@article {OA1863,
	title = {Time?frequency analysis methods to quantify the time-varying microstructure of sleep EEG spindles: Possibility for dementia biomarkers?},
	journal = {Journal of Neuroscience Methods},
	volume = {185},
	number = {1},
	year = {2009},
	note = {n/a},
	pages = {133{\textendash}142},
	abstract = {<p>The time-varying microstructure of sleep EEG spindles may have clinical significance in dementia studies and can be quantified with a number of techniques. In this paper, real and simulated sleep spindles were regarded as AM?FM signals modeled by six parameters that define the instantaneous envelope (IE) and instantaneous frequency (IF) waveforms for a sleep spindle. These parameters were estimated using four different methods, namely the Hilbert transform (HT), complex demodulation (CD), matching pursuit (MP) and wavelet transform (WT). The average error in estimating these parameters was lowest for HT, higher but still less than 10\% for CD and MP, and highest (greater than 10\%) for WT. The signal distortion induced by the use of a given method was greatest in the case of HT and MP. These two techniques would necessitate the removal of about 0.4 s from the spindle data, which is an important limitation for the case of spindles with duration less than 1 s. Although the CD method may lead to a higher error than HT and MP, it requires a removal of only about 0.23 s of data. An application of this sleep spindle parameterization via the CD method is proposed, in search of efficient EEG-based biomarkers in dementia. Preliminary results indicate that the proposed parameterization may be promising, since it can quantify specific differences in IE and IF characteristics between sleep spindles from dementia subjects and those from aged controls.</p>
},
	url = {http://oa.uninova.pt/1863/},
	author = {Ktonas, PY and Golemati, S. and Xanthopoulos, P. and Sakkalis, V. and Ortigueira, M.D. and Tsekou, H. and Zervakis, M. and Paparrigopoulos, T. and Bonakis, A. and Economou, NT}
}
@conference {OA1869,
	title = {Potential dementia biomarkers based on the time-varying microstructure of sleep EEG spindles},
	booktitle = {2007 29th Annual International Conference of the IEEE Engineering in Medicine and Biology Society},
	year = {2007},
	note = {n/a},
	pages = {2464{\textendash}2467},
	abstract = {<p>The time-varying microstructure of sleep EEG spindles may have clinical significance in dementia studies. In this work, the sleep spindle is modeled as an AM-FM signal and parameterized in terms of six parameters, three quantifying the instantaneous envelope (IE) and three quantifying the instantaneous frequency (IF) of the spindle model. The IE and IF waveforms of sleep spindles from patients with dementia and normal controls were estimated using the time-frequency technique of complex demodulation (CD). Sinusoidal curve-fitting using a matching pursuit (MP) approach was applied to the IE and IF waveforms for the estimation of the six model parameters. Specific differences were found in sleep spindle instantaneous frequency dynamics between spindles from dementia subjects and spindles from controls.</p>
},
	url = {http://oa.uninova.pt/1869/},
	author = {Ktonas, PY and Golemati, S. and Xanthopoulos, P. and Sakkalis, V. and Ortigueira, M.D. and Tsekou, H. and Zervakis, M. and Paparrigopoulos, T. and Soldatos, CR}
}
@conference {OA315,
	title = {Comparative analysis of time-frequency methods estimating the time-varying microstructure of sleep EEG spindles},
	booktitle = {Information Technology Applications in Biomedicine},
	year = {2006},
	note = {n/a},
	month = {October},
	abstract = {n/a},
	url = {http://oa.uninova.pt/315/},
	author = {Xanthopoulos, P. and Golemati, S. and Sakkalis, V. and Ktonas, PY and Manuel Ortigueira and Zervakis, M. and Paparrigopoulos, T. and Tsekou, H. and Soldatos, CR}
}
