Use of push button as trigger
Hi,
I want to do erp test with cyton board and want to use two push button for getting stimulus event . Like,
seeing square, want to trigger one push button and seeing triangle another push button. But not sure how to connect with the board ? Is it same as using digital pin D17, D18 ?
Comments
One button is wired by default. Others could be done externally.
https://docs.openbci.com/docs/02Cyton/CytonExternal#utilize-the-on-device-push-button
Usually ERP / P300 is done with an opto isolator / external trigger, shown later on the same page. P300 needs very precise timing to do signal averaging to increase signal to noise level. Operator input functions should really be done with your laptop keyboard and input processing program. NOT with the Cyton button.
William
not clear. How to use laptop keyboard for event marking?
A P300 experiment is controlled by your software:
https://backyardbrains.com/experiments/p300
[your past threads]
https://openbci.com/forum/index.php?p=/discussion/2344/p300-is-negative-time-scale-negative-polarity
https://openbci.com/forum/index.php?p=/discussion/2307/connect-external-audio-signals-to-cyton
https://openbci.com/forum/index.php?p=/discussion/2107/external-audio-triggers-oddball-paradigm-increase-sampling-frequency
On previous threads you mentioned the use of an external Arduino, that sends oddball beep boop audio tones. This same Arduino then has TWO external trigger wires going to Cyton. These should go through an opto-isolator for best reliability. Both digital signals. One wire goes true with one audio tone frequency, the other wire for the other freq.
If you have operator input via buttons (perhaps to register some aspect of your experiment), this should happen via the laptop keyboard. Any type of keyboard entry is not going to have sufficient time accuracy to use for your P300 signal averaging. But operator input button(s) COULD be used to indicate some aspect of the operator desires or perceptions as part of your experiment. P300 can only be done with precisely aligned signal averaging.
In that BackyardBrains thread, they used precisely timed stimuli, that were registered with the EEG. My understanding is that your Arduino presents the tones on it's own terms and not precisely clocked. Obviously you could also connect external buttons to the Arduino, if that was part of your experiment paradigm.
Hi William,
Thanks for the information. May my question was not cleared . I wanted to something like, "https://irenevigueguix.wordpress.com/2016/06/07/motor-imagery-vs-motor-execution-and-right-hand-vs-left-hand-with-openbci-32bit-board/"
. And it is solved. Thanks.
Another thing, can you tell me is there any eeg test related to shape ( triangle /square ) orientation ? I am trying to search on google.
Glad you found Irene's post. Your original question mentioned ERP / P300, which requires a precise external trigger aligned with the presented stimuli. Irene's page is oriented toward a Motor Imagery experiment; where she wants to correlate hand / motor movement with motor strip activation. In that case, timing is not as critical. Are you doing P300 or MI?
The BCI oddball paradigm should be able to apply to any stimuli, visual, audio, etc,
https://www.google.com/search?q=bci+oddball
It's commonly used in BCI Speller programs.
https://www.google.com/search?q=bci+oddball+speller
I am doing P300. Just wanted to do with the push button also.
Now I need to do some eeg test about shape orientation but I have no idea what is that and how to do. Lets see.
"I am doing P300. Just wanted to do with the push button also."
Are you still sending external trigger digital signals from your Arduino to Cyton? (Corresponding to audio high or low tone?) I thought that used TWO of the input pins. Are you using the opto-isolator?
Your operator push button signals could just as easily come in via the laptop keyboard. Since they are not as precisely timed.