871 research outputs found
Computational approaches to psychiatry
No full textA major reason for disappointing progress of psychiatric diagnostics and nosology is the lack of tests which enable mechanistic inference on disease processes within individual patients. The resulting inability to pursue formal differential diagnosis has forced the field to stick to symptom-based diagnostic schemes with limited predictive validity concerning treatment response and clinical outcome. A promising new approach is the use of computational modeling for inferring mechanisms which generate observed behavior and brain activity in psychiatric patients. However, while this computational approach to psychiatry is rapidly gaining attention, much work remains to be done to finesse existing computational models, making them 'fit for practice' in a clinical setting and proving their validity in longitudinal studies. This review outlines recent methodological advances and strategies in this regard, focusing on generative models which infer mechanistically interpretable parameters (of computational or physiological processes) from measured behavior and brain activity. © 2013 Elsevier Ltd
Bloed en bloedderivaten: streven naar nul risico
No full textMet dertien jaar ervaring op de dienst biologische standaardisatie en virologie van het WIV, is de veiligheid van bloedderivaten meer dan vertrouwd terrein voor Esther Mathys. De beschikbaarheid van de producten hangt volledig af van de goodwill van de bloedgevers (die in ons land niet vergoed worden) en de producten moeten steeds van onberispelijke kwaliteit zijn.</p
Sang et dérivés sanguins:vers le risque zéro
No full textTreize années de présence dans le service de standardisation biologique et de virologie de l'ISP ont permis à Esther Mathys de posséder une connaissance approfondie de la sécurité des produits dérivés du sang. Des produits dont la disponibilité est totalement dépendante de la bonne volonté des donneurs (un acte purement gratuit dans notre pays) et dont la qualité doit être irréprochable.</p
Sechelleptus variabilis VandenSpiegel & Golovatch 2007
No full textSechelleptus variabilis VandenSpiegel & Golovatch, 2007 Fig. 2 Material examined Holotype UNION OF THE COMOROS • ♂; Mohéli, Fomboni; 12°15′ S, 043°45′ E; 21 May 2003; dead wood; R. Jocqué and D. VandenSpiegel leg.; BE_RMCA_MYR.Dip.21733. New material FRANCE – Department of Mayotte (Comoros archipelago) • ♂; Mereni, back of mangrove; 19 Nov. 2019; hand collecting; D. VandenSpiegel and A. Mathys leg.; BE_RMCA_MYR.Dip.22878 • 1 ♂, 1 ♀; same collection data as for preceding; 21 Nov. 2019; BE_RMCA_MYR.Dip.22879 • 1 ♂; same collection data as for preceding; BE_RMCA_MYR.Dip.22983 • 1 ♂, 1 ♀; Mont Benara; 12°52′ S, 045°09′ E; 21 Nov. 2019; hand collecting & sieving, litter; D. VandenSpiegel and A. Mathys leg.; BE_ RMCA_MYR.Dip.22883 • 1 ♂; Mont Combani, 500 m before Lodge; 12°47′ S, 045°09′ E; 15 Nov. 2019; sieving; litter; D. VandenSpiegel and A. Mathys leg.; BE_RMCA_MYR.Dip.22930. Remarks In the original description of the species, the length unit given for the specimens’ sizes is wrong and should have been cm instead of mm. Correct measurements are: length ♂♂: 3.4–8.0 cm; ♀♀: 5.0– 7.0 cm; midbody width 0.34–0.5 cm and 0.3 – 0.5 cm, respectively. Taking this modification into account, the recently collected specimens agree with the description (VandenSpiegel & Golovatch 2007).Published as part of Vandenspiegel, Didier, Henrard, Arnaud & Mathys, Aurore, 2021, Sechelleptus arborivagus sp. nov., a new arboreal spirostreptid millipede (Diplopoda, Spirostreptidae) endemic to Mayotte Island (Comoros Archipelago), Indian Ocean, pp. 1-21 in European Journal of Taxonomy 755 (1) on pages 7-8, DOI: 10.5852/ejt.2021.755.1395, http://zenodo.org/record/496600
Funktionelle und effektive Konnektivität
No full textZusammenfassung
Neurophysiologische und bildgebende Verfahren zur Messung von Hirnaktivität, wie fMRI oder EEG, werden in den Neurowissenschaften eingesetzt, um Prozesse funktioneller Spezialisierung und funktioneller Integration im menschlichen Gehirn zu untersuchen. Funktionelle Integration kann auf zwei verschiedene Arten beschrieben werden: funktionelle Konnektivität und effektive Konnektivität. Während die funktionelle Konnektivität lediglich statistische Abhängigkeiten zwischen Zeitreihen beschreibt, erfordert das Konzept der effektiven Konnektivität ein mechanistisches Modell der kausalen Effekte, die den beobachteten Daten zu Grunde liegen. Dieser Artikel fasst die konzeptionellen und methodischen Grundlagen moderner Techniken für die Analyse funktioneller und effektiver Konnektivität auf der Basis von fMRI und elektrophysiologischen Daten zusammen. Ein besonderer Schwerpunkt liegt dabei auf dem Dynamic Causal Modelling (DCM), einem neuen Verfahren zur Analyse nichtlinearer neuronaler Systeme. Diese Methode besitzt ein vielversprechendes Potenzial für klinische Anwendungen, z. B. zur Entschlüsselung pathophysiologischer Mechanismen bei Hirnerkrankungen und zur Etablierung neurophysiologisch fundierter diagnostischer Klassifikationen.
Abstract
Neurophysiological and imaging procedures to measure brain activity, such as fMRI or EEG, are employed in neuroscience to investigate processes of functional specialisation and functional integration in the human brain. Functioal integration can be described in two distinct ways: functional connectivity and effective connectivity. Whereas functional connectivity merely describes the statistical dependence between two time series, the concept of effective connectivity requires a mechanistic model of the causative effects upon which the data to be observed are based. This article summarises the conceptual and methodological principles of modern techniques for the analysis of functional and effective connectivity on the basis of fMRI and electrophysiological data. Particular emphasis is placed on dynamic causal modelling (DCM), a new procedure for the analysis of non-linear neuronal systems. This method has a highly promising potential for clinical applications, e. g., for decoding pathological mechanisms in brain diseases and for the establishment of neurologically valid diagnostic classifications
Sechelleptus arborivagus Vandenspiegel & Henrard & Mathys 2021, sp. nov.
No full text<i>Sechelleptus arborivagus</i> sp. nov. <p>urn:lsid:zoobank.org:act: 0F7B3368-17F8-4CAD-8B11-C34B564FE8DE</p> <p>Figs 3–8</p> Diagnosis <p> A medium-sized arboreal millipede with relatively long legs, particularly similar to <i>S. variabilis</i> by sharing the structure of the male first leg and rather simple gonopods with the metaplica widened and a little higher than proplica, the latter without lateral cone. The two species differ by the gonotelopodite being apically divided in two branches in <i>S. arborivagus</i> sp. nov. and simple in <i>S. variabilis.</i></p> Etymology <p>Referring to the ecology of the species, which has always been observed climbing trees.</p> Material examined <p> <b>Holotype</b></p> <p> FRANCE – <b>Department of Mayotte</b> (Comoros archipelago) • ♂; Mt. Tchaourembo; 12°52′14″ S, 045°08′44″ E; 540–550 m a.s.l.; 25 Nov. 2019; D. VandenSpiegel and A. Mathys leg.; on tree; by hand; GenBank accession numbers: MW168813 (COI), MW148622 (16S rRNA); BE_RMCA_MYR. Dip.22874.</p> <p> <b>Paratypes</b></p> <p> FRANCE – <b>Department of Mayotte</b> (Comoros archipelago) • 1 ♂, 1 ♀; same collection data as for holotype; GenBank accession numbers: MW168814 (COI), MW148623 (16S rRNA); BE_RMCA_ MYR.Dip.22875 • 9 ♀♀; same collection data as for holotype; GenBank accession numbers: MW168815 (COI), MW148624 (16S rRNA); BE_RMCA_MYR.Dip.22876.</p> Additional material <p> FRANCE – <b>Department of Mayotte</b> (Comoros archipelago) • 1 ♀; Mt. Benara; 12°52′ S, 045°11′ E; 23 Jan. 1999; R. Jocqué and G. De Smet leg.; forest; by hand; GenBank accession numbers: MW148621 (16S rRNA); BE_RMCA_MYR.Dip.17917.</p> Description <p> <b>Holotype</b></p> <p>With 57 body rings (plus telson, no apodous rings); ca 100 mm long, 7 mm wide.</p> <p>LIVE COLORATION (Fig. 3). Head, collum, antennae, telson, anal valves and legs uniformly light brownish to dark brownish. Metazonae light brown to red-brown. Posterior margin of metazonites dark brown.</p> <p>HEAD. Smooth. Each eye patch with circa 60 ommatidia arranged in seven horizontal rows (Fig. 4A), Labrum with three smoothly rounded teeth and a single row of 21 short labral setae (Fig. 4G). Clypeus with four supra-labral setae, two on each side (Fig. 4G). Antennae moderately long (Fig. 3), protruding back to ring 2. Relative length of antennomeres: 1>2>3=4=5>6. Terminal antennomere (disc) with four large sensory cones located together inside a membranous area. Each of antennomeres 5 and 6 apicolaterally with a field of narrow and long sensilla basiconica (Fig. 4B). Gnathochilarium, usual for spirostreptideans (Fig. 4D). Prementum (pm) smooth and straight, not depressed. Mentum (me) smooth. Lamellae linguales each with two strong apical setae, one equally strong seta behind these, plus, basally, an oblique line of four setae. Stipites with a basal longitudinal field of setae, lateral margin in distal half with a row of setae; one isolated, subapical, stout seta or sensillum; cardo small, kidney-shaped. Mandibles (Fig. 4E, F) with stipes devoid of differentiation. Odontomere (od) long, moveable. Sectile edge (se) of psectromere (ps) with four lobes; eight pectinate lamellae (pl). One wide molar furrow (mf).</p> <p>COLLUM. Smooth, ventrally with six longitudinal furrows, anteroventral angle 80–90°.</p> <p>BODY RINGS. Prozonae smooth. Metazonae with longitudinal striae ventrally from ca ⅔ ring length below ozopore. Ozopores located on metazonae, starting with ring 6, located close to, but not touching the suture between pro- and metazonae. Limbus simple (Fig. 4H). Defensive glands well-developed (Fig. 4I).</p> <p>TELSON. Preanal ring with a shallow submarginal depression. Anal valves smooth, without submarginal depression. Hypoproct, small, widely triangular.</p> <p>LEGS. Length 0.45–0.5 × body diameter, postfemoral and tibial pads (Fig. 4J) from third male leg-pair until beyond midbody, pads decreasing in size posteriorly; claw large, curved (Fig. 4K). First pair of male legs with a well-developed prefemoral process ending in an inward curved tip (Fig. 5A). Coxosternum with a laterobasal field of four strong setae on anterior side.</p> <p>GONOPODS (Figs 5B–E, 6). Sternum (st) triangular, not reaching as far distad as paracoxite (px). Metaplica (mp) higher than proplica, rounded apically (Fig. 5C; mp). Proplica with straight sides, in apical part with scattered short setae, ending apically in a more or less spiniform mesapical projection (Fig. 5C; mpp) and a well-developed, apicolateral, lamellose lobe (Fig. 6C; al); telopodite (Fig. 5B, E; tlp) long and slender, without a distinct demarcation between femoral and postfemoral parts, femorite with a small and pointed antetorsal process (Fig. 5E; ats), postfemorite spiralled, ribbon-shaped, broad and long, with a divided tip, the longer branch carrying the terminal opening of the solenomere (Fig. 5B; sl).</p> <p> <b>Paratypes</b></p> <p>Male similar to holotype.</p> <p>Female coloration as in male, but generally larger in size than male (up to 120 mm long 9 mm wide (58–61 body rings plus telson, no apodous rings). Vulvae located in membranous pouches attached to coxae 2 and 3 and to the inner lateral margin of ring 1, simple, consisting of two simple, subequallysized, moderately sclerotized valves, the aboral valve with an apical cluster of setae; ridge between valves covered with a lateral longitudinal operculum (Fig. 7).</p> Distribution <p>The species seems endemic to Mayotte (Fig. 8).</p> Affinities <p> On the basis of the gonopod structure having the telopodite with a spine arising well distad of the knee, a ribbon-shaped distal part, and a small free solenomerite arising just near the apex, the new species is manifestly a new member of the large genus <i>Sechelleptus</i>. Following the key published by Jeekel in 1999, <i>arborivagus</i> keys out close to <i>sulcicollis</i> and <i>macilentus</i>. Indeed the three species have a rather simple gonocoxite with a distally widened metaplica without a strong lateral cone but the new species do not show the small lateral uncus present on the metaplica of <i>sulcicolis</i> and possess a more or less spiniform mesapical projection on the proplica which is not present in <i>sulcicolis</i> neither in <i>macilentus</i>. By the overall shape of the male first leg and gonocoxite, the new species seems to be especially close to <i>S. variabilis</i>, also from the Comoros, but it differs strikingly by the structure of the gonotelopodite (in <i>S. variabilis</i> the gonotelopodite has a simple and pointed tip carrying the terminal opening of the seminal groove whereas in the new species the gonotelopodite has a divided tip, the longer branch carrying the terminal opening of the seminal groove) as well as by the larger body size and the longer and curved claws (Fig. 4K vs Fig. 2C). Other important differences concern the defensives glands, large in <i>S. arborivagus</i> sp. nov. (Fig. 4I) (vs inconspicuous in <i>S. variabilis</i> (Fig. 2A)), and the size of eyes: in the new specie the eyes are larger and include 60 ± 5 ommatidia (n = 10) arranged in 12 rows; whereas in <i>S. variabilis</i> the eyes, smaller, include 34 ± 3 (n = 10) ommatidia arranged in 9 rows.</p> Natural history <p> Most of the specimens belonging to the new species were collected on Mt Tchaourembo (see Fig. 8) in a forest fragment at 500–550 m a.s.l. All specimens were seen in trees and never in pairs, the males being rare (sex ratio> <b>1/6</b>). The species possesses enlarged ommatidia, relatively long legs with strongly curved tarsal claws, as well as a tendency for specimens to secrete extremely copiously from their defensive glands when irritated. Such modifications are considered by several authors as an adaptation to tree climbing and to arboreal life (Enghoff & Enghoff 1976; Hoffman & Howell 1983; VandenSpiegel 2001).</p> Discussion <p> Millipede systematics is mainly based on male gonopods because they use to be species-specific (Bond <i>et al</i>. 2003). However, studies based on DNA have demonstrated that molecular divergence in different millipede groups may not reflect divergence in morphology-based identifications and may hide considerable variation (Bond & Sierwald 2002; Bond <i>et al</i>. 2003; Adams <i>et al</i>. 2009; Mwabvu <i>et al</i>. 2013, 2015; Tinago <i>et al</i>. 2017). Although our relatively small taxon sampling, the phylogenetic analysis strongly recovers <i>Sechelleptus</i> as monophyletic and discriminates at least two or three different groups. Furthermore, the mean inter-specific distance values (14.9% for COI and 5.1% for 16S) were remarkably similar to previous studies that reported the presence of high genetic divergence among population of different spirostreptid species (Mwabvu <i>et al</i>. 2013, 2015), suggesting the existence of more than one species in those taxa. It is argued that high level of divergence between identified spirostreptid species may indicate that changes in genital morphology occur rather slowly relative to the high rate of substitution in mitochondrial sequences (especially for COI), and may underestimate species diversity. This also appears to be the case among the different forms of Mayottan <i>Sechelleptus</i>, which also share strongly similar gonopods. At the first glance, the new species of <i>Sechelleptus</i> seems to be a giant form of <i>S. variabilis.</i> However, although only subtle morphological differences are observed within the gonopods, the comparatively large body size and the behavior of <i>S. arborivagus</i> sp. nov. are remarkable. These observations finally corroborate our molecular analyses that clearly show sufficient genetic difference between the different <i>Sechelleptus</i> species collected on Mayotte (22.6% for COI and 6.6% for 16S between <i>S. arborivagus</i> sp. nov. and <i>S. variabilis</i>).</p> <p> The genetic analyses also suggest the presence of another different species, i.e., DU1, although its phylogenetic position remains unresolved. This unique specimen found at Mont Combani is a sub-adult female that could not allow a formal identification, but, judging from its general appearance, appears to be an intermediate from between the two <i>Sechelleptus</i> species collected on Mayotte. The genetic divergences, along with adaptations to arboreal life observed in the novel species, may indicate an “adaptive micro-radiation” on Mayotte Island or even the Comoros. However, the inclusion of more specimens, including adult males, in phylogenetic analyses is needed to test this hypothesis and evaluate the status of that putative new species.</p>Published as part of <i>Vandenspiegel, Didier, Henrard, Arnaud & Mathys, Aurore, 2021, Sechelleptus arborivagus sp. nov., a new arboreal spirostreptid millipede (Diplopoda, Spirostreptidae) endemic to Mayotte Island (Comoros Archipelago), Indian Ocean, pp. 1-21 in European Journal of Taxonomy 755 (1)</i> on pages 8-16, DOI: 10.5852/ejt.2021.755.1395, <a href="http://zenodo.org/record/4966001">http://zenodo.org/record/4966001</a>
Bootstrapping chiral CFTs at genus two
No full textGenus two partition functions of 2d chiral conformal field theories are given by Siegel modular forms. We compute their conformal blocks and use them to perform the conformal bootstrap. The advantage of this approach is that it imposes crossing symmetry of an infinite family of four point functions and also modular invariance at the same time. Since for a fixed central charge the ring of Siegel modular forms is finite dimensional, we can perform this analytically. In this way we derive bounds on three point functions and on the spectrum of such theories
Cortical Coupling Reflects Bayesian Belief Updating in the Deployment of Spatial Attention
No full textThe deployment of visuospatial attention and the programming of saccades are governed by the inferred likelihood of events. In the present study, we combined computational modeling of psychophysical data with fMRI to characterize the computational and neural mechanisms underlying this flexible attentional control. Sixteen healthy human subjects performed a modified version of Posner's location-cueing paradigm in which the percentage of cue validity varied in time and the targets required saccadic responses. Trialwise estimates of the certainty (precision) of the prediction that the target would appear at the cued location were derived from a hierarchical Bayesian model fitted to individual trialwise saccadic response speeds. Trial-specific model parameters then entered analyses of fMRI data as parametric regressors. Moreover, dynamic causal modeling (DCM) was performed to identify the most likely functional architecture of the attentional reorienting network and its modulation by (Bayes-optimal) precision-dependent attention. While the frontal eye fields (FEFs), intraparietal sulcus, and temporoparietal junction (TPJ) of both hemispheres showed higher activity on invalid relative to valid trials, reorienting responses in right FEF, TPJ, and the putamen were significantly modulated by precision-dependent attention. Our DCM results suggested that the precision of predictability underlies the attentional modulation of the coupling of TPJ with FEF and the putamen. Our results shed new light on the computational architecture and neuronal network dynamics underlying the context-sensitive deployment of visuospatial attention.
SIGNIFICANCE STATEMENT:
Spatial attention and its neural correlates in the human brain have been studied extensively with the help of fMRI and cueing paradigms in which the location of targets is pre-cued on a trial-by-trial basis. One aspect that has so far been neglected concerns the question of how the brain forms attentional expectancies when no a priori probability information is available but needs to be inferred from observations. This study elucidates the computational and neural mechanisms under which probabilistic inference governs attentional deployment. Our results show that Bayesian belief updating explains changes in cortical connectivity; in that directional influences from the temporoparietal junction on the frontal eye fields and the putamen were modulated by (Bayes-optimal) updates
Morphological evolution of birds recently introduced to islands: patterns of diversification
No full textEvolution was originally considered to be observable only over geological time scales. It has recently become apparent that evolutionary changes can be detected over contemporary time periods. Exotic species often experience intense selection, making them good model systems for investigating evolutionary changes over contemporary time. We often know details of the introductions, such as exact time, location of the source population, founding propagule size, and establishment history. These details allow us to formulate hypotheses concerning the evolutionary changes expected in these species' exotic ranges.
I examined contemporary morphological evolution of passerine birds introduced to islands. Passerine birds have been introduced to many islands world-wide, making them conducive for examining patterns of insular evolution. In chapters one and two, I evaluated whether these species conform to the Island Rule, an ecogeographic rule based on the study of native insular species. It states that, on islands, small species should increase in body size while large species should decrease body size. All of the species I studied are small, therefore they were expected to increase in body size. I found equivocal results concerning the Island Rule. In chapter one, I found that the great kiskadee (Pitangus sulphuratus) follows the Island Rule, as it is larger in its exotic island range than in the native source range. However, in chapter two, I found no clear Island Rule pattern examining 39 insular populations. However, I did find a clear pattern of decrease in wing length and increase in tail length. Although these populations may not be following an overall Island Rule pattern, they are still adapting to their exotic environments. In chapter three, I evaluated among-island diversification of six passerine species introduced to the Hawaiian archipelago. Five of these six species show some morphological differentiation between islands, and at least some of this differentiation cannot be accounted for by genetic drift.
The results of this dissertation provide further support for the idea that evolutionary divergence can happen over contemporary time scales. The passerine bird populations examined in these chapters have adapted to local conditions, giving us insights into the genesis of evolutionary diversity.Ph.D.Includes bibliographical referencesby Blake Mathy
A Bayesian foundation for individual learning under uncertainty
No full textComputational learning models are critical for understanding mechanisms of adaptive behavior. However, the two major current frameworks, reinforcement learning (RL) and Bayesian learning, both have certain limitations. For example, many Bayesian models are agnostic of inter-individual variability and involve complicated integrals, making online learning difficult. Here, we introduce a generic hierarchical Bayesian framework for individual learning under multiple forms of uncertainty (e.g., environmental volatility and perceptual uncertainty). The model assumes Gaussian random walks of states at all but the first level, with the step size determined by the next higher level. The coupling between levels is controlled by parameters that shape the influence of uncertainty on learning in a subject-specific fashion. Using variational Bayes under a mean field approximation and a novel approximation to the posterior energy function, we derive trial-by-trial update equations which (i) are analytical and extremely efficient, enabling real-time learning, (ii) have a natural interpretation in terms of RL, and (iii) contain parameters representing processes which play a key role in current theories of learning, e.g., precision-weighting of prediction error. These parameters allow for the expression of individual differences in learning and may relate to specific neuromodulatory mechanisms in the brain. Our model is very general: it can deal with both discrete and continuous states and equally accounts for deterministic and probabilistic relations between environmental events and perceptual states (i.e., situations with and without perceptual uncertainty). These properties are illustrated by simulations and analyses of empirical time series. Overall, our framework provides a novel foundation for understanding normal and pathological learning that contextualizes RL within a generic Bayesian scheme and thus connects it to principles of optimality from probability theory
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