The brain: 

Dear noble brothers, man's brain is the biggest among other creatures in relation to the total    body weight, except the whale and the elephant.

If we compare the weight of the brain to the weight of the body, man’s brain would be the heaviest among all creatures, except for the whale and elephant.

The frontal lobe in the brain is the biggest lobe. In the past, scientists mistakenly thought that this lobe is a silent zone, but later on, they found out that it is responsible for the cognitive functions.

Thus, if it is damaged by an accident, if it bleeds, or if it is infected with benign tumor, the mental abilities will be weakened and moral disturbances will happen. 

This lobe helps man plan for his actions and words, so the frontal lobe controls man’s plans. What does Allah say about it? Allah, Exalted and Sublime be He, says: 

(Nay! If he ceases not, We will catch him by the forelock* A lying, sinful forelock!)

 [Al-Al'aq, 15-16]

Man lies and misbehaves due to plans he makes by his frontal lobe that is located under the frontal skull bones and near the forehead:

(Nay! If he ceases not, We will catch him by the forelock* A lying, sinful forelock!)

 [Al-Al'aq, 15-16]

Saying lies and making mistakes are initiated in the frontal lobe.

Furthermore, if someone is injured in a traffic accident, he suffers from brain hemorrhage, or he has benign tumor, which applies pressure on this lobe. This would affect his speech, morals, and actions.  

A doctor mentioned the health condition of a woman after suffering from an internal bleeding in her forehead. He said that her behavior was affected for some time, but after the body absorbed that bleeding, she returned to her normal personality. 

Thus, scientists concluded that cognitive functions and planning are some of the responsibilities of the frontal lobe. The Prophet, peace be upon him, said about this lobe: 

(O Allah, I am Your servant, son of Your servant, son of Your maidservant, my forelock is in Your hand, Your command over me is forever executed and Your decree over me is just.) 

[Among the Nawawi supplications, on the authority of Abi Musa Al-ash'ari]

Allah the Almighty says:

(Say: "It (this Qur'an) has been sent down by Him (Allah) Who knows the secret of the heavens and the earth. Truly, He is Oft-Forgiving, Most Merciful.")

[Al-Furqan, 6]

Scientists said, "Speech originates in the front lobe and the tongue executes it,

voluntary movement originates in this lobe and it is executed by the organs and senses of the body such as moving the eye (by its muscles), moving the head (by its muscles) and moving all other parts of the body. 

The frontal lobe is called the Nasiyah (forelock) in the Noble Quran: 

(Nay! If he ceases not, We will catch him by the forelock* A lying, sinful forelock!)

After the scientists invented the "magnetic resonance", they were able to measure blood flow inside the brain. They let someone lie under this device, and asked him about the meanings of some words, so blood flow to the frontal lobe increased.

This lobe is the area of thinking, reasoning, deduction, judgment, recognition, planning and movement. These facts explain why Allah the Almighty says: 

(There is not a moving (living) creature but He has grasped of its forelock…)

[Hud, 56]

It is said, "If Allah decrees something, He makes people amazed at His Wonders." This means Allah, Exalted and Sublime be He, has given us high cognitive power, so we will be called to account for every deed.

Allah, the Almighty says:    

(…and they will be seized by their forelocks and their feet.)

[Ar-Rahman, 41]

This indicates that man will be punished by seizing the spot that is considered the source of his deviated words and deeds.