[BTW, I'm still dictating these blogs using Dragon NaturallySpeaking. I'm trying to be alert for typographical errors caused by the software, but if you are still slipping by. I will have about a week between the time I wrote this blog, and the due date for the next blog. Hopefully medication and therapy will allow me to get back to typing by that time.]
Brain machine interfaces are important not just for "bionics" but also for interfaces that would allow quadriplegics and those with neurodegenerative diseases to interface with the outside world. One of the key questions in developing a brain machine interface is: What is the nature of the information that is to be interfaced? With sensory information such as been discussed in the two previous blogs, we need to know two things: (1) how much information do we want to input to the brain, and (2) what pattern does the brain expect to see? With the visual and auditory prosthetic discussed in Monday's blog, researchers and doctors utilize residual neural function in the eye and ear, respectively, and simply provide a pattern of electrical stimulation that is "mapped" in a manner similar to the normal input to retina or cochlea. Tactile and proprioceptive sensation, as required for an effective bionic limb, is a little bit more complex, since the inputs will likely need to be transmitted directly to the appropriate area of the brain that normally receives input from limbs. Likewise advanced improvements in visual and auditory prosthetics – the degree of sophistication required to truly replace sight and sound – will also need to provide inputs directly to the visual and auditory processing regions of the brain.
This problem is already being faced by the researchers working on the Revolutionizing Prosthetics program by DARPA, and that direct brain control of motor movements also necessitates interfacing with the part of the brain that normally controls muscles. Both of these problems require a means of either transmitting any electrical stimulus directly to the brain or reading the brains electrical activity and translating it to an external device. in many ways this is a separate field of neuroscience, termed Brain Machine Interfacing.
Brain Machine Interfacing, or BMI, is a field with two major goals: (1) understanding the normal brain "code" that corresponds to sensation, movement, memory, or any other cognitive function; (2) providing an appropriate "interface" between neurons and electronics. In many ways part one of BMI is no different from any of the studies of neuroscience, in which we try to better understand the functions of the brain. However, the particular goal of BMI with understanding the brain is to be able to point to specific patterns of neural activity and say "this represents an input" or "this represents a memory."
|"Utah array" http://www.sci.utah.edu/~gk/abstracts/bisti03/|
|"Michigan arrays" by NeuroNexus|
The field of neural prosthetics requires a number of developments before we can reach the goal of true "bionic" prosthetic organs and limbs. In addition, creation of "cyborgs", or cybernetic organisms, is even further in the future, requiring great advances in interfacing between the brain and external devices. In the next blog, I will finish this series on advanced prosthetics, bionics, and brain machine interfaces with the discussion of techniques for interfacing brains and computers by means of "reading" brain activity without electrodes implanted in the brain.
Until next time, take care of your brain. It's better than a poke in the eye with a sharp… electrode!