Dual task interference during gait in patients with unilateral vestibular disorders

<p>Abstract</p> <p>Background</p> <p>Vestibular patients show slower and unsteady gait; they have also been shown to need greater cognitive resources when carrying out balance and cognitive dual tasks (DT). This study investigated DT interference during gait in a middle-aged group of subjects with dizziness and unsteadiness after unilateral vestibular neuronitis and in a healthy control group.</p> <p>Methods</p> <p>Fourteen individuals with subacute unilateral vestibular impairment after neuronitis and seventeen healthy subjects performed gait and cognitive tasks in single and DT conditions. A statistical gait analysis system was used and spatio-temporal parameters were considered. The cognitive task, consisting of backward counting by three, was tape recorded and the number of right figures was then calculated.</p> <p>Results</p> <p>Both patients and controls showed a more conservative gait during DT and between groups significant differences were not found. A significant decrease in cognitive performance during DT was found only in the vestibular group.</p> <p>Conclusions</p> <p>Results suggest that less attentional resources are available during gait in vestibular patients compared to controls, and that a priority is given in keeping up the motor task to the detriment of a decrease of the cognitive performance during DT.</p

WoMMBAT: A user interface for hierarchical Bayesian estimation of working memory capacity

The change detection paradigm has become an important tool for researchers studying working memory. Change detection is especially useful for studying visual working memory, because recall paradigms are difficult to employ in the visual modality. Pashler (Perception & Psychophysics, 44, 369–378, 1988) and Cowan (Behavioral and Brain Sciences, 24, 87–114, 2001) suggested formulas for estimating working memory capacity from change detection data. Although these formulas have become widely used, Morey (Journal of Mathematical Psychology, 55, 8–24, 2011) showed that the formulas suffer from a number of issues, including inefficient use of information, bias, volatility, uninterpretable parameter estimates, and violation of ANOVA assumptions. Morey presented a hierarchical Bayesian extension of Pashler’s and Cowan’s basic models that mitigates these issues. Here, we present WoMMBAT (Working Memory Modeling using Bayesian Analysis Techniques) software for fitting Morey’s model to data. WoMMBAT has a graphical user interface, is freely available, and is cross-platform, running on Windows, Linux, and Mac operating systems

Gene duplications and evolution of vertebrate voltage-gated sodium channels

Author Posting. © The Author(s), 2006. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Journal of Molecular Evolution 63 (2006): 208-221, doi:10.1007/s00239-005-0287-9.Voltage-gated sodium channels underlie action potential generation in excitable tissue. To establish the evolutionary mechanisms that shaped the vertebrate sodium channel a-subunit (SCNA) gene family and their encoded Nav1 proteins, we identified all SCNA genes in several teleost species. Molecular cloning revealed that teleosts have eight SCNA genes, comparable to the number in another vertebrate lineage, mammals. Prior phylogenetic analyses had indicated that teleosts and tetrapods share four monophyletic groups of SCNA genes and that tandem duplications selectively expanded the number of genes in two of the four mammalian groups. However, the number of genes in each group varies between teleosts and tetrapods suggesting different evolutionary histories in the two vertebrate lineages. Our findings from phylogenetic analysis and chromosomal mapping of Danio rerio genes indicate that tandem duplications are an unlikely mechanism for generation of the extant teleost SCNA genes. Instead, analysis of other closely mapped genes in D. rerio supports the hypothesis that a whole genome duplication was involved in expansion of the SCNA gene family in teleosts. Interestingly, despite their different evolutionary histories, mRNA analyses demonstrated a conservation of expression patterns for SCNA orthologues in teleosts and tetrapods, suggesting functional conservation.The authors’ work was supported by NIH grants (NS 38937; AEN, ADT and ABR, NS 25513; HHZ and YL and NSF IBN 0236147; MCJ)

Assessing circadian rhythms in propofol PK and PD during prolonged infusion in ICU patients

This study evaluates possible circadian rhythms during prolonged propofol infusion in patients in the intensive care unit. Eleven patients were sedated with a constant propofol infusion. The blood samples for the propofol assay were collected every hour during the second day, the third day, and after the termination of the propofol infusion. Values of electroencephalographic bispectral index (BIS), arterial blood pressure, heart rate, blood oxygen saturation and body temperature were recorded every hour at the blood collection time points. A two-compartment model was used to describe propofol pharmacokinetics. Typical values of the central and peripheral volume of distribution and inter-compartmental clearance were VC = 27.7 l, VT = 801 l, and CLD = 2.73 l/min. The systolic blood pressure (SBP) was found to influence the propofol metabolic clearance according to Cl (l/min) = 2.65·(1 − 0.00714·(SBP − 135)). There was no significant circadian rhythm detected with respect to propofol pharmacokinetics. The BIS score was assessed as a direct effect model with EC50 equal 1.98 mg/l. There was no significant circadian rhythm detected within the BIS scores. We concluded that the light–dark cycle did not influence propofol pharmacokinetics and pharmacodynamics in intensive care units patients. The lack of night–day differences was also noted for systolic blood pressure, diastolic blood pressure and blood oxygenation. Circadian rhythms were detected for heart rate and body temperature, however they were severely disturbed from the pattern of healthy patients

Identification of a Key Amino Acid of LuxS Involved in AI-2 Production in Campylobacter jejuni

Autoinducer-2 (AI-2) mediated quorum sensing has been associated with the expression of virulence factors in a number of pathogenic organisms and has been demonstrated to play a role in motility and cytolethal distending toxin (cdt) production in Campylobacter jejuni. We have initiated the work to determine the molecular basis of AI-2 synthesis and the biological functions of quorum sensing in C. jejuni. In this work, two naturally occurring variants of C. jejuni 81116 were identified, one producing high-levels of AI-2 while the other is defective in AI-2 synthesis. Sequence analysis revealed a G92D mutation in the luxS gene of the defective variant. Complementation of the AI-2− variant with a plasmid encoded copy of the wild-type luxS gene or reversion of the G92D mutation by site-directed mutagenesis fully restored AI-2 production by the variant. These results indicate that the G92D mutation alone is responsible for the loss of AI-2 activity in C. jejuni. Kinetic analyses showed that the G92D LuxS has a ∼100-fold reduced catalytic activity relative to the wild-type enzyme. Findings from this study identify a previously undescribed amino acid that is essential for AI-2 production by LuxS and provide a unique isogenic pair of naturally occurring variants for us to dissect the functions of AI-2 mediated quorum sensing in Campylobacter

Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion