Thanks, Alfonso.  We did reference the Henson and Penny materials with the following write up:

"A two-stage partitioned variance approach mixed within-/between-subjects ANCOVA model (Henson, 2015; Henson and Penny, 2003) was used to examine for a three-way interaction in ICC and ILC values between groups (i.e., between-subject factor; surgical patients > non-surgical controls) and two within-subject factors (e.g., time = 6-week > baseline; and working memory load = 2-back > 1-back). In this two-stage analysis approach, interaction images were first computed for each subject, after which they were entered into a second-level, random effects two-sample analysis with covariates in SPM12."

I hope I explained the Henson & Penny method correctly, and I guess the reviewer isn't familiar with this approach?

As for the need for follow-up post-hoc analyses, we found a significant region associated with the group (-1 1) x time-condition (-1 1 1 -1) interaction.  I plotted the interaction in a figure, but as you and the reviewer suggest I would need to show post-hoc analyses.  What contrasts would you recommend to tease the interaction apart?  I will plot the bars for each group x condition x time, but would I suspect it would be preferable to also have hard numbers and results to support the interaction.

Thanks again,
Jeff