Volume 1, Issue 4 
4th Quarter, 2006


Scope and Resolution in Neural Prosthetics and Special Concerns for the Emulation of a Whole Brain

Randal Koene, Ph.D.

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KoeneWithin this applied neuroscience, what is distinctive about whole brain emulation? Whole brain emulation specifically initializes evolving intelligence in another substrate with the recognizably individual minds of human beings. Whether 1,000 years of development will show a significant difference between a society to which were added only entirely artificial descendants created by human minds, or which include descendants of human minds, is an open question. Whatever that answer may be, a belief in the utility of the scientific method automatically qualifies whole brain emulation for the same consideration. 

The main difference between the expressed sentiments of individual scientists is their estimate of the time spans required to reach these milestones of understanding. Now I would like to contrast general function and subject specific prostheses.

Koene
Image 5: General vs. Subject Specific Prosthese

Both cochlear implants and retinal prostheses in their current form are largely general function prosthetics. You can think of a wooden leg that is supplied only in a standard length. For examples of current subject specific prostheses, consider instead modern prosthetic legs or wigs and dental implants.

Dental implants actually have been around for quite a long time. Ancient Egyptians used shells to make dental implants that were forced into the jaw bone, presumably without modern anesthetics. The subject specific aspect appears rather quickly when you deal with neural prostheses. For instance, the comparison of brains of musicians and non-musicians has clearly shown the plasticity and adaptation of the brain to experience.

Thus the prosthetic corpus callosum and motor cortex of a musician, to be satisfactory, would have to be more than a general function prosthetic. This is important for every patient who receives a neural prosthetic. Imagine the prosthetic substrate that is needed to preserve the neo cortical memory representations of your grandchildren.

Here I mention Eric Kandel, because he so clearly demonstrated the significant processes of memory formation that change not only the active state, but also the physical morphology of our brain as a result of experience.[1] As a medical procedure, moving into brain emulation in health care, whole brain emulation need not be the result of a whole series of separate neural prosthetic replacements. Instead, here are some examples of ideal or wholesale approaches. 

Koene
Image 6: Brain Emulation in Health Care

The procedure that probably involves the fewest advances in instrumentation is to remove and fixate, then section in a microtome, followed by systemic microscopy and then three-dimensional and functional reconstruction, in a computer for instance. This procedure is being actively developed as a research tool. The lab of Bruce McCormick at Texas A&M University developed knife edge scanning and is acquiring multi-terabyte data sets of mouse brain for reconstruction efforts in the Blue Brain Project.[2]

In a slightly different approach, the lab of David Kleinfeld at UCSD is acquiring similar data using an all optical approach involving two- photon microscopy and the sequential ablation of layers of the fixated brain using short pulses of a laser.[3] A more complicated procedure that’s popular for its gradual, potentially less disruptive approach is to infuse the brain in vivo with a large number of nanoscale machines; nanobots that can either record brain morphology and active states or themselves take over neural functions. 

Any medical procedure that leads to whole brain emulation will have to address the subjective experience: How whole is the prosthetic in terms of personal identity and self awareness? That can include a range of personal characteristics and sensations; characteristics such as specific faculties and behavior, sensations such as the perceived continuity of physical and mental existence. Consequently, experimental emulation of invertebrates and animal brains can test technologies, but neither can provide adequate feedback about this subjective experience. 

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Footnotes
1.The
Eric Kandel Research laboratory has focused on developing reductionist approaches to learning designed to explore the molecular mechanisms of memory storage and to uncover new aspects of neuronal signaling. October 25, 2006 3:40PM EST (back to top)

2. Biography of Bruce H. McCormick, Texas A&M University.  October 29, 2006 4:14PM EST (back to top)

3. Biography of David Kleinfeld, Ph.D., UCSD. October 29, 2006 4:17PM EST (back to top)

 

 

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