Interoception is the mind's ability to sense its internal state. While traditionally studied as a whole-body experience, researchers now suggest breaking it into specialized domains. One key domain, cardioception, focuses on how the brain perceives signals from the heart.

This involves unique neural pathways and specialized structures that highlight the heart’s role in regulating not just physical health but also emotional states.

The Heart’s Sensory Networks
The heart’s interactions with the nervous system are crucial for its steady functioning. Extrinsic networks connect the brain and spinal cord to the heart. Being pretty vital for us, the heart also possesses an intrinsic network known as the cardiac nervous system or the "little brain".

These networks involve various neurons, including the sensory vagus nerve, that relay heart signals to the brainstem and beyond. Complex feedback loops allow the brain to adjust the heart’s activity, like pace and how powerful is shall contract, ensuring homeostasis.

Recent discoveries also reveal unconventional pathways, such as pressure-sensitive receptors in the olfactory bulb, yes, the nose, which detect changes in arterial pressure and influence brain functions. This multidimensional communication highlights evolution’s intricate design.

Reflexes and Behavioral Responses
Cardiac reflexes, like the baroreflex, are essential for regulating blood pressure and heart rate. However, these internal organ reflexes also influence mental states and behavior.

For instance, the baroreflex not only stabilizes blood pressure but also promotes non-REM sleep. On the other hand, faster heart rates can trigger anxiety, illustrating how heart activity impacts emotional responses.

Studies have shown that regions like the insular cortex play a central role in processing heart-related signals, directly linking physiological changes to fear and stress responses.

These insights help explain why therapies targeting the heart, such as beta-blockers, can alleviate anxiety symptoms. And why feeling a sudden change in your heart rythm, however benign, may elicit distress.

Beyond Conventional Pathways
Recent research challenges the traditional view that the brain relies solely on incoming nerve signals for interoception. Instead, is seems that critical information about the immediate state of the heart can reach the brain directly.

For example, mechanosensory receptors in the brain detect arterial pressure changes, showing a direct response to the heart’s mechanical activity. Similarly, astrocytes in specific brain regions sense drops in blood flow and trigger corrective responses to stabilize cardiac function.

This growing understanding of cardioception is reshaping our understanding of how the brain integrates signals from the heart to regulate physiological states and behavior, too. By uncovering the heart’s multifaceted connections to the brain, researchers are not only advancing basic science but also creating innovative therapeutic possibilities.

About the scientific paper:

First author: Jonathan W. Lovelace, USA
Published in: Neuron, November 2024
Link to paper:https://www.cell.com/neuron/fulltext/S0896-6273(24)00730-X?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS089662732400730X%3Fshowall%3Dtrue