Multifractality Versus (Mono-) Fractality as Evidence of Nonlinear Interactions Across Timescales: Disentangling the Belief in Nonlinearity From the Diagnosis of Nonlinearity in Empirical Data

This article addresses the still popular but incorrect idea that monofractal (sometimes called “fractal” for short) structure might be a definitive signature of nonlinearity and, as a corollary, that monofractal analyses are nonlinear analyses. That this point (i.e., “fractal = nonlinear”) is incorrect remains novel to many readers. We suspect that unfamiliarity with autocorrelation has helped eclipse the linearity of fractal structure from more popular appreciation. In this article, in order to explain the linear nature of monofractality and its difference from multifractality, we present an introduction to the autocorrelation function and review short-lag memory, nonstationary motions, and the intermediary set of fractionally integrated processes that conventional fractal analyses quantify. Understanding from our own experiences how surprising the linearity of fractals is to accept, we attempt to make our points clear with as much graphic depiction as math. We hope to share our own experiences in struggling with this potentially strange-sounding idea that, really, monofractals are linear while at the same time contrasting them to multifractals that can indicate nonlinearity.     

Belief in a Werther Effect: third-person effects in the perceptions of suicide risk for others and the moderating role of depression

Werther Effect research has almost solely focused on the behavioral level of media effects. Clinically relevant predispositions like depression as well as the moderating role of media effects on a perceptional level have been omitted so far. To bridge this gap, we reanalyzed the data of an experiment conducted by Rustad, Small, Jobes, Safer, and Peterson: volunteer students' ratings for their self-risk of depression and suicide as well as their perceptions of others' suicide risk were investigated. While a Werther Effect could not be observed, there is a general overestimation of media influences on others--presumed Werther Effects--that are moderated by the personal degree of depression.     

Interference with reelin signaling in the lateral entorhinal cortex impairs spatial memory

Entorhinal neurons receive extensive intracortical projections, and form the primary input to the hippocampus via the perforant pathway. The glutamatergic cells of origin for the perforant pathway are distinguished by their expression of reelin, a glycoprotein involved in learning and synaptic plasticity. The functional significance of reelin signaling within the entorhinal cortex, however, remains unexplored. To determine whether interrupting entorhinal reelin signaling might have consequences for learning and memory, we administered recombinant receptor-associated protein (RAP) into the lateral entorhinal cortex (LEC) of young Long-Evans rats. RAP prevents reelin from binding to its receptors, and we verified the knockdown of reelin signaling by quantifying the phosphorylation state of reelin’s intracellular signaling target, disabled-1 (DAB1). Effective knockdown of reelin signaling was associated with impaired performance in the hippocampus-dependent version of the water maze. Moreover, inhibition of reelin signaling induced a localized loss of synaptic marker expression in the LEC. These observations support a role for entorhinal reelin signaling in spatial learning, and suggest that an intact reelin signaling pathway is essential for synaptic integrity in the adult entorhinal cortex.     

The nicotinic acetylcholine receptor gene CHRNA4 is associated with negative emotionality

Knock-out studies in mice suggest a role of the CHRNA4 gene in anxiety. In the present study we extend this finding to humans by means of a genetic association study. In a sample of N = 574 healthy White participants, the CHRNA4 rs1044396 polymorphism is related to the common variance of several conceptualizations of negative emotionality. Compared to carriers of at least one T-allele, carriers of the homozygous C/C genotype described themselves as more anxious and emotionally unstable on various psychometric personality questionnaires. The scope of the genetic effect is remarkable because other prominent genetic markers for anxiety show specificity for the diagnostic tool used. The present study is the first study that demonstrates the relevance of the CHRNA4 gene for negative emotionality in humans and sets a starting point for further investigations that could inform on the treatment of various affective psychiatric disorders.     

On the control of visual fixation durations in free viewing of complex images

The mechanisms for the substantial variation in the durations of visual fixations in scene perception are not yet well understood. During free viewing of paintings, gaze-contingent irrelevant distractors (Exp. 1) and non-gaze-related time-locked display changes (Exp. 2) were presented. We demonstrated that any visual change-its onset and offset-prolongs the ongoing fixation (i.e., delays the following saccade), strongly suggesting that fixation durations are under the direct control of the stimulus information. The strongest influence of distraction was observed for fixations preceded by saccades within the parafoveal range (<5° of visual angle). We assume that these fixations contribute to the focal in contrast to the ambient mode of attention (Pannasch & Velichkovsky, Visual Cognition, 17, 1109-1131, 2009; Velichkovsky, Memory, 10, 405-419, 2002). Recent findings about two distinct "subpopulations of fixations," one under the direct and another under the indirect control of stimulation (e.g., Henderson & Smith, Visual Cognition, 17, 1055-1082, 2009), are reconsidered in view of these results.     

Social brain development and the affective consequences of ostracism in adolescence

Recent structural and functional imaging studies have provided evidence for continued development of brain regions involved in social cognition during adolescence. In this paper, we review this rapidly expanding area of neuroscience and describe models of neurocognitive development that have emerged recently. One implication of these models is that neural development underlies commonly observed adolescent phenomena such as susceptibility to peer influence and sensitivity to peer rejection. Experimental behavioural evidence of rejection sensitivity in adolescence is currently sparse. Here, we describe a study that directly compared the affective consequences of an experimental ostracism manipulation (Cyberball) in female adolescents and adults. The ostracism condition led to significantly greater affective consequences in the adolescents compared with adults. This suggests that the ability to regulate distress resulting from ostracism continues to develop between adolescence and adulthood. The results are discussed in the context of models of neurocognitive development.     

Illusory own body perceptions: Case reports and relevance for bodily self-consciousness

Neurological disorders of body representation have for a long time suggested the importance of multisensory processing of bodily signals for self-consciousness. One such group of disorders – illusory own body perceptions affecting the entire body – has been proposed to be especially relevant in this respect, based on neurological data as well as philosophical considerations. This has recently been tested experimentally in healthy subjects showing that integration of multisensory bodily signals from the entire body with respect to the three aspects: self-location, first-person perspective, and self-location, is crucial for bodily self-consciousness. Here we present clinical and neuroanatomical data of two neurological patients with paroxysmal disorders of full body representation in whom only one of these aspects, self-identification, was abnormal. We distinguish such disorders of global body representation from related but distinct disorders and discuss their relevance for the neurobiology of bodily self-consciousness.