Diminished neural responses predict enhanced intrinsic motivation and sensitivity to external incentive
Cognitive Affective & Behavioral Neuroscience (2015) - Comment
pubmed: 25348668  doi: 10.3758/s13415-014-0324-5  issn: 1531-135x  issn: 1530-7026 

Karen E. Marsden, Wei Ji Ma, Edward L. Deci, Richard M. Ryan, Pearl H. Chiu