Visual P300 and the self-directedness scale of the Temperament and Character Inventory.

Reduced amplitude of the P300 event-related brain potential has been associated with several psychopathological conditions and is thought to represent brain dysfunction in such conditions. Predisposition to personality disorders and psychopathology in general is also associated with low scores on the self-directedness (SD) scale of the Temperament and Character Inventory. The present preliminary study investigated the relationship between amplitudes of P300 elicited by rare target stimuli in a visual oddball task and SD scores in 58 healthy participants. P300 was found to be significantly reduced in subjects with low SD, as supported by correlational analysis and by comparison of groups formed on the basis of SD scores. This finding may be relevant to prior findings indicating reduced P300 amplitudes in a variety of psychopathological conditions and suggests that a common vulnerability factor, reflected in the low SD personality scores, may contribute to the P300 reduction in psychiatric populations.

The P300 brain potential is reduced in smokers.

RATIONALE: Tobacco smoking is the most prevalent type of substance abuse, yet its biobehavioral etiology is little understood. Identification of differences between smokers and non-smokers on basic characteristics of neurocognitive functioning may help to elucidate the mechanisms of tobacco dependence. OBJECTIVES: This study assessed the relationship between smoking status and the P300 component of event-related potential (ERP) while controlling for potential confounders such as alcoholism, drug abuse, and psychopathology. METHODS: The ERP responses elicited by a visual oddball task were measured at the mid-parietal site in 905 current smokers, 463 ex-smokers, and 979 never smokers. RESULTS: P300 amplitude was significantly lower in current cigarette smokers compared to never-smokers. Ex-smokers did not differ significantly from never-smokers. P300 reduction was also associated with alcoholism, drug dependence, and family density of alcoholism. However, after controlling for smoking, only family density of alcoholism remained a significant predictor of P300 amplitude. CONCLUSIONS: The results indicate a significant effect of smoking status on P300 amplitude which is additive to family history of alcoholism and suggest that either (1) long-term tobacco smoking may produce a reversible change in brain function, or (2) reduced P300 may be a marker of risk for nicotine dependence.

[Galvanic skin response as a reflection of the decision-making process when time is insufficient]. / Kozhno-gal'vanicheskaia reaktsiia kak otrazhenie protsessa priniatiia resheniia v usloviiakh defitsita vremeni.

Amplitude and latency of skin galvanic response ( SGR ) was studied in 15 healthy subjects in two experimental programs. The first program demanded to perform a motor act as quickly as possible if all the three signals were the same, the second one demanded a motor act if at least one of the signals differed from the other two. Following series of signals were presented: 1--all the three signals being the same, 2--the first one differed from the others, 3,4--correspondingly, the second or the third signal differed from the others. The amplitude of SGR was found to increase, and its latency was found to decrease when the decision was taken under the conditions of time deficit. Thus, SGR reflects the process of decision taking rather than pretuning of the motor act.