title: Exploring high-frequency oscillation as a marker of brain ischemia using S-transform.
abstract: Brain injury, such as hypoxic-ischemia produced in brain after cardiac arrest, is known to alter somatosensory evoked potential (SSEP) signals, thus serving a diagnostic role. This study explores the high-frequency oscillation (HFO) in SSEP recorded in a rat model of asphyxial cardiac arrest. To best characterize this complex oscillatory activity, several time-frequency representation strategies are implemented and compared. The S-transform (ST) is found to precisely localize the HFO in temporal-spectral space. More, the 'phase ST'-the inter-trial coherence (ITC) sensitively detects the phase-locked activities in HFO. Using ST and ITC, we explored the evolution of HFO during early recovery from brain injury. A discrepancy between the amplitude of HFO, which increases over time, and its phase, which stays time-invariant, is revealed here. The recovery dynamics of HFO mirrors that of N10 in terms of their amplitudes, which suggests HFO as a prelude of large-scale cortical responses. In addition, statistics shows the amplitudes of HFOs have different levels (p < 0.05) and recovery dynamics (p=0.03) between the good- and bad-outcome groups. We consider the HFO to be reflective of the health of thalamocotical circuitry in brain ischemia.
authors.affiliation: Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. dwu18@jhu.edu
authors.forename: Dan
authors.initials: D
authors.lastname: Wu
authors.forename: Anastasios
authors.initials: A
authors.lastname: Bezerianos
authors.forename: Huaijian
authors.initials: H
authors.lastname: Zhang
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Jia
authors.forename: Nitish V
authors.initials: NV
authors.lastname: Thakor
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002545:Brain Ischemia / Q000150:complications / Q000503:physiopathology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005583:Fourier Analysis; D006323:Heart Arrest / Q000150:complications / Q000503:physiopathology; D008297:Male; D015233:Models, Statistical; D051381:Rats; D017208:Rats, Wistar; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors; D058067:Wavelet Analysis
chemical_list: D015415:Biomarkers