Forelock is a lock of hair growing from the front of the head. 
Forelock means lock of hair at forehead. In explanation of Allah’s ayath: ‘We shall seize him by the forelock’, Al Faraa said; ‘it is the forehead that He (Allah) shall seize Abu Jahl to drag him i.e., a sign of humiliation and disgrace.’
No! If he does not desist, We will surely drag him by the forelock - A lying, sinning forelock. Quran Surah Alaq 96:15-16 Further Allah says: The criminals will be known by their marks, and they will be seized by the forelocks and the feet. Quran Surah Rahman 55:41 and Allah says in Quran, “Indeed, I have relied upon Allah , my Lord and your Lord. There is no creature but that He holds its forelock. Indeed, my Lord is on a path [that is] straight." Quran Surah Hud 11:56
Al Alousi said, “The forelock as described in the ayath, indicates in the first place that this person is lying and sinful, and due to Abu Jahl’s obstinate lying and sins, every part of him is lying and sinning.” Al Alousi also said; “The forelock is specifically mentioned here because the cursed Abu Jahl used to take good care of it by combing and perfuming, and because seizing the forelock is the utmost humiliation for any Arab…”
Like all vertebrate brains, the human brain develops from three sections known as the forebrain, midbrain and hindbrain. Each of these contains fluid-filled cavities called ventricles. The forebrain develops into the cerebrum and underlying structures. 
Man’s brain contains the following main lobes
For each lobe, there is a functional role, which is at the same time complementary to the other body functions. Having dissected the forehead, the frontal lobe was found to be the part lying behind. The frontal lobe is characterized, apart from the animal counterpart, with the regions responsible for behaviour and speech being developed and distinct as per the anatomic and functional levels.
1- Primary Motor Area that helps move the voluntary muscles of the left side of the body.
2- Secondary Motor Area that helps move the voluntary muscles of the right side of the body.
3- Frontal Eye Field that helps move eyes to the opposite sides compatibly.
4- Motor Speech Area of Broca that coordinates movements among organs of speech, such as larynx, tongue and face.
5- Pre-Frontal Cortex, which lies directly behind the forehead, represents the bigger part of the frontal lobe, and its function is responsible for forming the person’s character and also has an effect in determining the ability of taking initiative and judgment.
The miracle side in the above Quranic ayath and the Honourable Hadith of the Prophet is that they refer very accurately to the frontal lobe, lying deep at man’s forelock, as being the centre of decision to control man’s actions of truthfulness, lying, right, wrong, balance or perversion. This has been revealed by modern scientific studies in the second half of the 20th century.
The brain is surrounded with three membranes, among which is the cerebral spinal fluid (CSF), which has the function of protection, feeding and cooling.
It has been found that the brain inside the skull weighs 50 gm, although the real weight is 1700 gm. The physical principle states that the volume of the object immersed in fluid is equal to the volume of displaced fluid. Therefore, it is of the Almighty Creator’s decree that we do not feel the brain weight, as it floats in the CSF, which originates from a special area in the brain called “the corogy plexus”, and rotates inside and comes out of another area such as the domestic water net. This cycle occurs five times a day. As Muslims do before prayer times, the brain get ablution 5 times a day ... ! We prostrate on the frontal lobe which has the centre of decision making. 
The Cerebrum: The cerebrum or cortex is the largest part of the human brain, associated with higher brain function such as thought and action. The cerebral cortex is divided into four sections, called "lobes": the frontal lobe, parietal lobe, occipital lobe, and temporal lobe. …What do each of these lobes do?
The human brain is divided into two hemispheres, the left and right, connected by a structure called the corpus callosum. The hemispheres are strongly, though not entirely, symmetrical. The left brain controls all the muscles on the right-hand side of the body; and the right brain controls the left side. One hemisphere may be slightly dominant, as with left- or right-handedness.
The popular notions about "left brain" and "right brain" qualities are generalizations that are not well-supported by evidence. Still, there are some important differences between these areas. The left brain contains regions involved in speech and language (Broca's area and Wernicke's area). The left brain is also associated with mathematical calculation and fact retrieval. The right brain plays a role in visual and auditory processing, spatial skills and artistic ability, though these functions involve both hemispheres. 
According to an article published in Brainfacts.org in 2013: ‘Although several brain areas appear to play a role in deception, the most consistent finding across multiple FMRI(functional magnetic resonance imaging) studies is that activity in the prefrontal cortex increases when people lie. The prefrontal cortex, situated just behind the forehead, is a collection of regions responsible for executive control (the ability to regulate thoughts or actions to achieve goals). Executive control includes cognitive processes such as planning, problem solving, and attention — all important components of deception — so it’s no surprise the prefrontal cortex is active when we lie. Dishonesty requires the brain to work harder than honesty, and this effort is reflected by increased brain activity. Studies even show people take longer to respond when lying.’ 
All that we have seen so far shows us one clear fact: the Qur'an is such a book that all the news related in it has proved to be true. Facts about scientific subjects and the news given about the future, facts that no one could have known at the time, were announced in its verses. It is impossible for this information to have been known with the level of knowledge and technology of the day. It is clear that this provides clear evidence that the Qur'an is not the word of man. The Qur'an is the word of the Almighty God, the Originator of everything and the One Who encompasses everything with His knowledge. In one verse, God says on the Qur'an "Do they not then consider the Quran carefully? Had it been from other than Allah, they would surely have found therein much contradictions." (Qur'an Surah 4:82) Not only are there no inconsistency in the Qur'an, but every piece of information it contains reveals the miracle of this divine book more and more each day.
What falls to man is to hold fast to this divine book revealed by God, and receive it as his one and only guide. In one of the verses, God calls out to us:
"And this is a Book We have sent down and blessed, so follow it and have fear of God so that hopefully you will gain mercy." (Qur'an Surah 6:155)
In His other aayaath, Allah remarks: "Say: 'It is the truth from your Lord. Let anyone who wishes to, believe, and let anyone who wishes to, disbelieve.'" (Qur'an Surah 18:29)