Chronically implantable, closed-loop neuromodulation devices with concurrent sensing and stimulation hold promise for better understanding the nervous system and improving therapies for neurological disease. Concurrent sensing and stimulation are needed to maximize usable neural data, minimize time delays for closed-loop actuation, and investigate the instantaneous response to stimulation. Current systems lack concurrent sensing and stimulation primarily because of stimulation interference to neural signals of interest. While careful design of high performance amplifiers has proved useful to reduce disturbances in the system, stimulation continues to contaminate neural sensing due to biological effects like tissue-electrode impedance mismatch and constraints on stimulation parameters needed to deliver therapy. In this work we describe systematic methods to mitigate the effect of stimulation through a combination of sensing hardware, stimulation parameter selection, and classification algorithms that counter residual stimulation disturbances. To validate these methods we implemented and tested a completely implantable system for over one year in a large animal model of epilepsy. The system proved capable of measuring and detecting seizure activity in the hippocampus both during and after stimulation. Furthermore, we demonstrate an embedded algorithm that actuates neural modulation in response to seizure detection during stimulation, validating the capability to detect bioelectrical markers in the presence of therapy and titrate it appropriately. The capability to detect neural states in the presence of stimulation and optimally titrate therapy is a key innovation required for generalizing closed-loop neural systems for multiple disease states.

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This paper develops a model for relating input current harmonic content to real power consumption for variable electronic loads, specifically for loads' actively controlled inverters energized by an uncontrolled rectification of the utility. This model serves as the basis for a method for estimating and disaggregating the power consumption of variable speed drives (VSDs) and rectifier loads from other constant power loads. This method can be used for nonintrusive power monitoring. The approach described in this paper uses the approximate switching function of the rectifier to derive the best estimating function for the fundamental current harmonic from a finite set of current harmonics uniquely associated with the operation of the drive. Experimental results show that the proposed VSD power and harmonic estimator can track VSD power consumption for monitoring given knowledge or an estimate of the input current harmonic content.