Laboratory measured behavioral impulsivity relates to suicide attempt history

The purpose of this study was to examine the relationship between laboratory behavioral measured impulsivity (using the Immediate and Delayed Memory Tasks) and suicidal attempt histories. Three groups of adults were recruited, those with either: no previous suicide attempts (Control, n = 20), only a single suicide attempt (Single, n = 20), or multiple suicidal attempts (Multiple, n = 10). As hypothesized, impulsive responses increased with the number of suicide attempts (Control < Single < Multiple). This study helps to demonstrate how laboratory behavioral measures of impulsivity can be used to discriminate groups based on suicidal histories among samples not currently exhibiting significant suicidal behaviors.     

A formal model for structuring local perceptions of environmental space

The problem of constructing computational models of space that mimic those found in human spatial reasoning is addressed. This paper extends a formal model that addressed point objects in a 2D world to include the presence of line objects and barriers. The problem consists of determining an appropriate global model for the spatial configuration given a sequence of local views or observations. A formal model is proposed based on constraint network theory. The model leads to the identification of stable regions within which perceptual information about the environment changes slowly, and zones of transition within which the perceptual information changes more quickly. A special case of transition zones is a gateway, which may be viewed as a kind of discontinuity or singularity in the model. It is expected that the model obtained will be used to mimic human mental representations of navigable outdoor environments.     

Do age of onset and course of illness define biologically distinct groups within atypical depression?

Illness course separates patients with atypical depression into tricyclic responders and nonresponders as does perceptual asymmetry. The authors therefore investigated whether the course-of-illness parameters would define groups within atypical depression differing in brain laterality. Patients with atypical depression were assessed for illness course and brain laterality. Two patient groups were defined, 1 with onset prior to age 20 plus a very chronic course, and a 2nd group having later onset or less chronic illness. Patients reporting early onset of very chronic dysphoria showed significantly less right-ear (left-hemisphere) accuracy and also differed in characteristic perceptual asymmetry when compared to patients with later onset or less chronicity. Course of illness may usefully define more homogeneous depressive subgroups within atypical depression.     

Commission error rates on a continuous performance test are related to deficits measured by the Benton Visual Retention Test

This study is one in a series investigating the relationship between impulsive behavior on a Continuous Performance Test (i.e., the Immediate and Delayed Memory Task) and other cognitive deficits measured by clinical instruments. Forty-two adolescents were selected for two groups, controls and hospitalized patients with disruptive behavior disorders. Each adolescent completed the Immediate and Delayed Memory Task and the Benton Visual Retention Test. Our main findings were that, even when controlling for IQ, the Immediate and Delayed Memory Task commission errors were associated with adverse Benton performance, but only in the patient group. These results may be explained by a shared association between processes of impulsivity and other deficits of executive control that may interfere with successful performance of the Benton.     

Perirhinal cortex lesions impair context aversion learning

Rats with perirhinal cortex lesions were compared with sham controls on a conditional discrimination in which saccharin was paired with LiCl in context 1, but paired with saline in context 2. Perirhinal-lesioned rats were slightly slower to acquire the discrimination but reached control levels by the end of acquisition. Both groups showed transfer to familiar tap water, consuming less in context 1 than in context 2. Unlike sham rats, perirhinal rats failed to show an aversion to context 1 on a place choice test. These data provide neuroanatomical support for the postulated difference between Pavlovian conditioning and conditional learning.     

A Kripke Semantics for the Logic of Gelfand Quantales

Gelfand quantales are complete unital quantales with an involution, *, satisfying the property that for any element a, if a b a for all b, then a a* a = a. A Hilbert-style axiom system is given for a propositional logic, called Gelfand Logic, which is sound and complete with respect to Gelfand quantales. A Kripke semantics is presented for which the soundness and completeness of Gelfand logic is shown. The completeness theorem relies on a Stone style representation theorem for complete lattices. A Rasiowa/Sikorski style semantic tableau system is also presented with the property that if all branches of a tableau are closed, then the formula in question is a theorem of Gelfand Logic. An open branch in a completed tableaux guarantees the existence of an Kripke model in which the formula is not valid; hence it is not a theorem of Gelfand Logic.     

Chronic stress-induced alterations in mouse colonic 5-HT and defecation responses are strain dependent

Mood disorders and chronic stress are frequently associated with gastrointestinal (GI) symptoms including diarrhoea or constipation. Locally produced serotonin [5-hydroxytryptamine (5-HT)] regulates GI motility and is a key factor in the pathophysiology of stress-associated GI disorders. We aimed to establish whether chronic stress can differentially affect faecal output and colon 5-HT concentration in two inbred mouse strains: BALB/c and C57BL/6 which differ in their ability to cope with stress. Adult male BALB/c and C57BL/6 mice were restrained for 2?h daily for 10 days. Defecation was monitored during each stress session. Twenty-four hours after the last session of stress, plasma corticosterone concentration was higher than control in both strains, indicative of a physiological effect of chronic stress; however, stress-induced diarrhoea was more persistent in C57BL/6 mice. Basal concentration of colon 5-HT was higher in C57BL/6 mice, and stress elicited an increase in colon 5-HT only in this strain. Finally, na?ve BALB/c mice had a higher sensitivity (incidence of diarrhoea) to 5-HT (0.33?mg/kg, i.p.) than C57BL/6 mice. Our results suggest that differential defecation responses to stress may be associated with colon 5-HT concentration, which may in turn reflect the individual sensitivity to 5-HT. In addition, C57BL/6 mice emerge as a relevant model for studying GI alterations induced by chronic stress.