9:30, SPEC-L6.1
SENSOR ARRAYS IN THE MICRO-ENVIRONMENT OF THE BRAIN
D. ANDERSON, K. OWEISS, S. BIERER
Technology for recording action potentials from the nervous system has changed in recent years from single or at most two or three neurons to tens of neurons recorded from geometrically precise arrays of recording sites. To fully exploit these research opportunities, signal delivery and processing are key factors. We desire not only sort the array input into neural channels but locate neurons with respect to the array so they can be later identified in histology and serve to further decode the activity of each neuron. The distribution of a neuron's signal across the sensor array is predictive of the cell location at least in projection onto the array but also in the dimension above the array. To achieve 3-dimensional locating power, careful estimation of signal strength at each site must be achieved taking into account the distance and the field distortion for all anticipated source positions. Achieving this independent of source strength appears to be feasible.

9:50, SPEC-L6.2
CALCULATION OF THE KULLBACK-LEIBLER DISTANCE BETWEEN POINT PROCESS MODELS
C. GRUNER, D. JOHNSON
We have developed a method for quantifying neural response changes in terms of the Kullback-Leibler distance between the intensity functions for each stimulus condition. We use empirical histogram estimates to characterize the intensity function of the neural response. A critical factor in determining the histogram estimates is selection of bin-width. In this work we analytically derive the Kullback-Leibler distance between two Poisson processes and two dead time modified Poisson processes in terms of the bin-width selected. Our results show that for constant intensity processes having the same number of expected counts, the distance between the dead time modified processes will be larger than between the Poisson processes.

10:10, SPEC-L6.3
SPATIO-TEMPORAL SIGNAL PROCESSIING FOR MULTISUBJECT FUNCTIONAL MRI STUDIES
V. SOLO, P. PURDON, E. BROWN
We consider signal estimation for functional MRI studies on multiple subjects. There are two major issues; alignment or registration of images across subjects; and using the multi-subject information to capture covariance information: we discuss only the latter. Capturing this covariance information properly can lead to great improvements in statistical efficiency beyond what simple averaging can offer as well as compact description of group features.

10:30, SPEC-L6.4
BRAIN-CONTROL INTERFACES FOR SENSORY AND MOTOR PROSTHETIC DEVICES
K. MOXON
Injury and disease to the central nervous system often leaves patients with full cognitive ability but a loss of communication between the brain and sensorimotor systems of the rest of the body. During the past 30 years there has been tremendous progress in the development of prosthetic devices that stimulate peripheral nerves and muscles to restore movement of paralyzed limbs in these patients. However, control systems for these prosthetic devices that interface directly with brain signals carrying information about the intent to move and methods for returning sensory feedback to the brain are just beginning to be developed. We present a ceramic-based, multi-site electrode system capable of 1) recording from large numbers of neurons across several brain regions 2) stimulating neural tissue to restore sensory feedback and 3) measuring local concentrations of neuromodulators. Preliminary data from the rat suggest that this system can be used to record neural signals carrying information about the intent to move and restore sensory perception. Issues relating to interfacing with the brain's hierarchical and distributed information processing systems will be discussed.

10:50, SPEC-L6.5
SOUND PROCESSING FOR COCHLEAR IMPLANTS
D. EDDINGTON, W. RABINOWITZ, L. DELHORNE
Cochlear implants are devices designed to provide a measure of hearing to the deaf. Most deaf individuals have lost the ability to translate sound into the patterns of electric activity normally present on the 30,000 fibers of the auditory nerve. Because these patterns of activity are the inputs to the brain that result in sound sensation, cochlear implants deliver electric stimuli to these fibers in an attempt to artificially elicit patterns of spike activity that mimic the patterns present in a normal-hearing ear. We introduce cochlear implants by describing the signal processing used by current devices. Measurements of patient performance in quiet and in noise are used to demonstrate the limitations of today's devices and to introduce the avenues of current research that show promise for improving the performance of these devices.

11:10, SPEC-L6.6
MATRIX FORMULATION OF A UNIVERSAL MICROBIAL TRANSCRIPT PROFILING SYSTEM
J. FITCH, J. NG, B. SOKHANSANJ
DNA chips and microarrays are used to profile gene transcription. Unfortunately, the initial fabrication cost for a chip and the reagent costs to amplify thousands of open reading frames for a microarray are over $100K for a typical 4 Mbase bacterial genome. To avoid these expensive steps, a matrix formulation of a universal hybrid chip-microarray approach to transcript profiling is demonstrated for synthetic data. Initial considerations for application to the 4.3 Mbase bacterium Yersinia pestis are also presented. This approach can be applied to arbitrary bacteria by recalculating a matrix and pseudoinverse. This approach avoids the large upfront expenses associated with DNA chips and microarrays.