Impulsivity is a defining characteristic of adolescence. Compared to adults, for example, adolescents engage in higher rates of drug and alcohol experimentation, risky sexual practices, and criminal activity. Such behavior may reflect reduced sensitivity to long-term consequences for behavior during adolescence. Recently, our lab has attempted to refine mouse procedures to study developmental trends in decision making in the laboratory. In the present experiment, we examined sensitivity to delayed rewards in C57BL/6J (B6) and DBA/2J (D2) mice during adolescence and adulthood using an adaptation of a two-week delay discounting procedure developed by Adriani & Laviola (2003) [Behavioral Neuroscience, 117,[695][696][697][698][699][700][701][702][703]. During training, mice could choose between a 20-or 100-ul drop of milk delivered after a 1-s delay. During testing, the delay to the large drop of milk was increased from 1 to 100 seconds. As the delay to the larger volume increased, preference shifted to the smaller, more immediate option. In adolescence, both strains showed similar shifts in preference. In contrast, adult B6 mice were less sensitive to increasing delays than were adult D2 mice, who continued to perform much as their adolescent counterparts. A subsequent resistance-to-extinction test ruled out the possibility that the slower change in the adult B6 mice was due to perseverative responding. The present findings suggest that B6 and D2 strains may be differentially suited to uncovering the biological mechanism of short-term and long-term patterns of impulsive behavior.
KeywordsImpulsivity; Delay Discounting; Development; Resistance to Extinction; C57BL6/6J; DBA/2JThe adolescent undergoes profound neural, physiological, behavioral, and social changes during in the transition from childhood to adulthood. Although the adolescent period is important for establishing the individual as an independent adult, it is also a period of developmental vulnerability (Casey, Jones, & Hare, 2008;Steinberg, 2005). Adolescent behavior is often described as impulsive, risky, and sensation-driven, reflecting increased tendencies for adolescents to engage in unsafe sexual practices, dangerous driving, criminal behavior, and experimentation with controlled substances (Arnett, 1992;Chambers, Taylor, & Potenza, 2003;Crews, He, & Hodge, 2007;Spear, 2000). In fact, potentially maladaptive Corresponding Author: Questions regarding this manuscript should be directed to Jonathan W. Pinkston, Department of Behavior Analysis, University of North Texas, Denton, TX 76209, jonathan.pinkston@unt.edu or Richard Lamb, Department of Psychiatry, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229 lamb@uthscsa.edu. Jonathan Pinkston is now at the University of North Texas.
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