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Grandmother Cells

Neuroscientist Christof Koch of Caltech and Itzhak Fried, who is both a neuroscientist and a practicing neurosurgeon at UCLA Medical School, recently uncovered evidence for a neural coding scheme long ago discarded as implausible. This scheme had been disparaged as the "grandmother cell" hypothesis, because in its reductio ad absurdum version it implies that our memory banks dedicate a single neuron to each person, place, or thing that inhabits our thoughts -- such as Grandma. Most theorists assume that such a complex concept must be supported by large populations of cells, each of which corresponds to one component of the object -- like the bun, the bifocals, and the woolen sweater of Grandma.

Yet Fried and Koch have found neurons that act very much like grandmother cells. Their subjects were epileptics who had electrodes temporarily inserted into their brains to provide information that could guide surgical treatment. The researchers monitored the output of the electrodes while showing the patients images of animals, people, and other things. A neuron in the amygdala of one patient spiked only in response to three quite different images of Bill Clinton -- a line drawing, a presidential portrait, and a group photograph. A cortical cell in another patient responded in a similar way to images of characters from The Simpsons. In future experiments, Koch and Fried plan to show patients photographs of their grandmothers to see if they can locate actual grandmother cells.

It makes intuitive sense, Koch says, that our brains should dedicate some cells to people and things frequently in our thoughts. He adds that his findings might seem less surprising if one realizes that neurons are much more than simple "threshold" switches that fire whenever incoming pulses from other neurons exceed a certain level. A typical neuron receives input from thousands of other cells, some of which inhibit rather than encourage the neuron's firing. The neuron may in turn encourage or suppress firing by some of those same cells in complex positive or negative feedback loops.

In other words, a single neuron may resemble less a simple switch than a customized minicomputer, sophisticated enough to distinguish your grandmother from Grandma Moses. If this view is correct, meaningful messages might be conveyed not just by hordes of neurons screaming in unison but by a small group of cells whispering, perhaps in a terse temporal code.

If true, I wonder if you could zap that single Grandma neuron -- and as a consequence not recognize your Grandma the next time you saw her.  Surely, there must be other neural cells that also recognize her features in as efficient a way as the cell you zapped.  But....maybe not?  These studies have been done with small electrodes implanted within the human cortex.  You could easily induce a few volts running the opposite way, down the electrode, to kill a particular neural cell (and possibly a few others in the neighborhood -- too bad).  They do these electrode implants on patients suffering from epilepsy to identify where exactly in the cortex the epileptic seizures emanate from, so they can excise them later through surgery.

If you ran into a neuron that was associated with an unreasonable fear or phobia, or a really bad memory, you might indeed want to zap it away.  Personally, I'd like to zap the cell that remembers "Sparks", a particularly nasty bully boy who inhabited my neighborhood when I was a small child -- a guy who gave me a lot of grief growing up.  It would do me no good to kill Sparks physically now, 50+ years later, since his legacy would remain in my brain.  But if I could kill the legacy itself -- that is truly an enticing thought!

Unlike Jim Carey in Eternal Sunshine of the Spotless Mind, I'd not want to expunge the memories of my ex-girlfriends, ex-wife or other lovers.  In the fullness of time, I've managed to survive and overcome the hurt & pain of lost love.  It was not a particularly easy thing to do -- and it would have been unbearable except for the knowledge that almost everyone has to do it at some point in their lives.  Love hurts, but the memory of its burning pain is one thing I'd rather not lose.  It measures off the dues paid to be a human being.

There would probably be a number of other things I'd want to expunge from my brain, but for the fact that my nature doesn't include a large proportion of vengeance.  Sure, I've had a few asshole bosses and colleagues over the years that gave me some grief, but I can't say that I harbor any ill-will towards them.  Perhaps that's because they ultimately self-destructed, in the fullness of time -- and I watched it happen, while I myself survived.  At any rate, they don't plague my ongoing thoughts, nor my dreams.

I could wish to expunge the burned-in images of Nazi atrocities, or the killing fields of Pol Pot, or the starvation occurring in Africa due to current political unrest.  To what end?  These images will repeat forever, given mankind's propensity for mayhem.  There is no keeping up with them.  Call me callous, but I don't internalize them to the point that I lose any sleep over it.

I have no images of child abuse that I can throw in the burning barrel, nor any memories of such a powerful negative nature that I would want them gone forever.  I barely even remember my childhood, and so I would not want to lose any significant part of it -- other than that Sparks guy!


"How happy is the blameless vestal's lot!  The world forgetting, by the world forgot.  Eternal sunshine of the spotless mind!  Each pray'r accepted, and each wish resign'd." -- Alexander Pope

Much of this material extracted from:  http://www.american-buddha.com/myth.mind.control.htm


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