Targeting distinct facets of anhedonia via transcutaneous auricular vagus nerve stimulation: Effects on heart rate variability and reward-based behavior.
Rachele Grimaldi, Ezgi Uzun, Martino Schettino et al.
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In 30 seconds
This randomized, within-subject crossover study tested active versus sham transcutaneous auricular vagus nerve stimulation (taVNS) in participants with higher (n = 34) and lower (n = 34) depressive symptomatology. Compared with sham, taVNS increased willingness to exert effort for rewards, particularly when reward probability was low; this effect was more pronounced among participants with higher depressive symptoms. Effects on heart rate variability varied with baseline HRV and depressive status, while reward learning did not significantly change. Self-reported anxiety decreased across groups.
Key findings
- TaVNS increased effort for rewards, particularly at low reward probabilities, with a stronger effect in participants with higher depressive symptoms.
- HRV responses depended on baseline HRV and depressive status: in the lower-symptom group, HRV rose at low baseline levels and fell at high levels, with opposite patterns in the higher-symptom group.
- Reward learning, measured with the Probabilistic Reward Task, showed no significant effect of taVNS.
- Self-reported anxiety decreased with taVNS across both groups.
Why it matters
Anhedonia can involve reduced motivation as well as altered reward learning. The findings suggest taVNS may affect effort allocation even when reward learning is unchanged, and that autonomic responses may differ according to baseline HRV and depressive symptoms. These results help clarify which reward-related processes might be responsive to stimulation, but do not establish clinical benefit.
What to keep in mind
The study involved a single stimulation session, limiting conclusions about sustained effects.