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AcquisitionSettingForMEGRecording

This page will help you to define your MEG acquisition settings before to record your data. You will find detailed information in the manual Acquisition software.

You can define your acquisition settings from acquisition software interface by clicking on "Change" button corresponding to "Acquisition". One window opens with all channels that you can record (MEG, EEG, Auxilliary, MISC). You can also define your sampling frequency from this window, different filtering (data stored after recordings are strictly raw) and you can activate or deactivate Maxshield noise compensation.

MEG channels

By default, all MEG channels are selected (al MEG channel boxes activated).

Auxilliary channels

Select EEG 61, EEG 62 and EEG 63 to record EOG H and V as well as ECG. Right click on EEG 61 and 62 and select EOG. Right click on EEG 63 and select ECG. EOG H and V and ECG will be displayed on bipolar EEG channels during acquisition.

Event definition

You will able to define your events by clicking on the button "change" corresponding to On-line Averaging. The top part of the corresponding window is used to define all your events (stimuli) in binary coding. You will find detailed information in the manual Acquisition software.

Based on the TTL value that you attribuated to your event in your stimulation script, this one has to be converted in binary format in the acquisition setting. You will find a conversion table giving you all conversions from decimal to binary coding for all values from 0 to 255 (corresponding to the eight bits used to code the triggers)

NB: the binary code in the table has to be read from the left to the right !!!

For the example given in the E-prime section, you will code your events

event1: TTL value =17, corresponding to in binary code to 10001000 event2: TTL value = 81, corresponding to in binary code to 10001010 etc...

Recommendations:

It is largely recommended to define your events in your acquisition setting in order to have all information in your original recording file. This is even imperative if you want to use on-line averaging.

However, you can choose to switch this step because you can easily define your triggers afterwards by reading STI channels (with fieldtrip, LENA tools or other...) and recoding your events.

It is also recommended to define an event for the subject's response. For example, if your subject is asked to press the right thumb button, you will have a TTL signal on STI 16 (see the table). Your response event can be defined by the value 1 on the 16th bit.