Memory Explained
The past is never past,
At least while we are alive.
Our memories, though volatile,
Being both ephemeral and re-cognized,
No doubt have some basic persistence.
But how does this past remain,
And what kind of substance
Could there be
That lives outside time?
What makes it so strong
That it can survive
The merciless climate of the brain?
And in what storm’s eye does it reside
In the center of the maelstrom
Of the change and growth of cells?
What be this grain that persists
Among the shifting sands of time?
All this we shall show
And answer soon
In the search for lost time.
Our rememberings try to describe
Reality as it really was experienced,
But, that sheer essence may elude,
Although some general outline remains.
Then, too, we add to it, subtract from it
And reconnect by association to the new.
Lo, the subjective metes out our reality;
While the objective lies furthest removed.
Perhaps, we may have a memory
That returns from a taste of butterscotch
From which Grandma’s home then arises,
And then of connections further becoming.
How do some crumbs, here, and of the past
Waft back as vapours unto our present?
Do the senses of smell and taste,
Yet more fragile and more insubstantial,
Bear a unique burden of memory,
As more enduring and faithful,
Rising up past the ruins of the rest?
Just noting the butterscotch,
Back then,
Without its tasting,
Would not have made the mark.
Everything is connected
Within the mind,
Each germ of recollection
Ballooning into a revelation.
Time mutates some ancient pastimes,
And so they are not wholly recaptured,
And sometimes rather fallible,
Even altered more by the call to mind,
Yet they are there.
A memory begins as a changing
Connection between two neurons.
The strength of the synapse changes
So that the neurons can communicate.
Thus, the taste of memory
Also activates
The neurons downstream
To do with one’s childhood days.
The neurons have been
Inextricably entwined,
Yet, too, reconsolidate upon recall.
How do we remember
Long after we have forgotten?
How do such apparitions reappear,
Some with no suggestion of their origin,
And sink and swell, float and change,
Withering the acids of time’s reflux?
The memory making process need proteins
For the cellular construction of remembrance,
Yet the life of a protein is but 14 days.
And some hippocampal neurons die,
And some are born anew,
Yet some memory seems immutable.
Does the mind constantly reincarnate?
Aye, our memories must be made
Of a material stronger than cells,
And must be quite specific as well.
While each neuron has but a single nucleus,
It has a teeming mass of dendritic branches,
Connecting to other neurons
At dendritic synapses,
Such as the branches of two trees
Touching in a forest.
So, it is at these tiny crossings
That memories are made;
Not in the trunk of the neuronal tree,
But in its sprawling canopy.
What marks a specific branch
As a memory?
What molecule awaits
The taste of butterscotch?
It has to turn on mRNA
To help make the proteins.
It’s name is
Cyptoplasmic polyadenenylaton
Element binding protein,
A tough assignment of a name
For even my memory to recall,
So, how about CPEB, for short.
Since it was in the brain’s memory center,
Scientists looked for it in sea slugs,
Amazingly finding it in the slug’s neurons.
Upon removing it, the sea slugs
Could not remember a darn thing!
But how does it work,
Existing outside of time?
Well, it has a series of repetitions
In its amino acid repetitions:
QQQLQQQQQQBQLQQQQ,
Where Q is glutamine.
Looking for similar odd repetitions,
What looked like a prion was found!
They are pathogens
Of earth’s nastiest diseases.
However, they are everywhere,
And have two distinct states,
As no other proteins do,
One active and one inactive.
Without guidance from above,
They can switch states
And alter proteomic structure
Without changing DNA,
And then transmit their
New, infectious structure
To neighboring cells
With no transfer of genetic material.
Biology’s sacred rules are violated!
In the brain, CREB proteins are
Sturdy enough to resist time,
They being virtually indestructible.
Yet, they have plasticity,
Being free of the genetic substrate,
To change their shapes,
Creating or erasing a memory.
When we think,
The neurotransmitters
Serotonin and dopamine
Are released by neurons,
Which switch the CPEB protein
Into its active state
By changing their very structure.
The activated CPEB marks
A specific dendritic branch
As a memory,
Recruiting the requisite mRNA
Needed to maintain
Long-term remembrance.
And, yet, prions have
An element of randomness
Built into their structure
Due to the inscrutable
Laws of protein folding
And stoichiometry,
Even becoming active
For no reason.
Ah, such contingency
Is just like Proust predicted:
The remembrance of things past
May not be the remembrance
Of things as they were.
Due to unpredictable and unstable prions,
We have some essential randomness,
For memory obeys nothing outside of itself.