EPrime - motion stim issues

Thu Aug 18 23:04:38 UTC 2011

Hi Lisa,

It looks like this 'hybrid' movie/still solution is causing more
problems than it solves. Like Presentation, you probably would like to
use some script to create/present the graphics. Unfortunately, E-Basic
only has limited support for creating graphics on the fly (text,
lines, rectangles and ellipses), and I'm not sure if your stimuli
could be drawn by those primitives. However, pre-created static
bitmaps (as movies) can be a workaround for painting more complex
graphics objects. Programming moving objects is not extremely
difficult, and if I remember correctly, there is an example available
on the pst support site
(http://www.pstnet.com/support/samples.asp?Mode=View&SampleID=8)  When
the graphics objects themself change, you might run into difficulties
when the computer hardware cannot keep up with the number of required
bitmaps and desired frame rate. Using movies will probably the only
working solution in that case. I think I would include the ISI's in
the movie so it becomes a single file that can be played without
interruption. ISI durations cannot be set at runtime this way, unless
you use the technique described below.

In some cases is also possible to use an external (DLL) library to
create complex stimuli at run time (gabor patches, gradient fills,
...). Such an external library could be used to create bitmaps or
movies on the fly, which then can be loaded by eprime.  However, this
requires in-depth knowledge of a programming language such as C++
because such a specific library probably doesn't exist yet.  I used
this technique before to create audio files and complex bitmap
sequences. (If you have EPrime version 1, you might have a look at the
attached example. This will display a changing ellipse with a gradient
fill that can be defined at runtime in EPrime)

Best,
Paul

2011/8/18 Lisa Levinson <lml1934 at gmail.com>:
> 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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>
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