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Multiplexed, data structure-based enriched physiological event marker system

Filed under:

Derek Rollend (JHU/APL), Marcos Osorno (JHU/APL)

As has been stressed by international scientific standards committees, event markers allow for the alignment of experiment events with their associated physiological data in the post-processing phase of an experiment and are crucial for providing context in recorded measurements [1]. Current physiological data file formats only afford rudimentary event encoding schemes, including hexadecimal event codes with a separate user-defined lookup table file, and time-stamped experiment annotations [2, 3]. The latter requires synchronizing the data acquisition system and annotation-generating software. It becomes desirable then to simultaneously generate and record both experiment events and metadata (annotations) from multiple subjects in a unified form that is compatible with existing physiological data file formats.

To meet these goals, an alternative event marker method was developed. A data structure, loosely based on standard transmission protocol structures, was used in order to contain both an event description and a payload of associated event metadata or experiment behavioral data. This event marker system has been successfully demonstrated in an ongoing psychophysiological experiment where the total expected number of participants is between 100-200 volunteers. To alleviate the bookkeeping burden during the analysis phase of the experiment, participant identification, experiment identification, participant roles, and behavioral metadata have been packaged within event markers. This has enabled 1) human-readable, meaningful event descriptions to be overlaid on recorded EEG, ECG, EOG, and GSR signals, 2) quantifiable behavioral data for post-processing and machine learning based analysis, and 3) backup participant meta-data contained within the data file for information consistency checking during analysis.

1. Nuwer, Marc R. et al. “IFCN Standards IFCN standards for digital recording of clinical EEG.” Electroencephalography and Clinical Neurophysiology, Volume 106, Issue 3, 1998, Pages 259-261, ISSN 0168-5597.
2. Velde, Maarten van de et al. “Digital archival and exchange of events in a simple format for polygraphic recordings with application in event related potential studies.” ISSN 0013-4694,
3. Kemp, B. Olivan, J. "European data format 'plus' (EDF+)." ISSN 1388-2457, 10.1016/S1388-2457(03)00123-8.
Multiplexed, data structure-based enriched physiological event marker system
Experiment Setup and Event Marker Overview
Preferred presentation format: Poster
Topic: Electrophysiology

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