The somatosensory evoked response detection using coherence and different stimulation frequencies
This work aims at investigating the effects of the stimulation frequency in the somatosensory evoked response detection using coherence. Electroencephalographic (EEG) signals during somatosensory stimulation were collected from thirty-seven adult volunteers without history of neurological pathology using the 10–20 International System. All leads were referenced to the earlobe average. The stimulation was carried out throughout current pulses (200 µs width) applied to the right posterior tibial nerve (motor threshold intensity level) at the rates of 2, 5, 7 and 9 Hz (fe). The response detection was based on rejecting the null hypothesis of response absence (M = 500 epochs and significance level α = 0.05). The percentages of volunteers for whom the response was detected, for the frequency range from 2 and 100 Hz, were calculated for the four fe-values. Only the derivations Cz, C4, Pz and P4 presented frequencies with detection rates greater than 60%. In order to compare the effects of stimulation frequency in the percentage of detection, the proportion test was applied to the averaged detection rate of all frequencies from 2 to 100 Hz. The averaged detection rates for the four fe were compared two by two for each derivation, Cz, C4, Pz and P4. No statistically significant difference was found between the averaged detection rates in none of the considered derivations. This indicates that the higher stimulus frequency (9 Hz) can be used in order to obtain a reduction in the time of both averaging and response detection for a fixed-value M of EEG epochs.
KeywordsSomatosensory Evoked Potential Coherence stimulus frequency
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- 4.Miranda de Sá AMFL and Infantosi AFC. (2007) Measuring the synchronism in the ongoing Electroencephalogram during intermittent stimulation — a partial coherence-based approach. Med Biol Eng Comput 47(7): 443–452.Google Scholar
- 5.Moore D (2005) A Estatística Básica e sua prática. LTC Editora, Rio de Janeiro.Google Scholar