /ba/ produced a higher mean P1 amplitude than the 1 kHz tone burst (p=0.001).ConclusionsThe CAEP latencies recorded with the speech syllable became shorter with age. While both tone-burst and speech stimuli were appropriate for recording the CAEP, significantly bigger amplitudes were found in speech-evoked CAEP. The preliminary normative CAEP data provided in the present study may be beneficial for clinical and research applications in Malaysian children.

Need for Visual Pathway Examination of the Patient Prior to Bone Marrow Transplantation

Aim: Bone Marrow Transplantation is a treatment procedure usually applied for the patients suffering from leukemia. It is observed that some of these patients complain from partial vision loss few months after the operation whereas the routine visual examination of these patients are normal, therefore the aim of present work is to examine the visual pathway of these patients to search for the probable visual pathway degeneration of these patients using visual evoked potential (VEP). Method: 10 patients following bone marrow transplantation were selected randomly. These patients had this operation for at least one year before. Routine ophthalmological examination of them was normal or at most they had refractive error problem which could be corrected by suitable spectacles. Visual evoked potential was recorded in these patients. Latency (msec) and amplitude (μv) of VEP, P100 Peak was noted for each patient. Beside these patients, 10 people with healthy visual system were selected to compare the result of VEP in patients with healthy group following VEP recording. Result: It is observed that 4 patients had abnormal VEP pattern which was reflected either in latency or amplitude of VEP, P100 Peak. Conclusion: From the result of present work, one can conclude that VEP examination of patients following bone marrow transplantation is necessary prior to operation so that if any unexplained visual loss is observed after operation, the medical staff can follow the case for the probable reason for this malfunction.

New-Onset Alzheimer's Disease and Normal Subjects 100% Separated Statistically by P300 and ICA.

Previously, we described how patients with new-onset Alzheimer's disease were differentiated from healthy, normal subjects to 100% accuracy, based on the amplitudes of the nonrhythmic back-projected independent components of the P300 peak at the electroencephalogram electrodes and their latency in the response to an oddball, auditory evoked potential paradigm. A neural network and a voting strategy were used for classification. Here, we consider instead the statistical distribution functions of their latencies and amplitudes and suggest that the 2-sample Kolmogorov-Smirnov test based upon their latency distribution functions offers an alternative biomarker for AD, with their amplitude distribution at the frontal electrode fp2 as possibly another. The technique is general, relatively simple, and noninvasive and might be applied for presymptomatic detection, although further validation with more subjects, preferably in multicenter studies, is recommended. It may also be applicable to study the other P300 peaks and their associated interpretations.

Development and validation of chiral HPLC method for quantitative determination of hydrazine analogue in Argatroban monohydrate

Abstract Argatroban is an anticoagulant which is used as direct thrombin inhibitor. It consists of hydrazine analogue, which is probably similar to Argatroban. The single HPLC method is already reported in to United States Pharmacopeia (USP). In that method, Argatroban peak eluted as R-Argatroban and S-Argatroban while hydrazine analogue eluted as P1 and P2 peaks. The P2 peak of Hydrazine analogue is eluted as retention time of R-Argatroban peak. Therefore it was difficult to determine the accurate concentration of Hydrazine analogue in to Argatroban. The existing method is longer run time up to 102 min. The present HPLC method shows appropriate resolution between hydrazine analogue and Argatroban. The total run time reduces up to 40 min, which is a ∼2.5 time lesser than reported in literature. In present method hydrazine analogue and Argatroban are eluted to be 9.0 min and 12.5 min respectively. The effective chromatographic separations are achieved on YMC chiralart cellulose-SC, 250×4.6 mm, 5μ column and normal phase with linear elution. The mobile phase was uniform mixture of methanol, acetonitrile, dichloromethane, trifluoroacetic acid, triethylamine with ratio of 30:50:920:3:4 and delivered flow rate 0.7 mL/min. Analysis is performed on UV/PDA detector with detection wavelength is adjusted at 259 nm. The injection volume is 5μL and column oven temperature is 35°C. The present method is accurate and precise as well as linear in the range of LOQ to 150 % level. The finalized concentration of hydrazine analogue for limit of detection and quantitation is 0.003 and 0.010%. The correlation coefficient of hydrazine analogue is 0.99947. The recovery for ranged between 100.00 to 103.29%. In robustness study for of mobile phase flow rate and column oven temperature, no significant changes are observed in system suitability parameters and result. This method has been developed and validated using the ICH guideline Q2(R1).The new method is sensitive, precise, accurate, and rapid; it also qualifies all the criteria of linearity, stability, as well as robustness.