Cargando…

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

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 reliab...

Descripción completa

Detalles Bibliográficos
Autores principales: Williams, Nikolas S., McArthur, Genevieve M., Badcock, Nicholas A.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: PeerJ Inc. 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7879951/
https://www.ncbi.nlm.nih.gov/pubmed/33614271
http://dx.doi.org/10.7717/peerj.10700
_version_ 1783650616704237568
author Williams, Nikolas S.
McArthur, Genevieve M.
Badcock, Nicholas A.
author_facet Williams, Nikolas S.
McArthur, Genevieve M.
Badcock, Nicholas A.
author_sort Williams, Nikolas S.
collection PubMed
description 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 SynAmps(2) 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.
format Online
Article
Text
id pubmed-7879951
institution National Center for Biotechnology Information
language English
publishDate 2021
publisher PeerJ Inc.
record_format MEDLINE/PubMed
spelling pubmed-78799512021-02-18 It’s all about time: precision and accuracy of Emotiv event-marking for ERP research Williams, Nikolas S. McArthur, Genevieve M. Badcock, Nicholas A. PeerJ Neuroscience 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 SynAmps(2) 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. PeerJ Inc. 2021-02-09 /pmc/articles/PMC7879951/ /pubmed/33614271 http://dx.doi.org/10.7717/peerj.10700 Text en © 2021 Williams et al. https://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ) and either DOI or URL of the article must be cited.
spellingShingle Neuroscience
Williams, Nikolas S.
McArthur, Genevieve M.
Badcock, Nicholas A.
It’s all about time: precision and accuracy of Emotiv event-marking for ERP research
title It’s all about time: precision and accuracy of Emotiv event-marking for ERP research
title_full It’s all about time: precision and accuracy of Emotiv event-marking for ERP research
title_fullStr It’s all about time: precision and accuracy of Emotiv event-marking for ERP research
title_full_unstemmed It’s all about time: precision and accuracy of Emotiv event-marking for ERP research
title_short It’s all about time: precision and accuracy of Emotiv event-marking for ERP research
title_sort it’s all about time: precision and accuracy of emotiv event-marking for erp research
topic Neuroscience
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7879951/
https://www.ncbi.nlm.nih.gov/pubmed/33614271
http://dx.doi.org/10.7717/peerj.10700
work_keys_str_mv AT williamsnikolass itsallabouttimeprecisionandaccuracyofemotiveventmarkingforerpresearch
AT mcarthurgenevievem itsallabouttimeprecisionandaccuracyofemotiveventmarkingforerpresearch
AT badcocknicholasa itsallabouttimeprecisionandaccuracyofemotiveventmarkingforerpresearch