Life is a series of events—some are planned while others catch us completely by surprise. This holds true in the lab where the quality of experiments and data depend on accurately identifying, tracking, and sorting key events as they occur. Events like the introduction of stimuli and a test participant reaction directly impact data. Similarly, unplanned events, such as when a participant coughs or sneezes during a respiratory experiment, can affect overall data quality.
In this context, we define an “event” as piece of information associated with a specific time in a waveform. An event can capture points of interest within a file (e.g., subject moved, dose added) or on a particular channel (e.g., T-wave onset).
Whether intentional or not, critical events need to be easily located and identified by those running an experiment. Event marking provides the key to this by helping researchers eliminate outlier data while making it possible to locate data that is significant to the experiment. Today’s researchers benefit from data acquisition software that offers some form of event marking functionality to easily identify, label, and categorize such events. BIOPAC’s latest build of AcqKnowledge, for example, integrates extremely easy-to-use event marking tools that enable users to mark “quick events” with a simple tap of a function/hotkey for 17 different event categories, each containing multiple types of events.
“I’m struggling to think of any time you wouldn’t be using these,” said BIOPAC Technical Support Manager David Pollock as part of the recent webinar AcqKnowledge Bootcamp: Set Up Experiments to Facilitate Data Analysis. “They are critical to being able to interpret your data after you acquire it.”
The benefits of event markers include:
- Allowing researchers to differentiate stages of an experiment
- Making it easy to eliminate outlier data
- Allowing researchers to track and identify stimuli
- Providing control over event tracking, thus eliminating errors
A Tale of Two Studies
A pair of recent studies illustrate how data acquisition software like AcqKnowledge can streamline event marking. The first sought to test the viability of various commercial-off-the-shelf ECG sensors for monitoring stress levels in participants. Test participants used a manual button to self-mark stress events triggered by mental arithmetic tasks, startle response tests, and a cold-water response test. A BIOPAC MP Research System data acquisition unit provided a clinical baseline for comparison with the pair of COTS ECG monitors. The limitations of self-reported events were revealed when participants were found to have accidentally activated the stress “clicker” about 60% of the time.
A similar 2018 John Hopkins University study avoided this problem through both automated and researcher-controlled event marking. When examining how military commanders maintain combat effectiveness while responding to a range of potentially stressful battlefield situations, researchers employed AcqKnowledge to record event marks at the onset and offset of various stimuli. Physiological data was fed to an AcqKnowledge-equipped computer via a BIOPAC DAQ connected to an STP100C digital interface module. Event markers generated by both AcqKnowledge and E-Prime allowed researchers to easily identify stimuli as well as each task the participants performed by name, start time, end time, and duration.
Not leveraging the power of event marking tools can result in key experimental events being lost in a flood of data, potentially corrupting results. Check out this video tutorial to learn more about event marking with AcqKnowledge.
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