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Brain & Heart

MINI-REVIEW
Intrinsic cardiac neurons as the consulate

general of the brain in the heart: A review

Meha Fatima Aftab*
Human Electrophysiology Lab, Dow Institute of Medical Technology, Dow University of Health Sciences,
Karachi, Sindh, Pakistan

Abstract
Contrary to the prevailing understanding about one-way communication from brain
to heart, recent research has unveiled a two-way communication pathway between
these two organs, featuring the delivery of signals from the cardiac afferents to the
brain. While the medulla oblongata is known to send autonomic signals for cardiac
function regulation, 80% of the vagal afferents send signals to the brain for cardiac
regulation. The vagus nerve receives these signals from the intrinsic cardiac neurons,
often referred to as “the little brain of the heart.” Intrinsic cardiac neurons are neuronal
structures with the same biochemical profile as neurons, communicating with the
vagus nerve through acetylcholine and expresses markers of neuronal function
such as tyrosine hydroxylase and others. Intrinsic cardiac neurons also influence the
autonomic system, which can be studied through heart-rate variability measures.
Heart rate variability (HRV) is altered in many types of cardiac disorders and is a
well-known measure for studying short- and long-term disease-related variations in
cardiac function. Some psychiatric disorders such as post-traumatic stress disorder,
schizophrenia, and major depression also exhibited alterations in HRV. HRV is related
to heartbeat-evoked potentials (HEPs) and electrical potentials in the brain that are
*Corresponding author: influenced by the heart. HEPs are altered in disease states and can be impacted by
Meha Fatima Aftab
(meha.fatima@duhs.edu.pk) environmental factors. This paper reviews the existing literature concerning intrinsic
cardiac neurons and their possible role in heart-brain communication.
Citation: Aftab MF. Intrinsic cardiac
neurons as the consulate general
of the brain in the heart: A review.
Brain & Heart. 2024;2(2):2901. Keywords: Intrinsic cardiac ganglia; Neurocardiology; Heartbeat-evoked potentials;
doi: 10.36922/bh.2901 Cardiovascular disease; Psychiatric disorders
Received: February 7, 2024
Accepted: April 23, 2024
Published Online: May 2, 2024 1. Introduction
Copyright: © 2024 Author(s). Heart-brain communication has recently gained traction due to the discovery regarding
This is an Open-Access article the bi-directionality of this communication. The conventional understanding about the
distributed under the terms of the
Creative Commons Attribution heart-brain communication dictates that the brain sends signals to the heart to control
License, permitting distribution, cardiac functions. Nevertheless, an early clue suggesting the heart’s ability to communicate
1
and reproduction in any medium,
provided the original work is with the brain opened the door to understanding the bidirectional nature of this
properly cited. communication, ultimately leading to the discovery of intrinsic cardiac ganglia or intrinsic
2,3
Publisher’s Note: AccScience cardiac nervous system (ICNS) colloquially known as the brain inside the heart. Since
Publishing remains neutral with then, rigorous research in physiological and pathological processes has been conducted.
regard to jurisdictional claims in
published maps and institutional Yet, the mechanisms of heart-brain communication remain to be clarified. For instance,
affiliations. the molecular characterization of ICNS led to the discovery of both cardiac and neuronal

Volume 2 Issue 2 (2024) 1 doi: 10.36922/bh.2901