Fig 1.
The stimuli used in the present study.
Fig 2.
Flowchart diagram of the EEMD algorithm.
The parameters were assigned according to values used in the numerical simulations.
Fig 3.
Global averages of individual ERPs elicited by the two stimulus conditions CT and NCT.
The ERP amplitudes are normalized to zero mean and unitary standard deviation. ERPs for both conditions are superimposed onto each other, blue: Contour condition and green: Non-contour condition.
Fig 4.
They result from averaging individual global ERPs from 18 subjects.
Fig 5.
Head topography of the significant difference of the P100 signals.
Top: Early response, Bottom: Late response
Fig 6.
Head topography of the significant difference of the N200 signals.
Top: Early response, Bottom: Late response
Table 1.
Results of statistical tests of differences in mean ERP amplitudes for the event related potential N200 in early and late response areas. P- and T-values are reported for different significance levels: (*):α = 0.05, (**):α = 0.01, (***):α = 0.001
Fig 7.
EEMD decomposition on grand average ERPs.
Single subject ERPs were averaged over 18 subjects and are shown for two stimulus conditions: Contour and Non-contour. This signal is generated by averaging all signals from Fig 3 for the two conditions separately. Plots in the left column represent the averaged signal (on top) followed by its event-related intrinsic modes (ERMs). Plots in the right column present related Hilbert spectra for each of the corresponding ERMs in the left column.
Table 2.
Approach A: Test statistics for ERM4 and ERM5 from P100.
The table summarizes parameters of the test statistics (p-value, T-value) for ERM4 and ERM5 extracted from the ERP P100. An EEMD has been applied after averaging over trials to extract ERMs. P- and T-values are given for different confidence levels: (*):α = 0.05, (**):α = 0.01.
Table 3.
Approach A: Test statistics for ERM5, ERM6 and ERM7 from N200.
The table summarizes parameters of the test statistics for ERM5, ERM6 and ERM7 extracted from the N200 ERP. An EEMD has been applied after averaging over trials to extract ERMs. P- and T-values are given for different confidence levels: (*):α = 0.05, (**):α = 0.01.
Fig 8.
Early stimulus response at ERP P100.
Top Left: Standardized original ERPs for both stimulus conditions. Top Right: ERM5 for both stimulus conditions. Bottom: Head topographies showing locations of significant differences in ERM5 amplitudes for both stimulus conditions.
Fig 9.
Late stimulus response at ERP P100.
Top Left: Standardized original ERPs for both stimulus conditions. Top Right: ERM5 for both stimulus conditions. Bottom: Head topographies showing locations of significant differences in ERM5 amplitudes for both stimulus conditions.
Table 4.
Approach B: Test statistics for ERM4 and ERM5 from P100.
The table summarizes parameters of the test statistics (p-value, T-value) for ERM4 and ERM5 extracted from the ERP P100. An EEMD has been applied before averaging over trials. P- and T-values are given for different confidence levels: (*):α = 0.05, (**):α = 0.01, (***):α = 0.001.
Fig 10.
Early stimulus response at ERP N200.
Top Left: Standardized original ERPs for both stimulus conditions. Top Right: ERM5 for both stimulus conditions. Bottom: Head topographies showing locations of significant differences in ERM5 amplitudes for both stimulus conditions.
Fig 11.
Late stimulus response at ERP N200.
Top Left: Standardized original ERPs for both stimulus conditions. Top Right: ERM5 for both stimulus conditions. Bottom: Head topographies showing locations of significant differences in ERM5 amplitudes for both stimulus conditions.
Table 5.
Approach B: Test statistics for ERM5, ERM6 and ERM7 from N200.
The table summarizes parameters of the test statistics for ERM5, ERM6 and ERM7 extracted from the ERP N200. An EEMD has been applied before averaging over trials. P- and T-values are given for different confidence levels: *−α = 0.05, **−α = 0.01.
Fig 12.
Pooling of electrodes into 6 clusters and the electrocap layout.
Left: Notation refers to the right hemisphere. The left hemisphere is organized similarly with the electrodes with odd number.Right: It shows the two groups of electrodes related with early and late responses
Fig 13.
The ERM5 are averaged in pools of electrodes located on different regions.