I have mention scar tissue several times, so I should define this term.
This is a very early working of this doctrine. I have added a few explanatory sentences.
Scar tissue of the Soul (R. B. Thieme, Jr.)
1.	The mind, according to Ephesians 4:23, actually breaths. The word for "mind" emphasizes the function of the left lobe as a processor of doctrine; it is a staging area, not the final resting place of Bible doctrine. The left lobe has a processor which is called "breathing" and this implies the existence of lungs. The intake and the output of doctrine would be comparable to physiological breathing. Therefore, the definition "hardness of the heart" or "scar tissue of the mind" is the blackout of the left lobe resulting in the hardness of the right lobe.

2.	Mechanics. The malfunction of the grace apparatus for perception through negative volition causes a vacuum to open up in the left lobe, as per Ephesians 4:17. The left lobe is attacked by the opening of mátaios ( ) [pronounced MAT-ah-yoss], which is a vacuum that is opened up when negative volition towards God is expressed. Through this vacuum comes doctrines of demons and other types of Satanic propaganda which cause the blackout of the soul. At the time of the blackout of the soul the reversionistic believer lives under the intensification of reactor factors, emotional revolt, frantic search for happiness, and all of these things open up the mátaios ( ) [pronounced MAT-ah-yoss] (the vacuum of the soul). The result is the blackout of the soul which invariably causes scar tissue to form on the right lobe.

3.	Illustrations:

a.	First of all the illustration which is based upon a frantic search for happiness through the trend toward lasciviousness — Ephesians 4:19; 5:3.

b.	A second illustration is found in 1John 2:9,11 — the function of mental attitude sins. With the blackout of the soul and the hardness of the heart it is impossible to avoid the repercussions of mental attitude sins — for instance, those of Hymenaeus and Alexander, 1Timothy 1:20.

4.	Scar tissue and the reversionistic believer. The reversionistic believer develops scar tissue in the right lobe of the soul called the heart. It is built up on the basis of the fact that there is a blackout in the left lobe.

5.	Scar tissue and the unbeliever.

a.	The reversionistic unbeliever accumulates scar tissue or suffers from the hardness of the heart — 2Thessalonians 2:10-12, where it is called strong delusion.

b.	He is also found in 2Peter 2:22 where he is described as the dog returning to his vomit.

c.	However, scar tissue in the unbeliever or hardness of heart is removed at salvation — Isaiah 43:25; 44:22. For the unbeliever who remains in hardness of heart or strong delusion there is total disaster. One of the best illustrations in scripture is Judas Iscariot and his suicide which is described in great detail in Matthew 27:3-10. He became very emotional, felt sorry for what he had done, made restitution, and wound up committing suicide. The Pharaoh of Exodus is another illustration. The solution to scar tissue or hardness of the heart is the same in both cases. For the unbeliever it is response to the gospel by faith in Christ and for the believer it is reversion recovery through the intake of doctrine.
This was taken from R. B. Thieme, Jr.'s 1972 Ephesian Series, Lesson #59. A few explanatory comments were inserted.