Research Papers

Adaptive filtering to reduce global interference in evoked brain activity detection: a human subject case study

[+] Author Affiliations
Quan Zhang

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

Emery N. Brown

Massachusetts General Hospital, Department of Anesthesia and Critical Care, Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Department of Brain and Cognitive Sciences, Boston, Massachusetts 02114

Gary E. Strangman

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

J. Biomed. Opt. 12(6), 064009 (November 15, 2007). doi:10.1117/1.2804706
History: Received December 02, 2006; Revised May 08, 2007; Accepted June 12, 2007; Published November 15, 2007
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Following previous Monte Carlo simulations, we describe in detail an example of detecting evoked visual hemodynamic responses in a human subject as a preliminary demonstration of the novel global interference cancellation technology. The raw time series of oxyhemoglobin (O2Hb) and deoxyhemoglobin (HHb) changes, their block averaged results before and after adaptive filtering, together with the power spectral density analysis are presented. Simultaneous respiration and EKG recordings suggested that spontaneous low-frequency oscillation and cardiac activity were the major sources of global interference in our test. When global interference dominates (e.g., for O2Hb in our data, judged by power spectral density analysis), adaptive filtering effectively reduced this interference, doubling the contrast-to-noise ratio (CNR) for evoked visual response detection. When global interference is not obvious (e.g., in our HHb data), adaptive filtering provided no CNR improvement. The results also showed that the hemodynamic changes in the superficial layers and the estimated total global interference in the target measurement were highly correlated (r=0.96), which explains why this global interference cancellation method should work well when global interference is dominating. In addition, the results suggested that association between the superficial layer hemodynamics and the total global interference is time-varying.

© 2007 Society of Photo-Optical Instrumentation Engineers

Citation

Quan Zhang ; Emery N. Brown and Gary E. Strangman
"Adaptive filtering to reduce global interference in evoked brain activity detection: a human subject case study", J. Biomed. Opt. 12(6), 064009 (November 15, 2007). ; http://dx.doi.org/10.1117/1.2804706


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