Question:

Is there any science on how impressions form in the mind? What are impressions exactly?

Answer:

Impressions are formed by multiple exposure of the mind to the same stimulus repeatedly. For example: You feel that you are Abhishek, this is an impression. You were repeatedly called Abhishek when you were a toddler, initially you did not identify with the name but when mom and dad kept calling you that, you understood that it has something to do with you. Then you started growing up a little and you felt a connection when you heard the word Abhishek as it jogged up the memory of the impression. Then you grew up a little more and you understood that everybody responds to a different word. Mom does not respond to the word Dad and Dad does not respond to the word Mom. Then you figured it out that if you do not respond to the word Abhishek, then you will be yelled at. Thus you started responding to the word Abhishek and now you have the impression that you are Abhishek. Got it? Impressions are formed by multiple exposure of the mind to the same stimulus repeatedly.

Thus we have coffee impressions, pizza impressions, impressions of criticism and praise, impressions of bad and good smell, impressions of soft and hard touch, impressions of beautiful mountains and ugly garbage, etc.

So if you are understanding this, you will come to the conclusion that impressions are nothing but memory. When you create a raaga and dvesha, you are actually creating a memory. This memory can be twisted.

For e.g. You have a very faint memory of your own infant-hood, when you were a baby. You screamed when you were hungry so mommy rushed and fed you milk. So the impression created in you is that if you scream/shout/get angry, you receive what you want. We carry such incorrect impressions deep within our subconscious mind. This forms our Karma bag!

You may have a strong impression of hatred for someone from a past lifetime, but because the memory get blocked at death, we do not retain it as a memory anymore but it becomes an impression in our subconscious. We meet the same person again in this lifetime and get repulsed for no reason, it is just that memory at play but we are unable to see it. This is the mechanism of Karma!