EPrime - motion stim issues

[Lisa Levinson]

Yes, Presentation is better for this type of experiment, however, the
Presentation script was generated in a different lab and the lab I am
working in is not set up to use Presentation (requires a serial port
connection for which we have had issues with timing). So, you are 100%
correct, I have been jumping through complicated hoops for more time than I
will admit and while I have made progress the motion stim for this
experiment is just crazy difficult to figure out. Today I was going to
attempt to increase the duration of stimulus presentation to see if it is a
loading issue. Will let you know but any thoughts would be greatly
appreciated.



On Thu, Aug 18, 2011 at 1:26 PM, David McFarlane <mcfarla9 at msu.edu> wrote:

> Lisa,
>
> OK, I will ask the obvious dumb question.  If you already have a program
> that works in Presentation, why would you want to recreate it in E-Prime?
>  Although in principle E-Prime should be able to handle this, it may require
> jumping through a lot of complicated hoops, and it seems to me that
> Presentation makes a better platform for this type of task.
>
> -- David McFarlane, Professional Faultfinder
>
>
>
> At 8/16/2011 11:24 PM Tuesday, you wrote:
>
>> I am looking to replicate an experiment originally created in Presentation
>> for use with EPrime, part of an EEG experiment. The original experiment used
>> that software’s programming language to create a color and motion stimulus
>> that allowed the researchers to compare the parvocellular and magnocellular
>> visual pathways. I do not know EBasic and so I have created the color stim
>> in Photoshop and imported the image as a slide. While I am not able to
>> control luminance it appears very close to the original. The motion stim is
>> proving much more complicated. I created a vertically oriented sinusoidal
>> spatial frequency grating as an animation file in Final Cut (editing
>> software) and have been struggling ever since to make it work as intended.
>>
>> The experiment calls for a low frequency grating to traverse from left to
>> right for 100ms with inter-stimulus intervals anywhere from 500 ms to
>> 1000ms. Because the stimulus presentation is so short I don’t seem to be
>> able to use the video start/stop feature; additionally, randomizing the ISI
>> is not possible using this feature. I determined that one cycle of the
>> animation sequence is 31 frames and with a 60 frame per second animation
>> that means that I have 10 six frame sets per second (each set 100ms). I then
>> created 6 frame .avi files and loaded them sequentially. Because the
>> experiment calls for 320 trials I had the choice to load 320 files or create
>> a loop with 5 six frame sets, I opted for the loop. To allow for the
>> randomized ISI intervals I created jpeg files containing the final frame of
>> each set and then finished the sequence with my one remaining frame (5 six
>> frame sets plus one final still, making 31 frames).
>>
>> After loading the movie/still files (sequentially) it seems that even
>> though the stills(jpegs) were captured from the animation frames they are
>> not similar in size, so I have an inconsistency there – issue one. The other
>> issue is that the two images (movie/still) overlap rather than following in
>> sequence. One appears inside the other and the error message I get once I
>> abort is “unable to update frame.” I did eliminate the 500ms ISI but that
>> has not helped. I also tried to eliminated the jpeg files but then I can
>> only randomize the duration of the motion which should be consistent at
>> 100ms intervals. It is the time between presentations that should randomly
>> fall within 500 to 100ms.
>>
>> I am at a complete loss as to what to try next. HELP!
>>
>
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