Exposure to violence and suicide risk in adolescents: a community study

The prevalence of violence exposure is relatively unexplored in adolescents in European communities, and reports on the association between exposure to community violence and suicidal behavior are rare. The aim of this study was to investigate (1) the prevalence of community violence in a European urban adolescent sample, (2) the relationship between exposure to community violence and suicidal ideation/deliberate self-harm, and (3) the influence of depressive symptoms and aggressive behavior on this relationship. Self-report surveys were administered to a representative school-based sample of 1509 adolescents in Antwerp (Belgium). The prevalence rate of violence exposure was still high but lower than that reported in U.S. communities. Suicidal ideation and deliberate self-harm were both related to violence exposure. The gender-specific influence of depressive symptomatology and aggressive behavior on the association between exposure to violence and suicidal behavior suggests the need for further research.     

Timing precision in continuation and synchronization tapping

 Wing and Kristofferson (1973) have shown that temporal precision in self-paced tapping is limited by variability in a central timekeeper and by variability arising in the peripheral motor system. Here we test an extension of the Wing–Kristofferson model to synchronization with periodic external events that was proposed by Vorberg and Wing (1994). In addition to the timekeeper and motor components, a linear phase correction mechanism is assumed which is triggered by the last or the last two synchronization errors. The model is tested in an experiment that contrasts synchronized and self-paced trapping, with response periods ranging from 200–640 ms. The variances of timekeeper and motor delays and the error correction parameters were estimated from the auto-covariance functions of the inter-response intervals in continuation and the asynchronies in synchronization. Plausible estimates for all parameters were obtained when equal motor variance was assumed for synchronization and continuation. Timekeeper variance increased with metronome period, but more steeply during continuation than during synchronization, suggesting that internal timekeeping processes are stabilized by periodic external signals. First-order error correction became more important as the metronome period increased, whereas the contribution of second-order error correction decreased. It is concluded that the extended two-level model accounts well for both synchronization and continuation performance. Received: 16 November 1998 / Accepted: 21 April 1999     

Visual short-term memory during smooth pursuit eye movements

Visual short-term memory (VSTM) was probed while observers performed smooth pursuit eye movements. Smooth pursuit keeps a moving object stabilized in the fovea. VSTM capacity for position was reduced during smooth pursuit compared with a condition with eye fixation. There was no difference between a condition in which the items were approximately stabilized on the retina because they moved with the pursuit target and a condition in which the items moved across the retina because they were stationary in space. The reduction of capacity for position was eliminated when miniature items were presented on the pursuit target. Similarly, VSTM capacity for color did not differ between smooth pursuit and fixation. The results suggest that visuospatial attention is tied to the target during smooth pursuit, which impairs VSTM for the position of peripheral objects. Sensory memory during smooth pursuit was only slightly impaired.     

Intentional and unintentional contributions to nonspecific preparation: electrophysiological evidence

The authors hypothesized that there are distinct intentional and unintentional influences on nonspecific preparation for a future event. In 2 experiments, participants responded to an imperative stimulus (S-sub-2) that was presented equiprobably either 400 ms or 1,200 ms after the offset of a warning stimulus (S-sub-1). During the S-sub-1-S-sub-2 interval, the authors measured the contingent negative variation (CNV), an event-related brain potential reflecting nonspecific preparation. S-sub-1 provided either no information or reliable information about the duration of the impending S-sub-1-S-sub-2 interval, thereby allowing an intentional influence on the state of preparation. The effect of S-sub-1 information on the CNV was approximately additive to the effect of the S-sub-1-S-sub-2 interval that was used on the preceding trial. This supports the view that the preceding S-sub-1-S-sub-2 interval contributes unintentionally to the state of nonspecific preparation guided by a process of trace conditioning.     

On the selective relation of frontal cortical asymmetry and anger-out versus anger-control

The model of anterior asymmetry and emotion proposes an asymmetric representation of approach and withdrawal systems in the left and right anterior brain regions. Within this framework, 3 different concepts have been related to anterior asymmetry: affective valence, motivational direction, and behavioral activation. The aim of the present study was an empirical investigation into the relation between anterior cortical activity and questionnaire measures related to the 3 dimensions positive versus negative affect, approach versus withdrawal motivation, and behavioral activation versus inhibition. Subjects with relative greater left than right frontal cortical activity showed higher anger-out scores and lower anger-control scores. These results support the hypothesis that motivational direction is related to frontal asymmetry (approach-left and withdrawal-right). Furthermore, subjects with greater bilateral (left and right) frontal cortical activity showed higher behavioral activation scores. This finding might suggest that behavioral activation is related to approach and withdrawal motivation.     

A recurrent connectionist model of group biases

Major biases and stereotypes in group judgments are reviewed and modeled from a recurrent connectionist perspective. These biases are in the areas of group impression formation (illusory correlation), group differentiation (accentuation), stereotype change (dispersed vs. concentrated distribution of inconsistent information), and group homogeneity. All these phenomena are illustrated with well-known experiments, and simulated with an autoassociative network architecture with linear activation update and delta learning algorithm for adjusting the connection weights. All the biases were successfully reproduced in the simulations. The discussion centers on how the particular simulation specifications compare with other models of group biases and how they may be used to develop novel hypotheses for testing the connectionist modeling approach and, more generally, for improving theorizing in the field of social biases and stereotype change.     

Centripetal force draws the eyes,not memory of the target,toward the center

Many observers believe that a target will continue on a curved trajectory after exiting a spiral tube. Similarly, when observers were asked to localize the final position of a target moving on a circular orbit, displacement of the judged position in the direction of forward motion ("representational momentum") and toward the center of the orbit was observed (cf. T. L. Hubbard, 1996). The present study shows that memory displacement of targets on a circular orbit is affected by eye movements. Forward displacement was larger with ocular pursuit of the target, whereas inward displacement was larger with motionless eyes. The results challenge an account attributing forward and inward displacement to mental analogues of momentum and centripetal force, respectively.     

Observing one's hand become anarchic: an fMRI study of action identification

The self seems to be a unitary entity remaining stable across time. Nevertheless, current theorizing conceptualizes the self as a number of interacting sub-systems involving perception, intention and action (self-model). One important function of such a self-model is to distinguish between events occurring as a result of one’s own actions and events occurring as the result of somebody else’s actions. We conducted an fMRI experiment that compared brain activation after an abrupt mismatch between one’s own movement and its visual consequences with an abrupt mismatch between one’s own movement and somebody else’s visually perceived hand movement. A right fronto-parietal network was selectively active during a sudden mismatch between one’s own observed and performed hand action.     

Learning-induced arg 3.1/arc mRNA expression in the mouse brain

The effector immediate-early gene (IEG) arg 3.1, also called arc, encodes a protein interacting with the neuronal cytoskeleton. The selective localization of arg 3.1/arc mRNA in activated dendritic segments suggests that the arg 3.1/arc protein may be synthesized at activated post-synaptic sites and that arg 3.1/arc could participate in structural and functional modifications underlying cognitive processes like memory formation. To analyze whether learning itself is sufficient to trigger expression of arg 3.1/arc, we developed a one-trial learning paradigm in which mice learned to enter a dark compartment to escape from an aversively illuminated area. Arg 3.1/arc mRNA expression was analyzed by in situ hybridization in three groups of mice as follows: a control group with no access to the dark compartment, a learning group having access to the dark compartment for one trial, and a retrieval group having access to the dark compartment for two trials on consecutive days. All animals from the learning and retrieval groups escaped the illuminated area, and those tested 24 h later (retrieval group) showed a strongly reduced latency to enter the dark compartment, demonstrating the validity of our learning paradigm to induce long-term memory. Our results show that acquisition of a simple task results in a brain area-specific biphasic increase in arg 3.1/arc mRNA expression 15 min and 4.5 h post-training. This increase was detected specifically in the learning group but neither in the control nor in the retrieval groups. The pattern of arg 3.1/arc mRNA expression corresponds temporally to the two mRNA- and protein-synthesis-dependent periods of long-term memory formation. Our study provides the first unequivocal evidence that arg 3.1/arc expression is induced by a learning task and strongly suggests a role of arg 3.1/arc mRNA in the early and late cellular mechanisms underlying the stabilization of the memory trace.     

The appraisal basis of anger: specificity, necessity and sufficiency of components

The nature of the association between anger and 5 appraisal-action tendency components--goal obstacle, other accountability, unfairness, control, and antagonism--was examined in terms of specificity, necessity, and sufficiency. In 2 studies, participants described recently experienced unpleasant situations in which 1 of the appraisal-action tendency components was present or absent and indicated which emotions they had experienced. The results showed that (a) other accountability and arrogant entitlement, as an instance of unfairness, are specific appraisals ability for anger; and most important, (b) none of the components is necessary or sufficient for anger. The findings suggest that the relation between emotions and appraisal-action tendency components should be conceptualized instead as a contingent association, meaning that they usually co-occur.