Microsoft Word Kurzweil, Ray The Singularity Is Near doc

Scanning Using Nanobots.
Although these largely noninvasive means of scanning the brain from outside the skull are 
rapidly improving, the most powerful approach to capturing every salient neural detail will be to scan it from inside. 
By the 2020s nanobot technology will be viable, and brain scanning will be one of its prominent applications. As 
described earlier nanobots are robots that will be the size of human blood cells (seven to eight microns) or even 
smaller.
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Billions of them could travel through every brain capillary, scanning each relevant neural feature from up 
close. Using high-speed wireless communication, the nanobots would communicate with one another and with 
computers compiling the brain-scan database. (In other words, the nanobots and computers will all be on a wireless 
local area network.)
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A key technical challenge to interfacing nanobots with biological brain structures is the blood-brain barrier 
(BBB). In the late nineteenth century, scientists discovered that when they injected blue dye into an animal's 
bloodstream, all the organs of the animal turned blue with the exception of the spinal cord and brain. They accurately 
hypothesized a barrier that protects the brain from a wide range of potentially harmful substances in the blood, 
including bacteria, hormones, chemicals that may act as neurotransmitters, and other toxins. Only oxygen, glucose, 
and a very select set of other small molecules are able to leave the blood vessels and enter the brain. 
Autopsies early in the twentieth century revealed that the lining of the capillaries in the brain and other nervous-
system tissues is indeed packed much more tightly with endothelial cells than comparable-size vessels in other organs. 
More recent studies have shown that the BBB is a complex system that features gateways complete with keys and 
passwords that allow entry into the brain. For example, two proteins called zonulin and zot have been discovered that 
react with receptors in the brain to temporarily open the BBB at select sites. These two proteins playa similar role in 
opening receptors in the small intestine to allow digestion of glucose and other nutrients. 
Any design for nanobots to scan or otherwise interact with the brain will have to consider the BBB. I describe 
here several strategies that will be workable, given future capabilities. Undoubtedly, others will be developed over the 
next quarter century. 
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An obvious tactic is to make the nanobot small enough to glide through the BBB, but this is the least practical 
approach, at least with nanotechnology as we envision it today. To do this, the nanobot would have to be twenty 
nanometers or less in diameter, which is about the size of one hundred carbon atoms. Limiting a nanobot to these 
dimensions would severely limit its functionality. 
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An intermediate strategy would be to keep the nanobot in the bloodstream but to have it project a robotic arm 
through the BBB and into the extracellular fluid that lines the neural cells. This would allow the nanobot to 
remain large enough to have sufficient computational and navigational resources. Since almost all neurons lie 
within two or three cell-widths of a capillary, the arm would need to reach only up to about fifty microns. 

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Analyses conducted by Rob Freitas and others show that it is quite feasible to restrict the width of such a 
manipulator to under twenty nanometers. 
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Another approach is to keep the nanobots in the capillaries and use noninvasive scanning. For example, the 
scanning system being designed by Finkel and his associates can scan at very high resolution (sufficient to see 
individual interconnections) to a depth of 150 microns, which is several times greater than we need. Obviously 
this type of optical-imaging system would have to be significantly miniaturized (compared to contemporary 
designs), but it uses charge-coupled device sensors, which are amenable to such size reduction. 
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Another type of noninvasive scanning would involve one set of nanobots emitting focused signals similar to 
those of a two-photon scanner and another set of nanobots receiving the transmission. The topology of the 
intervening tissue could be determined by analyzing the impact on the received signal. 
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Another type of strategy, suggested by Robert Freitas, would be for the nanobot literally to barge its way past the 
BBB by breaking a hole in it, exit the blood vessel, and then repair the damage. Since the nanobot can be 
constructed using carbon in a diamondoid configuration, it would be far stronger than biological tissues. Freitas 
writes, "To pass between cells in cell-rich tissue, it is necessary for an advancing nanorobot to disrupt some 
minimum number of cell-to-cell adhesive contacts that lie ahead in its path. After that, and with the objective of 
minimizing biointrusiveness, the nanorobot must reseal those adhesive contacts in its wake, crudely analogous to 
a burrowing mole."
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Yet another approach is suggested by contemporary cancer studies. Cancer researchers are keenly interested in 
selectively disrupting the BBB to transport cancer-destroying substances to tumors. Recent studies of the BBB 
show that it opens up in response to a variety of factors, which include certain proteins, as mentioned above; 
localized hypertension; high concentrations of certain substances; microwaves and other forms of radiation; 
infection; and inflammation. There are also specialized processes that ferry out needed substances such as 
glucose. It has also been found that the sugar mannitol causes a temporary shrinking of the tightly packed 
endothelial cells to provide a temporary breach of the BBB. By exploiting these mechanisms, several research 
groups are developing compounds that open the BBB.
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Although this research is aimed at cancer therapies, 
similar approaches can be used to open the gateways for nanobots that will scan the brain as well as enhance our 
mental functioning. 
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We could bypass the bloodstream and the BBB altogether by injecting the nanobots into areas of the brain that 
have direct access to neural tissue. As I mention below, new neurons migrate from the ventricles to other parts of 
the brain. Nanobots could follow the same migration path. 
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Rob Freitas has described several techniques for nanobots to monitor sensory signals.
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These will be important 
both for reverse engineering the inputs to the brain, as well as for creating full-immersion virtual reality from 
within the nervous system. 
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To scan and monitor auditory signals, Freitas proposes "mobile nanodevices ... [that] swim into the spiral 
artery of the ear and down through its bifurcations to reach the cochlear canal, then position themselves as 
neural monitors in the vicinity of the spiral nerve fibers and the nerves entering the epithelium of the organ 
of Corti [cochlear or auditory nerves] within the spiral ganglion. These monitors can detect, record, or 
rebroadcast to other nanodevices in the communications network all auditory neural traffic perceived by 
the human ear." 
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For the body's "sensations of gravity, rotation, and acceleration," he envisions "nanomonitors positioned at 
the afferent nerve endings emanating from hair cells located in the ... semicircular canals." 
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For "kinesthetic sensory management ... motor neurons can be monitored to keep track of limb motions 
and positions, or specific muscle activities, and even to exert control." 
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"Olfactory and gustatory sensory neural traffic may be eavesdropped [on] by nanosensory instruments." 
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"Pain signals may be recorded or modified as required, as can mechanical and temperature nerve impulses 
from ... receptors located in the skin." 

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Freitas points out that the retina is rich with small blood vessels, "permitting ready access to both 
photoreceptor (rod, cone, bipolar and ganglion) and integrator ... neurons." The signals from the optic 
nerve represent more than one hundred million levels per second, but this level of signal processing is 
already manageable. As MIT's Tomaso Poggio and others have indicated, we do not yet understand the 
coding of the optic nerve's signals. Once we have the ability to monitor the signals for each discrete fiber 
in the optic nerve, our ability to interpret these signals will be greatly facilitated. This is currently an area 
of intense research. 
As I discuss below, the raw signals from the body go through multiple levels of processing before being 
aggregated in a compact dynamic representation in two small organs called the right and left insula, located deep in the 
cerebral cortex. For full-immersion virtual reality, it may be more effective to tap into the already-interpreted signals 
in the insula rather than the unprocessed signals throughout the body. 
Scanning the brain for the purpose of reverse engineering its principles of operation is an easier action than 
scanning it for the purpose of "uploading" a particular personality, which I discuss further below (see the "Uploading 
the Human Brain" section, p. 198). In order to reverse engineer the brain, we only need to scan the connections in a 
region sufficiently to understand their basic pattern. We do not need to capture every single connection. 
Once we understand the neural wiring patterns within a region, we can combine that knowledge with a detailed 
understanding of how each type of neuron in that region operates. Although a particular region of the brain may have 
billions of neurons, it will contain only a limited number of neuron types. We have already made significant progress 
in deriving the mechanisms underlying specific varieties of neurons and synaptic connections by studying these cells 
in vitro (in a test dish), as well as in vivo using such methods as two-photon scanning. 
The scenarios above involve capabilities that exist at least in an early stage today. We already have technology 
capable of producing very high-resolution scans for viewing the precise shape of every connection in a particular brain 
area, if the scanner is physically proximate to the neural features. With regard to nanobots, there are already four major 
conferences dedicated to developing blood cell-size devices for diagnostic and therapeutic purposes.
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As discussed in 
chapter 2, we can project the exponentially declining cost of computation and the rapidly declining size and increasing 
effectiveness of both electronic and mechanical technologies. Based on these projections, we can conservatively 
anticipate the requisite nanobot technology to implement these types of scenarios during the 2020s. Once nanobot-
based scanning becomes a reality, we will finally be in the same position that circuit designers are in today: we will be 
able to place highly sensitive and very high-resolution sensors (in the form of nanobots) at millions or even billions of 
locations in the brain and thus witness in breathtaking detail living brains in action.