What is the mind’s clock?

A group of 20,000 cells in the hypothalamus, called the suprachiasmatic nuclei (SCN), that determines an organism’s internal rhythm is referred to as the mind’s clock. Research led by Richter showed that these cells are situated in the frontal part of the hypothalamus and control the rhythmic circadian behaviour. In 1970, researchers located the specific target in the hypothalamus that was playing the leading role —a small group of 20,000 cells. This was confirmed by injecting radioactive amino acids into rats, which led to a change in their behaviour and internal clock. This tiny speck, its volume only one-third of a cubic millimetre, was called the “mind’s clock”.