[ExI] Cryonics punched cards and the brain

[John Clark]

On Sun, Jan 24, 2016 at 7:49 AM, Anders Sandberg <anders at aleph.se> wrote:

​> ​
> Neat. Generally LTP is seen as the first of a longer cascade of fixation
> of memories. Most research has been about cellular skeleton changes, but
> perineuronal nets might also work.
> It might actually be a good experiment for cryonics to see what the
> process does to these nets. (I think John mixed up the perioneuronal net
> (protein networks) with perineuronal space in the sleep reference. )
>

​
As I understand it ​
the extracellular matrix
​is​
 the space between brain cells
​ and that is where the ​
perineuronal net​
​is located along with a lot of fluid, and the volume of the ​
extracellular matrix
​changes a great deal ​between sleep and wakefulness so the net must be
tough enough to resist damage even when things get crowded.  But I'm no
expert on this so I may have misunderstood.

​> ​
> Incidentally, the Sejnowski lab had a nice result on the distribution of
> synaptic strengths:
> Bartol, T. M. Jr. Bromer, C. Kinney, J. P. Chirillo, M. A. Bourne, J. N.
> Harris, K. M. Sejnowski, T. J.
> <http://papers.cnl.salk.edu/index.php?SearchText=Bartol%2C%20T.%20M.%20Jr.%20Bromer%2C%20C.%20Kinney%2C%20J.%20P.%20Chirillo%2C%20M.%20A.%20Bourne%2C%20J.%20N.%20Harris%2C%20K.%20M.%20Sejnowski%2C%20T.%20J.>
>  Nanoconnectomic upper bound on the variability of synaptic plasticity,
> eLife, 4:e10778, 2015
>
> http://papers.cnl.salk.edu/PDFs/Nanoconnectomic%20upper%20bound%20on%20the%20variability%20of%20synaptic%20plasticity%202015-4475.pdf
> They show that each synapse stores at most about 4.7 bits. While their
> press material claims this is "an order of magnitude more" than previous
> estimates, the actual estimate most people have been doing is about one
> bit, so the difference isn't dramatic. But doing nanoconnectomics is an
> awesome method.
>

​I wish we knew how much redundancy there is in the brain, biological
operations are not nearly as reliable as the electronic operations we use
in computers so I would guess there must be a lot of
redundancy
​ to ensure accuracy.

 John K Clark

 ​
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