Severe Mental Illness and Acute Stress: A Study of Service Utilization in a Conflict Zone

Patients suffering from severe mental illness (SMI) are considered especially vulnerable to stress. In this study, their use of acute stress services in a military context affecting civilian populations was assessed, using naturally occurring data. The proportion of patients with a previously known SMI, defined as any chronic psychotic disorder or bipolar disorder, among all civilians examined at a center for treatment of stress during a military conflict versus at the ER in usual times, was compared, using the Chi square statistical test. Among 354 subjects examined at the center for treatment of stress, 12 had a SMI diagnosis. Among 404 subjects examined at the ER in usual times, 16 had a SMI diagnosis. Patients with SMI were under-represented, but not in a statistically significant manner, at the center for treatment of stress (χ² = 0.31, p = ns). Although these results may imply that patients with SMI are not more vulnerable to external stress than the general population, we believe that they may have difficulties in seeking immediate help in such traumatogenic contexts. In order to reduce the occurrence of PTSD and gain efficacy in the treatment of the primary disorder, psychiatric services should perhaps make a reaching out effort to identify and examine these patients in the community. .     

Advances in computational and statistical diffusion MRI

Computational methods are crucial for the analysis of diffusion magnetic resonance imaging (MRI) of the brain. Computational diffusion MRI can provide rich information at many size scales, including local microstructure measures such as diffusion anisotropies or apparent axon diameters, whole‐brain connectivity information that describes the brain's wiring diagram and population‐based studies in health and disease. Many of the diffusion MRI analyses performed today were not possible five, ten or twenty years ago, due to the requirements for large amounts of computer memory or processor time. In addition, mathematical frameworks had to be developed or adapted from other fields to create new ways to analyze diffusion MRI data. The purpose of this review is to highlight recent computational and statistical advances in diffusion MRI and to put these advances into context by comparison with the more traditional computational methods that are in popular clinical and scientific use. We aim to provide a high‐level overview of interest to diffusion MRI researchers, with a more in‐depth treatment to illustrate selected computational advances.     

Evaluating drug effectiveness in an office setting for children with attention deficit disorders

Stimulant medications have been demonstrated to be useful in treating groups of children with attention deficit disorders, but placebo effects and situational differences in behavior in individual cases need to be followed and assessed. A simple procedure for systematically assessing these factors in the individual child in the office setting is described and illustrated. The procedure provides an objective means of determining the drug and placebo effects on the reported problem behavior and the differences between parent and teacher perceptions of the behavior.     

From the Cover: Comparative analyses of animal-tracking data reveal ecological significance of endothermy in fishes

Despite long evolutionary separations, several sharks and tunas share the ability to maintain slow-twitch, aerobic red muscle (RM) warmer than ambient water. Proximate causes of RM endothermy are well understood, but ultimate causes are unclear. Two advantages often proposed are thermal niche expansion and elevated cruising speeds. The thermal niche hypothesis is generally supported, because fishes with RM endothermy often exhibit greater tolerance to broad temperature ranges. In contrast, whether fishes with RM endothermy cruise faster, and achieve any ecological benefits from doing so, remains unclear. Here, we compiled data recorded by modern animal-tracking tools for a variety of free-swimming marine vertebrates. Using phylogenetically informed allometry, we show that both cruising speeds and maximum annual migration ranges of fishes with RM endothermy are 2–3 times greater than fishes without it, and comparable to nonfish endotherms (i.e., penguins and marine mammals). The estimated cost of transport of fishes with RM endothermy is twice that of fishes without it. We suggest that the high energetic cost of RM endothermy in fishes is offset by the benefit of elevated cruising speeds, which not only increase prey encounter rates, but also enable larger-scale annual migrations and potentially greater access to seasonally available resources.In 1835, the British physician John Davy reported that skipjack tuna have body temperatures 10 °C higher than ambient waters and considered this fish an exception to the general rule that fishes are cold-blooded (1). It is currently known that at least 14 species of tuna (family Scombridae) and five species of shark (four species in the family Lamnidae and one species in the family Alopiidae) have the ability to retain metabolic heat via vascular countercurrent heat exchangers, and to maintain the temperature of slow-twitch, aerobic red muscle (hereafter denoted RM) significantly above that of the ambient water (2–7). This “RM endothermy” (see SI Materials and Methods for terminology) in fishes represents a remarkable example of convergent evolution, because bony fishes and cartilaginous fishes diverged as long as 450 million years ago (8). In addition to elevated RM temperature, tunas and endothermic sharks share a number of morphological (e.g., medially located RM), physiological (e.g., high metabolic rates), and ecological (e.g., highly mobile and predatory lifestyle) characteristics (9).RM endothermy is an energetically expensive thermal strategy (9), and its convergent evolution indicates that the extra energetic costs incurred by RM endothermy can be outweighed by some ecological advantages. This topic has been discussed intensively, and two primary, nonmutually exclusive hypotheses have been proposed: expansion of the thermal niche and elevated cruising speeds (2). The thermal niche hypothesis states that fishes with RM endothermy can tolerate a broader range of water temperatures and, thus, can expand their geographic niche. An increasing suite of evidence supports this hypothesis; tunas and endothermic sharks often range widely and dive well beneath the thermocline and, consequently, experience a broad temperature range (e.g., more than 20 °C in some species; refs. 10 and 11). However, some ectothermic species (e.g., blue shark) experience similar temperature ranges by diving deep (11, 12), suggesting that other factors may also affect the thermal preference and tolerance of pelagic fishes.The elevated cruising speed hypothesis states that elevated RM temperature enhances the power output of RM and, thereby, increases cruising speed of the fishes (2). This hypothesis is reasonable, because the contraction speed and power output of the isolated RM (13) and the sustained swim speed of ectothermic fishes in captivity (14) all increase with temperature within a species, at least within their normal temperature range. Surprisingly, however, a previous laboratory study found no differences in the sustained swim speeds between two Scombridae species with and without RM endothermy (15). As a result, evidence for the hypothesis is still lacking.If fishes with RM endothermy are shown to cruise faster in nature, what ecological benefits could they achieve from doing so? Fishes can increase prey encounter rates and, thus, potential energy gains by cruising faster (16); however, this benefit may be counteracted if energetic costs incurred by cruising faster and being endothermic are high. It is therefore important to examine whether the cost of transport (i.e., the energy needed to move a unit body mass over a unit distance) at their cruising speeds is higher for fishes with RM endothermy.In addition to the benefit of increased prey encounter rates, fishes with RM endothermy may be able to move greater distances in a given time period, such as a year, because of their fast cruising speed. Annual migrations are common in fishes, often between foraging grounds and reproductive habitats (10, 11, 17); therefore, it is hypothesized that fishes with RM endothermy exhibit annual migrations over larger spatial scales than fishes without it. If such difference is observed, large-scale migration could be an ecological advantage, because it allows the fishes with RM endothermy to better exploit seasonal peaks of resource abundance and avoid seasonal resource depression (18).Because of the rapid development and improvement of various data-recording or transmitting tags, information on fish movements in the wild is increasingly available, both from fine-scale (e.g., recording swim speed; ref. 19) and long-term (e.g., recording migration path; ref. 11) animal-tracking studies. Such information has provided much insight into the ecology of many species; however, no previous studies have examined the possible differences in the movement patterns or swimming energetics in nature between fishes with and without RM endothermy. In this study, therefore, we compiled data on cruising swim speed and migration range of fishes, recorded by various animal-tracking tools, both from the literature and our own fieldwork. We also estimated the cost of transport for each species swimming at each cruising speed. Using phylogenetically informed allometry, we examined whether fishes with RM endothermy (i) swim faster, (ii) have higher cost of transport, and (iii) exhibit larger-scale annual migrations.     

Prefrontal cortex white matter tracts in prodromal Huntington disease

Huntington disease (HD) is most widely known for its selective degeneration of striatal neurons but there is also growing evidence for white matter (WM) deterioration. The primary objective of this research was to conduct a large‐scale analysis using multisite diffusion‐weighted imaging (DWI) tractography data to quantify diffusivity properties along major prefrontal cortex WM tracts in prodromal HD. Fifteen international sites participating in the PREDICT‐HD study collected imaging and neuropsychological data on gene‐positive HD participants without a clinical diagnosis (i.e., prodromal) and gene‐negative control participants. The anatomical prefrontal WM tracts of the corpus callosum (PFCC), anterior thalamic radiations (ATRs), inferior fronto‐occipital fasciculi (IFO), and uncinate fasciculi (UNC) were identified using streamline tractography of DWI. Within each of these tracts, tensor scalars for fractional anisotropy, mean diffusivity, radial diffusivity, and axial diffusivity coefficients were calculated. We divided prodromal HD subjects into three CAG‐age product (CAP) groups having Low, Medium, or High probabilities of onset indexed by genetic exposure. We observed significant differences in WM properties for each of the four anatomical tracts for the High CAP group in comparison to controls. Additionally, the Medium CAP group presented differences in the ATR and IFO in comparison to controls. Furthermore, WM alterations in the PFCC, ATR, and IFO showed robust associations with neuropsychological measures of executive functioning. These results suggest long‐range tracts essential for cross‐region information transfer show early vulnerability in HD and may explain cognitive problems often present in the prodromal stage. Hum Brain Mapp 36:3717–3732, 2015. © 2015 Wiley Periodicals, Inc.