Wednesday, August 12, 2015

Grid Cells

Lately when I take a walk at night I have the impression that I am walking down a massive set of stairs and that my arms are softly flapping a small pair of cheap novelty chicken wings. I could be walking uphill and the sensation is still the same. My arms swing in their usual day-metered rhythm still the sensation sneaks in somewhere between the truth of the motion and consciousness of the movement. I have no memory to link this to. I do not recall ever dressing as a bird and walking down a huge set of stairs at night but the impression is there, assembled from a diverse array of physical or muscle memories. 

Some time ago, I was living in Washington Heights where a huge set of stairs are set and connect to 181st street. Down those stairs to the subway each morning and up those stairs home each night. They were massive and made of concrete. The paint long worn away from the steel tubing that ran as rails up the center and sides of the stairs.  Climbing one morning, after grabbing coffee and the Times, my hand idly gliding above the rail, the oxidation and subsequent polish by hand oils of the steel reminded me of a piece of playground equipment from my elementary school that blurred with a kind of polygonal climbing structure from a park I used to play at and the two seemed inseparable until my hand grazed an overgrown bush and I recalled a hedge I used to pass every day that was filled with little pumpkin shaped berries. There was a scent of spice and dusty wood that the hedge emitted. I realized then that I had been living in Manhattan in the same location for over five years and that the duration of my stay was second only to the house I grew up in and how little prepared I was upon leaving home for the constant transition that would mark my life in college and after. A welter of memories unlocked there and I stared emptily at the overgrown bush. I was alone on the massive stairs but could sense the city's eye on me, but I stayed still there and seemed to cache the memories there- that bush, some unnamed city shrub that grows despite all odds out of arsenic, cigarette butts and urine, became an outpost - a lobby for my long gone home.

The method of loci is a mnemonic aid credited to Simonides of Ceos.  Simonides was a poet known for his odes to Castor and Pollux.  Castor and Pollux were mythic twins born from a giant egg laid by Leda after she was raped by Zeus.  Zeus was a swan that time. Other times he was other animals.   One time he was a shower of gold.  Some versions have Helen of Troy and Clytemnestra as co-incubants in Leda's egg.  Castor was mortal and Pollux was immortal, but when Castor was killed, Pollux made a deal with Zeus.  They would split Pollux's immortality.  As a result, the twins split their time between Elysium and Hades. 

In 2005, scientists discovered that the hippocampus houses a type of neuron that controls spatial location, called a grid cell.  The grid cells are so named because if you connect the center of their firing fields they create a triangular grid.  Images of this grid look a little bit like a flattened segment of a geodesic dome.  Early in his talk, Everything I know, Buckminster Fuller describes how the triangle is nature's essential structure, that is, how anything in nature can be broken down into a finite number of triangles.  That the triangle provides an irreducible stability. Likewise, scientists claim that grid cells in essence project a Euclidian space upon our environment, that as we plot our way through any given space a neural grid lights up and guides us forward. We naturally triangulate.   

 The first person to see the hippocampus probably had not yet seen a seahorse and the first person to have seen both a seahorse and the hippocampus probably did not think to apply the shape of the animal to the corresponding shape within our neural anatomy.  It took time some time for that physiology to differentiate itself from the rest of the stuff that surrounds it, for it to be identified as its own kind of wrinkle and for its placement to be considered within the larger map of our behaviors. Seeing images online, it still may take a bit of a leap to find within the particular folds similarities to the ponies del mar, but the name has stuck.   The hippocampus houses our memories, emotions, and spatial relationships.

Female seahorses spray their eggs into the male.  The male fertilizes the eggs and carries them in a pouch until they're term.

 So Simonides, the poet, had just played a party in the house of nobleman names Scopas. Scopas screwed Simonides out of half of his pay. Soon after, a servant told Simonides that there were two young men who wanted to speak with him outside.  Simonides swallowed his outrage at the stingy host and walked past the revelers to see what they young men wanted. Once outside he found no one.  It was that kind of night and he began to get the sense that the host was playing a prolonged trick on him and he got up the nerve to go back inside and pick the man apart.  Scopas was a nobleman.  He shares a name with a famous sculptor who lived about a hundred years after Simonides of Ceos died, so the name Scopas lived on, even if the nobleman in question did not.  Simonides turned to rejoin the party just in time to see Scopas' roof fall in. Houses at that time used columns and lintels. If the house was stone, and I imagine it as stone, a single roof tile weighed 66 lbs. The roof would have been supported by the columns, which means one or more of the columns would have had to have buckled. Given Scopa's cheapness we can assume that he tried the same sharp deal with his builders and wound up with his roof in his lap.  Everyone inside his house was crushed. Simonides ran to get help and the people of Ceos worked through the night packing out the wreckage of Scopas' house in a vain search for survivors. When the wreckage was cleared, the remains were found but the party goers were unidentifiable.  When asked who was at the party, Simonides couldn't recall until he stepped through the wreckage. As he walked through he recalled the place settings and so could identify the remains of each person.  He required a means of organizing his thoughts and by walking he found his memory enabled by the space.

Castor and Pollux are frequently depicted on horseback. In art, they are identical.  Though they are depicted as identical, Pollux's ascribed parentage is the immortal Zeus, while Castor's is the mortal Tyndareus. It's odd that twins factor into a story about memory. Among the twins I know, I've usually had to identify a few subtle differences to tell them apart.  It's not unusual though that something so large as immortality would separate two people who were otherwise identical. In myth, the gods' favor is always inscrutable. The two brightest stars in the constellation Gemini are named for Castor and Pollux. Pollux, the brightest, is an orange-hued giant star 34 light years from earth.  Castor, the second brightest, is actually a cluster of six stars in a single system 54 light years from earth.  The rest of Gemini's 83 stars can be connected to appear like two stick figures arm in arm. From June 20 to July 20th, the sun is in Gemini.

A woman with a dress like a lost book of the bible, the book of stars, billowed by on an August morning breeze. This coolness is temporary but it calls out the signal changes soon to come. The light is changing. The sliver that cuts down Maiden Ln and bounces off of tower 4 has shifted by a degree that reduces the ambient refraction on the eastern bank of Broadway. A second beam from the east still creeps up Maiden Lane on a delay. The zip that people cross on the east bank of Church street has moved further west, lengthened past the point where I can catch the gap in the shadow. The light is starting to shed some of its summer leavening. The weight and scorch of July is all but lost within a given ray. Though the heat has returned, it has be born out differently- a trapped heat, a leftover heat, fuming down from the upper dome of the atmosphere laden with vaporous cargo.

It will be hard to forget how merciful an August evening can be in Brooklyn.  The trees that line the street, mostly plane trees, have grown lusty from the sun and rain. The leaves, heavy and thick, lace above the street to form a tunnel of green. Prospect Park lies ahead. In the tumble down dusk the shadows of the park's shaggy trees pulsate with all of the life missing from the hot cement streets, where the day's last heat radiates out leaving only a perfect cool respite. The city's details dimmed down to points of artificial light. 

As I pass each plane tree on my walk towards the park, the space between the nearest trees becomes apparent and while the tree from afar still look like a continuous canopy, the nearness reveals the character.  Just as when we look up with our naked eyes and the stars appear to be little more than pin points, with a telescope the difference that distance hides is revealed.  When looking to the past the events all cluster and it may seem for a moment that they disappear into single swathe of time, but taking a walk can open things back up.    

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