Variations of Simple Somatosensory Evoked Potentials in the First and Second Halves of Sleep

Abstract

Introduction: The study aims to investigate variations in brain responses to non-painful tactile stimulation on right hand in the first and second halves of NREM sleep. Materials and Methods: Sixteen healthy volunteers (9 female, mean age: 22.44±1.75) participated in the study. 40-channel NuAmps recording system [electroencephalography (EEG), electrooculography (EOG), and electromyography (EMG)], Embedded Microcontroller Stimulation Unit (EMISU), pneumatic stimulation unit (Somatosensory Stimulus Generator 4-D Neuroimaging), video recording system, and analysis PC were used during recordings. Single-type non-painful somatosensory stimulus was applied to the index and middle fingers of right hands of participant. All night long records of EEG, EOG, and EMG were classified into sleep stages according to American Academy of Sleep Medicine (AASM). As the variations in first and second halves of the NREM sleep were localized in central region, Cz electrode was investigated. Results: When the brain responses to non-painful tactile stimuli in NREM sleep were investigated, P50, N100, p200, N300, P450, N550, P900, and N_late responses were observed. When the responses in the first and the second halves of sleep were compared, latency of P900 response in the first half was significantly shorter than that in the second half; and amplitudes of N300 and P900 responses in the first half were significantly larger than that in the second half. Discussion: There are different stages in their sleep in the process and studies in the literature often seen where some sleep stages. However our results showed that the the time of night, during sleep, influences the brain responsiveness to non-painful tactile stimuli.

Keywords

• Sleep
• non-painful tactile stimulus
• NREM
• electroencephalography