The synchronization between the eye-tracker and the MEG data is trivial in this case, given that both data types are sampled by the MEG electronics. At the DCCN, we have the Eyelink DAC output connected to the CTF275 general-purpose ADC channels. These analog signals can subsequently be sampled and recorded with another data acquisition system. The Eyelink system has an optional Digital-to-Analog converter (DAC) card, which makes the eye position and pupil diameter available as analog signals. time data_eye_resampled = ft_resampledata ( cfg, data_eye ) cfg = data_combined = ft_appenddata ( cfg, data_eeg, data_eye_resampled ) Simultaneous MEG and eye-tracker recordings These are software generated and hence not in the CTF dataset.Īgain using the ft_databrowser you can check the data relative to the events.Ĭfg = cfg. There are then still 2 surplus Triggers with a value of 0 in the EDF file, which appear at the start and the end of the EDF. There are 9 triggers (without doubling) in the EDF explained by the fact that the recording of the EDF file, but not the MEG file, includes practice trials (because I usually start the recording of the EDF during practice to check whether the eye tracking looks okay). The Eyelink and CTF system might have different detection thresholds and different minimum durations of the TTL pulse, therefore it might show up in one dataaset and not the other. I have no clue where they would come from but suspect it to be a hardware glitch of the Bitsi box (which links the serial port of the presentation computer with the input of the CTF and Eyelink acquisition systems). These are not present in other subjects’ data sets from the same experiment. There are 2 triggers in the CTF file, that are not specified anywhere and should not be there (with a value of 64). ![]() ![]() This is mostly explained by each trigger onset and offset being represented in the Eyelink events, but only the onsets being represented in the CTF events. There are 1400 triggers in one, and 2822 triggers in the other. You need to run the EDF2ASC.EXE that can be downloaded here under MSDOS on the Eyelink computer and find your _.EDF recording as follows: To use FieldTrip for data analysis, you have to convert the EDF file to an ASCII text format using the Eyelink executable EDF2ASC.EXE. There are several ways to read (directly or indirectly) this data into MATLAB. The Eyelink 1000 output is an _.EDF file (eyelink data file). In this case the EyeLink computer records all data. It is possible to use the eye-tracker in combination with a behavioral task that involves stimuli (usually on a screen) and response, but without EEG or MEG recordings. We will only consider physiological data from the eye-tracker, from the EEG system, and from the MEG system. In the subsequent examples we will not consider integrating the physiological measurements with the data in these behavioral log files. With your presentation script on the stimulus presentation computer you can also write data to disk in the form of behavioral log files.
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