Epoch length brain connectivity


I am interested in assessing the functional connectivity between the insula and various other brain regions associated with pain perception. Given that my analysis is hypothesis-driven, I have chosen to employ phase-clustering (phase locking value) as the method to determine the functional connectivity. Additionally, I want to apply the orthoganlized amplitude envelope correlation, effectively incorporating both phase-based and amplitude-based approaches.

Unfortanetely, the experimental procedure cannot be modified as the MEG data is already in place. The data consists of 17 chronic pain patients and 17 healthy controls. They all underwent a CPM (Conditioned Pain Modulation) procedure: 1 block of 22 electrical stimuli, second block of 22 electrical stimuli with an icepack, followed by a third block of 22 electrical stimuli.

My objective is two-fold: first, to investigate disparities in connectivity between the two groups, and second, to examine connectivity changes triggered by the stimuli. My proposed strategy involves aggregating the data from all three blocks for each participant, resulting in an average of 66 stimuli per participant. But here is the crux, I am uncertain whether the epoch length is long enough. I am planning to have an epoch of 10s [-300ms, +700ms]. This time frame would encapsulate connectivity measurements both pre- and post-stimulus. Yet, I am uncertain if this duration is sufficient for capturing meaningful connectivity patterns. Considering the constraints of the available data, I seek your guidance on whether this epoch length is suitable or if an alternative approach is advisable.

Thank you for your assistance in advance!

You mean an epoch duration of 1s, correct?
It is pretty short indeed (only 700ms post-stim) depending on the slowest frequency of interest: you want to make sure at least one cycle of that frequency can be measured over the useful duration of the epoch (e.g., poststim) to assess phase locking. I would say that any frequency above theta would qualify though.