[FieldTrip] Adding external events to NIRS data

Jörn M. Horschig jorn at artinis.com
Mon Nov 18 10:30:52 CET 2019


Hi Josh,

 

FieldTrip is working based on sample numbers (resp. measurement time). Therefore, you need some way to convert the timestamps from E-Prime to sample numbers. The oxy3/4 file does have time information on the measurement start time, which you could use as an estimate for this (I am not sure right now if you get this information out via oxysoft2matlab, please check and if not I can add it and sent you an updated version of the script. In the meanwhile, take the information directly from Oxysoft). Together with the sample rate of the measurement, you then will get a more-or-less accurate mapping from E-Prime time stamps to measurement time. I am saying “more-or-less accurate”, because the measurement start time is the time you finished the Oxysoft measurement wizard, not necessarily the time of the first incoming sample. So, there might be some tens of milliseconds delay between the start of the measurement and the first sample of the measurement, thereby offsetting the triggers by that amount of time. 

 

In future, if you use E-Prime, best try to send triggers directly to Oxysoft, so that the events are inserted in the data stream directly. There are several ways possible for this, hardware or software based. If you want to know more, please mail me and I’ll forward the respective instructions.

 

With best regards,

Jörn

 

PS: you can also read in the oxy3 or oxy4 files directly in FieldTrip using the common FT functions like ft_preprocessing. No need to go the route via .nirs-files.

 

--

Jörn M. Horschig, PhD, Software Manager & Project Leader

 <http://www.artinis.com/> Artinis Medical Systems  | +31 481 350 980 |  Skype: support.artinis

 

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From: fieldtrip <fieldtrip-bounces at science.ru.nl> On Behalf Of Manning, Joshua
Sent: Thursday, November 14, 2019 6:12 PM
To: fieldtrip at science.ru.nl
Subject: [FieldTrip] Adding external events to NIRS data

 

Hi,

 

I am working with a data set that has events/responses taken from EPrime. We did not have the triggers sent to Oxysoft. I converted the NIRS data using oxysoft2matlab. I have an excel file that has trial types stored as a string, onsets response, durations of responses, and amplitudes. I am having difficulty adding the events/responses to the .nirs file. What is the best way to add these events to the NIRS data for analysis?

 

Thanks,

 

Josh

 

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