Multivariate Objective Response Detectors (MORD): Statistical Tools for Multichannel EEG Analysis During Rhythmic Stimulation

Abstract

The presence of cerebral evoked responses can be tested by using objective response detectors. They are statistical tests that provide a threshold above which responses can be assumed to have occurred. The detection power depends on the signal-to-noise ratio (SNR) of the response and the amount of data available. However, the correlation within the background noise could also affect the power of such detectors. For a fixed SNR, the detection can only be improved at the expense of using a longer stretch of signal. This can constitute a limitation, for instance, in monitored surgeries. Alternatively, multivariate objective response detection (MORD) could be used. This work applies two MORD techniques (multiple coherence and multiple component synchrony measure) to EEG data collected during intermittent photic stimulation. They were evaluated throughout Monte Carlo simulations, which also allowed verifying that correlation in the background reduces the detection rate. Considering the N EEG derivations as close as possible to the primary visual cortex, if N = 4, 6 or 8, multiple coherence leads to a statistically significant higher detection rate in comparison with multiple component synchrony measure. With the former, the best performance was obtained with six signals (O1, O2, T5, T6, P3 and P4).

Some thoughts on the interpretation of steady-state evoked potentials

“…If several harmonics are expected to be present in the signal, they may be assessed conjointly [15]. Sensitivity can be improved if the data of several electrodes are available [16]. As always with statistics, stating the hypothesis very precisely beforehand allows for choosing the most adequate test.…”

Rice Detector: Proposal of a Novel Objective Response Detection Technique

“…Moreover, the investigation of multivariate extensions of these techniques would allow obtaining detectors with higher performances for identification of visual (Felix et al, 2007) or somatosensory (Melges et al, 2012b) stimulation response. Finally, the frequencies with best detection rates were the same reported by Infantosi et al (2006) and Melges et al (2012b), which used uni and multivariate ORD.…”

Frequency-Domain Objective Response Detection Techniques Applied to Evoked Potentials: A Review

“…Assuming that the mean phase angle is uniformly distributed between 0 and 2, it can be showed, in a similar way to the performed to the CSM, that the asymptotical critical value for the MCSM can be expressed by (Felix et al, 2007) …”

“…This result was observed for different values of M epochs (100, 200, 400, 800) used in the calculation of the estimates. A comparison between the two techniques applied to the EEG during intermittent photic stimulation (Felix et al, 2007) has also resulted in higher detection percentages for the MC over the MCSM. By means of simulation, it was observed that the presence of noise correlated with the responses degrades the detection rates (Felix et al, 2007).…”

“…Thus, augmenting the number of derivations would imply increasing the detection rate. However, it did not occur in practical applications (Melges, 2009, Felix et al, 2007. This could be explained by the fact that the background activities are correlated and hence there would be no improvement by continuously adding new derivations.…”