Paired T-test in RS comparison

Submitted by Liz on

Dear Experts,

I am new to FSL and RS signal analysis, so I need a help to understand the methods and the results of a preliminary fcMRI study that my supervisor has been working through.

He wanted to test variation in connectivity within motor circuits at rest. It is a single group design with repeated measures, divided into three parts: baseline RS scan, task performance and control RS scan. The idea was to compare the two RS scans in order to see variation in connectivity after the task performance, thus expecting increase functional connectivity within motor circuits.

Given that this was an exploratory investigation  and also given the very low statistical power of our small sample (just 9 pps), final paired t-tests between the connectivity signals before and after the task were assessed using fixed effects. Preliminary results showed that before completing the task, as well as after, participants showed clear patterns of RS connectivity with the left-sided sensorimotor cortex seed region ( activated by the right-hand movement of the localizer task). At a group level, the RS connectivity included peaks within a sensorimotor network. Reduced connectivity within this network was identified after completing the task, compared to the baseline run (Z-statistics (Gaussianized T/F) were thresholded at Z> 2.3 using Gaussian-Random-Field Theory. Voxel height-corrected significance of p< .05 ).

My question is: how can we be confident of the significance of the reduction in connectivity (pre vs post task) without having defined a t score and a p value?

Many apologizes in advance for my –likely- stupid question but stats is not my forte.

Thank you so much for your help.