One of the inspiring things about science and technology is that amazing discoveries, inventions, and just curious and astonishing developments keep happening day by day, compounding on one another to create an impression of progress of the sort we do not always get from watching the world of politics. In this first edition of "Now for Something Completely Different" I have three articles on advances in synthetic and real brain circuits.
(Before and after schematics illustrating volatile memory properties induced by application of voltage inputs. Notice how the WO3-X-5 filament looks like a Christmas tree in blue snow, image credit: MANA, NIMS)
Kurzweil AI.net brings us the story of Synaptic electronic circuits that learn and forget like neural processes, which may pave the way for new classes of electronic devices that simulate, and mimic neural circuits in the brain, and may open up new means of researching those with memory problems, and smart people who can't find their keys when they get high.
Rui Yang, Kazuya Terabe and colleagues at the National Institute for Materials Science (NIMS), and the International Center for Materials Nanoarchitectonics (MANA) in Japan and at the California NanoSystems Institute/UCLA have developed “nanoionic” (processes connected with fast ion transport in all-solid-state nanoscale systems) devices capable of a broad range of neuromorphic and electrical functions. ...
Synaptic devices that mimic the learning and memory processes in living organisms are attracting interest as an alternative to standard computing elements to help extend performance beyond current physical limits. However, artificial synaptic systems have been hampered by complex fabrication requirements and limitations in the learning and memory functions they mimic. ...
“These capabilities open a new avenue for circuits, analog memories, and artificially fused digital neural networks using on-demand programming by input pulse polarity, magnitude, and repetition history,” the researchers conclude.
HP Labs researchers may have figured out a way to create a chip that generates neuron-like spikes (sharp signal pulses), using a combination of memristors and capacitors to create a spiking output pattern, Ars Technica reports.
Neurons encode information in the pattern and timing of spikes. The researchers used a simplified model of neurons based on sodium-potassium ion channels to turn the neuron on and off.
Each unit consists of a capacitor (to allow it to build up charge) in parallel to a memristor (which allows the charge to be released suddenly. The combination produces spikes of activity as soon as a given voltage threshold is exceeded.
For more information please read A scalable neuristor built with Mott memristors, by Matthew D. Pickett, Gilberto Medeiros-Ribeiro, R. Stanley Williams, in Nature Materials, 2012, DOI: 10.1038/NMAT3510
And, I'm unable to resist the exquisite symmetry from a little noticed post I did on December 7, 2012, entitled MIT and Harvard researchers create 3D brain tissues in petri disk, where I report sort of an opposite development, circuits of real brain tissue simulating the function of electric circuits "manufactured" using photomasking techniques similar to those developed for producing integrated circuit chips. Scientists at MIT and Harvard have developed an inexpensive way of Creating 3D brain tissues in a lab dish, using brain cells from the primary cortex of rats, opening up new areas of brain and neural research.
(Graphic credit: U. Gurkan et al./Advanced Materials)
Other researchers have been growing other organ tissues in petri dishes, but other organs are more homogenous than the brain. The "incredible heterogeneity" of the brain presents special challenges as the brain contains intricate interconnections of diverse cell types, such as inhibitory and excitatory neurons, glia cells, and other support networks. This new technique allows sequential layering of these different types of cells, embedding them in plastic gel screens similar to overhead projector sheets rather than the vastly more expensive scaffolding grids used in integrated circuit technology.
The new technique yields tissue constructs that closely mimic the cellular composition of those in the living brain, allowing scientists to study how neurons form 3D connections and to predict how cells from individual patients might respond to different drugs.
The work also paves the way for developing bioengineered implants to replace damaged tissue for organ systems, according to the researchers.
“We think that by bringing this kind of control and manipulation into neurobiology, we can investigate many different directions,” says Utkan Demirci, an assistant professor in the Harvard-MIT Division of Health Sciences and Technology (HST).
Researchers have managed to get the resolution of their gel layer tissue cubes down to a width of 10 microns, which is similar to the size of a body cell. Their current goal is to create a cubic millimeter of brain tissue consisting of 100,000 cells with 900 million connections. If we pause and think about that for a moment, we glimpse just the tip of the iceberg of the astounding complexity of a full human brain.
In the long term, the researchers hope to gain a better understanding of how to design tissue implants that could be used to replace damaged tissue in patients. Much research has been done in this area, but it has been difficult to figure out whether the new tissues are correctly wiring up with existing tissue and exchanging the right kinds of information.In future work, doctors may be able to take brain cells from patients with certain neurological disorders and turn them into stem cells that can be grown in these 3-D lab dishes to help develop drugs targeted to these disorders much more quickly than would be the case if experiments had to be done to brain cells still attached to humans, where research is limited by human research ethics committees. (ho, ho, ho! I"m joking here, but this research does raise the question of at what point do we need to worry about networks of brain cells "experiencing pain?" )
Maybe they need to hook these lab dish brains to some eyeballs, legs and vocal chords so they can do input-output tests. Of course, we need to start to prepare ourselves for the day one of these new lab dish creatures talks back and turns out to be smarter than we are. At the rate we are seeing such extraordinary advances in brain science this day may be sooner than we expect.
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Happy Holidays, Peace on Earth, and a Happy New Year