A new study helps explain why our sensitivity to external sensory stimuli fluctuates with the beating of our hearts.
According to popular culture, the brain and heart work in opposition to each other. The brain is the seat of rational, objective thought, while the heart is emotional and intuitive.
In reality, the activity of the two organs is intimately connected, with neither having a monopoly on reason or emotion.
Our hearts beat faster when we think about something exciting or frightening, for example. Conversely, an early morning jog can brighten our mood as our heart and lungs work harder.
A new study adds to evidence that the brain’s sensitivity to external sensory stimuli changes in step with the beating of the heart.
Researchers at the Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, and the Berlin School of Mind and Brain, both in Germany, set out to investigate this relationship.
Their study features in the journal Proceedings of the National Academy of Sciences of the United States of America.
The scientists recruited 37 volunteers and carried out a total of 960 trials. In 800 of these, they gave the participant a mild electric shock to either the middle or index finger of their left hand. The volunteers indicated when they detected the stimulus, and in which finger they felt it.
The researchers told the participants that every trial contained a stimulus, but in the remaining 160 trials, there was no such stimulus.
During each trial, the researchers used electroencephalography (EEG) to record electrical activity in the brain and electrocardiography (EKG) to record the electrical activity of the heart.
They discovered two mechanisms that they believe underpin how the heart influences sensory perception.
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