HomeRelationshipsThe science of heart coherence

In December 2022, DR. ROLLIN McCRATY, Director of Research at the Heart Math Institute, gave an online presentation at the international Heartfulness conference, “An Integrative Approach to Health and Well-being,” at Kanha Shanti Vanam. Here we share some highlights from his talk.

What Is coherence?

Most people have an intuitive understanding of coherence, but in the scientific community it’s a term and a concept used in every branch of science, from the macro to the micro scale. We use it to describe the behavior of the parts of a complex system. In a coherent system, those parts have to be communicating and talking to each other so there’s connectedness. It’s inherent to the concept of coherence, and it’s really a measure of the harmonious order of how all the parts of a system are working together.

A coherent system implies stability and energy efficiency. Another key concept of coherence is that in any system – whether it’s a human being, or any other scale we want to look at– there’s a greater wholeness than you can derive from the sum of the parts. This is why we chose to use this term in our research so many years ago.

Our research focuses on three primary domains: personal, social, and global. For the personal, we have spent many years looking at the coherence within our bodies, especially between the heart and brain. Socially, we can define the coherence of a group, whether that’s a family, a work team, a leadership team, or even a community. I won’t have a lot of time to go into global coherence, but I’ll give you a teaser.

The heart profoundly affects brain function

It probably isn’t a surprise to you that the heart sends far more information to the brain than the brain sends to the heart, but it is a big surprise for a lot of people in our medical communities in the Western world. It is not a new finding – it has been known since the late 1800s: in fact it’s basic anatomy.


There are neural channels by which the heart and brain communicate,
but the heart also communicates with the brain hormonally, energetically,
through the pressure waves it generates that affect every cell
and synchronizes all the cells in the body.

In the 1970s, there were some major discoveries that really shifted the paradigm in the field of psychophysiology. It was discovered that the neural traffic that the heart sends to the brain has profound effects on brain function. Two terms were introduced back then. The first is “cortical inhibition,” where the cortex or higher parts of the brain are inhibited when the heart is sending certain types of messages. The other term is “cortical facilitation,” which was introduced to describe the global effects that the activity of the heart has on the brain. Since then, we have a much deeper understanding of the mechanisms and how this all works.

The activity of the heart also has a lot to do with creating our emotional experience. The brain is largely interpreting the message that’s being sent to it from the heart, and I think that is why we intuitively and innately know when we fall in love with someone. We don’t say, “I love you with all of my brain,” right? We say, “I love you with all of my heart,” and there’s a deep physiological reason for that.

The activity of the heart has a lot to do with creating our emotional experience.
The brain is largely interpreting the message that’s being sent to it from the heart.

What they didn’t know back then was that the heart has its own intrinsic nervous system, which has been nicknamed “the heart brain” in the field of neural cardiology. The neural structures in the heart have now been proven to have short-term memory, long-term memory, neuroplasticity, neurogenesis – all of the functions of a functional brain. There are neural channels by which the heart and brain communicate, so the heart also communicates with the brain hormonally, and energetically, through the pressure and electromagnetic waves it generates that affects every cell and synchronizes all the cells in the body.

Zeroing in on the primary neural pathways, we have the vagus nerves, which are the two nerves that travel up through the front of the body. They are the primary pathways of the para sympathitic branch of the autonomic nervous system. They are very large nerves, with thousands of neural fibers, and 90% of those fibers are carrying information from the body to the brain. The majority of those afferent or ascending neural pathways are coming from the heart and the cardiovascular system, far more than any other system in the body. There are also ascending (afferent) neural pathways in the sympathetic branch, so it’s a very complex two-way traffic between the heart and the brain.

All of the neural connections coming down from the brain connect into the intrinsic cardiac nervous system, the heart brain, and then within the heart there are another 40,000 to 50,000 sensory neurons that are sensing things like rhythm, pressure, and about 80% of these neurons are sensing biochemistry.

If you were going to put in a system to detect what’s going on in the blood, to monitor hormones, neurotransmitters and so on, where would you put it? The heart makes obvious sense, so that all of the information is fed into the heart brain, and then up to the brain in different neural patterns.

The intrinsic cardiac nervous system can and does override the neural signals coming down from the brain, and at a functional level a heart has its own type of intelligence. In fact, in the papers from the 70s and 80s, people were talking about the heart as though it had a mind of its own before they knew about the intrinsic cardiac nervous system.

Heart rate variability

One of the tools that gives us a window into the dynamic communication between the heart and brain, and the activity within our autonomic nervous system, is heart rate variability. At a high level, we can measure the amount of variability a person has, and it reflects their health status, their capacity to self-regulate, and self-regulate thoughts, emotions, and behaviors.

Our ability to adapt is directly tied to our heartrate variability (HRV). Too little variability reflects a deep depletion within the nervous system. One of the leading reasons for that is chronic stress, and the second leading cause is pathology, e.g. diabetes, metabolic syndrome, etc. It also reflects inadequate function of the various levels of our self-regulatory system.


The intrinsic cardiac nervous system can and does override
the neural signals coming down from the brain,
and at a functional level a heart has its own type of intelligence.

So people who have behavioral management issues such as anger issues or panic attacks, often have low HRV. The time intervals between each consecutive pair of heartbeats is always changing. A small amount of variability is not a condition we want to see because it reflects system depletion, and is highly predictive of future health problems. In fact, low HRV for our age shows up oftentimes several years before the onset of cancer, diabetes, and so on, so it has a huge use in clinical assessment.

I want to go a little bit deeper. This graph is from a paper we published in the American Journal of Cardiology back in the mid 90s that was the first to show that the most reflective measure of our emotional state is the pattern of our heart rhythms, our heart rate variability. So on the left side we can see a jagged, chaotic rhythm, which is the rhythm that we have when we’re experiencing feelings like impatience, frustration, worry, or anxiety. If we get angry it’s way more chaotic. This quite literally reflects a desynchronization in the neural activity in our higher brain systems and within our nervous system. This is actually the type of a rhythm or pattern that’s been associated with cortical inhibition, where the brain doesn’t work very well.


The graph on the right shows the same person after they used a technique called heart-focused breathing (we’ve developed various different techniques to shift into that coherent rhythm).This rhythm naturally emerges when people experience heartfelt feelings like appreciation, gratitude, compassion, love. These types of emotions naturally shift us into what we now call coherent rhythm and that’s associated with cortical facilitation.

There’s a lot going on in that coherent state within our body, and it is a measure of the increasing synchronization in our higher brain and within our nervous system. It has a lot of benefits. Coherence is not the same thing as relaxation. When we’re in a coherent state (and more than 400 independent studies have confirmed this), there area broad range of health benefits like lower blood pressure, increased hormonal balance, faster recovery from heart disease and diabetes, better outcomes in education, and the list goes on.

We can teach people how to shift into that state very quickly, and we especially want to create those shifts in the moments when people are in challenging situations and want their mental faculties to work well.

To be continued.

To watch the full talk, go to https://www.youtube.com/watch?v=mm6MDe_ZwFc.

Illustrations by ANANYA PATEL


Dr. Rollin McCraty

Dr. Rollin McCraty

Rollin is a scientist, psychophysiologist, Executive Vice President and Director of Research at HeartMath Institute, member of the Global Coherence Steering committee, and project coordinator of GCI's Global Coherence Monitoring System. ... Read More