VEP(視覚性誘発電位)および脳波への喫煙の効果

The effects of cigarette smoking on the human CNS (Central Nervous System) were studied by VEP (Visual Evoked Potential) with 38 healthy male subjects (20～42 y. o., mean : 18. 6 cig./ day×8. 5 years). All subjects were deprived of smoking from the last night prior to the expriment. In the experimental session the subjects were asked to smoke two cigarettes (nicotine content 2. 7 mg/ cig.) in ten minutes after control recording. EEGs containing VEPs evoked by flash stimuli once every 5 second were recorded into the magnetic tape through the two derivations (2CH : O1→A1+2 and 5CH : O1→Cz) together with EEGs also through four other derivations, simultaneously. Reproducing the tape, VEPs from the two derivations were recorded, with 1000 msec of analysis time, for each recording session ; before, during and 10, 20, 30 min. after cigarette smoking.
The EEGs were subjected to the quantitative frequency analysis. VEPs were converted into a series of numbers and subjected to the computer processing and statistical assessment with special reference to the EEG changes. The subjects were divied into the two groups, heavy smoker group and light smoker group (more than/within 15 cig./ day), for further study. The following results were obtained.
1. In the waveforms of group mean VEP recorded from the two drivations, N4 appeared only during cigarette smoking. Latencies of P2～P4 were tended to increase during and after smoking, other latencies tended to decrease during smoking and then increased thereafter. Peak-to-peak amplitudes tended to increase, and then decrease thereafter. In the group mean VEP from 5CH, peak-to-peak amplitudes decreased during and after smoking. Conponent analysis with individual VEPs verified these changes in the group mean VEP significant. These changes in the VEPs were attributed to the early exciting (arousal) effect due to the nicotin attaining to the brain, followed by the inhibiting (sedative) effect due to the short half-life period and tachyphylaxis of nicotin.
2. The correlation coefficients between the number of cigarette smoked in one day and ratio of change of latencies and peak-to-peak amplitudes indicated that the effects of smoking above mentioned appeared more markedly with heavy smokers than with light smokers, indicating more increased susceptibility to nicotin due to cigarette abstinence with the former.
3. Quantitative frequency analysis of EEG indicated arousal effect by the decrease of θ and increase of peak α frequency, and sedative effect by the derease of β1, namely desynchronization. These" arousal sedative effect" corresponded with the VEP changes by cigarette smoking in the present study.