PRE-INTRODUCTION
Before you start, you should be aware that this is all a bit complicated.
You will need to be familiar with MATLAB, Macs and the Brainard/Peli Psychophysics
toolbox. You should also know how to calibrate your monitor for best results.
If any of the above mean nothing to you, stop now!
INTRODUCTION
The code we distribute here is what we use for running retinotopy scans
in our fMRI experiments. Broadly speaking, these stimuli can be grouped
into
1) Expanding rings
2) Rotating wedges
Expanding rings are flickering annuli that start in the middle of the screen and move towards the edge. Rotating wedges are flickering sectors that move around the center of the screen. They are useful because they generate distinctive patterns of activation in the early visual areas that can be used to determine visual field angle and eccentricity. Once again, if you are lost by now then stop.
OVERVIEW
The retinotopy code comprises a set of MATLAB m-files. These files
are in the Ret directory of the package that you downloaded along with
this readme. The file that you use to call the stimuli is ret.m Once you
have everything set up, you can type
ret
from the command line and a nice graphical interface will pop up to
allow you to configure the stimuli for an fMRI scan. It will work out how
many fMRI frames you have, how long the stimulus will last, what priority
to run the stimulus at etc etc. It will also allow you to choose from a
list of about 10 different variations on the basic themes of rotating wedges
and expanding rings. The retinotopy code is built on two software libraries
that you will also need.
BP - TOOLBOX
The first is the Brainard-Peli psychophysics toolbox which you can
download and install from the same website you got this readme from.
http://color.psych.ucsb.edu/psychtoolbox/index.html
It comes with its own installation instructions and we do not cover this here.
EXPTTOOLS
The second library is our own set of tools built on this toolbox. We
call this exptTools. You can download it from this website. http://white.stanford.edu/getRet.shtml
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HOW TO INSTALL EXPTTOOLS
Unzip the exptTools folder into your MATLAB toolbox directory. Then
bring up the path browser in MATLAB (hit the button on the toolbar that
looks like two folders on top of each other with barcodes to their right).
From the path browser, click the 'default path' button. This will tell
matlab to search the toolbox directory and include any new folders in there.
See if exptTools has been installed by typing
installCheckET
in matlab. you should see something on the command line telling you that the path is okay. Now be aware of this: To run psychophysics properly, you need to have a properly calibrated monitor. In fact, matlab needs to know a lot about your monitor: its frame rate, the color of its phosphors, its size, position, the number of bits in the video card and other things like that. We store all this information in a set of files, called displayParams.m gamma.mat spectra.mat These files are in a default folder on our machines:
Applications:Matlab:MRI:Displays:Default
exptTools expects these files to exist when it initiates. If they don't,
you will get a set of errors. You might get something working (if exptTools
defaults to something useful). More often than not, you will get garbage.
We have included some sample display calibration files in the retinotopy
code distribution. We have also changed the retinotopy code so that it
uses these sample files rather than looking in the default folder above.
But this is for demonstration purposes only. Our monitors are not your
monitors and our frame rates will be different to yours as well. That means
that the timings for the retinotopies will be wrong. Do not email us about
this. Or anything. You are welcome to examine the code to see what we have
done and modify it to your hearts' content but we cannot provide technical
support on this. It is hard enough making it work on our >own< machines.
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RUNNING THE RETINOTOPY CODE
Once both these libraries are in place, you can run the retinotopy code. Extract the code in retinotopyCode.zip to a directory called 'ret' somewhere in your directory path. Change to this directory in MATLAB and type ret Now you can start debugging your installation.
Happy retinotopies
VISTA lab