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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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