Dimensions of impulsive behavior in adolescents: laboratory behavioral assessments.

Impulsivity is a multifaceted construct that defines a range of maladaptive behavioral styles. The present research aimed to identify different dimensions of impulsive behavior in adolescents from a battery of laboratory behavioral assessments. In one analysis, correlations were examined between two self report and seven laboratory behavioral measures of impulsivity. The correlation between the two self report measures was high compared to correlations between the self report and laboratory behavioral measures. In a second analysis, a principal components analysis was performed with just the laboratory behavioral measures. Three behavioral dimensions were identified -- "impulsive decision-making", "impulsive inattention", and "impulsive disinhibition". These dimensions were further evaluated using the same sample with a confirmatory factor analysis, which did support the hypothesis that these are significant and independent dimensions of impulsivity. This research indicates there are at least three separate subtypes of impulsive behavior when using laboratory behavioral assessments with adolescent participants.

A web-based contingency management program with adolescent smokers.

The present study evaluated a new 30-day Web-based contingency management program for smoking abstinence with 4 daily-smoking adolescents. Participants made 3 daily video recordings of themselves giving breath carbon monoxide (CO) samples at home that were sent electronically to study personnel. Using a reversal design, participants could earn money for continued abstinence during the treatment phases (CO < or =5 ppm). All participants were compliant with the treatment (submitting 97.2% of samples), and all achieved prolonged abstinence from smoking.

Adolescent smokers rate delayed rewards as less certain than adolescent nonsmokers.

This research compared adolescent smokers (n=45) and nonsmokers (n=35) on ratings of certainty about receiving delayed rewards during a delay discounting procedure. Consistent with a previous finding [Patak, M., Reynolds, B., 2007. Question-based assessments of delay discounting: do respondents spontaneously incorporate uncertainty into their valuations for delayed rewards? Addict. Behav. 32, 351-357] participants generally rated the delayed rewards as increasingly uncertain with longer delays, and ratings of certainty were correlated with delay discounting (r=.37). Also, the adolescent smokers rated the delayed rewards as significantly less certain than the nonsmokers. These findings indicate that adolescents who smoke cigarettes evaluate delayed outcomes as less certain than adolescents who do not smoke cigarettes.

Laboratory and self-report assessments of impulsive behavior in adolescent daily smokers and nonsmokers.

This research compared adolescent daily smokers (n=25) and nonsmokers (n=26) on different measures of impulsivity. Assessments included question-based measures of delay (DDQ) and probability (PDQ) discounting, a measure of behavioral disinhibition (go-stop task), and a self-report measure of impulsivity (Barratt Impulsiveness Scale-Adolescent). Adolescent smokers were more impulsive on the DDQ and Barratt Impulsiveness Scale--Adolescent but not on the PDQ or the go-stop task. However, there was a significant interaction between smoking status and gender on the go-stop task, with male smokers performing less impulsively on this measure than male nonsmokers--an effect not observed with the female adolescents. These findings indicate that adolescents who smoke cigarettes are more impulsive with respect to some, but not all, types of impulsivity than are adolescents who do not smoke.

Question-based assessments of delay discounting: do respondents spontaneously incorporate uncertainty into their valuations for delayed rewards?

This research was designed to determine if, and to what extent, participants incorporate uncertainty into their valuations for delayed rewards when completing measures of delay discounting, even though uncertainty is not specified in the delay-discounting questions. Twenty-four adolescent participants completed a question-based measure of delay discounting and immediately following answered questions about perceived certainties of receiving the delayed rewards. Results showed that respondents rated the delayed rewards as increasingly uncertain with longer delays. Also, ratings of uncertainty were correlated with rate of delay discounting (r=0.55). These findings suggest participants automatically evaluate delayed rewards as uncertain when using this assessment procedure. The current finding may hold important implications for future addiction research in interpreting why addicted persons often discount more by delay than non-addicted controls, i.e., delay to reward or uncertainty about delayed rewards?

Nucleus accumbens lesions decrease sensitivity to rapid changes in the delay to reinforcement.

Both humans and non-humans discount the value of rewards that are delayed or uncertain, and individuals that discount delayed rewards at a relatively high rate are considered impulsive. To investigate the neural mechanisms that mediate delay discounting, the present study examined the effects of excitotoxic lesions of the nucleus accumbens (NAC) on discounting of reward value by delay and probability. Rats were trained on delay (n=24) or probability discounting (n=24) tasks. Following training, excitotoxic lesions of the NAC were made by intracranial injections of 0.5 microl 0.15 M quinolinic acid (n=12) or vehicle (n=12) aimed at the NAC (AP +1.6, ML +/-1.5, DV -7.1). NAC lesions did not alter performance in animals tested with a constant delay (4s) or probability (0.4) of reinforcement. However, when tested with between session changes in the delay (0, 1, 2, 4, and 8s) of reinforcement, the lesioned rats had flatter discount curves than the sham group, indicating that they were less sensitive to frequent changes in the delay to reward. In contrast, the NAC lesions did not affect discounting of probabilistic rewards. NAC lesions impaired the ability to adapt to frequent between session changes in the delay to reward but did not increase or decrease discounting when the delay was held constant across sessions. NAC lesions may disrupt the ability of the animals to predict the timing of delayed rewards when the delay to reward is changed frequently.