In Surah Al-Hajj (22:46), the Quran declares:
"For indeed, it is not the eyes that become blind, but it is the hearts within the chests that become blind."
The Quran attributes to the heart (qalb) a function of perception, understanding and spiritual discernment. Many verses associate the heart with reason, faith, understanding and guidance. This conception contrasts with the modern materialist view that reduces the heart to a mere mechanical pump.
Modern cardiology has nevertheless revealed that the heart is far more than a pump. The heart possesses its own intrinsic nervous system, a complex network of about 40,000 neurons sometimes called the "little brain" of the heart. This cardiac nervous system is capable of processing information, making local decisions and communicating bidirectionally with the brain via the vagus nerve and the autonomic nervous system.
Research conducted notably by the HeartMath Institute has shown that the heart communicates with the brain through several pathways: neurological (via the vagus nerve), biochemical (via hormones), biophysical (via pressure waves) and energetic (via electromagnetic fields). Heart rate directly influences brain regions involved in emotional processing and decision-making.
The concept of heart coherence — a state where the heart rhythm becomes regular and harmonious — has been associated with improved emotional regulation, mental clarity and overall well-being. Studies have shown that positive emotional states such as gratitude, compassion and serenity produce a coherent heart rhythm, while negative emotions such as stress and anxiety produce a chaotic and incoherent rhythm.
The convergence between the Quranic verse and modern cardiology is remarkable: the Quran, revealed in the 7th century, attributes to the heart a function of perception and discernment. Modern science confirms that the heart is a complex organ endowed with its own nervous system, capable of processing information and influencing cognition and emotions.
Level of evidence: The existence of the heart's intrinsic nervous system and its bidirectional communication with the brain are firmly established by cardiological research. Broader interpretations about the heart's "perception" belong to an emerging field of research and should be considered with caution. The convergence with the Quranic verse is suggestive but falls within a scientific interpretation of the text.