What is memory? Memory or smriti is recreation of things already perceived by the mind. For instance, a person may not always recollect what he ate the previous day, but if he thinks hard, the items that were eaten will flash in the mind. Daily, we are constantly recollecting things perceived in the past.
How does one activate memory? There are two ways: internal and external. The internal way is to revive the undistorted image of perceived incidents in the nerve cells. Perception in the primary stage is registered in the unit mind through the nerve cells, and the vibrations of those perceptions remain embedded in the nerve cells. Some cells carry vibrations of knowledge, others the vibrations of action. Microcosms with brains do not have much difficulty in creating ideas at the psychic level carried through inferences because the vibrations in the nerve cells remain undistorted for quite some time.
If the external factors necessary for the revival of memory remain undisturbed for some time, one can more easily recreate events already perceived. But, after a lapse of much time, when the external factors necessary for the recreation of that image change drastically, it becomes difficult for the brain to remember the details of the event. At this stage, to recollect the image, one has to penetrate the chitta of the unit mind. Of course, once an incident is recollected, its impression remains understood for some time before it finally disappears.
Thus the brain is nothing more than a worldly machine for mental recollection. Its various parts assist the mind in various ways. But the permanent abode of memory is the chitta. So, even though an impression has faded from the nerve cells, the mind can recreate the impression by its own power. When the brain assists in the recollection of any event or fact it is called “cerebral memory”.
The human mind has three stages: crude, subtle and causal. There are also three states in human existence: wakeful, dream and sleep. The crude mind remains active during the wakeful state and the causal mind remains active during sleep. The causal mind is the repository of infinite knowledge. Whatever samskaras we recreate in the wakeful and dream states remain stored in the causal mind. When the causal mind sleeps we call it “death”. After death the disembodied mind floats in the vast space with its unexpressed samskaras. Later on, with the cooperation of the mutative principle, the disembodied mind finds a suitable physical base. The memory of its past life remains awake for approximately the first five years of its new life. Although the child remains in a new physical environment, mentally it continues to live the joys and sorrows of its previous life. That is why children sometimes laugh and cry in their sleep.
To re-experience past events one does not need the cooperation of the old brain. The newly-born mind has not yet had time to build a close relationship with the new brain. The revival of experiences of past lives is what we call “extra-cerebral memory”, and is principally the task of the causal mind. Through sadhana human beings attain a certain degree of control over the relative factors. After a long journey of hundreds of years one begins to visualise the samskaras of one’s past lives. He will intensify his spiritual practice and advance rapidly towards Parama Purusha.