Subject: Re: [AUDITORY] Software/code for insertion of a large number of triggers. From: Bob Masta <audio@xxxxxxxx> Date: Fri, 6 Sep 2013 09:14:31 -0400 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>
I assume you are talking about an evoked potentials experiment, where you basically want to record the stimulus along with the response. But you are not really interested in the stimulus itself, just the timing of the onset. The way I do this with my Daqarta software is to generate the stimulus (tone burst, typically) on one stereo channel, and an exactly aligned pulse on the other. The tone burst output is sent to the subject, while the pulse version is sent back to one of the input channels. The other input channel receives the EEG response from the subject. I start the pulse at the moment of onset of the tone burst (the start of the rise portion), which then serves as the reference for latency measurements. That's also the trigger event for averaging, although Daqarta allows positive or negative trigger delay relative to this point. (Positive delay allows the averager time window to be later than the trigger event, but still exactly aligned. Negative delay allows you to see what led up to the trigger event.) Note that with the above approach there is no need for a .WAV file with triggers. The triggers are generated and the response is averaged in real-time, so all you need to save is the final averaged result. (You *could* save the raw file with both the pulse and response channels, but there is normally no need for that.) This way. there is no separate processing step, and *way* less raw data to keep track of. The only reason I can think of to post-process is if you are doing some sort of tricky "hoop jumping" artifact rejection. Daqarta has a simple scheme that omits from the average any frame that includes any value outside of a specified range you select. It also shows you when frames are being rejected, so you can deal with it right then. That's important if (say) the subject animal's anesthetic is wearing off and it's starting to twitch... you not only don't waste time collecting bad data that would later be rejected by post-processing, but you also get more good data from an experiment. Best regards, Bob Masta -------------------- On 6 Sep 2013 at 8:36, Pragati Rao wrote: > Dear All, > > I have to insert triggers for an EEG experiment (almost 3000 triggers) into > a wav file. Adobe audition or Goldwave can be used for this purpose. The > process is very time consuming. Does anyone know of a more time-efficient > way of doing this? Perhaps a MATLAB code? > > I tried getting the sound presentation software to send cue events, but I > was advised by presentation (neurobehavioral system) to have this trigger > information within the sound file (so that timing information is precise). > > Any help is appreciated. > > Thanks, > Pragati Rao, > PhD Candidate and Research Audiologist, > Room 1.612, Level 1, > Australian Hearing Hub, > 16 University Avenue, > Macquarie University, > NSW 2109 > > > http://www.hearingcrc.org/people/pragati-mandikal-vasuki > http://www.ling.mq.edu.au/cll/team.html > Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis www.daqarta.com Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!