scholarly journals It’s all about time: precision and accuracy of Emotiv event-marking for ERP research

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e10700
Author(s):  
Nikolas S. Williams ◽  
Genevieve M. McArthur ◽  
Nicholas A. Badcock
Keyword(s):  
Event Related Potential ◽  
Temporal Position ◽  
Parallel Port ◽  
Serial Port ◽  
Eeg Data ◽  
Research Grade ◽  
The Mean ◽  
Precision And Accuracy ◽  
Auxiliary Device ◽  
Statistical Noise

Background The use of consumer-grade electroencephalography (EEG) systems for research purposes has become more prevalent. In event-related potential (ERP) research, it is critical that these systems have precise and accurate timing. The aim of the current study was to investigate the timing reliability of event-marking solutions used with Emotiv commercial EEG systems. Method We conducted three experiments. In Experiment 1 we established a jitter threshold (i.e. the point at which jitter made an event-marking method unreliable). To do this, we introduced statistical noise to the temporal position of event-marks of a pre-existing ERP dataset (recorded with a research-grade system, Neuroscan SynAmps2 at 1,000 Hz using parallel-port event-marking) and calculated the level at which the waveform peaks differed statistically from the original waveform. In Experiment 2 we established a method to identify ‘true’ events (i.e. when an event should appear in the EEG data). We did this by inserting 1,000 events into Neuroscan data using a custom-built event-marking system, the ‘Airmarker’, which marks events by triggering voltage spikes in two EEG channels. We used the lag between Airmarker events and events generated by Neuroscan as a reference for comparisons in Experiment 3. In Experiment 3 we measured the precision and accuracy of three types of Emotiv event-marking by generating 1,000 events, 1 s apart. We measured precision as the variability (standard deviation in ms) of Emotiv events and accuracy as the mean difference between Emotiv events and true events. The three triggering methods we tested were: (1) Parallel-port-generated TTL triggers; (2) Arduino-generated TTL triggers; and (3) Serial-port triggers. In Methods 1 and 2 we used an auxiliary device, Emotiv Extender, to incorporate triggers into the EEG data. We tested these event-marking methods across three configurations of Emotiv EEG systems: (1) Emotiv EPOC+ sampling at 128 Hz; (2) Emotiv EPOC+ sampling at 256 Hz; and (3) Emotiv EPOC Flex sampling at 128 Hz. Results In Experiment 1 we found that the smaller P1 and N1 peaks were attenuated at lower levels of jitter relative to the larger P2 peak (21 ms, 16 ms, and 45 ms for P1, N1, and P2, respectively). In Experiment 2, we found an average lag of 30.96 ms for Airmarker events relative to Neuroscan events. In Experiment 3, we found some lag in all configurations. However, all configurations exhibited precision of less than a single sample, with serial-port-marking the most precise when paired with EPOC+ sampling at 256 Hz. Conclusion All Emotiv event-marking methods and configurations that we tested were precise enough for ERP research as the precision of each method would provide ERP waveforms statistically equivalent to a research-standard system. Though all systems exhibited some level of inaccuracy, researchers could easily account for these during data processing.

RADIOIMMUNOASSAY OF OESTRONE AND OESTRADIOL IN THE PERIPHERAL PLASMA OF THE DOMESTIC FOWL IN VARIOUS PHYSIOLOGICAL STATES AND OF HYPOPHYSECTOMIZED AND OVARIECTOMIZED FOWLS

1974 ◽  
Vol 75 (1) ◽  
pp. 133-140 ◽  
Author(s):  
B. E. Senior
Keyword(s):  
Bovine Serum Albumin ◽  
Serum Albumin ◽  
Diethyl Ether ◽  
Bovine Serum ◽  
Domestic Fowl ◽  
Laying Hens ◽  
Peripheral Plasma ◽  
The Mean ◽  
Precision And Accuracy ◽  
Chicken Ovary

ABSTRACT A radioimmunoassay was developed to measure the levels of oestrone and oestradiol in 0.5–1.0 ml of domestic fowl peripheral plasma. The oestrogens were extracted with diethyl ether, chromatographed on columns of Sephadex LH-20 and assayed with an antiserum prepared against oestradiol-17β-succinyl-bovine serum albumin using a 17 h incubation at 4°C. The specificity, sensitivity, precision and accuracy of the assays were satisfactory. Oestrogen concentrations were determined in the plasma of birds in various reproductive states. In laying hens the ranges of oestrone and oestradiol were 12–190 pg/ml and 29–327 pg/ml respectively. Levels in immature birds, in adult cockerels and in an ovariectomized hen were barely detectable. The mean concentrations of oestrone and oestradiol in the plasma of four non-laying hens (55 pg/ml and 72 pg/ml respectively) and one partially ovariectomized hen (71 pg/ml and 134 pg/ml respectively) were well within the range for laying hens. It is evident that the large, yolk-filled follicles are not the only source of oestrogens in the chicken ovary.

scholarly journals Eliciting and Recording Event Related Potentials (ERPs) in Behaviourally Unresponsive Populations: A Retrospective Commentary on Critical Factors

2021 ◽  
Vol 11 (7) ◽  
pp. 835
Author(s):  
Alexander Rokos ◽  
Richard Mah ◽  
Rober Boshra ◽  
Amabilis Harrison ◽  
Tsee Leng Choy ◽  
...  
Keyword(s):  
Event Related Potentials ◽  
Stimulus Presentation ◽  
Event Related Potential ◽  
Critical Factors ◽  
Healthy Elderly ◽  
States Of Consciousness ◽  
Long Latency ◽  
Eeg Data ◽  
Related Potentials ◽  
The Relationship

A consistent limitation when designing event-related potential paradigms and interpreting results is a lack of consideration of the multivariate factors that affect their elicitation and detection in behaviorally unresponsive individuals. This paper provides a retrospective commentary on three factors that influence the presence and morphology of long-latency event-related potentials—the P3b and N400. We analyze event-related potentials derived from electroencephalographic (EEG) data collected from small groups of healthy youth and healthy elderly to illustrate the effect of paradigm strength and subject age; we analyze ERPs collected from an individual with severe traumatic brain injury to illustrate the effect of stimulus presentation speed. Based on these critical factors, we support that: (1) the strongest paradigms should be used to elicit event-related potentials in unresponsive populations; (2) interpretation of event-related potential results should account for participant age; and (3) speed of stimulus presentation should be slower in unresponsive individuals. The application of these practices when eliciting and recording event-related potentials in unresponsive individuals will help to minimize result interpretation ambiguity, increase confidence in conclusions, and advance the understanding of the relationship between long-latency event-related potentials and states of consciousness.

An Electrophysiological Measure of Temporal Resolution in Normal Subjects Using Frequency Modulated Signals

2002 ◽  
Vol 11 (1) ◽  
pp. 42-49
Author(s):  
Devin L. McCaslin ◽  
Lawrence L. Feth ◽  
Gary P. Jacobson ◽  
Pamela J. Mishler
Keyword(s):  
Temporal Resolution ◽  
Mismatch Negativity ◽  
Normal Subjects ◽  
Single Step ◽  
Event Related Potential ◽  
Frequency Range ◽  
Temporal Properties ◽  
Step Duration ◽  
The Mean ◽  
Modulated Signals

This investigation was conducted to determine whether an exogenous event-related potential called the mismatch negativity (MMN) would change systematically in response to frequency-modulated signals with varying temporal properties. Both N1 and P2 waveforms were recorded for 50-ms frequency-modulated signals from normal hearing listeners. The standard stimuli for this investigation were continuous sweep tones with center frequencies of 1000 Hz that traversed a frequency range of 200 Hz in a single step. The rare stimuli were signals that traversed the same frequency range in two, four, six, or eight discrete steps. Results suggest that for the 10 participants, 1) the mean MMN peak-to-peak amplitude and mean area decreased significantly with decreases in step duration, 2) MMN area amplitude was the best indicator of psychophysical performance for the two magnitude measures, and 3) MMN onsets and peak latencies did not show either a significant increase or decrease in latency as step duration decreased.

ENZYMATISCH-FLUOROMETRISCHE BESTIMMUNG DER CORTISOLBINDUNGSKAPAZITÄT DES PLASMA

1967 ◽  
Vol 56 (1) ◽  
pp. 99-106 ◽  
Author(s):  
K. Leybold ◽  
J. Rieper ◽  
L. Weissbecker
Keyword(s):  
Binding Capacity ◽  
Liver Microsomes ◽  
Mean Value ◽  
Female Rats ◽  
Plasma Samples ◽  
Simple Method ◽  
Adult Men ◽  
The Mean ◽  
Precision And Accuracy

ABSTRACT A simple method for the determination of cortisol-binding capacity is described. For saturation of the cortisol-binding proteins, plasma samples are incubated with an excess of cortisol. In the next step NADPH and liver microsomes of female rats are added. The microsomal Δ4-3-ketosteroid hydrogenase only reduces non protein-bound cortisol to tetrahydrocortisol-5α. Then the steroids are extracted by dichloromethane, and after some purification steps analyzed by fluorometry. Tetrahydrocortisol gives practically no fluorescence. The cortisol determined by this method corresponds to protein-bound cortisol and indicates the extent of cortisolbinding capacity. Precision and accuracy of the method were found to be good. The values of cortisol-binding capacity obtained by our method are compared with the results of other authors. The mean value of adult men was 25.5 ± 3.4 μg/100 ml, that of pregnant women, mens IX-X, 42.3 ± 4.2 μg/100 ml.

scholarly journals Decreased P2 Waveform Reflects Impaired Brain Executive Function Induced by 12 h of Low Homeostatic Sleep Pressure: Evidence From an Event-Related Potential Study

2021 ◽  
Vol 15 ◽  
Author(s):  
Lingjing Zeng ◽  
Haijing Wu ◽  
Jialu Li ◽  
Haiteng Wang ◽  
Songyue Xie ◽  
...  
Keyword(s):  
Executive Function ◽  
Response Time ◽  
Visual Processing ◽  
Repeated Measures ◽  
Young Male ◽  
Event Related Potential ◽  
Peak Latency ◽  
Peak Amplitude ◽  
Eeg Data ◽  
The Impact

Homeostatic sleep pressure can cause cognitive impairment, in which executive function is the most affected. Previous studies have mainly focused on high homeostatic sleep pressure (long-term sleep deprivation); thus, there is still little related neuro-psycho-physiological evidence based on low homeostatic sleep pressure (12 h of continuous wakefulness) that affects executive function. This study aimed to investigate the impact of lower homeostatic sleep pressure on executive function. Our study included 14 healthy young male participants tested using the Go/NoGo task in normal resting wakefulness (10:00 am) and after low homeostatic sleep pressure (10:00 pm). Behavioral data (response time and accuracy) were collected, and electroencephalogram (EEG) data were recorded simultaneously, using repeated measures analysis of variance for data analysis. Compared with resting wakefulness, the participants’ response time to the Go stimulus was shortened after low homeostatic sleep pressure, and the correct response rate was reduced. Furthermore, the peak amplitude of Go–P2 decreased significantly, and the peak latency did not change significantly. For NoGo stimulation, the peak amplitude of NoGo–P2 decreased significantly (p < 0.05), and the peak latency was significantly extended (p < 0.05). Thus, the P2 wave is likely related to the attention and visual processing and reflects the early judgment of the perceptual process. Therefore, the peak amplitude of Go–P2 and NoGo–P2 decreased, whereas the peak latency of NoGo–P2 increased, indicating that executive function is impaired after low homeostatic sleep pressure. This study has shown that the P2 wave is a sensitive indicator that reflects the effects of low homeostatic sleep pressure on executive function, and that it is also an important window to observe the effect of homeostatic sleep pressure and circadian rhythm on cognitive function.

scholarly journals Comparative analysis of two-group supervised classification algorithms in the study of P300-based brain-computer interface

2019 ◽  
Vol 252 ◽  
pp. 03010
Author(s):  
Małgorzata Plechawska-Wójcik ◽  
Monika Kaczorowska ◽  
Bernadetta Michalik
Keyword(s):  
Comparative Analysis ◽  
Supervised Classification ◽  
Brain Computer Interface ◽  
Event Related Potential ◽  
Computer Interface ◽  
Linear Discriminant ◽  
Process Comparison ◽  
Eeg Data ◽  
Comparative Accuracy ◽  
Supervised Classification Methods

The main goal of the paper is to perform a comparative accuracy analysis of the two-group classification of EEG data collected during the P300-based brain-computer interface tests. The brain-computer interface is a technology that allows establishing communication between a human brain and external devices. BCIs may be applied in medicine to improve the life of disabled people and as well for entertainment. The P300 is an event-related potential (ERP) appearing about 300 ms after the occurrence of the stimulus of visual, auditory or sensory nature. It is based on the phenomenon observed in anticipation for a target event among non-target events. The 21-channel 201 Mitsar amplifier was used during the experiment to store EEG data from seven electrodes placed on the dedicated cap. The study was conducted on a group of five persons using P300 scenario available in OpenVibe software. The experiment was based on three steps the classifier learning process, comparison and averaging of the obtained result and the final test of the classifier. The comparative analysis was performed with the application of two supervised classification methods: Linear Discriminant Analysis (LDA) and Multi-layer Perceptron (MLP). The preliminary data analysis, extraction and feature selection was performed prior to the classification.

Performance Evaluation of CEA Assay on Beckman Coulter UniCel DxI 800

2019 ◽  
Vol 152 (Supplement_1) ◽  
pp. S20-S20
Author(s):  
Qing Wei ◽  
Robert Hardy ◽  
Liyun Cao
Keyword(s):  
Reference Range ◽  
Limit Of Detection ◽  
Measurement Range ◽  
Surgical Removal ◽  
Primary Colorectal Cancer ◽  
Serum Cea ◽  
The Mean ◽  
Precision And Accuracy ◽  
Patient Prognosis ◽  
High Level

Abstract Carcinoembryonic antigen (CEA) is a glycoprotein normally found in embryonic entodermal epithelium. Increased levels may be found in patients with primary colorectal cancer or other malignancies. CEA levels are not useful in screening the general population for undetected cancers. However, CEA levels provide important information about patient prognosis, recurrence of tumors after surgical removal, and effectiveness of therapy. The aim of this study was to assess the analytical performance of CEA assay on a Beckman Coulter UniCel DxI 800. The linearity, sensitivity, reference range, precision, and accuracy were evaluated following CLSI guidelines. The within-run and between-run precisions were assessed by analyzing QC material at low and high levels of concentrations. The accuracy was assessed by comparison of 152 patient serum CEA on DXI with CEA on a previously established ADVIA Centaur System. The analytical measurement range was determined to be linear between 0.00 and 951.3 ng/mL with a slope of 0.976 and intercept of 0.075. The limit of blank (LOB) was determined as 0.03 ng/mL and the limit of detection (LOD) was 0.1 ng/mL. The reference range was verified as 0.0 to 3.0 ng/mL (nonsmokers) and 0.0 to 5.0 ng/mL (smokers). The within-run CVs for CEA were 4.4% at the low level of 2.239 ng/mL and 2.5% at the high level of 38.1 ng/mL. The between-run CVs at low and high levels were 4.4%, and 4.0%, respectively. Comparison of CEA on the Beckman Coulter UniCel DxI 800 with CEA on the ADVIA Centaur System of 152 patient samples showed the slope was 1.541 (95% CI, 1.515-1.567) with an intercept of 0.17 and a correlation coefficient of 0.9943 (Deming). The mean bias between Beckman and ADVIA was 6.49 (41.71%). In summary, our data demonstrate that CEA assay on the Beckman Coulter UniCel DxI 800 has good linearity and precision. There is also good correlation between CEA tested on the Beckman Coulter UniCel DxI 800 and on the ADVIA Centaur System with a positive bias.

scholarly journals Suppressing cosmic variance with paired-and-fixed cosmological simulations: average properties and covariances of dark matter clustering statistics

2020 ◽  
Vol 496 (3) ◽  
pp. 3862-3869 ◽  
Author(s):  
Anatoly Klypin ◽  
Francisco Prada ◽  
Joyce Byun
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Initial Conditions ◽  
Cosmological Parameters ◽  
Average Density ◽  
Covariance Matrices ◽  
Acoustic Oscillations ◽  
Galaxy Clustering ◽  
The Mean ◽  
Statistical Noise

ABSTRACT Making cosmological inferences from the observed galaxy clustering requires accurate predictions for the mean clustering statistics and their covariances. Those are affected by cosmic variance – the statistical noise due to the finite number of harmonics. The cosmic variance can be suppressed by fixing the amplitudes of the harmonics instead of drawing them from a Gaussian distribution predicted by the inflation models. Initial realizations also can be generated in pairs with 180○ flipped phases to further reduce the variance. Here, we compare the consequences of using paired-and-fixed versus Gaussian initial conditions on the average dark matter clustering and covariance matrices predicted from N-body simulations. As in previous studies, we find no measurable differences between paired-and-fixed and Gaussian simulations for the average density distribution function, power spectrum, and bispectrum. Yet, the covariances from paired-and-fixed simulations are suppressed in a complicated scale- and redshift-dependent way. The situation is particularly problematic on the scales of Baryon acoustic oscillations where the covariance matrix of the power spectrum is lower by only $\sim 20{{\ \rm per\ cent}}$ compared to the Gaussian realizations, implying that there is not much of a reduction of the cosmic variance. The non-trivial suppression, combined with the fact that paired-and-fixed covariances are noisier than from Gaussian simulations, suggests that there is no path towards obtaining accurate covariance matrices from paired-and-fixed simulations – result, that is theoretically expected and accepted in the field. Because the covariances are crucial for the observational estimates of galaxy clustering statistics and cosmological parameters, paired-and-fixed simulations, though useful for some applications, cannot be used for the production of mock galaxy catalogues.

scholarly journals Indexing the graded allocation of visuospatial attention using anticipatory alpha oscillations

2011 ◽  
Vol 105 (3) ◽  
pp. 1318-1326 ◽  
Author(s):  
Ian C. Gould ◽  
Matthew F. Rushworth ◽  
Anna C. Nobre
Keyword(s):  
Reaction Times ◽  
Neural Mechanism ◽  
Visuospatial Attention ◽  
Event Related Potential ◽  
Response Preparation ◽  
Beta Band ◽  
Top Down ◽  
Alpha Oscillations ◽  
Time Frequency ◽  
Eeg Data

Lateralization in the desynchronization of anticipatory occipitoparietal alpha (8–12 Hz) oscillations has been implicated in the allocation of selective visuospatial attention. Previous studies have demonstrated that small changes in the lateralization of alpha-band activity are predictive of behavioral performance but have not directly investigated how flexibly alpha lateralization is linked to top-down attentional goals. To address this question, we presented participants with cues providing varying degrees of spatial certainty about the location at which a target would appear. Time-frequency analysis of EEG data demonstrated that manipulating spatial certainty led to graded changes in the extent to which alpha oscillations were lateralized over the occipitoparietal cortex during the cue-target interval. We found that individual differences in alpha desynchronization contralateral to attention predicted reaction times, event-related potential measures of perceptual processing of targets, and beta-band (15–25 Hz) activity typically associated with response preparation. These results support the hypothesis that anticipatory alpha modulation is a plausible neural mechanism underlying the allocation of visuospatial attention and is under flexible top-down control.

scholarly journals A two for one special: EEG hyperscanning using a single-person EEG recording setup

2021 ◽  
Author(s):  
Caitriona Douglas ◽  
Antoine Tremblay ◽  
Aaron J Newman
Keyword(s):  
Event Related Potential ◽  
Oscillatory Activity ◽  
Simultaneous Acquisition ◽  
Single Person ◽  
Eeg Data ◽  
Stimulus Timing ◽  
Audio Data ◽  
Eeg Recordings ◽  
Post Hoc ◽  
Precise Time

EEG hyperscanning refers to recording electroencephalographic (EEG) data from multiple participants simultaneously. Many hyperscanning experimental designs seek to mimic naturalistic behavior, relying on unpredictable participant-generated stimuli. The majority of this research has focused on neural oscillatory activity that is quantified over hundreds of milliseconds or more. This contrasts with traditional event-related potential (ERP) research in which analysis focuses on transient responses, often only tens of milliseconds in duration. Deriving ERPs requires precise time-locking between stimuli and EEG recordings, and thus typically relies on pre-set stimuli that are presented to participants by a system that controls stimulus timing and synchronization with an EEG system. EEG hyperscanning methods typically use separate EEG amplifiers for each participant, increasing cost and complexity — including challenges in synchronizing data between systems. Here, we describe a method that allows for simultaneous acquisition of EEG data from a pair of participants engaged in conversation, using a single EEG system with simultaneous audio data collection that is synchronized with the EEG recording. This allows for the post-hoc insertion of trigger codes so that it is possible to analyze ERPs time-locked to specific events. We further demonstrate methods for deriving ERPs elicited by another person’s spontaneous speech, using this setup.

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