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StimulusPresentation and StimulusCode

Posted: 08 Jun 2009, 11:56
by Marco Rotonda
Hi there...
still trying to check the triggers that StimulusPresentation puts in the StimulsCode vector...
I'm using this configuration:
Neuroscan.exe
FieldTripBuffer.exe
StimulusPresentation.exe

I'm presenting a sound with the StimulusPresentation and there is the StimulusCode on the .dat final file.
With a microphone I'm recording the sound presented that send a TTL to the serial port of neuroscan.
If I see the NeuroscanEvents they are delayed of 40ms.
It seems like a block delay.
So which one is the "right" trigger? the one from StimulsPresentation or the one from neuroscan? The delay could be done from the FieldtripBuffer?

Thanks in advance

Posted: 09 Jun 2009, 05:41
by Marco Rotonda
to explain it a bit better...
I'm trying to follow the chain...
In the configuration I wrote should be like this (please tell me if I'm wrong)...
The signal coming from the neuroscan arrive to the FTB and then to StimulusPresentation... now a stimulus is sent and a marker is placed in the final eeg (StimulusCode)... when a stimulus is sent (in the example above I use a sound) I've sent a ttl to neuroscan so another trigger is placed in the eeg... of course this event (neuroscanevent) is placed in a different block (some time is passed form the original, the first moment I register the signal, to when I give a sound)... the blocksize of neuroscan is 40ms... so what I've seen is just right this... the difference from the StimulusCode (it should be the trigger when I give a stimulus) and the neuroscanevent (the trigger when actually a subject receive a stimulus) are 40ms apart...
the problem rise to choose the right trigger on which do some analysis... I hope it's a bit more clear...

Posted: 09 Jun 2009, 10:34
by Marco Rotonda
I've added a silence of 40ms at the stimuli so that they should be corrcet...