Behavioral differences among 129 substrains: Implications for knockout and transgenic mice.

Most knockout (KO) mice are produced with embryonic stem cells derived from a 129 strain. Because most KO strains are backcrossed to B6 yet retain a portion of their genome from 129, especially around the ablated target locus, phenotypes previously attributed to the ablated locus may be due to passenger 129 genes. Thus, the authors decided to test several 129 substrains for their behavioral characteristics. Seven 129 substrains were put through a battery of tasks to determine their behavioral profiles. Differences were found in anxiety-related behaviors in the zero-maze, habituation to the open field, and cued fear conditioning. All strains successfully performed the rotorod task. The behavioral differences observed may have important implications for the interpretation of data and show divergence of behavioral performance in these 129 substrains. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Incubation effect: Role of awareness in an immediate versus delayed test of conditioned emotionality.

"The purpose of the study was to test the view that conditioned emotionality, as measured by the GSR, increases after a delay and that this increase is greater when the subject is aware of the relation between the CS and UCS. Certain words were associated with shock. The subject was aware of the relation between one word and shock but was unaware of the relation between a second word and shock. The GSR to these words was compared to the GSR to a word not associated with shock." The results confirmed the hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Behavioral differences among 129 substrains: Implications for knockout and transgenic mice": Erratum.

Reports an error in the original article by M. N. Cook et al (Behavioral Neuroscience, 2002[Aug], Vol 116[4], pp. 600-611). In Figure 2A, an asterisk appears beside the habituation score (.56) for the P3 substrain. The result was not significant. An asterisk should appear beside the habituation score (.39) for the S6 substrain. (The following abstract of this article originally appeared in record 2002-17253-009.) Most knockout (KO) mice are produced with embryonic stem cells derived from a 129 strain. Because most KO strains are backcrossed to B6 yet retain a portion of their genome from 129, especially around the ablated target locus, phenotypes previously attributed to the ablated locus may be due to passenger 129 genes. Thus, the authors decided to test several 129 substrains for their behavioral characteristics. Seven 129 substrains were put through a battery of tasks to determine their behavioral profiles. Differences were found in anxiety-related behaviors in the zero-maze, habituation to the open field, and cued fear conditioning. All strains successfully performed the rotorod task. The behavioral differences observed may have important implications for the interpretation of data and show divergence of behavioral performance in these 129 substrains. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Strain differences in zebrafish (Danio rerio) social roles and their impact on group task performance.

“Key” individuals in a social group are those that are centrally connected and thus serve as a hub for information flow across the group. From this position, they have the potential to have a powerful influence on group dynamics and performance. Here, we use metrics from social network theory to identify Key individuals in groups of 3–4 zebrafish (Danio rerio), and to measure the impact of removing those individuals from the group. We compared the results for two genetically distinct strains of zebrafish and found that although their social dynamics were superficially similar, one strain (Scientific Hatcheries, SH) responded to social perturbation, whereas the other (Parganas North, PN) did not. For both strains, groups that retained their Key fish performed better on a simple group foraging-learning task than did those from which the Key fish had been removed. However, the SH strain learned the task more quickly than did the PN strain, perhaps in part because of sex differences in task performance or because of strain differences in the reaction to experimental disturbance. We also confirm the utility of measures of social dynamics and social role that can be estimated reliably from very short observation sessions and by relatively untrained observers. These results set the stage for future research into the genetic mechanisms underlying social roles and group learning in vertebrates. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Strain differences in maintenance of cocaine self-administration and their relationship to novelty activity responses.

The authors previously demonstrated that Fischer 344 (F344) and Lewis inbred rats differ in acquisition of cocaine self-administration. Other studies show that acquisition and maintenance of drug self-administration are predicted by locomotor activity in a novel environment among outbred Sprague-Dawley rats. The present study was designed to determine whether this relationship extended to F344 and Lewis rats. In Experiment 1, F344, Lewis, and Sprague-Dawley rats were trained to self-administer cocaine and tested with several doses under fixed- and progressive-ratio schedules of reinforcement. Self-administered infusions and ineffective active lever presses--those emitted during infusion and time-out periods--were assessed. In Experiment 2, separate sets of rats of each strain were examined for locomotor responses (distance traveled and center time) under novelty conditions. Results show that F344 rats self-administer more cocaine than Lewis or Sprague-Dawley rats under both schedules and emit more ineffective lever presses--a possible measure of craving. Strain comparisons of locomotor responses suggest that center time, not activity, relates to self-administration behavior. Maintenance studies of cocaine self-administration rather than acquisition may better reflect vulnerability to addiction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Negro-white differences in intelligence test performance: A new look at an old problem.

Negro-white differences on mental tests are evaluated in this paper, which was prepared at the suggestion of the Society for the Psychological Study of Social Issues (Division 9 of the American Psychological Association). "The evidence against the assumption of native differences in intelligence test performance between Negroes and whites still seems to me to be very convincing." There is "no scientifically acceptable evidence for the view that ethnic groups differ in innate abilities. This is not the same as saying that there are no ethnic differences in such abilities… . The science of psychology can offer no support to those who see in the accident of inherited skin color or other physical characteristics any excuse for denying to individuals the right to full participation in American democracy." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult age differences in episodic memory: Further support for an associative-deficit hypothesis.

This study further tested an associative-deficit hypothesis (ADH; M. Naveh-Benjamin, 2000), which attributes a substantial part of older adults' deficient episodic memory performance to their difficulty in merging unrelated attributes-units of an episode into a cohesive unit. First, the results of 2 experiments replicate those observed by M. Naveh-Benjamin (2000) showing that older adults are particularly deficient in memory tests requiring associations. Second, the results extend the type of stimuli (pictures) under which older adults show this associative deficit. Third, the results support an ADH in that older adults show less of an associative deficit when the components of the episodes used are already connected in memory, thereby facilitating their encoding and retrieval. Finally, a group of younger adults who encoded the information under divided-attention conditions did not show this associative deficit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic differences in startle gating-disruptive effects of apomorphine: Evidence for central mediation.

Strain differences in sensitivity to dopamine agonist-induced disruption of prepulse inhibition (PPI) may be a useful model for the genetics of PPI deficits in neuropsychiatric disorders. Compared with Long-Evans (LE) rats, Sprague-Dawley (SD) rats are more sensitive to the PPI-disruptive effects of the DA agonist apomorphine. The authors tested the hypothesis that this strain difference reflects brain function rather than peripheral physiology. Significant SD > LE PPI-disruptive effects of apomorphine were observed despite equal apomorphine levels in SD and LE rats in forebrain regions that regulate PPI. SD > LE PPI-disruptive effects of apomorphine were also independent of peripheral versus central route of administration. This model for PPI genetics is sensitive to differences in central rather than peripheral substrates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in coping styles and implications for depressed mood.

Based on a sample of young adults in Miami-Dade County, Florida, this paper examined the extent to which there were sex differences in 3 coping style types: problem focused, emotion focused, and avoidance focused (Endler & Parker, 1990). Further examined were the extent to which sex differences in coping styles could be explained by sex differences in chronic strain; the extent to which sex differences in depressed mood could be explained by sex differences in coping style; and whether the effects of different coping style types on depressed mood varied by sex. Results suggested somewhat complex relationships among sex, coping, chronic strain, and depression. No sex differences in the use of problem-focused coping were observed when statistical controls for socioeconomic status were applied; however, women more often used avoidance-focused techniques. Although female respondents more often used emotion-oriented strategies compared to male respondents, such use did not prove to be fundamentally harmful for women. In fact, the effects of using emotion-focused strategies, such as the expression of feelings, reduced depressed mood for women, but not for men. Implications for practice and policy are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in the development of sensation seeking and impulsivity during adolescence: Further evidence for a dual systems model.

Consistent with social neuroscience perspectives on adolescent development, previous cross-sectional research has found diverging mean age-related trends for sensation seeking and impulsivity during adolescence. The present study uses longitudinal data on 7,640 youth from the National Longitudinal Study of Youth Children and Young Adults, a nationally representative sample assessed biennially from 1994 to 2006. Latent growth curve models were used to investigate mean age-related changes in self-reports of impulsivity and sensation seeking from ages 12 to 24 years, as well individual differences in these changes. Three novel findings are reported. First, impulsivity and sensation seeking showed diverging patterns of longitudinal change at the population level. Second, there was substantial person-to-person variation in the magnitudes of developmental change in both impulsivity and sensation seeking, with some teenagers showing rapid changes as they matured and others maintaining relatively constant levels with age. Finally, the correlation between age-related changes in impulsivity and sensation seeking was modest and not significant. Together, these results constitute the first support for the dual systems model of adolescent development to derive from longitudinal behavioral data. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Age differences in social preferences among Taiwanese and mainland Chinese: The role of perceived time.

Socioemotional selectivity theory holds that as people recognize the inevitable constraint of time imposed by mortality, their social goals change, motivating them to limit social contacts to those with whom they are emotionally close. This theory was tested among Taiwanese and Mainland Chinese. As predicted, results showed that older adults (aged 60–90 years) in both cultures were more likely than younger adults (aged 18–30 years) to prefer familiar social partners who were most likely to provide emotionally close social interactions. Mainland Chinese, who as a group have shorter actuarial life expectancy, were more likely to prefer familiar social partners than were Taiwanese. These age and cultural differences were eliminated when differences in perceived time were statistically controlled for. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Norms for experiencing emotions in different cultures: Inter- and intranational differences.

Within- and between-nations differences in norms for experiencing emotions were analyzed in a cross-cultural study with 1,846 respondents from 2 individualistic (United States, Australia) and 2 collectivistic (China, Taiwan) countries. A multigroup latent class analysis revealed that there were both universal and culture-specific types of norms for experiencing emotions. Moreover, strong intranational variability in norms for affect could be detected, particularly for collectivistic nations. Unexpectedly, individualistic nations were most uniform in norms, particularly with regard to pleasant affect. Individualistic and collectivistic nations differed most strongly in norms for self-reflective emotions (e.g., pride and guilt). Norms for emotions were related to emotional experiences within nations. Furthermore, there were strong national differences in reported emotional experiences, even when norms were held constant. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gender differences in emotional risk for self- and other-directed violence among externalizing adults.

Objective: Women and men generally differ in how frequently they engage in other- and self-directed physical violence and may show distinct emotional risk factors for engagement in these high-impact behaviors. To inform this area, we investigated gender differences in the relationship of emotional tendencies (i.e., anger, hostility, and anhedonic depression) that may represent risk for other-directed violence (i.e., physical fighting, attacking others unprovoked) and self-directed violence (i.e., self-injury, suicide attempts). Method: The ethnically diverse sample consisted of 372 adults (252 men and 120 women age 18–55) with a history of criminal convictions. Facets of emotional risk assessed with the Aggression Questionnaire (Buss & Warren, 2000) and Mood and Anxiety Symptom Questionnaire (Watson et al., 1995) were entered simultaneously as explanatory variables in regression analyses to investigate their unique contributions to other- and self-directed physical violence in men and women. Results: Analyses revealed that anhedonic depressive tendencies negatively predicted other-directed violence and positively predicted self-directed violence in men and women, consistent with a model of depression in which aggression is turned inward (Henriksson et al., 1993). Gender differences, however, emerged for the differential contributions of anger and hostility to other- and self-directed violence. Trait anger (i.e., difficulty controlling one's temper) was associated with other-directed violence selectively in men, whereas trait hostility (i.e., suspiciousness and alienation) was associated with self- and other-directed violence among women. Conclusions: The divergent findings for trait anger and hostility underscore the need to examine gender-specific risk factors for physical violence to avoid excluding potentially useful clinical features of these mental health outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Low efficacy opioids: Implications for sex differences in opioid antinociception.

It is becoming increasingly evident that the sex of an organism is a critical determinant of responsiveness to opioid analgesics. However, the factors that determine the magnitude and direction of sex differences in opioid antinociception have not been fully elucidated. One factor that has received attention is the relative efficacy of the opioid. This review summarizes recent findings in which opioid efficacy was systematically manipulated as an independent variable to probe underlying sex differences in opioid system function. Overall, in rodents and nonhuman primates, υ and κ opioids are generally more potent and effective in males than in females. The data indicate that although sex differences in the potency of high efficacy opioids such as morphine are generally less than 3.0-fold, sex differences with lower efficacy opioids can be greater than 90-fold. Moreover, that these drugs can function as full agonists in males while functioning as antagonists in females under identical conditions suggests some fundamental sex difference in opioid system function. In addition to efficacy, a number of other variables can affect the outcomes of these studies, including the drug history, genotype, and nociceptive stimulus modality, duration, and intensity. These factors may interact with opioid efficacy to determine the specific conditions under which sex differences are observed. The testing of low efficacy opioids by other laboratories and under other experimental conditions will determine the extent to which this variable affords a strategic research tool. The potential utility of low efficacy opioids in other domains of behavioral pharmacology is also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Feelings change: Accounting for individual differences in the temporal dynamics of affect.

People display a remarkable variability in the patterns and trajectories with which their feelings change over time. In this article, we present a theoretical account for the dynamics of affect (DynAffect) that identifies the major processes underlying individual differences in the temporal dynamics of affective experiences. It is hypothesized that individuals are characterized by an affective home base, a baseline attractor state around which affect fluctuates. These fluctuations vary as the result of internal or external processes to which an individual is more or less sensitive and are regulated and tied back to the home base by the attractor strength. Individual differences in these 3 processes—affective home base, variability, and attractor strength—are proposed to underlie individual differences in affect dynamics. The DynAffect account is empirically evaluated by means of a diffusion modeling approach in 2 extensive experience-sampling studies on people's core affective experiences. The findings show that the model is capable of adequately capturing the observed dynamics in core affect across both large (Study 1) and shorter time scales (Study 2) and illuminate how the key processes are related to personality and emotion dispositions. Implications for the understanding of affect dynamics and affective dysfunctioning in psychopathology are also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age differences in overlapping-task performance: Evidence for efficient parallel processing in older adults.

Two psychological refractory period (PRP) experiments were conducted to examine overlapping processing in younger and older adults. A shape discrimination task (triangle or rectangle) for Task I (TI) and a lexical-decision task (word or nonword) for Task 2 (T2) were used. PRP effects, response time for T2 increasing as stimulus onset synchrony (SOA) decreased, were obtained for both age groups. The effect of word frequency on T2 was smaller at the short SOA than at the long SOA, reflecting slack effects, which were larger for older than younger adults in both experiments. These results suggest that older adults can perform lexical access of T2 in parallel with the processing of T2, at least as efficiently as younger adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increased immobility in an automated forced swimming test following lesion of the habenula in rats: Absence of evidence for a contribution from motor impairment.

The effects of lesions of the habenula on responses during a forced swimming test (FST) were examined. Active behavior, documented by turns on a drum immersed in a water tank, were reduced in lesioned rats. Lesioned rats also demonstrated an inability to escape from the water by climbing onto the drum when it was locked in position at the end of the test. There was a tendency for lesioned rats to show more activity in open-field tests either after the FST or independent of such prior testing. Lesioned rats showed no motor or postural abnormalities and were able to maintain position for longer than controls during a rotating rod test. Collectively, the results are compatible with the suggestion that lesions of the habenula impair the ability to change motor strategies under stress but indicate such failures may not be ascribed to gross motor impairment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in referrals to a rehabilitation facility for the physically disabled: A research note.

Sex ratios for inpatient and outpatient referrals to a Department of Rehabilitation Medicine and to its psychological services were examined for six general diagnostic categories of injury and disease and compared with known proportions of males and females in the population in these categories. Of the diagnostic categories, only referrals of patients suffering from cerebral vascular accident (CVA) revealed sex ratios significantly different from population estimates. Problems in interpreting the statistics and in judging the adequacy of the estimated sex ratios, which may be confounded by differential age expectancies, were disclosed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Personality and the psychological refractory period: No evidence for an extraversion- or intelligence-related effect.

The psychological refractory period (PRP) refers to a major bottleneck of information processing that becomes evident when participants are required to respond to two signals (S1 and S2) presented in rapid succession. Typically, the response to S2 becomes increasingly delayed with decreasing stimulus onset asynchrony between S1 and S2. Several studies suggest differences in speed of sensorimotor information processing between introverts and extraverts. Speed of information processing is also positively related to mental ability. The present study investigates whether these individual differences in speed of information processing may reflect differences in PRP. For this purpose 80 female undergraduates were tested with a standard PRP design using an auditory two-choice Task 1 and a visual two-choice Task 2. Although a general PRP effect could be shown, there was no evidence for extraversion- or intelligence-related differences in PRP. These findings indicate that the PRP effect represents a robust phenomenon which is largely independent of extraversion- and intelligence-related individual differences in speed of information processing. (PsycINFO Database Record (c) 2011 APA, all rights reserved)