Introduction
Humans have the remarkable ability to adapt to environmental pressures through learning – a process that is accompanied by heterogeneous changes in brain structure and function. Parsing the neurophysiological mechanisms of learning can provide a better understanding of how the brain fine-tunes its organization and dynamics to accurately and efficiently accomplish day-to-day tasks. Importantly, such alterations continue to impact future behaviors well beyond the critical period over which learning occurs in a manner that is unique to each individual \cite{Painter2014,Tobler2005}. These and related empirical observations have resulted in a shift in investigational paradigms that seek to understand the general mechanisms of learning and the ensuing variability in these processes that drive inter-individual differences in behavior \cite{Squire1992}.