Criteria for robustness of heteroclinic cycles in neural microcircuits.

Copyright © 2011 Ashwin et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.We introduce a test for robustness of heteroclinic cycles that appear in neural microcircuits modeled as coupled dynamical cells. Robust heteroclinic cycles (RHCs) can appear as robust attractors in Lotka-Volterra-type winnerless competition (WLC) models as well as in more general coupled and/or symmetric systems. It has been previously suggested that RHCs may be relevant to a range of neural activities, from encoding and binding to spatio-temporal sequence generation.The robustness or otherwise of such cycles depends both on the coupling structure and the internal structure of the neurons. We verify that robust heteroclinic cycles can appear in systems of three identical cells, but only if we require perturbations to preserve some invariant subspaces for the individual cells. On the other hand, heteroclinic attractors can appear robustly in systems of four or more identical cells for some symmetric coupling patterns, without restriction on the internal dynamics of the cells

Multi-neuronal refractory period adapts centrally generated behaviour to reward

Oscillating neuronal circuits, known as central pattern generators (CPGs), are responsible for generating rhythmic behaviours such as walking, breathing and chewing. The CPG model alone however does not account for the ability of animals to adapt their future behaviour to changes in the sensory environment that signal reward. Here, using multi-electrode array (MEA) recording in an established experimental model of centrally generated rhythmic behaviour we show that the feeding CPG of Lymnaea stagnalis is itself associated with another, and hitherto unidentified, oscillating neuronal population. This extra-CPG oscillator is characterised by high population-wide activity alternating with population-wide quiescence. During the quiescent periods the CPG is refractory to activation by food-associated stimuli. Furthermore, the duration of the refractory period predicts the timing of the next activation of the CPG, which may be minutes into the future. Rewarding food stimuli and dopamine accelerate the frequency of the extra-CPG oscillator and reduce the duration of its quiescent periods. These findings indicate that dopamine adapts future feeding behaviour to the availability of food by significantly reducing the refractory period of the brain's feeding circuitry

Review of family, couples and systemic therapy outcome research 2000-2009

These tables present the result of a systematic collation of empirical studies of outcomes over 10 years of English language publication in refereed journals. The Review is intended to be a resource for practitioners and researchers, as a readily available source of recent research publications on specific conditions. For this purpose a description of the main aspects of each study has been provided in a standard form. A full alphabetical listing of references is provided from page 98. A substantial further study, primarily by Emma Silver and Natasha Nascimento, involves a detailed coding of each article so that we can report trends and patterns in the research. This project is currently being written up for journal submission. An account of the methodology will be provided in that publication. In summary: The listing does not include review articles that did not report original data. We have taken a broad definition of family, couple and systemic therapy, and most of the articles were identified by searching electronic data-bases with a variety of keywords, then reviewing every publication to select those that fitted our criteria

Escitalopram reduces attentional performance in anxious older adults with high-expression genetic variants at serotonin 2A and 1B receptors

Older adults are among the most vulnerable to adverse cognitive effects of psychotropic medications and, therefore, the personalization of psychotropic treatment based on adverse drug reactions in this demographic is of great importance. We examined changes on neuropsychological tests of attention attributable to selective serotonin reuptake inhibitor (SSRI) treatment in anxious older adults. We also examined whether variation in serotonin receptor genes was associated with reduced attentional performance with SSRIs. We examined change from pre- to post-treatment in two attention measures – digit span and coding – in 133 adults aged ≥60 yr with generalized anxiety disorder in a 12-wk trial of escitalopram vs. placebo. We also examined attentional change in relation to genetic variability in four central serotonin receptors: the serotonin transporter and serotonin 1A, 2A and 1B receptors. Digit span scores were significantly lowered in patients receiving escitalopram relative to placebo, indicating reduced attentional performance attributable to the SSRI. Individuals with high-transcription variants in the receptors 5-HTR(2A) rs6311 and 5-HTR(1B) rs11568817 had greater reductions in attention with SSRI treatment compared to placebo. We conclude that SSRIs reduce attention in older adults, particularly in those with high-expression genetic variants at the serotonin 2A and 1B receptors. Analysing neuropsychological changes with SSRIs in relation to genetic variation in the serotonin system may be a useful strategy for detecting subgroups of older adults who are more susceptible to side-effects of SSRIs. These results, if confirmed, could lead to the personalization of SSRI use to reduce adverse neurocognitive effects

Glucose metabolism in pregnancy at high altitude

WSTĘP. Celem badania była ocena wrażliwości na insulinę oraz funkcji komórek b związanych z niższą glikemią na czczo u kobiet ciężarnych przebywających na dużych wysokościach w porównaniu z ciężarnymi mieszkającymi na poziomie morza. MATERIAŁ I METODY. W badaniu uczestniczyło 215 kobiet w 8-42 tygodniu ciąży, mieszkających w Peru. Rekrutację przeprowadzono w miejscowościach Cerro de Pasco, która znajduje się 4370 m (14 340 stóp) nad poziomem morza, oraz w Limie, leżącej na wysokości poziomu morza. Grupę kontrolną stanowiły 53 kobiety, które nie były w ciąży (22 w Cerro de Pasco i 31 w Limie). Glikemię, insulinemię oraz stężenie C-peptydu i proinsuliny na czczo zmierzono w próbkach krwi uzyskanych z żyły odłokciowej w godzinach 8.00–10.00, wcześniej pacjentki nie przyjmowały pokarmów przez 10–14 godzin. Insulinooporność oraz funkcje komórek b obliczono z zastosowaniem modelu oceny homeostazy. WYNIKI. Stężenie C-peptydu na czczo oraz funkcja komórek b były podobne, stężenie insuliny oraz proinsuliny na czczo były niższe, natomiast insulinooporność była wyższa u kobiet przebywających na większej wysokości. WNIOSKI. Niższa glikemia na czczo u kobiet ciężarnych przebywających na obszarach położonych wyżej w porównaniu z ciężarnymi zamieszkującymi na poziomie morza przy podobnym wydzielaniu insuliny wiąże się z większą obwodową wrażliwością na insulinę. Zjawisko to może częściowo tłumaczyć niższą masę urodzeniową dzieci matek z obszarów położonych wysoko nad poziomem morza.OBJECTIVE. To assess insulin sensitivity and b-cell function associated with lower maternal fasting plasma glucose levels at high altitude compared with sea level. RESEARCH DESIGN AND METHODS. We studied 215 pregnant women at 8–42 weeks of gestation in Peru. The women were recruited from Cerro de Pasco, which is situated 4,370 m (14,340 feet) above sea level, and Lima, which is at sea level. We also examined 53 nonpregnant control subjects (22 in Cerro de Pasco and 31 in Lima). Fasting plasma glucose, insulin, C-peptide, and proinsulin concentrations were measured in samples obtained from the antecubital vein between 8:00 A.M. and 10:00 A.M. after an overnight period of fasting for 10–14 h. Insulin resistance and b-cell function were calculated using homeostasis model assessment. RESULTS. Fasting C-peptide levels and b-cell function were similar, fasting concentrations of insulin and proinsulin were lower, and insulin sensitivity was higher at high altitude compared with sea level. CONCLUSIONS. Maternal fasting plasma glucose that is lower at high altitude than at sea level in the presence of similar insulin secretion is associated with higher peripheral insulin sensitivity. This may partly explain the lower birth weights at high altitudes

Characterisation of archaeological waterlogged wood by pyrolytic and mass spectrometric techniques

1) Department of Chemistry and Industrial Chemistry, University of Pisa, via Risorgimento 35. 56126 Pisa, Italy ; 2) IRNAS-CSIC, Seville, Spain; E-mail address: [email protected] combination of two techniques based on analytical pyrolysis and mass spectrometry, including direct exposure-MS (DE-MS) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), was used to study the chemical composition of waterlogged archaeological wood. In particular, the two techniques were used to chemically characterise samples of archaeological wood from the excavation of the Site of the Ancient Ships of Pisa San Rossore in Pisa (Italy). The data were compared to those of native sound wood of the same species. The results highlight that DE-MS is a valuable technique for the characterisation of archaeological wood. DE-MS allows us to use a minimal sample size and to perform the analysis in a few minutes, thus avoiding the long wet-chemical procedures that are commonly used to characterise wood. The results also confirm the importance of Py-GC/MS as a tool for shedding light on the chemical modifications of wood in archaeological objects. The analyses demonstrated that waterlogged wood from the site of Pisa San Rossore have undergone an extensive loss of polysaccharides together with partial demethylation of lignin units, both guaiacyl and syringyl monomers. In fact, catechols and methoxy catechols were identified among the pyrolysis products of the waterlogged wood samples.The authors wish to thank Dott.ssa G. Giachi (Restoration Laboratories of the Archaeological Superintendence of Tuscany, Florence, Italy) for providing archaeological wood samples and for her valuable support and collaboration. Funding was provided by the Archaeological Superintendence of Tuscany and by the Italian MIUR (PRIN Cofin05).Peer reviewe