ECHOES kit tool: an integrated system to track and

check in real time the latency and jitter of the triggering

process

In ERP research, precise timing is essential as we identify the ERP components through topography, amplitude, and particularly their latency.

Literature indicates that cognitive states or specific subject groups may exhibit variations in their ERP amplitudes and latencies.

Hence, ensuring the accuracy of your marker timing is a vital element of your research outcomes.

Prior to initiating a study involving EEG recording, particularly in the ERP domain, it is prudent to verify that the setup, encompassing both software and hardware, is functioning as intended to preclude any unforeseen issues during the data analysis phase.

Regrettably, it is not always apparent when the timing is inaccurate.

For instance, if a hardware trigger does not align with the exact timing of the associated event, two adverse outcomes may occur.

Firstly, a consistent delay between the event trigger and the actual event may arise, known as latency.

Secondly, the delay between the event trigger and the event may fluctuate, referred to as jitter. A stable latency means that temporal components might manifest earlier or later; for example, a P300 may emerge a few milliseconds beyond the anticipated time. However, significant jitter is more problematic because it smoothens the ERP waveform when averaged, altering its appearance and eliminating high-frequency elements.

Ideally, one would aim for zero latency and jitter.

Since achieving this is nearly unattainable, the next best approach is to minimize both effects.

Furthermore, if the latency is consistent, it can be compensated for in the analysis, provided its precise magnitude is known.

The Echoes system is poised to be invaluable in all standard experiments where the exactness and precision of trigger timing are critical. This tool could indeed become an indispensable ally for high-quality setups and experiments. It can also be utilized to assess the features of your stimulus delivery system and potentially uncover and rectify hidden errors.

For instance, how can one ensure that the auditory or visual stimulus trigger is jitter-free?

Is the stimulation software performing as advertised? What about the hardware? And the interaction between them?

The Echoes kit allows you to verify whether the hardware's stimulus trigger timing is as expected.

Consider this scenario: You are conducting an Auditory Oddball experiment where a participant listens to auditory stimuli and is tasked with identifying the infrequent ones. This setup is expected to induce a stimulus-locked P300 peak in the EEG data. In such a typical ERP experiment, the accuracy of marker timing is crucial for averaging the samples to capture the desired peak.

However, if the software-generated marker is imprecise or subject to jitter, the EEG data will be synchronized with an incorrect segment of the auditory signal.

This discrepancy arises due to the inherent latency from the moment the trigger is sent (at the start of the data processing, i.e., the script's initiation) to the actual output of the stimulus: processing the auditory or visual file, or even running the script, requires time.

This latency varies based on your computer's configuration, such as the sound or graphics driver, and can be affected by the size or format of the files, encrypted images, etc.

The Echoes kit package allowing you to be aware in real time of critical issue, at the early stages of your protocol design step, you can work to reduces the standard deviation and enhances the signal amplitude.

This is due to Echoes' real-time latency value monitoring for each trigger, allowing for immediate corrective measures.

More reliable markers lead to greater statistical significance and, consequently, superior quality results.

The Echoes kit package enables extensive data extraction from your setup. It allows for the real-time detection and correction of jitters and delays in any setup, enhancing the quality of all your experiments.