# online control of visual stimuli **URL:** \ **Category:** Uncategorized\ **Created:** [November 7, 2001, 11:17am UTC](https://psychtoolbox.discourse.group/t/online-control-of-visual-stimuli/1085 "2001-11-07T11:17:50Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![Allen\_Ingling](https://avatars.discourse-cdn.com/v4/letter/a/a183cd/32.png) [@Allen\_Ingling](https://psychtoolbox.discourse.group/u/Allen_Ingling)\ **Post date:** [November 7, 2001, 11:17am UTC](https://psychtoolbox.discourse.group/t/online-control-of-visual-stimuli/1085/1 "2001-11-07T11:17:50Z")
Dear forum participants, I'm measureing neuronal activity and eye movements in awake cats in response to various stimuli. Now I want to manipulate the visual stimuli on the fly, as a function of eye-position. For presentation of visual stimuli I recently moved to the psychophysics toolbox. As the intended manipulations of the visual stimuli are computationally intensive, we are using a Power Mac G4 (867 Mhz, OS 9.2). Sadly, it has no serial port anymore, only usb, firewire and ethernet. My eye-tracker (Fourward technology, dual purkinje eye-tracker) gives analog output. (This is sampled simultaneously with the neural signals in a dedicated system, independent of the visual stimulation.) Thus, I've to do a strategic decision on how to link the analog signals to the video hardware. After reading messages 190 and following, 581, 584, and a few others I see 3 options: First, use a second computer (mac or pc) to A/D convert the eye-tracker signals and communicate them to the Mac via ethernet, setup some communication from within matlab/psychophysics toolbox. Problem: Does this interfere with the rush function? Are functions available to read (synchronously ?) from the ethernet port every 40ms or so? Second, use a boxed A/D converter which connects to the USB port. Problem: I've found such devices only for the serial port. I've not found Mathlab routines to read from the USB port. Third, put in an interface card (maybe National Instruments) into the Mac and do everything from within one matlab script. Problem: I gather, that support of NI for Mac based solutions is getting patchy, and that the Matlab data aquisition toolbax and psychophysics toolbax do not really mix well. To make things slightly easier, I do not need perfect timestamps on the eye-positions, as the eye-tracker signal is already digitized in another, closed system. A log for post -hoc analysis what happened is enough. Do you have experience, recommendations, relevant software pertaining to this issue? Any comment is highly appreciated. Best, Peter -- PD Dr. Peter König +41-1-635 30 60 Institute of Neuroinformatics +41-1-635 30 53 (fax) ETH - University Zürich [http://www.ini.unizh.ch/~peterk](http://www.ini.unizh.ch/~peterk) Winterthurerstr. 190 [peterk@...](mailto:peterk@...) 8057 Zürich