The human brain contains major lobes which are: frontal lobe, occipital lobe, temporal lobe and parietal lobe.
Each lobe has an exclusive role and at the same time, performs complementary roles with other organs of the body.
After dissecting the upper part of the forehead, it was discovered that the frontal lobe of the brain is the hidden organ, and that it is different from its animal counterpart in the sense that the regions responsible for behaviour and speech are advanced and prominent as far as anatomy and functions are concerned.
There was a cruel, oppressive tribal leader named Abu Jahl who lived during the time of the Prophet ﷺ. Allah revealed this ayah of the Qur’an to warn him. Allah is not calling this person a liar, but calls his forehead/forelock (the front part of the brain) ‘lying’ and ‘sinful’, and warns him to stop.
This is an indication of one of the many miracles of the Qur’aan. That the Qur’aan acknowledges the functions of the frontal lobe over a thousand years before we found out today with modern science.
The forelock, which is the upper part of the forehead, is responsible for traits such as truthfulness and lying, and sinfulness and righteousness. It is also the part of our brain that we use for making decisions and logical thinking
Allah tells us that He has a grasp of each one of our forelocks… the same part we make sujud (prostration in Salaah) to Allah with. We lower the most important part of who we are in humbleness to Allaah.
This frontal lobe is what makes human beings logical thinkers, in contrast to animals who react mainly due to emotional motivations. When they are hungry, they eat. When they feel tired they sleep. They do not consider staying awake, fasting and so on for logical reasons. This is something that makes humans unique.