TY - JOUR
T1 - Describing the nonstationarity level of neurological signals based on quantifications of time-frequency representation
AU - Tong, Shanbao
AU - Li, Zhengjun
AU - Zhu, Yisheng
AU - Thakor, Nitish V.
N1 - Funding Information:
Manuscript received July 1, 2006; revised December 11, 2006. This work was supported in part by the NSFC under Grants 60601012 and 60671058, FANEDD and the funding of Shanghai Jiao Tong University for Young Faculties. N.V.T. is also supported by the NIH under Grant 1RO1HL71568. Asterisk indicates corresponding author. *S. Tong is with the Biomedical Engineering Department, Shanghai Jiao Tong University, Jiao Yi Lou Building, Room 411, 1954 Huashan Road, Shanghai, 200240, China (e-mail: shanbao.tong@gmail.com).
PY - 2007/10
Y1 - 2007/10
N2 - Most neurological signals including electroencephalogram (EEG), evoked potential (EP) and local field potential (LFP) have been known to be time varying and nonstationary, especially in some pathological conditions. Currently, the most widely used quantitative tool for such nonstationary signals is time-frequency representation (TFR) which demonstrates the temporal evolution of different frequency components. However, TFR does not directly provide a quantitative measure of nonstationarity level, e.g., how far the process deviates from stationarity. In this study, we introduced three different quantifications of TFR (qTFR) to characterize the nonstationarity level of the involving signals: 1) degree of stationarity (DS); 2) Shannon entropy (SE) of the marginal spectrum; and 3) Kullback-Leibler distance (KLD) between a TFR and a uniform distribution. These descriptors provide quantitative analysis of stationarity of a signal such that the stationarity of different signals could be compared. In this study, we obtained the TFRs of the EEG signals before and after the hypoxic-ischemic (HI) brain injury and examined the stationarity of the EEG. DS, SE, and KLD can indicate the nonstationarity change of EEG at each frequency following the HI injury, especially in the upper δ-and lower θ-band (e.g., [2 Hz, 8 Hz]) as well as in the β2 band (e.g., [22 Hz-26 Hz]). Moreover, it is shown that the stationarity of the EEG changes differently in different frequencies following the HI injury.
AB - Most neurological signals including electroencephalogram (EEG), evoked potential (EP) and local field potential (LFP) have been known to be time varying and nonstationary, especially in some pathological conditions. Currently, the most widely used quantitative tool for such nonstationary signals is time-frequency representation (TFR) which demonstrates the temporal evolution of different frequency components. However, TFR does not directly provide a quantitative measure of nonstationarity level, e.g., how far the process deviates from stationarity. In this study, we introduced three different quantifications of TFR (qTFR) to characterize the nonstationarity level of the involving signals: 1) degree of stationarity (DS); 2) Shannon entropy (SE) of the marginal spectrum; and 3) Kullback-Leibler distance (KLD) between a TFR and a uniform distribution. These descriptors provide quantitative analysis of stationarity of a signal such that the stationarity of different signals could be compared. In this study, we obtained the TFRs of the EEG signals before and after the hypoxic-ischemic (HI) brain injury and examined the stationarity of the EEG. DS, SE, and KLD can indicate the nonstationarity change of EEG at each frequency following the HI injury, especially in the upper δ-and lower θ-band (e.g., [2 Hz, 8 Hz]) as well as in the β2 band (e.g., [22 Hz-26 Hz]). Moreover, it is shown that the stationarity of the EEG changes differently in different frequencies following the HI injury.
KW - Electroencephalogram (EEG)
KW - Kullback-Leibler distance
KW - Shannon entropy
KW - Stationarity
KW - Time-frequency representation (TFR)
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U2 - 10.1109/TBME.2007.893497
DO - 10.1109/TBME.2007.893497
M3 - Article
C2 - 17926676
AN - SCOPUS:34548828889
SN - 0018-9294
VL - 54
SP - 1780
EP - 1785
JO - IEEE Transactions on Biomedical Engineering
JF - IEEE Transactions on Biomedical Engineering
IS - 10
ER -