StimulusPresentation and StimulusCode

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Marco Rotonda
Posts: 15
Joined: 19 Nov 2008, 09:20

StimulusPresentation and StimulusCode

Post by Marco Rotonda » 08 Jun 2009, 11:56

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

Marco Rotonda
Posts: 15
Joined: 19 Nov 2008, 09:20

Post by Marco Rotonda » 09 Jun 2009, 05:41

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...

Marco Rotonda
Posts: 15
Joined: 19 Nov 2008, 09:20

Post by Marco Rotonda » 09 Jun 2009, 10:34

I've added a silence of 40ms at the stimuli so that they should be corrcet...

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