Open field habituation learning is improved by nicotine and attenuated by mecamylamine administered posttrial into the nucleus accumbens

Using the paradigm of habituation learning in the open field, we tested the effects of unilateral microinjections of the agonist nicotine (8.0, 40.0, and 80.0 microg) and the nicotine receptor antagonist mecamylamine (0.1, 1.0, 10.0 microg) into the core of the nucleus accumbens. When injected posttrial, that is, immediately after the first exposure to the open field, nicotine dose-dependently enhanced behavioral habituation during the test on the following day, indicating a facilitation of memory, whereas mecamylamine impaired habituation at the highest dose, but not at the two lower doses. When injected 5 h after the learning trial, nicotine (40 microg) and mecamylamine (10 microg) impaired habituation on the subsequent day. A control experiment did not provide evidence for possible proactive effects of mecamylamine. These findings are discussed with respect to the possible behavioral functions of cholinergic, and especially nicotinic, mechanisms in the nucleus accumbens. They may also be relevant for understanding cholinergic-linked psychopathologies such as Alzheimer's disease, since the nucleus accumbens is one of the sites where cholinergic neurons are lost in this neurodegenerative disease.     

Electroencephalographic registration of low concentrations of isoamyl acetate

Previous research has demonstrated electroencephalogram (EEG) changes in response to low-odor concentrations, resulting in near-chance detection. Such findings have been taken as evidence for olfaction without awareness. We replicated and extended previous work by examining EEG responses to water-water control, 0.0001, 0. 001, 0.01, and 1 ppm isoamyl acetate (IAA) in water paired with water only. Detection was above chance (>50%) for.001 and above, and alpha decreased only to those concentrations, suggesting that EEG changes corresponded to IAA awareness. However, when correct trial EEGs were compared to incorrect trial EEGs during.001 ppm, right posterior/central alpha decreased during incorrect trials and alpha decreased more globally (including frontal sites) during correct trials. These data may not reflect awareness or unawareness per se. Instead, results are discussed regarding activation of perceptual systems in the posterior region during incorrect trials and the activation of frontal action systems during a subset of correct trials.     

Adolescent Ego-Development Trajectories and Young Adult Relationship Outcomes

Adolescent ego-development trajectories were related to close-relationship outcomes in young adulthood. An adolescent sample completed annual measures of ego development from ages 14 through 17. The authors theoretically determined and empirically traced five ego-development trajectories reflecting stability or change. At age 25, the sample completed a close-relationship interview and consented for two peers to rate the participants'ego resiliency and hostility. Participants who followed the profound-arrest trajectory in adolescence reported more mundane sharing of experiences, more impulsive or egocentric conflict-resolution tactics, and less mature interpersonal understanding in their young adult relationships, and their young adult peers described these participants as more hostile. Participants who attained or maintained higher levels of ego development in adolescence reported more complex sharing of experiences, more collaborative conflict-resolution strategies, and greater interpersonal understanding, and their young adult peers rated them as less hostile and as more flexible.     

The effects of concurrent verbal and visual tasks on category learning

Current theories of category learning posit separate verbal and nonverbal learning systems. Past research suggests that the verbal system relies on verbal working memory and executive functioning and learns rule-defined categories; the nonverbal system does not rely on verbal working memory and learns non-rule-defined categories (E. M. Waldron & F. G. Ashby, 2001; D. Zeithamova & W. T. Maddox, 2006). However, relatively little research has explored the importance of visual working memory or visual processing for either system. The authors investigated the role of working memory (Experiment 1a and 1b), visual processing (Experiment 2), and executive functioning for each system, using a concurrent task methodology. It was found that visual tasks with high executive functioning demands and verbal tasks with high or low executive demands disrupted rule-defined learning, whereas any visual task, regardless of executive functioning demand, disrupted non-rule-defined learning. Taken together, these results confirm the importance of verbal working memory and executive functioning for the verbal system and provide new evidence for the importance of visual processing for the nonverbal system. These results help to clarify understanding of the nonverbal system and have implications for multiple systems theories of category learning (F. G. Ashby, L. A. Alfonso-Reese, A. U. Turken, & E. M. Waldron, 1998).     

Familial risk of early suicide: variations by age and sex of children and parents

To determine familial risk of early suicide, data on cause of death of all Dutch residents aged 20-55 years who died between 1995 and 2001 were linked to data of their parents. Men whose father died by suicide had a higher odds of suicide themselves, relative to men whose father died of other causes (Odds Ratio (OR): 2.5; 95% confidence interval: 1.8-3.6). This effect was slightly stronger in the case of mother's suicide (OR: 3.4; 2.3-5.0). The same effect was observed for women, for suicide by father (OR: 2.2; 1.3-3.7) and mother (OR: 4.6; 2.6-8.0). The odds of suicide increased with decreasing age at death of parent. Parental suicide is predictive for offspring suicide. Our data suggest that the predictive value is higher in case the mother died by suicide, particularly if the mother died by suicide at a young age.