Eprime triggers to EEG out of sync

Sun Aug 31 18:03:34 UTC 2014

Hi Ryan, et al.,

What is “this post”? AFAIK, most people have successfully sent triggers using E-Prime (that’s probably why there are few messages suggesting anything else!), accurately timed, and indeed, the number of publications with EEG and E-Prime must be in the hundreds by now. I have never had a problem with out of sync triggers myself. In general, you always set triggers, and the software used for recoding is insignificant – of course you can change them with MATLAB (using whatever toolbox, e.g. SPM, EEGLAB), but that doesn’t change timing. In general, any EEG amp worth its salt will come with dedicated E-Prime packaged – find them on their website. In other words: post-hoc labelling isn’t an alternative: it’s just a way that you change “124” – the byte sent over parallel port, for instance, to “Stimulus Onset, VERB”.

In general, I use two types of triggers:

*Timing critical: particularly onset of the stimulus. You can use the “.onsetsignalenabled” (not sure about the exact phrase, being out of office at the moment) and so on for that (search here or elsewhere). Only needs to be a bit – the stimulus is ON NOW. This you need to code before the stimulus X happens (e.g. X.onsetsignalenabled). E-Prime then ensures the trigger is sent at the time the monitor refreshes, rather than at some other odd moment that isn’t related to the stimulus.

*Timing non-critical: data, in other words. I send loads of data nowadays with the following:

Writeport outport, 254

Sleep 1 ‘sleep is necessary because triggers can overwrite one another. 

 ‘…Then start writing all sorts of more bytes

For i = 2 to 100,

                Writeport outport, i

                Sleep 1

                Writeport outport, 0 ‘to avoid problems with repetitions.

                Sleep 1

Next i

‘ Ending with 

Writeport outport, 255

(search for outport elsewhere). 

The deal is that afterwards, you concatenate the data in between (the …then start writing bit, here resulting in trigger values 2 to 100 being send), so that basically, you can afterwards always recode the Timing critical event using the triggers that precede it. 

Hope that helps. 

Best,

Michiel

From: e-prime at googlegroups.com [mailto:e-prime at googlegroups.com] On Behalf Of armina
Sent: 31 August 2014 14:29
To: e-prime at googlegroups.com
Subject: Re: Eprime triggers to EEG out of sync

Hi Ryan,

A few years ago we did it, it's quite simple. Now I am far from my working place and from the needed computer so I cannot tell you the exact InLine and the rest but the idea is the following. We've sent TTL signals from the lamps (you have 5 lamps on the SRB, just flash/sleep them). Each lamp signal was going to a separate channel. So, you have 5 channels to code/mark whatever you want. You may vary duration of the signal, number of the signals, duration between the TTL signals, and the channel. it gives you practically unlimited number of different markers :) you can have several markers for each trial and you never get lost in them. each channel can be set for something particular, say, one channel for sentence onset, another for specific components within the sentence (with each component having its specific marker), etc. This system was easy to structure and to use. Hope it helps.

good luck,

armina

On Sunday, 31 August 2014 00:05:53 UTC+3, Ryan Blything wrote:

Hi everyone,

I came across this post because I am going to be trying a similar thing in my experiment such that we will be using e-prime v.1 to present audio stimuli and we are interested in setting markers so that they are not just at the onset of stimuli - but also at a number of specific points in each sentence (e.g. onset of the verb, noun, preposition). This would require having several markers for each trial and Im wondering about the best way to go about this? One way is through code but no one seems to have managed to do this successfully that Im aware of. How did it go for any of you? Im quite new to e-prime and SPM (which we will use to analyse data) so I would appreciate any advice before I continue.

An alternative option Ive heard about is post-hoc labelling, which would be done in SPM, post-hoc working from the onset triggers provided by e-prime (and psuedo-marking points later in the sentence). Im not very familiar with SPM but am I right in thinking that as long as the onset of the sentence is marked accurately, then we can - post hoc - set markers anywhere we want in the data thereafter? This may be the most ideal solution because I have 200 sentences, each of which must be labelled separately (so that I can recognise each one). Apparently e-prime is limited to sending out 250 labels so perhaps post-hoc multiple labelling is the answer. I would appreciate any thoughts any of you may have.

Many Thanks,

Ryan

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