Characteristics of Vertex Wave during Light Sleep according to Age

Address for correspondence Ki-Young Jung, MD Department of Neurology, Korea University Medical Center, Korea University College of Medicine, 73 Inchon-ro, Seongbuk-gu, Seoul 136-705, Korea Tel: +82-2-920-6649 Fax: +82-2-925-2472 E-mail: jungky@korea.ac.kr Objectives: Vertex wave during sleep is a hallmark of light sleep and related to brain development. We examined voltage characteristics of vertex wave according to age. Methods: Electroencephalographys were selected from routine waking and sleep EEG database. The inclusion criteria were that the age of subjects was more than 4 years old; EEG showed at least 5 typical vertex waves with no abnormal findings; the neurologic examination and neuroimaging findings were normal. EEGs were classified into 7 groups according to their age. Five to 20 epochs which included the time 320 ms before and after the maximum negativity of a vertex wave from each EEG record were selected. Voltage characteristics including amplitude and topographic distribution were evaluated. Intracerebral source location of vertex wave from each age group was identified using low resolution electromagnetic tomography (LORETA). Results: Amplitude of vertex wave was highest in the youngest age group, decreased with age thereafter. Voltage topography showed maximum negativity over central vertex area bilaterally in all age group, which did not show any significant difference among age group. Normalized amplitude of vertex waves showed significant main effect of location (df=1.356, F= 115.843, p<0.001). Interaction between age and location was also significant (df=4.088, F=3.327, p=0.016). However, age did not show any main effect on amplitude of vertex wave. Post-hoc analysis showed amplitude of group 1 (5 to 9 years), compared with other age groups, was significantly lowered only in Fz electrode. LORETA image showed maximum current density in the mid to posterior cingulate gyri, which was similar across all age groups. Conclusions: Our study suggests that vertex waves might be related to arousal response during sleep, although exact mechanism is still unclear. J Korean Sleep Res Soc 2012;9:5-9