Arrested development? Reconsidering dual-systems models of brain function in adolescence and disorders

The dual-systems model of a ventral affective system, whose reactivity confers risks and liabilities, and a prefrontal control system, whose regulatory capacities buffer against these vulnerabilities, is an intuitive account that pervades many fields in the cognitive neurosciences--especially in the study of populations that differ from neurotypical adults, such as adolescents or individuals with affective or impulse regulation disorders. However, recent evidence that is inconsistent with dual-systems models illustrates the complexity of developmental and clinical variations in brain function. Building new models to account for this complexity is critical to progress in these fields, and will be facilitated by research that emphasizes network-based approaches and maps relationships between structure and function, as well as brain and behavior, over time.     

Cognitive vulnerability to depression: a comparison of the weakest link, keystone and additive models

Multiple theories of cognitive vulnerability to depression have been proposed, each focusing on different aspects of negative cognition and utilising different measures of risk. Various methods of integrating such multiple indices of risk have been examined in the literature, and each demonstrates some promise. Yet little is known about the interrelations among these methods, or their incremental validity in predicting changes in depression. The present study compared three integrative models of cognitive vulnerability: the additive, weakest link, and keystone models. Support was found for each model as predictive of depression over time, but only the weakest link model demonstrated incremental utility in predicting changes in depression over the other models. We also explore the correlation between these models and each model's unique contribution to predicting onset of depressive symptoms.     

The Need for a Revolution in the Philosophy of Science

There is a need to bring about a revolution in the philosophy of science, interpreted to be both the academic discipline, and the official view of the aims and methods of science upheld by the scientific community. At present both are dominated by the view that in science theories are chosen on the basis of empirical considerations alone, nothing being permanently accepted as a part of scientific knowledge independently of evidence. Biasing choice of theory in the direction of simplicity, unity or explanatory power does not permanently commit science to the thesis that nature is simple or unified. This current ‘paradigm’ is, I argue, untenable. We need a new paradigm, which acknowledges that science makes a hierarchy of metaphysical assumptions concerning the comprehensibility and knowability of the universe, theories being chosen partly on the basis of compatibility with these assumptions. Eleven arguments are given for favouring this new ‘paradigm’ over the current one. This revised version was published online in August 2006 with corrections to the Cover Date.     

Individual Behavior Consistencies as Interactive Styles: Their Relation to Personality

Two experimental studies were carried out in order to find within-subject consistencies as individual differences in a concurrent choice situation simulating risk-taking. In a first experiment, six adults were exposed to different values of probability and numbers of reinforcement in a task involving betting on two simultaneous horse races displayed on a microcomputer monitor. In the second experiment, two subjects were exposed to a within-session replication of the first experiment. The results in both experiments support the reliability of within-subject consistencies when experimental tasks are built as open contingencies. The conceptual and experimental implications of the data are discussed in relation to the study of personality.

     

Are defeat and entrapment best defined as a single construct?

The concepts of defeat and entrapment have been employed in evolutionary accounts of clinical phenomena such as depression and suicide. Recently theorists have argued that both concepts may be best conceptualised as a single distinct factor. The current study is the first to empirically test this assertion. A sample of 305 students completed measures of defeat and entrapment. Their responses were then analysed via exploratory factor analysis. The results strongly suggest that a single factor underlies both defeat and entrapment. These findings have considerable implications for past studies and theoretical accounts that rely on the distinction between defeat and entrapment.     

Do health behaviors explain the effect of neuroticism on mortality? Longitudinal findings from the VA Normative Aging Study

Studies have shown that higher levels of neuroticism are associated with greater risk of mortality. Yet what accounts for this association? One major theoretical position holds that persons higher in neuroticism engage in poorer health behaviors, such as smoking and excessive drinking, thus leading to earlier death. We tested this hypothesis using 30-year mortality in 1788 men from the VA Normative Aging Study. Using proportional hazards (Cox) models we found that one health behavior, smoking, attenuated the effect of neuroticism on mortality by 40%. However, 60% remained unexplained, suggesting that the effects of other pathways (e.g., biological) also influence the relationship between neuroticism and mortality.     

Enhanced long-term and impaired short-term spatial memory in GluA1 AMPA receptor subunit knockout mice: Evidence for a dual-process memory model

The GluA1 AMPA receptor subunit is a key mediator of hippocampal synaptic plasticity and is especially important for a rapidly-induced, short-lasting form of potentiation. GluA1 gene deletion impairs hippocampus-dependent, spatial working memory, but spares hippocampus-dependent spatial reference memory. These findings may reflect the necessity of GluA1-dependent synaptic plasticity for short-term memory of recently visited places, but not for the ability to form long-term associations between a particular spatial location and an outcome. This hypothesis is in concordance with the theory that short-term and long-term memory depend on dissociable psychological processes. In this study we tested GluA1^−/− mice on both short-term and long-term spatial memory using a simple novelty preference task. Mice were given a series of repeated exposures to a particular spatial location (the arm of a Y-maze) before their preference for a novel spatial location (the unvisited arm of the maze) over the familiar spatial location was assessed. GluA1^−/− mice were impaired if the interval between the trials was short (1 min), but showed enhanced spatial memory if the interval between the trials was long (24 h). This enhancement was caused by the interval between the exposure trials rather than the interval prior to the test, thus demonstrating enhanced learning and not simply enhanced performance or expression of memory. This seemingly paradoxical enhancement of hippocampus-dependent spatial learning may be caused by GluA1 gene deletion reducing the detrimental effects of short-term memory on subsequent long-term learning. Thus, these results support a dual-process model of memory in which short-term and long-term memory are separate and sometimes competitive processes.     

Aging and the structure and long-term stability of the internalizing spectrum of personality and psychopathology

Structural psychopathology research has identified two broad factors--internalizing and externalizing--that account for comorbidity among many common mental disorders. Evaluating the utility of these factors for nosology, research, and treatment entails expanding beyond a cross-sectional understanding to how these factors evolve over time. We tested factorial invariance of internalizing in three age cohort groups--35 years and under (n = 1,729), 36-50 years (n = 2,719), and over 50 years (n = 2,601)--as well as the long-term stability of internalizing within individuals. Internalizing showed a notable degree of invariance between cohorts and within cohorts over time; long-term internalizing stability was equivalently moderate-to-high in each cohort.