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Research Papers

Adaptive filtering for global interference cancellation and real-time recovery of evoked brain activity: a Monte Carlo simulation study

[+] Author Affiliations
Quan Zhang

Harvard Medical School, Massachusetts General Hospital, Neural Systems Group, 13th Street, Building 149, Room 2651, Charlestown, Massachusetts 02129

Emery N. Brown

Department of Anesthesia and Critical Care, Massachusetts General Hospital, Department of Brain and Cognitive Sciences, Harvard-MIT Division of Health Science and Technology, Massachusetts Institute of Technology

Gary E. Strangman

Harvard Medical School, Massachusetts General Hospital, Neural Systems Group, 13th Street, Building 149, Room 2651, Charlestown, Massachusetts 02129

J. Biomed. Opt. 12(4), 044014 (July 16, 2007). doi:10.1117/1.2754714
History: Received December 02, 2006; Revised April 18, 2007; Accepted April 20, 2007; Published July 16, 2007
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The sensitivity of near-infrared spectroscopy (NIRS) to evoked brain activity is reduced by physiological interference in at least two locations: 1. the superficial scalp and skull layers, and 2. in brain tissue itself. These interferences are generally termed as “global interferences” or “systemic interferences,” and arise from cardiac activity, respiration, and other homeostatic processes. We present a novel method for global interference reduction and real-time recovery of evoked brain activity, based on the combination of a multiseparation probe configuration and adaptive filtering. Monte Carlo simulations demonstrate that this method can be effective in reducing the global interference and recovering otherwise obscured evoked brain activity. We also demonstrate that the physiological interference in the superficial layers is the major component of global interference. Thus, a measurement of superficial layer hemodynamics (e.g., using a short source-detector separation) makes a good reference in adaptive interference cancellation. The adaptive-filtering-based algorithm is shown to be resistant to errors in source-detector position information as well as to errors in the differential pathlength factor (DPF). The technique can be performed in real time, an important feature required for applications such as brain activity localization, biofeedback, and potential neuroprosthetic devices.

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© 2007 Society of Photo-Optical Instrumentation Engineers

Citation

Quan Zhang ; Emery N. Brown and Gary E. Strangman
"Adaptive filtering for global interference cancellation and real-time recovery of evoked brain activity: a Monte Carlo simulation study", J. Biomed. Opt. 12(4), 044014 (July 16, 2007). ; http://dx.doi.org/10.1117/1.2754714


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