ALT Altered food liking in depression is driven by the macronutrient composition of the depicted food. We analyzed wanting and liking ratings of patients with major depressive disorder (MDD) and matched healthy control participants. Patients with MDD reported lower food wanting, whereas food liking was primarily associated with symptoms of anhedonia. We then evaluated whether the macronutrient composition of the food accounted for differences in ratings. This led to a substantial improvement in models and showed that patients with MDD show specific deficits for food rich in fat and protein.

ALT Across 17 studies, the meta-analysis shows moderate evidence against an effect of taVNS on pupil dilation. A: Contour-enhanced funnel plot showing standard error and observed outcome for each included study, grouped by stimulation type. Studies applying continuous (tonic) stimulation are depicted in pink, while studies applying pulsed (phasic) stimulation are depicted in green. B: Bayes factor (BF, log-transformed) robustness plot. BF are plotted across prior distributions differing in their width. The plot shows moderate evidence for H0 across all studies (in black). After grouping by stimulation type, we find strong evidence for H0 for continuous stimulation (in pink) and moderate evidence for H1 for pulsed stimulation (in green). C: Forest plot of all included studies, showing no effect across all included studies (mean = 0.14, CI [0.01, 0.27] for taVNS compared to sham. D: We assessed the risk of bias for all studies using a standardized checklist.

ALT Motivational symptoms of MDD are difficult to treat and we tested whether previously discovered acute invigorating effects of taVNS also occur in patients with MDD. Accordingly, we found that taVNS boosted invigoration across groups in the first session and taVNS-induced gains persisted into the second session. In patients with MDD, taVNS-induced gains in invigoration evolved over trials and were mirrored in increases in wanting, suggesting instrumental conditioning of subjective value that also persisted into the second session. Notably, we also replicated that taVNS boosted invigoration for less wanted rewards in healthy participants while patients with MDD showed instant improvements in subjective reward ratings. To conclude, our results highlight distinct dynamics of instrumental learning elicited by taVNS in HCP and MDD.

ALT The vagal afferent pathway and its theorized function in allostatic behavior. Interoception encodes bodily demands that arise once an allostatic set point, such as a sufficient nutrient supply, is unmet. Interoceptive signals can be evoked by changes in bodily states (e.g., lack of nutrients) or emulated by vagus nerve stimulation (VNS).