Microelectromechanical systems (MEMS)

Micromachining exploits the technologies used by the integrated-circuit industry to produce microsensors, microactuators, and microsystems. Circuits can be integrated with MEMS devices, so that device performance can be improved, high-speed computation performed locally, and microactuators controlled. A feasible example of a complete microsystem applicable to neuroengineering is an integrated fluid-delivery microsystem with on-chip chemical microsensors, integrated circuitry, and microactuators. The microsystem could be operated in a closed-loop fashion by using the integrated circuits to amplify the sensory signals, decide on a course of action, and activate the appropriate microactuators (such as microvalves and micropumps) to deliver the optimal amount of fluid to precise locations. The proposed neuroengineering faculty actively pursuing MEMS research include Gang Chen, Chih-Ming Ho, Jack Judy, and C.J. Kim.

Signal Processing

Abeer Alwan's group is developing mathematical models of speech perception, with the goal of facilitating reliable verbal communication between individuals and between humans and machines. Her group is focused on improving signal processing techniques, thereby enabling the next generation of hearing aids to be better, smaller, and more cost-effective. Helen Na's group has focused its attention on tomographic image reconstruction, image processing, multi-dimensional signal processing, and ionospheric imaging. Research interests are in the area of image processing with an emphasis on image formation, processing, enhancement and analysis, particularly in systems with restricted data acquisition. The NET Program encourages students to apply advances in signal processing to the understanding of the neural circuits involved in sensory processing, especially in the auditory and visual systems.

Photonics

Gregory Bearman, James Lambert, and Michael Storrie-Lombardi, from JPL, are exploring the applications of 3-dimensional image and spectral analysis (by optical coherence tomography, imaging spectroscopy, and Raman spectroscopy) via fiberoptic probes for in situ, nanometer-level chemical analysis, functional mapping, and imaging. These technologies provide the ability to image cellular and subcellular structures and even to monitor cellular chemistry in real time. Applications of this technology to neuroengineering include the monitoring of extracellular (and ultimately of intracellular) environment and the analysis of signal processing during sensation and motor activity. JPL has also pioneered new techniques for in situ drug intervention and tissue analysis. By combining the power of real-time chemical monitoring with MEMS technology and signal processing, it should be possible to analyze and regulate pattern generation in locomotion, respiration, and other systems. JPL has been on the forefront of nanoscale sensors for chemical, thermal, physical and electromagnetic analysis for many years in support of its NASA mission to explore our solar system robotically.

Locomotion and Pattern Generation

Reggie Edgerton's laboratory has been a center of research on neuromuscular physiology, focusing on the neural control of movement in experimental animals and on the neural plasticity of the spinal cord. Collaborative efforts with JPL address intramuscular chemistry, force and current distribution using implantable microdetectors and fiber optic links, and collaborative work with the laboratory of Niranjala Tillakaratne examines the molecular and cellular mechanisms that underlie neural plasticity. Parallel work, in the laboratory of Bruce Dobkin, addresses mechanisms of activity-dependent plasticity in human locomotion. Finally, Alan Garfinkel and Michael Storrie-Lombardi (JPL), with other JPL and industrial collaborators, are developing a mathematical model for neural circuitry and physiology, treating locomotion as a coupled neural-biomechanical system. A systematic understanding of the neural and muscular bases of locomotion will be accelerated by the use of analytic and robotic methods developed in SEAS and at JPL, and such collaborative projects are already under way. Similarly, work in the laboratory of Jack Feldman and his collaborators addresses the molecular, synaptic, cellular, and network events that generate respiratory patterns.

Central Movement Control

Marie-Françoise Chesselet's laboratory employs behavioral, anatomical, and molecular techniques to study central regulation and dysfunction in the control of movement. A challenge for the future will be to extend this analysis to genetically engineered animals. This extension will only be possible with the miniaturization of automated measurements of movement and with the ability to deliver extremely small volumes of pharmacological and physiological agents, using technologies such as those developed by Chang and Kim. Furthermore, imaging technology developed by JPL will be invaluable in following neuronal plasticity in vivo. Similarly, Istvan Mody's laboratory is developing analytic and pharmacological methods for studying and altering neural signaling, focusing particularly on the question of how the changing balance of excitation and inhibition leads to sustained changes in neuronal excitability. Experimental approaches include chronic in vivo recordings, patch-clamp recordings in brain slices and in acutely isolated animal or human neurons, infrared and fluorescent video microscopy with simultaneous recordings, and measurements of intracellular calcium. In vivo studies would be greatly enhanced by the availability of real-time monitoring using the techniques being developed in the groups of Lambert and Bearman at JPL.

Processing of Sensory Information

Another laboratory seeks to understand the neuronal circuit mechanisms that underlie visual processing by dissecting circuit operations using a genetic cell-ablation technique. Their recent work has focused on the retina: they stimulate photoreceptors with computer-generated images while recording the responses of the retinal output neurons (the ganglion cells). By ablating specific classes of interneurons, they can perturb the transfer of information from input to output, allowing them to test computational models. Current studies focus on how the retina processes motion information, while future studies will extend this analysis to higher brain areas, including the visual cortex. One of the main goals of this work is to understand the collective behavior of all of the components of a neural network. This work requires the ability to monitor the electrical activity of many neurons simultaneously, which has been very difficult with conventional electophysiological techniques. Recent advances in micromachining and MEMS has opened the door to new strategies for multi-cell recording. Collaborative reserach is investigating the use of micromachining and other MEMS technologies to produce such devices.

Peter Narins' laboratory studies the vertebrate auditory system, particularly focusing on the interaction between acoustic and seismic signals at the level of the auditory nerve, the role of individual hair cell channel currents in the development of frequency tuning, and the biophysical basis for sound stimulation in the inner ear. This work interfaces with that of Alwan's laboratory, which focuses on developing quantitative models of human speech perception and production -- attending to the acoustic, electrical, and mechanical characteristics of the ear and the oral cavity.

 

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