A Novel Method To Simultaneously Record Spinal Cord Electrophysiology And Electroencephalography Signals

People often close their eyes and "feel" the surrounding environment with their hearts to get a nuanced sensory experience.To explore the effect of eyes-open(EO)and eyes-closed(EC)on somatesthesia,the first experiment recruited 16 healthy subjects and measured their sensory thresholds during they opened and closed eyes under light and dark conditions.It was found that subjects were more sensitive during EC condition,however,this difference of sensitivity was only observed under light condition,which proved that the previous hypothesis about the results was reasonable.To further explore the physiological mechanisms that lead to the difference in somatesthesia between EO and EC conditions,the second experiment focused on the central nervous system and broke through technical limitations—developed a novel method to simultaneously record spinal cord electrophysiology(SCE)and electroencephalography(EEG)signals.To explore the differences between EEG and SCE signals during different states and validate the performance of the novel method,the study used a classical resting-state study design with two experimental conditions:eyes-closed and eyes-open.The second experiment recruited nine postherpetic neuralgia patients implanted with a spinal cord stimulator,which was modified to record SCE signals simultaneously with EEG signals.The results of the second experiment showed:(1)In EEG signals,the spectral power in the delta frequency band,which showed a topographical distribution maximal in the frontal-central region of the brain,was significantly lower in the EC condition than in the EO condition,while the spectral power in the alpha frequency band,which was maximally distributed at the occipital region of the brain,was significantly higher in the EC condition than in the EO condition.(2)In SCE signals,the spectral power in the delta frequency band was also significantly lower in the EC condition than in the EO condition,while the spectral power in the alpha frequency band was marginally higher in the EC condition than in the EO condition.(3)The spectral power of delta and alpha frequency bands was able to predict EC/EO behaviors,and these two band powers maybe jointly encode EC/EO behaviors;combining EEG and SCE signals achieved better prediction performance,so EEG and SCE signals were shown to contain complementary information about EC/EO behaviors.(4)Causal connectivity analysis suggested that electrophysiological signals in the spinal cord probably received top-down regulation from the brain and this regulation could be reflected in the delta band oscillations.Combining the results of the two experiments,this study found that there was a top-down regulation in delta-band oscillations from the brain to the spinal cord,which might reflect inhibition effects of the brain on somatosensory afferent through delta oscillations,as for behaviors,more sensitive somatesthesia during EC condition.In addition,this study also demonstrated the validity of simultaneous SCE-EEG recording and showed that the novel method was a valuable tool to investigate the brain-spinal interaction.With this method,we can better unite knowledge about the brain and the spinal cord for a deeper understanding of the functions of the whole CNS.