How are we synchronizing Artinis NIRS devices with other data streams?

General

Mar 12

When measuring with multiple systems simultaneously the commonly asked question is: “How are we going to synchronize our data streams?” Many instruments cannot be coupled directly but most do have a way of producing a trigger signal or have the capability to record one. We at Artinis Medical Systems always strive to make research as easy as possible. Therefore, we have developed both hardware-based and software-based options for data synchronization. In this blog we will explore the different options and discuss the advantages and disadvantages of each and provide a guide for sending hardware events and software events to Oxysoft.

Every hardware options we have uses either a cable or a device to send a trigger to multiple systems simultaneously. One way to do so is via our wireless event-generator (PortaSync), which generates a wireless digital (Bluetooth) and wired signal which can be used as an instantaneous synchronization trigger. When all systems record the trigger, the temporal position of the trigger can be used to (re)align the different datastreams. When connecting the PortaSync via Bluetooth, the latency is about 100-200 milliseconds, which is far below the commonly observed NIRS-derived physiological deviations in the hemodynamic signals. However, in specialized research paradigms with high-frequency signals like e.g. eye-tracking or EMG even lower latencies are requried.

We also have wired-only options (ParallelSync cable), as these cables transmit instantaneous analogue signals, there is no latency. All hardware options require extra hardware, hence the name, and parallel ports are unfortunately generally not incorporated in modern laptops anymore. Therefore, it can be more convenient to use a software-based synchronization approach.

Any software package that can access the DCOM interface can send triggers to Oxysoft. Since Oxysoft 3.0.103 this feature is implemented in Oxysoft, if you would like to use this feature too for older software versions, please contact our application specialists. This enables e.g. Matlab and E-Prime to directly send trigger signals to Oxysoft for synchronization of the datastreams and as analysis aid.

To summarize, the following steps have to be performed for automated triggering to Oxysoft.

You have to register Oxysoft as a DCOM-interface once.
Start a measurement in Oxysoft.
Whenever you have set-up your NIRS-measurement and feel like you can start your experiment, run your experimental paradigm in e.g. E-Prime and Matlab.
The events generated will be automatically added to your measurement in Oxysoft.

Subsequently, data analysis can be performed within Oxysoft or the data can be exported effortlessly to e.g. Homer2, FieldTrip or NIRS-SPM using our proprietary Oxysoft2Matlab-tool. We have a detailed step-by-step tutorial on how to automatically send triggers for e.g. E-Prime and Matlab available. If you would like to receive this tutorial, please contact our application specialists and they will gladly help you further.