Role of serotonin in human aggressive behaviour

This study aimed to evaluate a peripheral serotonergic marker, ³H-imipramine (³H-IMI) binding to platelet membranes, in a group of severely aggressive subjects (A), institutionalized since childhood for mental retardation, as compared with suicide attempters (S) and healthy controls (H). The maximum binding capacity of ³H-IMI to platelet membranes was statistically lower in (A) and (S) than in (H). In addition, a statistically significant difference was observed between the Bmax values of aggressive subjects and those of suicide attempters. No changes in the dissociation constant (Kd) of IMI binding were observed. These data provide further supporting evidence for the hypothesis of an abnormality of the 5HT system in aggressive behaviour and suggest that such an abnormality, as reflected by platelet markers, is more severe in suicide attempters. © 1993 Wiley-Liss, Inc.     

On Canonicity and Strong Completeness Conditions in Intermediate Propositional Logics

By using algebraic-categorical tools, we establish four criteria in order to disprove canonicity, strong completeness, w-canonicity and strong w-completeness, respectively, of an intermediate propositional logic. We then apply the second criterion in order to get the following result: all the logics defined by extra-intuitionistic one-variable schemata, except four of them, are not strongly complete. We also apply the fourth criterion in order to prove that the Gabbay-de Jongh logic D₁ is not strongly w-complete. This revised version was published online in June 2006 with corrections to the Cover Date.     

Short-term limb immobilization affects motor performance

C. Ghez, J. Gordon, and M. R Ghilardi (1995; J. Gordon, M. R Ghilardi, & C. Ghez, 1995; R. L. Sainburg, M. R Ghilardi, H. Poizner, & C. Ghez, 1995) have found that proprio-ceptive deafferentation impairs feedforward and feedback mechanisms that control reaching movements. In the present study, the authors found immobilization-induced changes in limb kinematics, including joint motion, in 32 healthy participants who performed out-and-back movements before and after 0, 6, or 12 hr of immobilization of the left arm. Control participants did not undergo the arm immobilization procedure. Immobilization for 12 hr, but not 6 hr, caused trajectories with increased hand-path areas and altered interjoint coordination. The abnormalities were smaller in amplitude but similar in quality to those reported in deafferented patients (R. L. Sainburg et al.). In addition, movement onset point significantly drifted after immobilization. Thus, short-term limb disuse can affect interjoint coordination by acting on feedforward mechanisms. These behavioral alterations are potentially related to cortical plastic changes.     

The dreaming brain/mind, consciousness and psychosis

Several independent lines of research in neurobiology seem to support the phenomenologically-grounded view of the dreaming brain/mind as a useful model for psychosis. Hallucinatory phenomena and thought disorders found in psychosis share several peculiarities with dreaming, where internally generated, vivid sensorimotor imagery along with often heightened and incongruous emotion are paired with a decrease in ego functions which ultimately leads to a severe impairment in reality testing. Contemporary conceptualizations of severe mental disorders view psychosis as one psychopathological dimension that may be found across several diagnostic categories. Some experimental data have shown cognitive bizarreness to be equally elevated in dreams and in the waking cognition of acutely psychotic subjects and in patients treated with pro-dopaminergic drugs, independent of the underlying disorder. Further studies into the neurofunctional underpinnings of both conditions will help to clarify the use and validity of this model.