The neural correlates of retrieval and procedural strategies in mental arithmetic: A functional neuroimaging meta‐analysis

Mental arithmetic is a complex skill of great importance for later academic and life success. Many neuroimaging studies and several meta‐analyses have aimed to identify the neural correlates of mental arithmetic. Previous meta‐analyses of arithmetic grouped all problem types into a single meta‐analytic map, despite evidence suggesting that different types of arithmetic problems are solved using different strategies. We used activation likelihood estimation (ALE) to conduct quantitative meta‐analyses of mental arithmetic neuroimaging (n = 31) studies, and subsequently grouped contrasts from the 31 studies into problems that are typically solved using retrieval strategies (retrieval problems) (n = 18) and problems that are typically solved using procedural strategies (procedural problems) (n = 19). Foci were compiled to generate probabilistic maps of activation for mental arithmetic (i.e., all problem types), retrieval problems, and procedural problems. Conjunction and contrast analyses were conducted to examine overlapping and distinct activation for retrieval and procedural problems. The conjunction analysis revealed overlapping activation for retrieval and procedural problems in the bilateral inferior parietal lobules, regions typically associated with magnitude processing. Contrast analyses revealed specific activation in the left angular gyrus for retrieval problems and specific activation in the inferior frontal gyrus and cingulate gyrus for procedural problems. These findings indicate that the neural bases of arithmetic systematically differs according to problem type, providing new insights into the dynamic and task‐dependent neural underpinnings of the calculating brain.     

Vector autoregression, structural equation modeling, and their synthesis in neuroimaging data analysis

Vector autoregression (VAR) and structural equation modeling (SEM) are two popular brain-network modeling tools. VAR, which is a data-driven approach, assumes that connected regions exert time-lagged influences on one another. In contrast, the hypothesis-driven SEM is used to validate an existing connectivity model where connected regions have contemporaneous interactions among them. We present the two models in detail and discuss their applicability to FMRI data, and their interpretational limits. We also propose a unified approach that models both lagged and contemporaneous effects. The unifying model, structural vector autoregression (SVAR), may improve statistical and explanatory power, and avoid some prevalent pitfalls that can occur when VAR and SEM are utilized separately.     

Cognitive factors associated with subclinical delusional ideation in the general population

Cognitive biases have been found to be associated with delusions in schizophrenia and schizotypy. In the current study, we examined the relationship between subclinical delusional ideation, measured using the Peters Delusions Inventory, and cognitive biases including the bias against disconfirmatory evidence (BADE), 'jumping to conclusions', and need for closure, evaluated using the computerized BADE program, in a sample of 117 healthy, non-psychiatric controls. Our results suggest that subclinical delusional ideation is associated with BADE, greater need for closure, a 'jumping to conclusions' response style, and a tendency to rate absurd and unlikely interpretations of an event as more plausible, which might be indicative of insufficient evidence integration or 'liberal acceptance'. These cognitive biases, which occur in a much milder fashion than seen in typical deluded patient samples, may nonetheless additively play a role in the development of delusional ideation, and suggest common pathways seen in healthy and psychiatric samples.     

Screening for psychosocial risk in pediatric cancer

Major professional organizations have called for psychosocial risk screening to identify specific psychosocial needs of children with cancer and their families and facilitate the delivery of appropriate evidence‐based care to address these concerns. However, systematic screening of risk factors at diagnosis is rare in pediatric oncology practice. Subsequent to a brief summary of psychosocial risks in pediatric cancer and the rationale for screening, this review identified three screening models and two screening approaches [Distress Thermometer (DT), Psychosocial Assessment Tool (PAT)], among many more articles calling for screening. Implications of broadly implemented screening for all patients across treatment settings are discussed. Pediatr Blood Cancer 2012; 59: 822–827. © 2012 Wiley Periodicals, Inc.     

Chrysobactin siderophores produced by Dickeya chrysanthemi EC16

The plant pathogen Dickeya chrysanthemi EC16 (formerly known as Petrobacterium chrysanthemi EC16 and Erwinia chrysanthemi EC16) was found to produce a new triscatecholamide siderophore, cyclic trichrysobactin, the related catecholamide compounds, linear trichrysobactin and dichrysobactin, and the previously reported monomeric siderophore unit, chrysobactin. Chrysobactin is comprised of L-serine, D-lysine, and 2,3-dihydroxybenzoic acid (DHBA). Trichrysobactin is a cyclic trimer of chrysobactin joined by a triserine lactone backbone. The chirality of the ferric complex of cyclic trichrysobactin is found to be in the Λ configuration, similar to Fe(III)-bacillibactin, which contains a glycine spacer between the DHBA and L-threonine components and is opposite that of Fe(III)-enterobactin, which contains DHBA ligated directly to L-serine.     

Development of spatial and verbal working memory capacity in the human brain

A core aspect of working memory (WM) is the capacity to maintain goal-relevant information in mind, but little is known about how this capacity develops in the human brain. We compared brain activation, via fMRI, between children (ages 7-12 years) and adults (ages 20-29 years) performing tests of verbal and spatial WM with varying amounts (loads) of information to be maintained in WM. Children made disproportionately more errors than adults as WM load increased. Children and adults exhibited similar hemispheric asymmetry in activation, greater on the right for spatial WM and on the left for verbal WM. Children, however, failed to exhibit the same degree of increasing activation across WM loads as was exhibited by adults in multiple frontal and parietal cortical regions. Thus, children exhibited adult-like hemispheric specialization, but appeared immature in their ability to marshal the neural resources necessary to maintain large amounts of verbal or spatial information in WM.     

Controlled inspiration depth reduces variance in breath-holding-induced BOLD signal

Recent studies have shown that blood oxygen level dependent (BOLD) response amplitude during short periods of breath holding (BH) measured by functional magnetic resonance imaging (fMRI) can be an effective metric for intersubject calibration procedures. However, inconsistency in the depth of inspiration during the BH scan may account for a portion of BOLD variation observed in such scans, and it is likely to reduce the effectiveness of the calibration measurement. While modulation of BOLD signal has been correlated with end-tidal CO2 and other measures of breathing, fluctuations in performance of BH have not been studied in the context of their impact on BOLD signal. Here, we studied the degree to which inspiration depth corresponds to BOLD signal change and tested the effectiveness of a method designed to control inspiration level through visual cues during the BH task paradigm. We observed reliable differences in BOLD signal amplitude corresponding to the depth of inspiration. It was determined that variance in BOLD signal response to BH could be significantly reduced when subjects were given visual feedback during task inspiration periods. The implications of these findings for routine BH studies of BOLD-derived neurovascular response are discussed.     

Mapping and correction of vascular hemodynamic latency in the BOLD signal

Correlation and causality metrics can be applied to blood-oxygen level-dependent (BOLD) signal time series in order to infer neural synchrony and directions of information flow from fMRI data. However, the BOLD signal reflects both the underlying neural activity and the vascular response, the latter of which is governed by local vasomotor physiology. The presence of potential vascular latency differences thus poses a confound in the detection of neural synchrony as well as inferences about the causality of neural processes. In the present study, we investigate the use of a breath holding (BH) task for characterizing and correcting for voxel-wise neurovascular latency differences across the whole brain. We demonstrate that BH yields reliable measurements of relative timing differences between voxels, and further show that a BH-derived latency correction can impact both functional connectivity maps of the resting-state default-mode network and activation maps of an event-related working memory (WM) task.