27 September 2010

Micro-Electronic Brain Implant Supervises Brain Re-Wiring

When the human brain is damaged from trauma, stroke, infection, or tumour etc., the damaged tissue does not re-grow itself spontaneously. Instead, the person must learn to compensate for the loss of function. Some brain plasticity may occur, as undamaged parts of the brain take responsibility for some of the functions which the destroyed parts previously carried out. But damaged brain does not heal.

Researchers at Case Western Reserve University intend to change that, by using implanted electronics devices which can help teach the brain how to re-wire itself to allow disconnected parts of the brain to become connected -- and functional -- again.
Pedram Mohseni, a professor of electrical engineering and computer science at Case Western Reserve University, and Randolph J. Nudo, a professor of molecular and integrative physiology at Kansas University Medical Center, believe repeated communications between distant neurons in the weeks after injury may spark long-reaching axons to form and connect.

Their work is inspired by the traumatic brain injuries suffered by ground troops in Afghanistan and Iraq.

...Mohseni has been building a multichannel microelectronic device to bypass the gap left by injury. The device, which he calls a brain-machine-brain interface, includes a microchip on a circuit board smaller than a quarter. The microchip amplifies signals, called neural action potentials, produced by the neurons in one part of the brain and uses an algorithm to separate these signals – brain spike activity - from noise and other artifacts. Upon spike discrimination, the microchip sends a current pulse to stimulate neurons in another part of the brain, artificially connecting the two brain regions.

...During the next four years, they expect to understand the ability to rewire the brain in a rat model and to determine whether the technology is safe enough to test in non-human primates. If tests show the treatment is successful in helping recovery from traumatic brain injury, the researchers foresee the possibility of using the approach in patients 10 years from now. _Eurekalert
Here is an abstract of a paper published by Mohseni in an IEEE publication from 2008:
This paper reports on the design, implementation, and performance characterization of a high-output-impedance current microstimulator fabricated using the TSMC 0.35 mum 2P/4M n-well CMOS process as part of a fully integrated neural implant for reshaping long-range intracortical connectivity patterns in an injured brain. It can deliver a maximum current of 94.5 muA to the target cortical tissue with current efficiency of 86% and voltage compliance of 4.7 V with a 5-V power supply. The stimulus current can be programmed via a 6-bit DAC with an accuracy better than 0.47 LSB. Stimulator functionality is also verified with in vitro experiments in saline using a silicon microelectrode with iridium oxide (IrO) stimulation sites. _IEEEXplore
The technology for such interventions is in the early stages. The researchers are also working on devices which can be used for a broad range of neurological and psychiatric conditions, and in conjunction with neurosurgery and standard post-surgical rehabilitation.

Eventually such devices will probably be implanted into a damaged area of brain, along with an artificial matrix seeded with a person's own stem cells and growth factors. The devices will be wired to "bridge" from healthy brain on one side of the lesion to healthy brain on other sides of the lesion (corresponding to interrupted pathways). The electronic signals will not only help guide a re-wiring of the brain, but they should also guide the re-growth of new replacement brain tissue of specific replacement types.

Anyone who has read the science fiction novel "Old Man's War" by John Scalzi, should recognise some of the intent behind the early stage, rudimentary devices being developed at Case Western -- and to see where the technology may be heading.

More on a related topic from Brian Wang

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