The brain and heart are connected in many ways, including through nerves, the heart’s nervous system, and the heart’s ability to produce oxytocin:
Nerves
Nerves connect the brain to the heart, allowing the brain to control the heart’s rate and receive information about how hard it’s working.
Heart’s nervous system
The heart has its own nervous system, sometimes called the “little brain”, which contains around 40,000 neurons. This system can learn, remember, feel, and sense, and can act independently of the brain in the head. The heart’s nervous system receives information from the brain about the body’s internal state and environment, and adjusts outputs like blood pressure and heart rate. The heart also sends information to the brain through nerve pathways, which can influence perception, decision making, and other cognitive processes.
Oxytocin
The heart produces oxytocin, a hormone that can act as a neurotransmitter and is involved in cognition, trust, friendship, and tolerance. The heart produces similar concentrations of oxytocin as the brain. 
Some evidence suggests that there is a strong connection between heart and brain health. For example, cardiovascular diseases can lead to brain diseases like stroke, dementia, and cognitive impairment. Other factors that can influence both heart and brain health include blood pressure and physical activity. 
“For more than two thousand years, the Heart Sutra has been part of the daily life of millions of Buddhists. This concise text, so rich and laden with meaning, concentrates the very heart of Buddhism into a powerful and evocative teaching on the interdependence of all reality.

In Essence of the Heart Sutra, the Dalai Lama masterfully unpacks the Heart Sutra so that any reader can benefit from its teachings—teachings meant to help us release ourselves from suffering and live with true compassion. Comprised of his “Heart of Wisdom” talks, originally delivered to thousands of listeners in 2001, the book offers the Dalai Lama’s commentary as well as his easy-to-follow overview of Buddhist philosophy that places the sutra within its historical and philosophical context. With additional contributions”