Using Objective Response Detection techniques for detecting the tibial somatosensory evoked response with different stimulation rates

Abstract

This work investigates the influence of the stimulus frequency in the performance of two Objective Response Detection (ORD) techniques, the Magnitude-Squared Coherence (MSC) and the Component Synchrony Measure (CSM), as applied in somatosensory stimulation. Electroencephalographic signals were collected (10-20 International System) from forty adult volunteers without history of neurological pathologies. The stimuli were applied to the right posterior tibial nerve at the frequencies of 2, 5, 7 and 9 Hz and motor threshold intensity level. The detection was based on the rejection of the null hypothesis of response absence (significance level α=0.05 and M=100 and 500 epochs). The performances of the MSC at the four stimulation frequencies were compared, two-by-two, using the Proportion Test applied to the mean percentage rates in the total (2-100 Hz) and optimal (20-60 Hz) bands. The same was proceeded to the CSM. The evaluated derivations were Cz, C4, Pz and P4. No significant difference was found for any studied technique (MSC or CSM), any M-value, at any derivation. Thus, the highest stimulation frequency (9 Hz) can be used in order to obtain a reduction in the time of response detection in an ORD approach for a fixed M-value.

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

“…However, this frequency increase is known to cause changes in the SEP waveform (Chiappa, 1997, p. 307 and 323), whose characteristics are the basis for neurophysiologic monitoring. Fortunately, the detection rates obtained with an ORD approach is not statistically modified for different stimulation frequencies, as it was shown in a recent study of ours (Melges et al, 2011a). In this case, the use of the higher investigated frequency 9 Hz, represent a gain of 9:5 in the time of detection, if we consider the very often used stimulation frequency (5 Hz).…”

“…Figure 7 presents the detection rates for derivation [Cz] and M = 200 epochs. In this figure it is possible to visualize the similarity in the profile of the detection percentage tracings, showed to be statistically equivalent for the maximum response frequency band, for both M = 100 and 500 epochs (Melges et al, 2011a). .…”

“…More recently, Melges et al (2011a) showed that, although the variation of the stimulation frequency to values higher than 5 Hz produces distortion in the tibial nerve SEP waveform, hampering the visual inspection, the detection rates obtained with the MSC (and CSM) are statistically equivalent for different stimulation frequencies. Hence, higher values can be used in order to fasten the detection.…”

Rice Detector: Proposal of a Novel Objective Response Detection Technique

“…The stimulation was applied to the right posterior tibial nerve at the frequency of 5 Hz and at the motor threshold intensity level. Further details about the experimental protocol and signal acquisition were described in (Melges et al, 2011). The local ethics committee (CEP-HUCFF/UFRJ) approved this research and all volunteers gave written informed consent to participate.…”

“…Such techniques are based on statistical tests and, therefore, allow inferring about the sensorial response occurrence with a previously established significance level (false positives). One of the univariate frequency-domain ORD techniques with most promising results in the somatosensory response detection is the MagnitudeSquared Coherence (MSC) (Melges et al, 2008;2011). The univariate techniques are, in general, easier to apply for both clinical and surgical monitoring, since they allow a more compact acquisition apparatus, by recording only one EEG derivation.…”