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

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.

Research highlights▶ Stimulation frequency influences the somatosensory evoked potential waveform. ▶ The Magnitude-Squared Coherence is not influenced by stimulation frequency. ▶ The Component Synchrony Measure is not influenced by stimulation frequency. ▶ The stimulation frequency of 9 Hz should be used for a more rapid SEP detection.