Glucose-powered neuroelectronics

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 157-164).A holy grail of bioelectronics is to engineer biologically implantable systems that can be embedded without disturbing their local environments, while harvesting from their surroundings all of the power they require. As implantable electronic devices become increasingly prevalent in scientific research and in the diagnosis, management, and treatment of human disease, there is correspondingly increasing demand for devices with unlimited functional lifetimes that integrate seamlessly with their hosts in these two ways. This thesis presents significant progress toward establishing the feasibility of one such system: A brain-machine interface powered by a bioimplantable fuel cell that harvests energy from extracellular glucose in the cerebrospinal fluid surrounding the brain. The first part of this thesis describes a set of biomimetic algorithms and low-power circuit architectures for decoding electrical signals from ensembles of neurons in the brain. The decoders are intended for use in the context of neural rehabilitation, to provide paralyzed or otherwise disabled patients with instantaneous, natural, thought-based control of robotic prosthetic limbs and other external devices. This thesis presents a detailed discussion of the decoding algorithms, descriptions of the low-power analog and digital circuit architectures used to implement the decoders, and results validating their performance when applied to decode real neural data. A major constraint on brain-implanted electronic devices is the requirement that they consume and dissipate very little power, so as not to damage surrounding brain tissue. The systems described here address that constraint, computing in the style of biological neural networks, and using arithmetic-free, purely logical primitives to establish universal computing architectures for neural decoding. The second part of this thesis describes the development of an implantable fuel cell powered by extracellular glucose at concentrations such as those found in the cerebrospinal fluid surrounding the brain. The theoretical foundations, details of design and fabrication, mechanical and electrochemical characterization, as well as in vitro performance data for the fuel cell are presented.by Benjamin Isaac Rapoport.Ph.D

Neural prosthetics for paralysis : algorithms and low-power analog architectures for decoding neural signals

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2007.Includes bibliographical references (leaves 119-122).This thesis develops a system for adaptively and automatically learning to interpret patterns of electrical activity in neuronal populations in a real-time, on-line fashion. The system is primarily intended to enable the long-term implantation of low-power, microchip-based recording and decoding hardware in the brains of human patients in order to treat neurologic disorders. The decoding system developed in the present work interprets neural signals from the parietal cortex encoding arm movement intention, suggesting that the system could function as the decoder in a neural prosthetic limb, potentially enabling a paralyzed person to control an artificial limb just as the natural one was controlled, through thought alone. The same decoder is also used to interpret the activity of a population of thalami neurons encoding head orientation in absolute space. The success of the decoder in that context motivates the development of a model of generalized place cells to explain how networks of neurons adapt the configurations of their receptive fields in response to new stimuli, learn to encode the structure of new parameter spaces, and ultimately retrace trajectories through such spaces in the absence of the original stimuli.(cont.) Qualitative results of this model are shown to agree with experimental observations. This combination of results suggests that the neural signal decoder is applicable to a broad scope of neural systems, and that a microchip-based implementation of the decoder based on the designs presented in this thesis could function as a useful investigational tool for experimental neuroscience and potentially as an implantable interpreter of simple thoughts and dreams.by Benjamin Isaac Rapoport.S.M