Cardiac interoception impacts behavior and brain-wide neuronal dynamics

We sought to explore the question as to whether an animals behavior can be modified by internal physiological changes. We focused on the optomotor response, in which an animal moves in response to visual gratings, because it is quantitative, robust, and evolutionarily conserved. Using larval zebrafish, we demonstrate that engagement in the optomotor response is inversely related to heart rate. We modulate heart rate by external threat, activation or blockade of the sympathetic nervous system, pharmacological blockade of the cardiac pacemaker channel, and direct optogenetic pacing of the heart, and find that the correlation persists through all perturbations. We find neurons in the primary sensory ganglia and several regions of the brain whose activity reflects changes in heart rate, some more active during bradycardia and some during tachycardia. Specifically, we show that the area postrema, known to be a center of cardiovascular integration, shows particularly strong encoding of heart rate, both following threat and during optogenetic cardiac pacing. We suggest that there may be neural mechanisms to assess heart rate changes over time, and that this interoceptive measurement is used to regulate other neural circuits and behavioral output.