In The Gospel of Sri Ramakrishna / Volume 1 / Rules for Householders and Monks, Ramakrishna Paramahansa makes the following claim.
Sir, why does a man become deluded by worldly objects?
It is because he lives in their midst without having realized God. Man never succumbs to delusion after he has realized God. The moth no longer enjoys darkness if it has once seen the light.
To be able to realize God, one must practise absolute continence. Sages like Sukadeva are examples of an urdhareta. (A man of unbroken and complete continence.) Their chastity was absolutely unbroken. There is another class, who previously have had discharges of semen but who later on have controlled them. A man controlling the seminal fluid for twelve years develops a special power. He grows a new inner nerve called the nerve of memory. Through that nerve he remembers all, he understands all.
(By 'nerve of memory' he probably means medhā nāḍī)
Is the claim (marked in bold) backed by scriptures?
Also, is he talking about a visible nerve (that which can be observed under a microscope) or an invisible one on the spiritual plane?