Parallel Port to USB Converter - fNIRS and Jitter

[David Brush]

Hello,

I have a couple of questions, and I was hoping someone could help shed some light as I am relatively new to E-Prime.

The first question I have is in regards to connecting my laptop to fNIRS. For the purposes of this study, I would like to be able to run the E-Prime tasks through the laptop. As this laptop does not have a parallel port, I was wondering if it would be at all possible to use a parallel port to usb converter to remedy this. If so, is there a recommended model or brand? I also would like to confirm that using a converter will not cause a signal delay, as reaction time is a factor. In addition, would using a converter disrupt the ability to use markers/triggers?

My second question relates to stimulus presentation. I ran an optimization script to determine Jitter timing, but I am not sure how to implement it. What would be the best way to go about adding jitter to my task?

Thank you in advance for your help!

Best,

David Brush

[JACanterbury]

Hello David,

Whilst there are usb to parallel port adapters on the market and I've no reason to believe they wouldn't work fine with printers and other slower peripherals, I'd be wary about using them in situations where precision timing was required.  If you are planning to use it to generate events like stimulus onset/offset then the variation in the accuracy of the timings of the events that would be caused by the USB bus could be an issue. This article by Gary Freegard from Swansea University http://psy.swan.ac.uk/staff/freegard/Response%20Box%20Report.pdf is certainly worth reading.

Unless anyone else has first hand experience that it will be fine then I'd suggest you get hold of a PC with an integral parallel card.

Cheers,

John

[Adam Stone]

Which fNIRS machine do you have? We use an ETG-4000 with E-Prime, and currently use an USB to Serial converter, using the SerialDevice in E-Prime to send event markers. Our studies don't require very precise timing measurements (we can live with a 100-200ms offset) and it works very well. 

Jitter info can be found elsewhere by searching within this group. I use a Nested List with various jitter times in 250ms steps (4000, 4250, 4500, 4750, etc.) and have E-Prime randomly sample from that nested list to give me randomized jitter intervals. 

[David Brush]

Thank you both for the responses. The input has been extremely helpful thus far. The machine I have is a 20 optode NIRSport 88 system. It is encouraging to hear that you are able to use a converter without significant delays. Our fNIRS machine uses parallel ports, but the laptop I will be using has a serial port and a usb port. Any recommendations as to whether it would be better to use the serial or usb? Two of the tasks I will be running are the Stroop task and a variation of the Flanker task. 

Also, thank you for the information regarding jitter.