I want to ask how memories are formed, and more importantly, stored. What is the material correlate for the experience of memory? They are recalled from the past into the present, so that means that there's some substance that "stores" past senses in a coherent manner, right? Are there identified neurochemicals that "lock in" memories? Or is it specific networks of nerves that retain patterns? If the latter, doesn't that mean that most of the brain is just neuropathways configured to restore recollections? Is the brain mostly a storage bin?

I've heard that whales devote a lot of brainspace for recognizing their environment for navigation purposes.

Also, I am not asking about mind/brain distinctions. I would like to know the physical reasons for recollections.