EPrime - motion stim issues

[David McFarlane]

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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