The impact of visual flow stimulation on anxiety, dizziness, and body sway in individuals with and without fear of heights

Individuals with acrophobia experience anxiety and dizziness when exposed to heights. It may be that their balance system is disturbed and that they therefore have to rely more strongly on visual information.We tested this hypothesis by exposing 20 individuals with high fear of heights and 20 healthy control participants to nine different visual flow stimuli through a head mounted display, thereby inducing a conflict between visual input and somatosensory information. Anxiety and dizziness were assessed repeatedly by means of self-reports, while resultant body sway was measured continuously with a force plate individuals stood on.Individuals with fear of heights felt more anxious and dizzier, and also showed stronger body sway than healthy control participants.Merely receiving visual balance information contradictory to somatosensory balance information is sufficient to induce anxiety, dizziness, and body sway in individuals with fear of heights. An underlying balance dysfunction may contribute to the development of height phobia.     

Are we on a learning curve or a treadmill? The benefits of participative group goal setting become apparent as tasks become increasingly challenging over time

A large body of research has pointed to the utility of individual and group goal setting as a performance enhancement strategy. However, group goal setting is more complex than individual goal setting as the group context often strengthens the desire for voice and the possibility of resistance. In line with this idea, we test the prediction that goal‐related performance improvements should be more marked where groups participate in goal setting rather than having goals imposed—particularly as they become increasingly hard to achieve. These ideas are tested in two experiments (N_groups = 27, 72). Both confirm the capacity for group goal setting to enhance brainstorming performance. More importantly, both studies also show that the benefits of participative goals relative to imposed goals becomes more marked as goals become more difficult over time. In line with social identity and self‐categorization principles, we suggest that this is because increases in participatively set goals appear to provide opportunities for collective self‐actualization and self‐enhancement while increases in imposed goals do not. Copyright © 2008 John Wiley & Sons, Ltd.     

Computing finite models by reduction to function-free clause logic

Recent years have seen considerable interest in procedures for computing finite models of first-order logic specifications. One of the major paradigms, MACE-style model building, is based on reducing model search to a sequence of propositional satisfiability problems and applying (efficient) SAT solvers to them. A problem with this method is that it does not scale well because the propositional formulas to be considered may become very large.We propose instead to reduce model search to a sequence of satisfiability problems consisting of function-free first-order clause sets, and to apply (efficient) theorem provers capable of deciding such problems. The main appeal of this method is that first-order clause sets grow more slowly than their propositional counterparts, thus allowing for more space efficient reasoning.In this paper we describe our proposed reduction in detail and discuss how it is integrated into the Darwin prover, our implementation of the Model Evolution calculus. The results are general, however, as our approach can be used in principle with any system that decides the satisfiability of function-free first-order clause sets.To demonstrate its practical feasibility, we tested our approach on all satisfiable problems from the TPTP library. Our methods can solve a significant subset of these problems, which overlaps but is not included in the subset of problems solvable by state-of-the-art finite model builders such as Paradox and Mace4.     

Behavioral deficits and subregion-specific suppression of LTP in mice expressing a population of mutant NMDA receptors throughout the hippocampus

The NMDA receptor (NMDAR) subunit GluN1 is an obligatory component of NMDARs without a known functional homolog and is expressed in almost every neuronal cell type. The NMDAR system is a coincidence detector with critical roles in spatial learning and synaptic plasticity. Its coincidence detection property is crucial for the induction of hippocampal long-term potentiation (LTP). We have generated a mutant mouse model expressing a hypomorph of the Grin1^N598R allele, which leads to a minority (about 10%) of coincidence detection-impaired NMDARs. Surprisingly, these animals revealed specific functional changes in the dentate gyrus (DG) of the hippocampal formation. Early LTP was expressed normally in area CA1 in vivo, but was completely suppressed at perforant path-granule cell synapses in the DG. In addition, there was a pronounced reduction in the amplitude of the evoked population spike in the DG. These specific changes were accompanied by behavioral impairments in spatial recognition, spatial learning, reversal learning, and retention. Our data show that minor changes in GluN1-dependent NMDAR physiology can cause dramatic consequences in synaptic signaling in a subregion-specific fashion despite the nonredundant nature of the GluN1 gene and its global expression.According to Hebb''s postulate, neurons require a molecular mechanism to detect synchronous activity in order to change the strength of synaptic connectivity (Hebb 1949). NMDA receptors (NMDARs) are molecular coincidence detectors, and selective NMDAR antagonists block the induction of long-term potentiation (LTP) in both the dentate gyrus (DG) and CA1 regions of the hippocampus (Bliss and Collingridge 1993; Martin et al. 2000). NMDARs have been long known for their role in spatial learning, but more recently have been implicated in other forms of cognitive function and dysfunction (Gruart et al. 2006; Whitlock et al. 2006; Castner and Williams 2007; Kristiansen et al. 2007; Wilson and Linster 2008).Neuronal NMDARs are hetero-tetrameric ligand-gated ion channels typically comprised of two types of subunits. Two copies of the mandatory GluN1 subunit (or NR1 subunit [Collingridge et al. 2009] encoded by Grin1) are associated with two copies from the GluN2 family, GluN2A–D (or NR2A–D). The GluN1 subunit is expressed ubiquitously both spatially and temporally throughout the developing and adult brain. Global knockout mice models of the GluN1 subunit are postnatally lethal within hours after birth (Forrest et al. 1994; Li et al. 1994), and cell-specific GluN1 mice knockouts (Tsien et al. 1996; Nakazawa et al. 2002; McHugh et al. 2007; Niewoehner et al. 2007) have provided insights on how specific synapses and regional neuronal networks are dependent on NMDAR function.The early postnatal lethality of the global GluN1 knockout is in contrast to the null mutants of the four AMPA receptor genes and other major synaptic proteins, such as αCaMKII (Silva et al. 1992a,b; Jia et al. 1996; Zamanillo et al. 1999; Meng et al. 2003). This can be at least partially explained by the absence of any close GluN1 homologs, which could functionally compensate for the absence of the GluN1 subunit. Recombinant expression studies defined the GluN1 subunit as a mandatory component of NMDARs. This constellation provides a specific opportunity to test whether different local neuronal subnetworks are affected differentially by mutant Grin1 alleles associated with subtle alterations of the functional properties of NMDARs.GluN1 subunits with the N598R point mutation (GluN1^R) yield functional NMDARs that are Mg²⁺ insensitive and Ca²⁺ impermeable (Burnashev et al. 1992; Mori et al. 1992). The Grin1^N598R allele that codes for GluN1^R subunits is a gain-of-function mutation that is dominant lethal, even in heterozygous and hemizygous lines (Single et al. 2000; Rudhard et al. 2003). NMDARs with GluN1^R subunits do not act as coincidence detectors and, interestingly, mice expressing exclusively the GluN1^R allele lack whisker-related pattern formation in the neonate brainstem (Rudhard et al. 2003).To investigate the functional importance of GluN1 subunits with the N598R point mutation, we took advantage of the generation of a variant mutant line of mice (GluN1^Rneo/+) expressing a minority (around 10%) of these mutant NMDARs. Even though the majority of the NMDARs are normal, all neurons expressing NMDARs will contain a subset of receptors carrying this mutation.Therefore, this mouse model is an ideal candidate to study the impact of subtle alterations of NMDAR function on different neuronal networks, such as those comprising the hippocampal formation.Studies examining region-specific targeted disruption of GluN1 expression in subregions of the hippocampus have revealed subtle yet important contributions of this NMDAR subunit in synaptic plasticity and spatial learning and memory. CA1-restricted knockout of GluN1 expression in the hippocampus caused impaired spatial learning and memory as well as reduced CA1-LTP (Tsien et al. 1996). In the case of the disruption of GluN1 expression in the DG region of the hippocampus, more subtle behavioral impairments were apparent, including the inability to discriminate between two similar contexts (pattern separation) and deficits in spatial working memory despite normal LTP in the CA1 region (McHugh et al. 2007; Niewoehner et al. 2007).Our GluN1^Rneo/+ mice differ from the region-specific GluN1 mutant mice in that they express the mutant hypomorph at the same level in different subregions of the hippocampus. Interestingly, we found that this allele leads to substantial differences in short- and long-term plasticity between area CA1 and the DG of the hippocampus. The specific impairment in the DG was accompanied by impaired spatial recognition, spatial learning, reversal learning, and retention. Our data establish the possibility of a circuit-specific phenotype caused by a mutant variant of a globally expressed major nonredundant synaptic protein.     

Handwriting movement analyses for monitoring drug-induced motor side effects in schizophrenia patients treated with risperidone

Epidemiologic studies indicate that nearly 60% of schizophrenia (SZ) patients treated with conventional antipsychotic drugs develop extrapyramidal side effects (EPS) such as parkinsonism and tardive dyskinesia. Although the prevalence of EPS has decreased due to the newer antipsychotics, EPS continue to limit the effectiveness of these medicines. Ongoing monitoring of EPS is likely to improve treatment outcome or compliance and reduce the frequency of re-hospitalization. A quantitative analysis of handwriting kinematics was used to evaluate effects of antipsychotic medication type and dose in schizophrenia patients. Twenty-seven schizophrenia patients treated with risperidone, six schizophrenia patients who received no antipsychotic medication and 47 healthy comparison participants were enrolled. Participants performed a 20-min handwriting task consisting of loops of various sizes and a sentence. Data were captured and analyzed using MovAlyzeR software. Results indicated that risperidone-treated participants exhibited significantly more dysfluent handwriting movements than either healthy or untreated SZ participants. Risperidone-treated participants exhibited lower movement velocities during production of simple loops compared to unmedicated patients. Handwriting dysfluency during sentence writing increased with dose. A 3-factor model consisting of kinematic variables derived from sentence writing accounted for 83% (r = .91) of the variability in medication dose. In contrast, we found no association between observer-based EPS severity ratings and medication dose. These findings support the importance of handwriting-based measures to monitor EPS in medicated schizophrenia patients.     

Sleep in children enhances preferentially emotional declarative but not procedural memories

Although the consolidation of several memory systems is enhanced by sleep in adults, recent studies suggest that sleep supports declarative memory but not procedural memory in children. In the current study, the influence of sleep on emotional declarative memory (recognition task) and procedural memory (mirror tracing task) in 20 healthy children (10-13 years of age) was examined. After sleep, children showed an improvement in declarative memory. Separate analysis with respect to the emotional stimulus content revealed that sleep enhances the recognition of emotional stimuli (p > .001) rather than neutral stimuli (p = .084). In the procedural task, however, no sleep-enhanced memory improvement was observed. The results indicate that sleep in children, comparable to adults, enhances predominantly emotional declarative memory; however, in contrast to adults, it has no effect on the consolidation of procedural memory.     

Keep ‘hoping’ for rationality: a solution to the backward induction paradox

We formalise a notion of dynamic rationality in terms of a logic of conditional beliefs on (doxastic) plausibility models. Similarly to other epistemic statements (e.g. negations of Moore sentences and of Muddy Children announcements), dynamic rationality changes its meaning after every act of learning, and it may become true after players learn it is false. Applying this to extensive games, we “simulate” the play of a game as a succession of dynamic updates of the original plausibility model: the epistemic situation when a given node is reached can be thought of as the result of a joint act of learning (via public announcements) that the node is reached. We then use the notion of “stable belief”, i.e. belief that is preserved during the play of the game, in order to give an epistemic condition for backward induction: rationality and common knowledge of stable belief in rationality. This condition is weaker than Aumann’s and compatible with the implicit assumptions (the “epistemic openness of the future”) underlying Stalnaker’s criticism of Aumann’s proof. The “dynamic” nature of our concept of rationality explains why our condition avoids the apparent circularity of the “backward induction paradox”: it is consistent to (continue to) believe in a player’s rationality after updating with his irrationality.     

Social Identity, Health and Well-Being: An Emerging Agenda for Applied Psychology

The social environment comprising communities, families, neighbourhoods, work teams, and various other forms of social group is not simply an external feature of the world that provides a context for individual behaviour. Instead these groups impact on the psychology of individuals through their capacity to be internalised as part of a person's social identity. If groups provide individuals with a sense of meaning, purpose, and belonging (i.e. a positive sense of social identity) they tend to have positive psychological consequences. The impact of these identity processes on health and well-being is explored in the contributions to this special issue. In this editorial, we discuss these contributions in light of five central themes that have emerged from research to date. These themes address the relationship between social identity and (a) symptom appraisal and response, (b) health-related norms and behaviour, (c) social support, (d) coping, and (e) clinical outcomes. The special issue as a whole points to the capacity for a social identity approach to enrich academic understanding in these areas and to play a key role in shaping health-related policy and practice.     

Inconsistencies in repeated refugee status decisions

Consistency in civil servant decisions is paramount to upholding judicial equality for citizens and individuals seeking safety through governmental intervention. We investigated refugee status decisions made by a sample of civil servants at the Swedish Migration Agency. We hypothesized, based on the emotional demands such decisions bring with them, that participants would exhibit a compassion fade effect such that refugee status was less likely to be granted over time. To test this, we administered a questionnaire containing brief presentations of asylum seekers and asked participants to judge how likely they would be to give refugee status to the person. Crucially the first, middle, and final case presented were matched on decision relevant characteristics. Consistent with our hypothesis, we saw a significant decline in ratings. These effects were accentuated by the amount of time a participant had worked at the agency, consistent with depletion of affective resources, and attenuated in workers with greater responsibility and additional training. We conclude that active regulation of empathic and affective responses to asylum seekers may play a role in determining the outcome in refugee status decisions.     

The role of motivation and volition in economic decisions: Evidence from eye movements and pupillometry

Economic decisions usually involve high stakes, real consequences, and some degree of personal risk. This article explores the impact of motivational and volitional states on economic decision processes in an incentivized lottery choice task. We investigated the patterns of decision time, choice, information search, and pupil dilation dependent on an experimental manipulation of motivation and volition, that is, the deliberative and the implemental mindset. The results indicated that choice preferences in economic decisions were robust and remained unaffected by motivational and volitional states, but decision processes were notably impacted. Decision makers in a deliberative state of mind searched for information more extensively and made slower decisions than the baseline. The implemental mindset was associated with more attention paid to the probability attributes of the gambles relative to the deliberative mindset. Furthermore, we observed that gamble outcomes that entailed no win at all (i.e., zero outcomes) played an important role for information search. These outcomes were largely disregarded in terms of predecisional information search but elicited pupillary responses similar to very high outcome lotteries. These results inform the current debate about the zero effect in risky choice. We also discuss the potential of eye-tracking studies of risky choice to dissolve ambiguities concerning the contributions of effort and arousal to modulating pupillary response. Implications for theoretical advances in decision research are discussed.