Effect of time of day on reward circuitry. A discussion of Byrne et al. 2017

Byrne and colleagues present a paper on a timely topic with potentially important results. However, we think that issues in the design and analysis complicate the interpretation and limit the generalizability of the findings. Specifically, the details of the small volume correction used in the primary analysis are not adequately described and, moreover, the results do not appear to be corroborated by the whole-brain analysis. In addition, the follow-up multilevel modeling, which is fundamental to the conclusions of the paper, is inherently circular thereby guaranteeing discovery of the reported effect. Finally, the study does not control for other factors that vary over the course of the day and are known to impact MRI measurements, and fails to link the neural results directly to any relevant behavior.