How Your Heart Influences What You Perceive and Fear

When you sense something from inside, it reduces the processing of external signals. When your heartbeat is going, it's loading up the seesaw on one side.

An experiment showed that when people were given a faint electrical stimulus to their finger, they were more likely to notice it during diastole and miss it during systole. When the heart pushes blood through your body during systole, it's possible to feel your pulse in your fingertips.

The systole doesn't inhibit the stimuli of fear. The systole not only activates inhibitory brain regions, but also the amygdala, an area that process the experience of fear. During systole, people can perceive fearful faces more intensely.

If you are in a state of fear, you don't want to be sensitive to pain. You want to run over broken glass to escape the threat. But you also want to be hyper-alert to danger in the environment.

• Researchers found eye movements often occur at systole, while we fix our gaze more often during diastole. During systole, we're least sensitive to the world.
• Another finding is that systole is more likely to enhance fear processing in people with anxiety. If you can change how threatening stimuli are, you may be able to get people out of anxiety states.