Cedrus Box

If you are running an fMRI paradigm at KKI, you will need to learn how to use the cedrus box. Each scanner has a cedrus RB-830. I couldn't find any pictures of it, but basically each button has it's own separate box and they can be velcroed together if you need more than one.


Note: at the scanner, a number is displayed on the actual button and then the button is connected to the scanner via a cord. If you follow the cord to where it is plugged in there will be another number. The number that is near the scanner is the one that will be sent to your computer as the response. In other words, the number on the actual button does not matter. (Also, I say this multiple times, but in XID mode, if button X is pressed, it is displayed as button X+1 on your computer).

Our lab does not currently have a Cedrus box, but the Bedny lab has been kind enough to let us borrow theirs when we need it. Their response box is model RB-740, pictured below. The RB-740 has mostly the same functionality as the one in the scanner, so it can be used to test our scripts in the lab. For documentation on this cedrus box, go to
this link

Keyboard Mode

Documentation here

The RB-740 has "keyboard mode" and it can act like a keyboard when you plug it into your computer and install the USB driver. However, the scanner cedrus box does not have this functionality. On the side of the RB-740 box, there are 4 tiny switches that determine the mode. If you switch the first one up this enables keyboard mode. The position of switches 2 and 3 determine the protocol. If you wanted to use ASCII protocol. for example, you would have switch 2 down and switch 3 up. If you have 1 up, you are in keyboard mode with ASCII protocol, if you have 1 down then you have to open the serial port to collect the output. As for switch 4, I really don't know its purpose so I just keep it down.

Using the cedrus box

Psychtoolbox has built-in functions for Cedrus response boxes. The documentation can be found by typing "help CedrusResponseBox" in the matlab command window or here

There is also helpful documentation on the godzilla website, but you must have a wired connection to the Hopkins internet or use off-campus internet/WIFI. To access this, go to this link and then click fMRI Support under Local Resources. Or it is in our dropbox.

CedrusResponseBox uses XID protocol so switches 2 and 3 must be down. The fMRI cedrus console is pictured in the "At the scanner" section below. In the blue box of that picture are 3 toggle switches. The left toggle switch is switch 2 and the center toggle is switch 3, again both of these toggle switches should be down for XID. Whenever changing between modes/protocols, you must reset the cedrus box. For the RB-740 that means disconnecting and reconnecting the USB from your computer. At the scanner, you will flip the third or right most toggle to reset the cedrus box.

MATLAB Scripts: get it here! Also, a script from one of our fMRI experiments (towers_color_fall71217.m) can be found there so you can see how the following code is used in a real script.

Highly recommended: explanation for the scripts on this page.

At the scanner

  • This is assuming you bring your own laptop to collect the responses

  • Set your laptop near the console pictured below

  • Turn on the console using the power toggle (in the pink box in the picture below), the green light above it should light up

  • Below the console (not pictured) there are 2 things you need to connect

  • a USB-USB from your laptop to the console that will collect button presses/releases

  • the green light (in the green box) will be lit if this connection has been made successfully

  • a VGA-VGA from your laptop to the console that will connect your display to the projector so the participant will see your laptop display in the scanner

  • As mentioned previously, switch both the left and center toggle down and flip the right toggle (in the blue box)

  • Now launch MATLAB (if you've already launched MATLAB, restart it)

  • Open this script, which can be found on the dropbox: checkCedrus.m

  • Make sure you list any possible cedrus ports

  • Run all of the code that is in part 1

  • If no error is displayed, the cedrus console is now connected to your computer (yay!)

  • If there is an error, try unplugging/resetting everything, reconnecting it and relaunching MATLAB

  • Once that works, run the second part of the checkCedrus script and start pressing the buttons on the console (in the red box)

  • when you press (not release) a button, the response should be displayed; remember if you press button X, X+1 will be displayed

  • after 10 seconds that part of the script should stop running

  • Now you need to make sure the buttons in the scanner work

  • Make sure the buttons are connected properly in the scanner

  • Then, have someone else go in and tell them to press the buttons while you run the second part of the script again

  • you may want to increase timeToWait so they have enough time to press a few buttons

  • When the buttons in the scanner room are pressed, the corresponding light (in the yellow box) should light up green

  • if this doesn't light up, you should tell the tech or restart the console

  • Again, whatever button lights up here (X) will be displayed on your computer as 1 more than that (X+1)

  • If you successfully connected the console to your laptop, and the button lights on the console are lighting up when the scanner buttons are being pressed, there should be no error with this part

  • If there is an error, just try to disconnect and reconnect everything and start from the beginning of this process