TimeCounter Adapter Inconsistent Across Sessions

Hi,

I've noticed in my task that when using the TimeCounter adapter using runtime v2 architecture, the duration of the scene is mostly consistent within a given session but inconsistent across sessions, and often shorter than the duration that I have specified in the runscene.m file. In the task I've attached, you can see that if you start the session and run, looking specifically at the Trace Interval (scene 3), the TimeCounter (tc3) Duration is set to 1500 ms.

On 5 different sessions, I've seen the duration mostly consistent in a given session (within 10ms), but widely different across sessions (1300 ms - 1500 ms). I've used both eventcodes and the MATLAB tic/toc function to confirm. Using eventcodes 105 (Trace Start) and 106 (Trace End), the attached plot shows the session-to-session variability I'm referring to. I've also included the latency test, and would add one more note -- during the task, the Frame Interval is usually between 30-50ms, and the Draw Time is 5-20ms, with most trials having 1-20 skipped frames.

The computer has a NVIDIA RTX 2070, and the display monitor has a 59.941 Hz refresh rate.

Any help would be much appreciated!

Thanks,

There are a couple of minor issues in the way that you measure the scene duration.

In the scene framework, all stimuli (visual, auditory, TTL, etc.) start at the first frame of the current scene and end at the first frame of the next scene. In the following code, for example, it seems that you think CS is off at 104, but that is not the case. The stimuli turned on at 103 are turned off at 105, so the timestamp of 104 does not mean anything.

run_scene(scene2,103);      % CS On
eventmarker(104);           % CS Off 
run_scene(scene3,105);     % Trace Interval

It is hardly necessary to call extra eventmarker() in the scene framework, unless the eventcode itself, not its timestamp, has some meaning to you.

You are printing something on the MATLAB command window with disp(). It used to be a source of huge delay, so I recommend you not to do so. Use dashboard(), instead, if you want to display something during the trial.

Your frame interval is too long. Since your refresh rate is ~60Hz, the interval should be 16-17 ms. I cannot tell whether it is because your computer is slow or the task is too complex.

Nevertheless, those things cannot explain the interval 200 ms shorter than the specified duration nor the session-by-session variability. I suggest running a simple code to verify the problem. Something like this.

bhv_code(10,'Event 10',20,'Event 20');

idle(100);

tc = TimeCounter(null_);
tc.Duration = 1500;
scene = create_scene(tc);
run_scene(scene,10);

idle(100,[],20);

The interval between 10 and 20 should be 1500 ms or one frame longer. If you still see an interval shorter than that, please send me the data file.

-----

I guess it is possible that your computer might calculate the refresh rate incorrectly. That can explain the session-by-session variability, but NIMH ML does not use the calculated refresh rate, if the system reports the rate as a fraction. What is your NIMH ML version? Please update it if it is not up to date.