by clicking the "Next" arrow.
by clicking on the page.
the page around when zoomed in by dragging it.
the zoom using the slider when zoomed-in.
by clicking on the zoomed-in page.
by entering text in the search field, and select "This Issue" or "All Issues"
by clicking on thumbnails to select pages, and then press the print button.
displays sections with thumbnails and descriptions.
displays a slider of thumbnails. Click on a page to jump.
allows you to browse the full archive.
about your subscription?
Mindful : October 2018
(presumably in silicon) a person’s mind, as Hay- worth and others dream. A decade after scien- tists unveiled the first such wiring diagram—of the roundworm C. elegans (302 neurons, 7,000 synapses)—connectomics is hot in pursuit of its Everest: the connectome of the 86-billion-neuron, 100-trillion-synapse human brain. Last year one of Hay worth’s colleag ues, Davi Bock, led a team that obtained electron microscopic images of the fruit fly brain and its 100,000 neurons, the initial step in mapping the first connectome of an actual brain. (C. elegans has a primitive nervous system, not a brain.) At the Allen Institute for Brain Science in Seattle, neuroscientists are taking the first steps toward a mouse connectome: They slice a one-cubic- millimeter chunk of mouse brain into 25,000 pieces, imaging each with an electron micro- scope that shows the neurons and axons. One cubic millimeter is one-thousandth of a mouse brain, or one-billionth of a human brain, Bock said. You begin to see why some scientists doubt this will ever work. The mouse proj- ect—again, just 0.1% of the brain, and 100,000 neurons—is costing tens of millions of dollars, and is only a baby mouse step toward a full mammalian connectome. But it took $3 billion and more than a decade to sequence the first human genome, compared to hours and $1,000 today. So, some would like to assume that mas- sive technological advances will bring a human connectome within scientific reach. To prepare for that day, a tech start-up called Nectome proposes to preserve brains with glutaraldehyde, as its founders did with a pig brain, winning an $80,000 science prize from the Brain Preservation Foundation. Because, as noted above, synapses fall apart quickly once life ceases, imaging a connectome requires a brain that’s just barely dead. This of course triggered the euthanasia fracas. Euthanasia is not, however, a requirement of this technology (should it ever come into being). People who die of natural causes could presumably have uploaders standing by. Before you dismiss this as sci-fi nonsense, note that Nectome has a $1 million grant from the National Institutes of Health for its preser- vation and connectome R&D. The preservation technique that won the prize from his founda- tion, Hay worth says, “appears to preserve the full range of structural and molecular features that modern neuroscientific theories postulate underlie the encoding of all of the types of long- term memories that make a person unique.” Someone undergoing the procedure “is electing to ‘hit pause’...in order to optimally preserve the full informational content of their brain.” Just to be clear, we’re not talking about reani- mation, cryonics-style. Hay worth and Nectome believe the future lies not in reviving the dead but in full-brain “emulation,” or recreating in digital form a brain’s wiring diagram and thus its information content. Nectome describes its mission as preserving a brain “well enough to keep all its memories intact: from that great chapter of your favorite book to the feeling of cold winter air, baking an apple pie, or having dinner with your friends and family. If mem- ories can truly be preserved...we believe that within the century it could become feasible to digitize your preserved brain and use that infor- mation to recreate your mind.” The scientific questions about brain emula- tion are as fascinating as they are unanswered. In addition to knowing which neurons connect with which—the basic connectome—do you also need to know the strength of each synapse? the firing patterns? the distribution of neurotrans- mitters? the subjective sense the brain’s owner gets when a particular synapse operates? Oh, and one little detail: The information con- tent of a cubic millimeter of brain tissue is about 1 petabyte of data, Bock says. An entire mouse brain comes to 1,000 petabytes. At 1 billion petabytes—1 petabyte being equal to 1 million gigabytes—the informational content of a single human brain exceeds the total storage capacity of the cloud today! But would-be brain emulators don’t let such details deter them. Instead, they predict, as a 2018 study did, that “eventually the reading of memories...will become the daily routine of con- nectomics.” Those wiring diagrams, including An unusually romantic view of connectomic innovation appears in the Netflix hit Black Mirror. In the episode “San Junipero,” two women meet in a simulated California party town (circa 1987): a paradise for the dead and dying, where, if they choose to have their minds uploaded, they can SCI-FI | Heaven on Earth? leave behind their lonely end- of-life. San Junipero gives them not only good times, but a second chance at human connection, self-expression, and healing. The question remains whether this use of tech represents a far extreme of escapism or a compassion- ate, human-made heaven. BECAUSE SYNAPSES FALL APART QUICKLY ONCE LIFE CEASES, IMAGING A CONNECTOME REQUIRES A BRAIN THAT’S JUST BARELY DEAD. brain science 36 mindful October 2018