In a recent study published in Nature,1 Hsueh et al. developed a non-invasive optogenetic approach to control heart rate in freely moving mice. Optically induced tachycardia elicited an anxiety-like state in risky contexts, with the posterior insular cortex mediating the apprehensive behaviours arising from cardiac pacing.
Whereas the link between emotions and bodily functions is part of the human experience, whether emotions are cause or consequence of their associated responses has been long debated by psychologists and neuroscientists. Does anxiety lead to an increased heart rate, or conversely, does a racing heart drive anxious behaviours? There is ample evidence linking mental and cardiac health. Clinical meta-analysis studies have shown an increased risk of heart disease in patients suffering from anxiety or stress-related disorders. Similarly, individuals with atrial fibrillation—a heart condition characterized by irregular and abnormal beating—have a higher prevalence of depression and its severity is associated with lower self-reported mental and physical health status.2 Although vagus nerve stimulation is clinically used to treat both conditions, little is known about the circuit mechanisms underlying heart-brain communication and how cardiac feedback to the brain, a process termed interoception, influences affective behavioural states.