“…Potential sources of longitudinal within-subject variance in fMRI recordings include, but are not limited to: habituation effects (Hamid et al, 2015), strategy shifts/practice effects (Kelly and Garavan, 2005), fatigue, lapses of attention, caffeine (Koppelstaetter and Poeppel, 2010; Liu et al, 2004), nicotine (Warbrick et al, 2012, 2011), time-of-day (Gaggioni et al, 2014; Schmidt et al, 2015), aging (Cliff et al, 2013; Koch et al, 2010), residual levels of physiological noise(Birn, 2012), distinct geometric distortions across sessions (Raemaekers et al, 2012), or progression of clinical conditions. As our understanding of natural within-subject variability in both neuronal and fMRI responses improves, additional factors may need to be added to this list.…”