What Is a Memory?

Neurosurgeon Michael Egnor raises an interesting question, one that many of us might never think to ask. What, exactly, is a memory? A secondary question might be how does a materialist metaphysics account for memories?

Egnor begins by arguing that contrary to popular belief, and even the belief of many neuroscientists and philosophers, the brain doesn't actually "store" memories. In fact, he claims, it can't store memories:

It's helpful to begin by considering what memory is -- memory is retained knowledge. Knowledge is the set of true propositions. Note that neither memory nor knowledge nor propositions are inherently physical. They are psychological entities, not physical things.

Certainly memories aren't little packets of protein or lipid stuffed into a handy gyrus, ready for retrieval when needed for the math quiz.

The brain is a physical thing. A memory is a psychological thing. A psychological thing obviously can't be "stored" in the same way a physical thing can. It's not clear how the term "store" could even apply to a psychological thing.

But what about storage as an engram, a pattern of electrochemical energy or proteins, that acts as a code for the information? Egnor doesn't think this explanation works either:

[C]onsider a hypothetical "engram" of your grandmother's lovely face that "codes" for your memory of her appearance. Imagine that the memory engram is safely tucked into a corner of your superior temporal gyrus, and you desire to remember Nana's face.

As noted above, your memory itself obviously is not in the gyrus or in the engram. It doesn't even make any sense to say a memory is stored in a lump of brain. But, you say, that's just a silly little misunderstanding. What you really mean to say is that the memory is encoded there, and it must be accessed and retrieved, and it is in that sense that the memory is stored.

It is the engram, you say, not the memory itself, that is stored.

But there is a real problem with that view. As you try to remember Nana's face, you must then locate the engram of the memory, which of course requires that you (unconsciously) must remember where in your brain Nana's face engram is stored .... So this retrieval of the Nana memory via the engram requires another memory (call it the "Nana engram location memory"), which must itself be encoded somewhere in your brain.

To access the memory for the location of the engram of Nana, you must access a memory for the engram for the location for the engram of Nana. And obviously you must first remember the location of the Nana engram location memory, which presupposes another engram whose location must be remembered. Ad infinitum.

Now imagine that by some miracle...you are able to surmount infinite regress and locate the engram for Nana's face in your superior temporal gyrus (like finding your keys by serendipity!). Whew! But don't deceive yourself -- this doesn't solve your problem in the least. Because now you have to decode the engram itself.

The engram would undoubtedly take the form of brain tissue -- a particular array of proteins, or dendrites or axons, or an electrochemical gradient of some specific sort -- that would mean "memory of Nana's face." But how can an electrochemical gradient represent a face?

Certainly an electrochemical gradient doesn't look like grandma -- and even if it did, you'd have to have a little tiny eye in your brain to see it to recognize that it looked like grandma.

The engram is a code, but if so we need a key to decode it. How do we access the key? How do we remember where the key is stored in the brain? The memory of where the key is stored must itself be coded somewhere in the brain which would require yet another memory to decode it, and so on:

And if you think that remembering your grandmother's face via an engram in your brain entails infinite regress, consider the conundrum of remembering a concept, rather than a face. How, pray tell, can the concept of your grandma's justice or her mercy or her cynicism be encoded in an engram? The quality of mercy is not [stored], nor can it be encoded. How many dendrites and axons for mercy?

You see the difficulty. We remember things all the time, but how often have we ever paused to ask ourselves what's going on when we remember? And whatever it is that's going on, how did such a highly specified and complex system evolve by random mutation and natural selection? And how are memories, like other aspects of consciousness (self-awareness, qualia, intentionality, free will), accounted for by a purely mechanical entity like a brain?

How then, you reasonably ask, can we explain the obvious dependence of memory on brain structure and function? While it is obvious that the memories aren't stored, it does seem that some parts of the brain are ordinarily necessary for memory.

And that's certainly true....In some cases the correspondence between brain and memory is one of tight necessity -- the brain must have a specific activity for memory to be exercised.

But the brain activity is not the same thing as the memory nor does it make any sense at all to say the brain activity codes for the memory or that the brain stores the memory.

For reasons such as Egnor calls to our attention some philosophers are rejecting the materialistic monism that has prevailed for the last century and a half and are returning for answers to some form or another of dualism. Dualism comes in many varieties, but what they all share in common is the view that the material aspect of a human being - the brain in particular - is not all there is to us.

Something else seems to be somehow involved in the phenomenon of remembering in particular and the phenomenon of consciousness in general. That something else, many philosophers believe, is an immaterial mind.

If that's true then not only is materialism false but the Darwinians' explanatory difficulties have significantly increased. How can something immaterial be subject to the physical evolutionary mechanisms that are postulated to explain the development of every aspect of the human species?

How can an immaterial mind be produced by matter and physical influences?

It's an enigma. At least for the naturalistic materialist.