Average Waveform Research Articles

Estimation of parameters for the electrostatic discharge current equation with real human discharge events reference using genetic algorithms

Thorough study of the electrostatic discharge (ESD) current equation shows that it may be different from the equation proposed in the IEC 61000-4-2 Standard. This problem is dealt with in this paper. Using a 2.5 GHz digital oscilloscope and a 50 Ω Pellegrini target as the measuring system, and a dc power supply to provide a charging voltage of 2 kVdc, a series of measurements were performed, so real human-to-metal ESD current waveforms were recorded. Treating the average waveform as a reference, a genetic algorithm (GA) was applied to the equation of the IEC 61000-4-2 Standard for the ESD current, in order to achieve its best fitting to the data set. Four different error norms were used for the GA applications. The best result of the applications of each of them was saved and compared to the others. Thus, a very satisfactory modification of the Standard's equation is presented, which is closer to the real ESD current waveform.

A neural decoding approach to auditory temporal assimilation

By constructing Gaussian Naive Bayes Classifiers, we have re-analyzed data from an earlier event-related potential (ERP) study of an illusion in time perception known as auditory temporal assimilation. In auditory temporal assimilation, two neighboring physically unequal time intervals marked by three successive tone bursts are illusorily perceived as equal if the two time intervals satisfy a certain relationship. The classifiers could discriminate whether or not the subject was engaged in the task, which was judgment of the subjective equality between the two intervals, at an accuracy of >79%, and from principal component scores of individual average ERP waveforms, we were able to predict their subjective judgments to each stimulus at an accuracy of >70%. Chernoff information, unlike accuracy or Kullback–Leibler (KL) distance, suggested brain activation associated with auditory temporal assimilation at an early pre-decision stage. This may provide us with a simple and useful neural decoding scheme in analyzing information processing of temporal patterns in the brain.

Identification of Abnormal Neuromagnetic Signatures in the Motor Cortex of Adolescent Migraine

To investigate the functional abnormalities of the motor cortices in children with migraine using magnetoencephalography (MEG) and a finger-tapping task. Cortical hyperexcitability has been reported in adults with migraine using MEG. Many children with migraine report difficulty with motor functioning. There is no report on motor-evoked magnetic activation in children with migraine using MEG and the latest signal processing methods. Ten children with migraine (all female, 9 right-handed and 1 left-handed, aged 13-17 years) and 10 age- and gender-matched healthy children were studied with a 275-channel MEG system. After hearing a unilateral, randomly presented sound cue (500 Hz, 30 milliseconds square tone), each subject immediately performed a brisk index finger tapping with either the right or the left index finger. The auditory stimuli consisted of 200 trials of square tone, 100 trials per ear, randomly distributed. The latency and amplitude of neuromagnetic responses were analyzed with averaged waveforms. Neuromagnetic sources were estimated using synthetic aperture magnetometry (SAM). SAM images were normalized for each participant for group comparison. In comparison with healthy children, children with migraine had prolonged latency of motor-evoked magnetic response in the right hemispheres during left finger movement (62.33 +/- 34.55 milliseconds vs 34.9 +/- 17.29 milliseconds, P < .05). In addition, children with migraine had stronger activation in the motor cortex during right finger movement (8097.46 +/- 5168.99 vs 4697.54 +/- 3194.74, P < .05). The results suggest that there are neurophysiological changes in the motor cortices of children with migraine that can be measured with neuromagnetic imaging techniques. The findings expand the ability to study the cerebral mechanisms of migraine using MEG and may facilitate the development of new therapeutic strategies in migraine treatment via alterations in cortical excitability.

Temporal variations of wall shear stress parameters in intracranial aneurysms—importance of patient-specific inflow waveforms for CFD calculations

To assess reliability of wall shear stress (WSS)calculations using computational fluid dynamics (CFD) dependent on inflow in internal carotid artery aneurysms (ICA). Six unruptured ICA aneurysms were studied. 3D computational meshes were created from 3D digital subtraction angiographic images (Axiom Artis dBA, Siemens Medical Solutions). Transient CFD simulations(Fluent, ANSYS Inc.) were performed for two inflow conditions: (1) idealized averaged waveform from normal subjects (ID) and (2) patient-specific waveform (PS)measured with 2D phase contrast magnetic resonance imaging. Stability of calculation was assessed by comparing mean WSS (<WSS>), temporal wall shear stress magnitude variation (Delta WSS), and oscillatory shear index(OSI, a measure of variation in the WSS direction) on the aneurysmal wall for both conditions. For all cases, mean relative difference (PS-ID) of WSS (<WSS>) was -15% (range -32% to 11%). Mean Delta WSS difference was -29.3% ( -100% to 67%). Mean OSI difference was 7.5% (-12% to 40%). Large variations in histograms of these parameters were noted. For accurate calculations of WSS parameters,patient-specific information on physiological flow may be necessary. Results obtained with averaged or idealized flow waveforms may have to be interpreted with caution.

Electrical Recording of Otoacoustic Emission

Conclusion: Otoacoustic emissions (OAEs) could be detectable as cochlear AC potentials. Spontaneous otoacoustic emissions (SOAEs) were detected either electrically or acoustically, while evoked otoacoustic emissions (EOAEs) could be detected electrically but not acoustically. Objective: Many lines of evidence support the hypothesis that SOAEs are produced by spontaneous mechanical oscillation within the cochlea, and perhaps motile properties of the outer hair cells. If this is the case, SOAEs, emitted acoustically in the external auditory meatus, could also be recorded electrically as cochlear AC potential. EOAE is also thought to be produced by vibration of the basilar membrane, generated by the backward-traveling waves. EOAE thus seems to be detectable electrically as cochlear AC potential. In the present study, SOAE and EOAE were recorded both acoustically and electrically in the guinea pigs to examine the correlation between electrically recorded SOAE (ER-SOAE) and acoustically recorded SOAE (AR-SOAE). In addition, a microphonics response (MPR) to tone pip was recorded to analyze the characteristics of the non-linear component and linear component of the AC responses. Results: (1) In 4 out of 20 guinea pigs (20%), SOAE could be detected both acoustically and electrically. (2) Electrical signals of SOAE had a better S/N ratio than acoustical signals. Generally, only some ER-SOAE could be detected acoustically. (3) Almost without exception, the prominent frequencies of multiple ER-SOAEs corresponded to the intermodulation distortion product, or harmonics. (4) ER-SOAEs were suppressed by hypoxia or intense sound exposure and reappeared upon rebreathing or discontinuation of the external tone. During recovery, prominent frequencies showed a transient downward shift in frequency. (5) SOAEs were synchronized in phase with an external tone in the spectral neighborhood of SOAE. The averaged waveform of SOAE synchronized with the external tone was the same with either acoustic or electrical signals. (6) The MPR to tone pip is composed of two components with different frequency characteristics and input/output functions. (7) The non-linear component delayed to cochlear microphonics was markedly saturated at the intensity level of 40 dB peak equivalent SPL. This component was a phase-lock response, not a frequency-locked one. (8) The non-linear component could be separated with Probst’s non-linear differential extraction technique. In the MPR to a 4-kHz tone pip, high-cut filtration at 3.5 kHz produced a waveform similar to the non-linear component separated by Probst’s method.

Electroencephalographic differences between WAG/Rij and GAERS rat models of absence epilepsy

The inbred Wistar Albino Glaxo Rats from Rijswijk (WAG/Rij) and the Genetic Absence Epilepsy Rats from Strasbourg (GAERS) are well-validated genetic models of absence epilepsy. Although they share similar characteristics including the spike-and-wave discharges (SWDs) in the EEG, some differences have been reported between both strains. This study aimed a systematic and detailed comparison of the SWD patterns of both strains in terms of the intensity, frequency and waveform morphology of the discharges by using exactly the same measurement and analysis techniques. The number, cumulative total duration and mean duration of SWDs were significantly higher in GAERS compared to WAG/Rij, while the discharge frequency was higher in the WAG/Rij. Furthermore, SWDs spectra and average SWD waveforms indicated that a single cycle of the SWD contains more energy in faster components such as spike and late positive transient in the GAERS. Additionally, WAG/Rij exhibited a significantly higher power between 8 and 14 Hz during the pre-SWD period. These clear phenomenological differences in the EEGs of both animal models suggest that these variables may represent basic phenotypic features of SWDs that should be sought after in the future studies that explore the genetic and molecular basis of absence epilepsy.

Neuromagnetic Signatures of Abnormal Excitability of Motor Cortices in Adolescent Migraine

Event Abstract Back to Event Neuromagnetic Signatures of Abnormal Excitability of Motor Cortices in Adolescent Migraine Xiaoshan Wang1*, Jing Xiang2, Yingying Wang2, Maria Pardos3, Lu Meng2, Scott W. Powers3, Marielle A. Kabbouche3 and Andrew D. Hershey3 1 Nanjing Brain Hospital, China 2 Cincinnati Children's Hospital Medical Center, United States 3 Cincinnati Children's Hospital Medical Center, Department of Neurology, United States Objective: The objective of the present study was to investigate the functional abnormalities of the motor cortices in adolescent migraine using magnetoencephalography (MEG) and a finger-tapping task. Background: Hyperexcitability of the primary somatosensory cortex has been reported in migraine using MEG. Many patients during a migraine also report difficulty with motor functioning. There is no report on motor-evoked magnetic activation in children with migraine with MEG and the latest signal processing methods. Methods: Ten children with migraine (all female, aged 13 to 17 years) and ten healthy children (all female, aged 12 to 17 years) were studied with a 275-channel MEG system. Each subject performed a brisk index finger tapping with either the right or the left index finger immediately after hearing a sound cue (500Hz, 30ms square tone); the stimuli consisted of 200 trials of square tone, 100 trials per ear, randomly distributed. The latency and amplitude of neuromagnetic responses were analyzed with averaged waveforms. Neuromagnetic sources were estimated using synthetic aperture magnetometry (SAM). SAM images were normalized for each participant for group comparison. Results: At least one neuromagnetic response was consistently identified in the MEG waveforms in the contralateral hemisphere to the unilateral finger tapping. In comparison to healthy children, children with migraine had prolonged latency of motor-evoked magnetic response in the right hemispheres during left finger movement (49.94±34.06 ms vs 21.21± 8.05 ms, p < 0.05). In addition, the SAM images indicated that children with migraine had stronger activation in the supplementary motor area during finger movement (8097.46±5168.99 vs 4697.54±3194.74, p < 0.05). Conclusion: The results suggest that there are measurable neuromagnetic abnormalities in children with migraine during finger tapping. The findings expand the ability to study the cerebral mechanisms of migraine and may facilitate the development of new therapeutic strategies in migraine treatment via alterations in cortical excitability with transcranial magnetic stimulation or other approaches. Conference: Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010. Presentation Type: Poster Presentation Topic: MEG: Clinical applications Citation: Wang X, Xiang J, Wang Y, Pardos M, Meng L, Powers SW, Kabbouche MA and Hershey AD (2010). Neuromagnetic Signatures of Abnormal Excitability of Motor Cortices in Adolescent Migraine. Front. Neurosci. Conference Abstract: Biomag 2010 - 17th International Conference on Biomagnetism . doi: 10.3389/conf.fnins.2010.06.00284 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 05 Apr 2010; Published Online: 05 Apr 2010. * Correspondence: Xiaoshan Wang, Nanjing Brain Hospital, Nanjing, China, wangxiaoshan71@yahoo.com.cn Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Xiaoshan Wang Jing Xiang Yingying Wang Maria Pardos Lu Meng Scott W Powers Marielle A Kabbouche Andrew D Hershey Google Xiaoshan Wang Jing Xiang Yingying Wang Maria Pardos Lu Meng Scott W Powers Marielle A Kabbouche Andrew D Hershey Google Scholar Xiaoshan Wang Jing Xiang Yingying Wang Maria Pardos Lu Meng Scott W Powers Marielle A Kabbouche Andrew D Hershey PubMed Xiaoshan Wang Jing Xiang Yingying Wang Maria Pardos Lu Meng Scott W Powers Marielle A Kabbouche Andrew D Hershey Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Analysis of P1 Latency in Normal Hearing and Profound Sensorineural Hearing Loss

ObjectivesP1 is a robust positivity at a latency of 50-150 msec in the auditory evoked potential of young children. It has been reported that over the first 2-3 years of life, there is a rapid decrease of the latency and the mean P1 latency in adults with normal hearing is approximately 60 msec. This study was designed to evaluate the change of the P1 latency in Koreans with normal hearing according to age and to compare this with the P1 latency of young patients with profound sensorineural hearing loss before and/or after cochlear implantation.MethodsAmong the patients who visited the Department of Otorhinolaryngology at Seoul National University Hospital from June 2007 to September 2009, the P1 response was recorded in 53 patients in the normal hearing group, in 13 patients in the pre-cochlear implantation (CI) group and in 10 patients in the post-CI group. A synthesized consonant-vowel syllable /ba/ was used to elicit the evoked responses. The evoked responses were collected using the center of the frontal head. For each subject, an individual grand average waveform was computed by averaging the ten recordings. The P1 latency was visually identified as a robust positivity in the waveform.ResultsFor the normal hearing group, the P1 latency showed the pattern of shortening as the age increased (coefficient, -0.758; P<0.001). For the pre-CI group, 10 cases showed delayed latencies and 3 cases did not show the P1 wave. For the post-CI group, the P1 latencies showed a less delayed tendency than those of the pre-CI group, but this was not statistically different.ConclusionThis report provides the standard value of the P1 latency at each age in Koreans for the first time and the findings support that the maturation of the central auditory pathways could be measured objectively using the P1 latency.

Efficacy of Independent Component Analysis on Twin Fetal Signal Extraction from fMCG data

Event Abstract Back to Event Efficacy of Independent Component Analysis on Twin Fetal Signal Extraction from fMCG data Nana Aba Mensah-Brown1*, Silvia Comani2 and Ronald Wakai1 1 University of Wisconsin , United States 2 University of Chieti, Italy We assess the overall performance of the FastICA algorithm on 13 sessions of normal and high-risk twins ranging from 20 weeks to 37 weeks’ gestation. The quality of the separated components was rated on: 1) percentage peak detection of QRS peaks 2) comparison of signal-to-noise ratio (SNR) of twin ICA datasets against SNR of raw match-filtered datasets 3) Magnitude of twin residue in each twin ICA dataset 4) Visual correlation of twin ICA datasets and raw datasets as a measure of distortion. 5) visibility of important cardiac cycle components such as QRS, p-wave and t-wave. The average peak detection for the twin datasets was 97.5±3.6%. The average SNR using ICA was 3.95±0.28 compared with the average SNR from the raw match-filtered data of 3.27±0.26. Twin residue averaged 67±4% before ICA and 45±3% after ICA, with an average noise:signal ratio of 29±2%. The average waveforms of the ICA and raw data, were aligned in time implying that the distortion in time was insignificant. However, the QRS phase distortion was largely noticeable in 8 of 26 subjects. Although the SNR of the ICA datasets was greater than that of the raw datasets, the amplitude of p-wave was significantly diminished in 8 of 26 studies. The fast ICA algorithm effectively separates twin datasets while enhancing the relative amplitude of the QRS complex, at times distorting its phase, and reducing the relative amplitude of the p and T waves. Conference: Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010. Presentation Type: Poster Presentation Topic: Fetal and neonatal biomagnetism Citation: Mensah-Brown N, Comani S and Wakai R (2010). Efficacy of Independent Component Analysis on Twin Fetal Signal Extraction from fMCG data. Front. Neurosci. Conference Abstract: Biomag 2010 - 17th International Conference on Biomagnetism . doi: 10.3389/conf.fnins.2010.06.00142 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 25 Mar 2010; Published Online: 25 Mar 2010. * Correspondence: Nana Aba Mensah-Brown, University of Wisconsin, Madison, United States, mensahbrown@wisc.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Nana Aba Mensah-Brown Silvia Comani Ronald Wakai Google Nana Aba Mensah-Brown Silvia Comani Ronald Wakai Google Scholar Nana Aba Mensah-Brown Silvia Comani Ronald Wakai PubMed Nana Aba Mensah-Brown Silvia Comani Ronald Wakai Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

A novel approach for enhancing the signal-to-noise ratio and detecting automatically event-related potentials (ERPs) in single trials

Brief radiant laser pulses can be used to activate cutaneous Aδ and C nociceptors selectively and elicit a number of transient brain responses in the ongoing EEG (N1, N2 and P2 waves of laser-evoked brain potentials, LEPs). Despite its physiological and clinical relevance, the early-latency N1 wave of LEPs is often difficult to measure reliably, because of its small signal-to-noise ratio (SNR), thus producing unavoidable biases in the interpretation of the results. Here, we aimed to develop a method to enhance the SNR of the N1 wave and measure its peak latency and amplitude in both average and single-trial waveforms. We obtained four main findings. First, we suggest that the N1 wave can be better detected using a central-frontal montage (Cc-Fz), as compared to the recommended temporal–frontal montage (Tc-Fz). Second, we show that the N1 wave is optimally detected when the neural activities underlying the N2 wave, which interfere with the scalp expression of the N1 wave, are preliminary isolated and removed using independent component analysis (ICA). Third, we show that after these N2-related activities are removed, the SNR of the N1 wave can be further enhanced using a novel approach based on wavelet filtering. Fourth, we provide quantitative evidence that a multiple linear regression approach can be applied to these filtered waveforms to obtain an automatic, reliable and unbiased estimate of the peak latency and amplitude of the N1 wave, both in average and single-trial waveforms.

Differences in Abdominal Muscle Activation Patterns of Younger and Older Adults Performing an Asymmetric Leg-Loading Task

To determine whether differences exist between younger (20-50 years) and older adults (>65 years) in abdominal muscle amplitudes, temporal patterns, and three-dimensional (3D) pelvic motion, while performing an asymmetric leg-loading task. Cross-sectional. Neuromuscular function laboratory. Ten healthy younger (33.3 +/- 7.7 years) and 10 healthy gender- and body mass index-matched older adults (69.0 +/- 6.6 years). Surface electromyograms from 6 abdominal muscle sites bilaterally and pelvic motions were simultaneously recorded. Root mean square (RMS) amplitude during the leg extension phase was calculated for each muscle. Ensemble average waveforms for the total exercise were analyzed using principal component (PC) analysis. Total angular displacement of the pelvis was calculated. Student t tests were performed on demographic and angular displacement data. Three-factor mixed model analysis of variances (group, muscle, side) tested main effects and interactions (P < .05) for the RMS amplitude and PC scores from the temporal waveforms. Bonferroni post-hoc analyses tested pair-wise differences. There were no between-group differences for the pelvic motions. Three PC patterns captured 85% of the variance in the waveforms. The external oblique (EO) RMS amplitudes were significantly (P < .05) higher than those of the other 3 muscle sites, similar for the PC1 scores which captured overall amplitude. The PC2 score for the internal oblique (IO) was significantly higher (P < .05) than that of all other muscles, illustrating a higher initial amplitude compared with later in the movement. There was a significant group by muscle interaction for PC3 scores, demonstrating group differences in temporal patterns. Both groups were able to minimize lumbopelvic motion and recruited their abdominal muscles to similar overall amplitudes, with the IO muscle activated to higher amplitudes early in the movement task. The older adult group demonstrated a distinctive drop in abdominal activity during the leg-lowering phase of the exercise and less symmetry among muscle sites.

Modeling single-trial LRP waveforms using gamma functions

The lateralized readiness potential (LRP) is a component of average event-related potentials that has proven very useful in the study of hand-specific motor preparation. We developed a model of single-trial LRP waveforms that produces realistic average waveforms for both stimulus-locked and response-locked averaging. This model may be useful in computer simulation studies of LRP scoring methods, and it may open up the possibility of ultimately retrieving trial-by-trial information about LRP activity.

Impact of sleep on arrhythmogenesis.

Sleep is generally considered to be a protected period, when the cardiovascular system benefits from the restorative influences of the sleeping brain. However, the dynamics of cardiovascular control during sleep can tax the capacity of the diseased coronary circulation and myocardium with surges in sleep-state–related autonomic activity and disruptions in airway function and central nervous system regulation. In this regard, sleep may constitute an autonomic stress test for the heart. The scope of sleep-related risk for atrial and ventricular arrhythmias is substantial. The major subgroups susceptible to adverse influences of surges in autonomic activity during sleep are those with ischemic heart disease, heart failure, and channelopathies (Table).1 It is significant that 20% of myocardial infarctions and 15% of sudden deaths occur at night in the United States.2 Most atrial arrhythmias in patients younger than 61 years of age have nocturnal onset.3 The young are not immune to risk, as sudden infant death syndrome (SIDS) claims 2500 lives in the United States annually.4 Cardiovascular risk is compounded by comorbid factors, most notably apnea, which affects an estimated 4% to 9% of the general population5 and is considerably more prevalent among obese individuals.6 The more common form is obstructive sleep apnea (OSA), with partial or complete collapse of the pharynx. Half of heart failure patients experience either OSA or central sleep apnea (CSA) with central nervous system–mediated periodic breathing, commonly referred to as Cheyne-Stokes respiration. Such cardiorespiratory disturbances profoundly alter autonomic nervous system activity and increase risk of arrhythmia, hypertension, and myocardial infarction. View this table: Table. Patient Groups at Potentially Increased Risk for Nocturnal Cardiac Events It is surprising, as recently underscored by Malhotra and Loscalzo,7 that the significance of cardiovascular risk during sleep may not be duly recognized within the cardiology community. The reasons are …

A Waveform Model for Near-Nadir Radar Altimetry Applied to the Cassini Mission to Titan

The radar altimeter of the Cassini mission to Titan operates in a transition region between pulse- and beam-limited conditions. Due to the specific observation geometry, low values of mispointing angle have been found to significantly affect altimeter impulse response (IR). This involves a nonconventional formulation of the system response which is the main goal of this paper. An analytical model of the average return power waveform, valid for near-nadir altimetry measurements, has been developed in order to cope with the particular operating conditions of Cassini mission. The model used to approximate the altimeter waveform is based on the same general assumptions of the classical Brown's model (1977) but exploits a flat surface response approximation by Prony's methods. Both theoretical considerations and simulated data have been taken into account to support the accuracy of the proposed model. To infer the main geophysical parameters describing surface topography from altimetry data, a parametric estimation procedure has been used. The maximum likelihood estimator procedure has been chosen since, in principle, it can assure optimal performance as a consequence of the analytical model we used to describe the system IR. Performances of the implemented method have been numerically evaluated through simulation of data received by CASSINI in high-resolution altimeter mode.

Single-Unit Stability Using Chronically Implanted Multielectrode Arrays

The use of chronic intracortical multielectrode arrays has become increasingly prevalent in neurophysiological experiments. However, it is not obvious whether neuronal signals obtained over multiple recording sessions come from the same or different neurons. Here, we develop a criterion to assess single-unit stability by measuring the similarity of 1) average spike waveforms and 2) interspike interval histograms (ISIHs). Neuronal activity was recorded from four Utah arrays implanted in primary motor and premotor cortices in three rhesus macaque monkeys during 10 recording sessions over a 15- to 17-day period. A unit was defined as stable through a given day if the stability criterion was satisfied on all recordings leading up to that day. We found that 57% of the original units were stable through 7 days, 43% were stable through 10 days, and 39% were stable through 15 days. Moreover, stable units were more likely to remain stable in subsequent recording sessions (i.e., 89% of the neurons that were stable through four sessions remained stable on the fifth). Using both waveform and ISIH data instead of just waveforms improved performance by reducing the number of false positives. We also demonstrate that this method can be used to track neurons across days, even during adaptation to a visuomotor rotation. Identifying a stable subset of neurons should allow the study of long-term learning effects across days and has practical implications for pooling of behavioral data across days and for increasing the effectiveness of brain-machine interfaces.

Simultaneously recorded EEG–fMRI: Removal of gradient artifacts by subtraction of head movement related average artifact waveforms

Electroencephalograms (EEGs) recorded simultaneously with functional magnetic resonance imaging (fMRI) are corrupted by large repetitive artifacts generated by the switched MR gradients. Several methods have been proposed to remove these distortions by subtraction of averaged artifact templates from the ongoing EEG. Here, we present a modification of this approach which accounts for head movements to improve the extracted template. Using the fMRI analysis package statistical parametric mapping (SPM; FIL London) the head displacement is determined at each half fMRI-volume. The basic idea is to apply a moving average algorithm for template extraction but to include only epochs that were obtained at the same head position as the artefact to be removed. This approach was derived from phantom EEG measurements demonstrating substantial variations of the artefact waveform in response to movements of the phantom in the MRI magnet. To further reduce the residual noise, we applied a resampling algorithm which aligns the EEG samples in a strict adaptive manner to the fMRI timing. Finally, we propose a new algorithm to suppress residual artifacts such as those occasionally observed in case of brief strong movements, which are not reflected by the movement indicator because of the limited temporal resolution of the fMRI sequence. On the basis of EEG recordings of six subjects these measures combined reduce the residual artefact activity quantified in terms of the spectral power at the gradient repetition rate and its harmonics by roughly 20 to 50% (depending on the amount of movement) predominantly in frequencies beyond 30 Hz.

Standardization of the measurement error in ERP recordings

Event Abstract Back to Event Standardization of the measurement error in ERP recordings Antti Paukkunen1, 2*, M. Järvenpää1, 3, 4 and R. Sepponen1 1 Electronics Department, Helsinki University of Technology, Finland 2 Graduate School of Electrical and Communications Engineering, Helsinki University of Technology, Finland 3 Department of Psychology, Helsinki University, Finland 4 Finish Centre of Excellence in Interdisciplinary Music Research, Finland One of the greatest challenges preventing the use of event-related potentials (ERP) in clinical diagnostics is low reliability and repeatability of the average waveforms. Advances in the measurement technique, technology, analysis methodology and means of validating the data have increased the reliability, but the ambivalence of single-patient measurements is still high. The measurement error cannot be standardized without control over the total quality. Increased number of trials would improve the signal-to-noise-ratio of the grand average, but the disadvantage is the fatigue of the patients. The major issue is to decide the optimal number of trials.This study presents a novel recording procedure for ERP studies where the amount of recorded trials is automatically adjusted online according to the initial quality of the data and the desired quality of the measurement outcome. The process was simulated offline using prerecorded ERP data from a MMN study. The preliminary results suggest that the repeatability of the average waveform and, thus, the reliability of the measurement were improved. However, further testing is required before the online implementation. Conference: MMN 09 Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications, Budapest, Hungary, 4 Apr - 7 Apr, 2009. Presentation Type: Poster Presentation Topic: Poster Presentations Citation: Paukkunen A, Järvenpää M and Sepponen R (2009). Standardization of the measurement error in ERP recordings. Conference Abstract: MMN 09 Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications. doi: 10.3389/conf.neuro.09.2009.05.146 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 26 Mar 2009; Published Online: 26 Mar 2009. * Correspondence: Antti Paukkunen, Electronics Department, Helsinki University of Technology, Espoo, Finland, antti.paukkunen@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Antti Paukkunen M. Järvenpää R. Sepponen Google Antti Paukkunen M. Järvenpää R. Sepponen Google Scholar Antti Paukkunen M. Järvenpää R. Sepponen PubMed Antti Paukkunen M. Järvenpää R. Sepponen Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Modified variance ratio for objective detection of transient evoked potentials in bottlenose dolphins (Tursiops truncatus)

Evoked potential studies have often relied on one or more human observers to visually assess the averaged waveforms and decide if a response is present. Although simple and easy to implement, response detection strategies based on human observers are inherently subjective and depend on the observers' experience and biases. To avoid these shortcomings, some recent marine animal studies utilizing auditory steady-state responses have applied frequency-domain, statistically based objective detection methods; however, statistically based objective methods have not yet been applied to marine animal tests involving transient evoked responses, which are normally analyzed in the time domain. The present study applied a modified version of the variance ratio F(SP) to determine the presence or absence of evoked responses in two bottlenose dolphins (Tursiops truncatus) stimulated with tone pips. The appropriate degrees of freedom for the statistical tests were empirically determined in four dolphins. The modified variance ratio was found to be a useful tool and to provide an objective statistical approach for the detection of transient evoked potentials.

Neural correlates of immediate and delayed word recognition memory: An MEG study

We investigated the neural correlates of immediate and delayed word recognition memory using whole head magnetoencephalography (MEG). Event-related potential (ERP) and event-related field (ERF) were simultaneously recorded from 10 subjects while performing a continuous recognition memory task. Subjects were required to determine whether the word was “new” (never before presented) or “old” (presented previously). Old items were presented either immediately or delayed with five intervening words, and the words presented only once were referred to as new words. The grand average ERP waveform showed that immediate repetition was associated with early P300 and absence of N400, while delayed repetition and new word were associated with late P300 and presence of N400. Three ERF components were observed for immediate repetition, while four components were observed for delayed repetition and new word conditions. M1 and M2 were observed across all stimulus-presentation conditions. M3 with medial temporal generators was observed only in delayed repetition and new word conditions. M4 was observed earlier in the immediate repetition than in the delayed repetition and new-word conditions. For M4 generators, cingulate gyrus activations were observed for all stimulus-presentation conditions. In addition, activations in the medial temporal areas were observed for both repetition conditions. These results suggest that immediate and delayed recognition memory have similar neural networks except for the additional involvement of medial temporal areas in delayed recognition memory. The functional roles of M3 and M4 peaks were discussed in terms of functional significance of N400 and early/late P300 ERP peaks, which correspond to M3 and M4, respectively.

Spontaneous firing properties of rat medial vestibular nucleus neurons in brain slices by infrared visual patch clamp technique

Domestic application of infrared patch clamp techniques on brain slices is limited. The key of the technique is to prepare high-quality brain slices. The present paper describes the preparation procedure of brainstem slices and the spontaneous firing properties of rat medial vestibular nucleus (MVN) neurons. By infrared differential interference contrast technique, neurons of rat MVN were visualized directly at the depth of 50–100 μm underneath the surface of slices. Firing activities of MVN neurons were recorded by the whole-cell patch clamp technique in artificial cerebrospinal fluid (ACSF) and low Ca2+-high Mg2+ fluid. The firing mode was more irregular and depressive in low Ca2+-high Mg2+ fluid than in ACSF. According to the averaged waveform of action potentials, cells were classified as the neurons with monophasic after-hyperpolarization potential (AHP), and the neurons with biphasic AHP. The resting membrane potential (RMP), input resistance (Rin) and membrane capacitance (Cm) of neurons were recorded and compared between groups. With infrared videomicroscopy, patch clamp recordings could be made under direct observation in freshly prepared brainstem slices. The discharge activities of MVN neurons were spontaneous and the firing mode was modulated by extracellular calcium concentration. The basic membrane properties of two types of neurons were not significantly different, while the differences in waveform might play a role in the segregation between tonic and kinetic cells.