Smoking induced changes in EEG two-dimensional maps and blood gas analysis.

The effects of smoking on mental function were investigated by the two-dimensional EEG mapping method, and the results were analyzed in conjunction with blood gas data that had been obtained simultaneously. Healthy medical students from the National Defense Medical College were used as the subjects for this experiment. They live in the same dormitory and a similar lifestyle to regular military personnel. Tests were carried out on two successive days, and in between the two testing sessions, each subject was requested to refrain from smoking for 24 hours. During the testing sessions, EEGs were recorded with eyes closed, before and after smoking. Two-dimensional maps were generated by unbiased polynomial interpolation for alpha activity. Various blood chemical measurements were made, among which, partial pressure of carbon dioxide (pCO2) and percentage of carbon monoxide hemoglobin (%COHb) were studied in relation to EEG changes. The smoking induced wide-spread amplitude decrease in the alpha maps. After 24 hours of withdrawal, alpha amplitude increased, although it decreased again when smoking resumed. Either the correlation between EEG amplitude and %COHb, or the correlation between EEG amplitude and pCO2, was examined in three regions (anterior: A, middle: M and posterior: P) of the two-dimensional maps in both slow and quick smokers. There were no correlations observed between changes in the EEG amplitude and changes in %COHb induced by smoking, in any of the three regions in either fast or slow smokers. However, there was a clear correlation between changes in the EEG amplitude and changes in pCO2 in quick smokers, the correlation coefficient being approximately -0.7. It is possible that this relationship was due to hyperventilation, since the same tendency was not observed in slow smokers.