Does Ventromedial Prefrontal Cortex Damage Really Increase Impulsiveness? Delay and Probability Discounting in Patients with Focal Lesions.

If the tendency to discount rewards reflects individuals' general level of impulsiveness, then the discounting of delayed and probabilistic rewards should be negatively correlated: The less a person is able to wait for delayed rewards, the more they should take chances on receiving probabilistic rewards. It has been suggested that damage to the ventromedial prefrontal cortex (vMPFC) increases individuals' impulsiveness, but both intertemporal choice and risky choice have only recently been assayed in the same patients with vMPFC damage. Here, we assess both delay and probability discounting in individuals with vMPFC damage (n = 8) or with medial temporal lobe (MTL) damage (n = 10), and in age- and education-matched controls (n = 30). On average, MTL-lesioned individuals discounted delayed rewards at normal rates but discounted probabilistic rewards more shallowly than controls. In contrast, vMPFC-lesioned individuals discounted delayed rewards more steeply but probabilistic rewards more shallowly than controls. These results suggest that vMPFC lesions affect the weighting of reward amount relative to delay and certainty in opposite ways. Moreover, whereas MTL-lesioned individuals and controls showed typical, nonsignificant correlations between the discounting of delayed and probabilistic rewards, vMPFC-lesioned individuals showed a significant negative correlation, as would be expected if vMPFC damage increases impulsiveness more in some patients than in others. Although these results are consistent with the hypothesis that vMPFC plays a role in impulsiveness, it is unclear how they could be explained by a single mechanism governing valuation of both delayed and probabilistic rewards.

Is it time? Episodic imagining and the discounting of delayed and probabilistic rewards in young and older adults.

Remembering and imagining specific, personal experiences can help shape our decisions. For example, cues to imagine future events can reduce delay discounting (i.e., increase the subjective value of future rewards). It is not known, however, whether such cues can also modulate other forms of reward discounting, such as probability discounting (i.e., the decrease in the subjective value of a possible reward as the odds against its occurrence increase). In addition, it is unclear whether there are age-related differences in the effects of cueing on either delay or probability discounting. Accordingly, young and older adult participants were administered delay and probability discounting tasks both with and without cues to imagine specific, personally meaningful events. As expected, cued episodic imagining decreased the discounting of delayed rewards. Notably, however, this effect was significantly less pronounced in older adults. In contrast to the effects of cueing on delay discounting, personally relevant event cues had little or no effect on the discounting of probabilistic rewards in either young or older adults; Bayesian analysis revealed compelling support for the null hypothesis that event cues do not modulate the subjective value of probabilistic rewards. In sum, imagining future events appears only to affect decisions involving delayed rewards. Although the cueing effect is smaller in older adults, nevertheless, it likely contributes to how adults of all ages evaluate delayed rewards and thus, it is, in fact, about time.

Structure and promoter analysis of murine CAD and ICAD genes.

Caspase-activated DNase (CAD) degrades chromosomal DNA during apoptosis, whereas ICAD (inhibitor of CAD) inhibits the CAD's DNase by binding to it. Here, we describe the assignment of murine CAD and ICAD genes to the distal part of murine chromosome 4. Molecular cloning and structural analysis indicated that CAD and ICAD genes are comprised of 7 and 6 exons, respectively. Two different ICAD mRNAs coding for two forms of ICAD proteins (ICAD-S and ICAD-L) were found to be produced by alternative splicing of intron 5. The CAD and ICAD mRNAs were detected ubiquitously in various murine tissues. Analyses of the promoter activity with a series of deletion mutants of their 5' flanking regions indicated that a 190-bp 5' flanking region of the CAD gene was sufficient to promote the transcription. Whereas, a 120-bp flanking region of ICAD gene was required to promote its transcription. These regions do not show similarity between CAD and ICAD genes, suggesting that expression of CAD and ICAD genes is regulated by different mechanisms.

Discriminant Analyses Of Preschool Masculinity And Femininity.

The nature of masculinity and femininity in the preschool years was investigated. Four criterion groups, Most Masculine boys, Least Masculine boys, Most Feminine girls, and Least Feminine girls, were selected from teachers' judgments of masculinity and femininity made by the method of pair comparisons. A covariance matrix of the teachers' personality ratings of these children was factor analyzed. Four factors were identified : Extraversion- Introversion, Social Adjustment, Competence, and an unnamed factor. A discriminant analysis on these factors indicated that MM boys were more extraverted, somewhat more competent and slightly more socially adjusted than LM boys. A second discriminant analysis indicated that M F girls were more socially adjusted, somewhat more competent and slightly more introverted than LF girls. The coefficient of congruence between the discriminant pat- terns for masculinity and femininity indicated that these constructs are not opposite ends of a continuum.