Investigating change in task-specific phase coherence following an intervention

EEG
#1

Hi all,

I’m aiming to investigate whether a brain stimulation intervention has an effect on task-related theta phase coherence in the frontoparietal network.

I’m concerned that if I observe an increase in phase coherence from pre-intervention to post-intervention that this doesn’t necessarily reflect a task-specific change in coherence, but could instead reflect a change in resting-state coherence. Ultimately, I need to somehow adjust the task-related phase coherence estimate for resting-state changes.

However, the task participants performed was a working memory n-back task. By nature, this task involves maintenance of information over several trials, and as such doesn’t really have a pre-stimulus baseline period. Moreover, the way I have estimated task-related phase coherence is inherently task-related (i.e., ISPC over trials), whilst the method for estimating resting-state coherence involves averaging ISPC over time - and so, the two measures are not exactly comparable and therefore I’m not sure it makes sense to subtract resting-state coherence from task-related coherence.

Does anyone have any advice for how I could measure task-specific modulation of theta phase coherence following an intervention when using an n-back task?

Thanks in advance for your suggestions!

Sam

#2

Hi Sam. I think in n-back tasks, the control condition is usually a 0-back (pressing a button for one specific target). Also, because this is a stimulation experiment, I presume you have a control group, e.g., sham stimulation or stimulation of a different brain region?

#3

Hi Mike,

It is usually 0-back, but unfortunately this task didn’t include a 0-back condition (frustrating!). Yes, there is a sham control group. They study was actually a combined cognitive training and stimulation study, so the sham group received the cognitive training but not the active brain stimulation.

Thanks,

Sam