Spatiotemporal variations of alpha and sigma band EEG in the waking-sleeping transition period

The aim of this study is to evaluate the spatiotemporal variation of alpha and sigma band EEGs during the waking-sleeping transition or hypnagogic period. Power and coherence from 7 EEG channels (Fp1, F7, Fz, C3, Pz, T5, O1) were studied using EEG records of the period of 5 min. before the onset of Stage 1 to 24 min. after the onset of Stage 1. The EEG spectra were computed for 4 frequency bands (alpha 1: 8.0-9.0 Hz, alpha 2: 9.5-11.0 Hz, alpha 3: 11.5-12.5 Hz, and sigma: 13.0-15.0 Hz). The power of alpha 1 and 2 bands initially started to decrease before the onset of Stage 1. Principal component analysis of the coherence yielded Generalized and Localized Components in each band. The Generalized Component was widespread across scalp areas, while the Localized Component was a restricted local area. The Generalized Components of alpha 1 and 2 bands reached stable levels of NREM sleep about 1 min. after the onset of Stage 1. The component of sigma band reached a stable level of NREM sleep about 0.6 min. before the onset of Stage 2, while the component of alpha 3 band reached a stable level of NREM sleep about 3.4 min. after the onset of Stage 2. These results suggest that the alpha-sigma band EEG structures during the waking-sleeping transition period may not be uniform across EEG bands and that the hypnagogic EEG changes may start before the onset of Stage 1 and continue for several minutes after the onset of Stage 2.     

The type A behavior pattern and immune reactivity to brief stress: change of volume of secretory immunoglobulin A in saliva

This article presents findings of a laboratory experiment on the association of the Type A behavior pattern with reactivity of secretory immune functioning to brief stress. 38 female undergraduate students classified as Type A (n = 19) or as Type B (n = 19) on the basis of their scores on the Kwansei Gakuin Type A scale performed a continuous arithmetic task in a situation in which they were exposed to aversive loud noise. Secretory immunoglobulin A (s-IgA) in saliva and autonomic measures (heart rate and frequency of eyeblink) were evaluated before and after the manipulation of stress. The volume of s-IgA at baseline was significantly higher for the Type A group than for the Type B group, suggesting that the former relative to the latter might be chronically higher in mucosal immune functioning. Also, the volume of s-IgA significantly increased after exposure to a brief stress for the Type B group but did not change for the Type A group, a finding which might indicate that the Type A group may have less immune reactivity to a brief stress.