Causal flow distribution of multi-channel electroencephalographs during visual working memory / 国际生物医学工程杂志

Objective The ability of working memory (WM) is to temporarily hold and manipulate information for cognitive tasks.The aim of this study was to investigate the causal flow distribution of multi-channel electroencephalographs (EEGs) during Sternberg visual WM task to help understand WM mechanism from the view of neural information transform.Methods Sixteen-channel EEGs were recorded from 8 healthy subjects during Sternberg task,total EEG data for 80 trials were recorded and preprocessed.The EEG powers for each channel were calculated via Fast Fourier transform (FFT).The feature channel was extracted based on the maximum power,and the feature frequency band for WM was determined by time-frequency analysis.The directed transfer function (DTF) and the value of causal flow in EEG feature frequency band were calculated.Results The EEG power focused on θ band (4-8 Hz) and at Fz channel.The maximum value of causal flow was located at Fz,and the first 4 maximum negative values of causal flow were at C3,C4,C5,C6.Conclusions The feature frequency band for WM is the θ band.The causal source (responsible region) is at Fz (frontal region) and the causal sinks are at C3,C4,C5,C6.

Epileptic foci lateralization from interictal scalp EEG by applying causal analysis / 国际生物医学工程杂志

Objective To lateralize epileptic foci in interictal electroencephalography (EEG) signal by using causal analysis method.Methods On the basis of frequency domain causal analysis,the adapted directed transfer function (ADTF),power spectrum weighted ADTF(psADTF) method was proposed by applying the power spectrum information in defined frequency band with normalized ADTF,to fit the frequency information features of different epileptic wave.EEG signals of two groups of 30 epilepsy patients were analyzed by psADTF.Group Ⅰ included 15 presurgical patients and 104 epilepsy spikes were picked from EEG signals.Group Ⅱ included 15 outpatient patients and 98 epilepsy spikes were picked from EEG signals.Results 96 of 104 spikes of group Ⅰ were lateralized properly by psADTF according to surgery sites,and the accuracy rate was 92％.94 of 98 spikes of group Ⅱ were lateralized properly by psADTF according to three technicians' judgments,with the accuracy rate of 96％.Conclusion Our results proves that the psADTF method over interictal EEG spikes can be a great help to clinical epileptic foci lateralization.