Not being aware of the pulse of our heart might help prevent anxiety, EPFL scientists found.
Although our heart beats constantly, most of the time we do not consciously notice it. Researchers at EPFL’s Center for Neuroprosthetics have shown that the brain actively filters out the sensations produced by the beating heart so they do not interfere with perception of the external world. For the first time, this team identified the brain region involved in that filtering process, and described how its activity changes when internal and external signals compete for awareness. Their findings are reported in the Journal of Neuroscience.
The EPFL team discovered that visual stimuli are harder to perceive when they coincide with the heartbeat. In other words, whenever a visual event is synchronized with the cardiac cycle, the brain appears less likely to process it fully, as if it suppresses information that is temporally aligned with bodily rhythms.
“We don’t see the same way a video camera does,” said Roy Salomon of the Laboratory of Cognitive Neuroscience, a co-author of the study. “Our perception is not a simple, objective recording of everything that falls on the retina. The brain selects which information becomes conscious. What surprised us was the extent to which signals from the heart influence that selection.”
To demonstrate this effect, the researchers first ran behavioral experiments with more than 150 volunteers. Participants viewed a flashing octagonal shape on a screen while their heartbeats were monitored. When the brief visual flashes were presented in sync with participants’ heartbeats, they were significantly less likely to detect the shape than when flashes occurred out of sync with the cardiac cycle.
What happens in the brain — an initial explanation
To uncover the neural basis of this effect, the team repeated the experiment while scanning participants in an MRI scanner. Their data pointed to a specific brain area: the insular cortex. This region showed reduced activity when visual events coincided with the heartbeat, and that reduction corresponded with decreased awareness of the visual stimulus. When flashes were not synchronized with the heartbeat, insular activity remained at its usual level and participants more readily perceived the octagon.
Salomon noted that early exposure to internal bodily signals such as the heartbeat may explain why the brain has developed a mechanism to suppress these ongoing sensations: “Because the heart beats from the very beginning of life, the nervous system has long been exposed to its signals. It makes adaptive sense that the brain downregulates those constant internal cues so they do not drown out information about the environment.”
Is awareness of one’s heartbeat related to anxiety?
Heightened awareness of heartbeat sensations has been observed in people with certain psychological conditions, including anxiety disorders. Patients with these disorders often report a clearer experience of their heartbeat than most people do. However, non-clinical individuals can also become acutely aware of their heart rate during moments of strong emotion, excitement or fear.
Whether a failure to suppress heartbeat sensations is a cause or an effect of anxiety remains an open question. The study does not establish a causal link, but it does show that under typical conditions most people are not consciously aware of their heartbeats and that the insular cortex plays a role in reducing that awareness. Understanding how this filtering mechanism varies across individuals and in clinical populations could help clarify the relationship between bodily awareness and emotional disorders.
Source: EPFL
Image source: The image is provided for illustrative purposes.
Original research: The study will appear in the Journal of Neuroscience.