Abstract
Accurate stimulus onset timing is critical to almost all behavioral research. Auditory, visual, or manual response time stimulus onsets are typically sent through wires to various machines that record data such as: eye gaze positions, electroencephalography, stereo electroencephalography, and electrocorticography. These stimulus onsets are collated and analyzed according to experimental condition. If there is variability in the temporal accuracy of the delivery of these onsets to external systems, the quality of the resulting data and scientific analyses will degrade. Here, we describe an approximately 200 dollar Arduino based system and associated open-source codebase that achieved a maximum of 4 microseconds of delay from the inputs to the outputs while electrically opto-isolating the connected external systems. Using an oscilloscope, the device is configurable for the different environmental conditions particular to each laboratory (e.g., light sensor type, screen type, speaker type, stimulus type, temperature, etc). This low-cost open-source project delivered electrically isolated digital stimulus onset Transistor-Transistor Logic triggers with an input/output delay of 4 μs, and was successfully tested with seven different external systems that record eye and neurological data.
Highlights
IntroductionCan inputs be multimodal (e.g., auditory stimuli, visual stimuli, somatosensory stimuli, etc.), but the output devices to which these input triggers are sent are potentially multimodal (e.g., EEG+eyetracking, EEG+fMRI, EcoG+stereo electroencephalography (SEEG)+eyetracking, etc.)
Multimodal experimentation in neuroscience research is becoming common practice
We found that the wires with Dupont connectors that came with most Arduino starter kits did not feel secure in the Arduino Mega ports, but the Adafruit wires definitely seated better
Summary
Can inputs be multimodal (e.g., auditory stimuli, visual stimuli, somatosensory stimuli, etc.), but the output devices to which these input triggers are sent are potentially multimodal (e.g., EEG+eyetracking, EEG+fMRI, EcoG+SEEG+eyetracking, etc.). Multimodal recordings from multimodal inputs pose technical challenges that relate to electrical interference, crosstalk, and temporal precision of stimulus onsets. The experiments in our neuroscience lab generally explored humans’ capabilities to do continuous ultra-fast face and sound detection (Martin et al, 2017, 2018a,b). The experiments operated at high speeds, and we needed to align the visual and auditory stimulus onsets with various combinations of recording equipment such as eye tracking, electroencephalography (EEG), stereo electroencephalography (SEEG), and electrocorticography (ECoG) (Fried et al, 2014). The delay for detecting and delegating the recorded triggers to external
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