too many trials/overlapping trials

Sameer Walawalkar sameer at ANDREW.CMU.EDU
Wed Feb 7 17:30:26 CET 2007

Thanks for the reply Robert. here's some more info.

> Dear Sameer,
> Maybe you could try
> cfg =  []    ;
> cfg.dataset = 'JD_012507_Beeps_One.fif' ;
> cfg.trialdef.eventtype  = '?';
> dum =  definetrial(cfg);
> and look what is printed on screen.

evaluating trialfunction 'trialfun_general'
the following events were found in the datafile
event type: 'STI101' with event values: 5      6      7      8      9
11     15  16388  16391  16392  16396
event type: 'STI301' with event values: 5.0003      5.0018 ...(many
event type: 'trial' with event values:
no trials have been defined yet, see DEFINETRIAL for further help
found 61361 events
created 0 trials

(I address another point at the bottom of the email. I have left the
following paragraphs in for refrence)

>> My first problem is, I should have 30 trials for this event. The file
>> contains a total of 60 trials, but the other 30 are for eventtype = 11
>> So it is clearly doing something wrong.
>> Next, I decided to see what is in cfg.trl and I get the Nx3 matrix that I
>> find the following problems with it
>> 1> each trial should be 4000 milli seconds long. That happens here,
>> however, there seem to be overlap between trials which does not make
>> sense. This is what leads to the double counting. Thus I get 4000 msec long
>> trials bunched in group of two where the second trial starts about 1000 to
>> 1300 msecs after the beginning of the first trial.
> Please have a look in cfg.event.
>> 2> If the first trial is at 8502, all subsequent trials should be in
>> increments of integral multiples of 4000 ( plus or minus a few). But that
>> does not seem to happen (and I am looking at on the leading trial of the
>> pair and discounting the trials that follow 1000 msecs later.)
> That means that there are events detected that are not supposed to be there
> according to your knowledge of the dataset. Could it be that both the
> positive and the negative flank of the trigger are detected?

I have looked into this as it was the first thing I suspected. What has
been confusing me is that it seems to be counting the rising flank of the
correct trigger and the falling flank of the earlier trigger, even though
the event type for the earlier trigger is different. I am looking for
cfg.trialdef.eventtype = 'STI101' and
cfg.trialdef.eventvalue = 7 or 11.
The earlier falling trigger  is 5,6 or 8.9 and so should not be considered
at all. I never use STI301


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