664 research outputs found
Hippocampus size predicts fluid intelligence in musically trained people
Introduction
Neurogenesis persists in the human adult hippocampus1 and the survival of new progenitor cells is enhanced by learning activities2. Using the musician's brain as a model for cortical plasticity, musical training induced functional adaptations of the hippocampus have been demonstrated3,4. Furthermore, there is evidence for a positive correlation between hippocampus size and fluid intelligence5, encompassing aspects of attention, working memory and executive functions6. Previous data strongly suggest that musical training impacts on such higher order cognitive functions7,14. Following these findings we hypothesize a linkage between hippocampus size and fluid intelligence in musically trained people.
Methods
Participants: Three groups - piano experts (E, n=20), piano amateurs (A, n=20) and nonmusicians
(N, n=19), matched by age and gender.
Task: short version of the Raven's Test, Advanced Progressive Matrices (time limit 15 minutes).
Structural MRI: manual segmentation8,9,10,11,12 of left (LH) and right (RH)
hippocampi done by a single investigator blinded for group belonging and ID of each
subject, software MRIcroN13 (Fig. 1)
Statistics: one-way ANOVAs on Raven performance and hippocampus volume; Fisher's r to
z transformations; robust multiple regression models for each hemisphere: (i) to predict Raven
performance by hippocampus volume and (ii) to test whether this prediction is modulated by
the factor of musical training. Robust regression analysis (implemented by statistical software
R) represents a valid alternative to least square regression analysis when data is potentially
contaminated by single influential observations.
Results
One way ANOVAs with three levels of expertise: no main effects of Expertise neither in
Raven's Test performance nor in hippocampus volumes. No main effect of Lateralization (Fig. 2).
Pooling of musicians (M=A+E) justified as no difference in predictive power exists between A and E, neither in the left nor in the right hemisphere. LH: z=0.84, p=0.401, RH: z=-0.45, p=0.623. Robust multiple regression analysis testing the prediction of Raven's performance by hippocampus size, modulated by
musicianship (two levels: N, M(A+E)):
- Left hemisphere: Significant interaction (t=2.221, p=.030), revealing that prediction of Raven's performance by hippocampus size is modulated by musical training: N (beta =.03) and M (beta =.46).
- Right hemisphere: Significant interaction (t=2.003, p=.050), revealing that prediction of
Raven's performance by hippocampus size is modulated by musical training: N (beta =.01) and M (beta =.38).
Conclusion
Hippocampus size significantly predicts fluid intelligence performance in musically experienced subjects but not in musically naïve ones. This result represents a striking additional corroboration of musicians' brain plasticity. It seems highly plausible that a longlasting complex activity like musical instrumental training from childhood into adulthood induced an increase in hippocampus size associated with enhanced logical reasoning. Further research is needed to investigate cognitive functions favored by musical training and possible consequent impact on the development of peculiar brain structures.
NB: This research was performed within the framework of an ongoing research project performed by Clara James (principal investigator) and postdoc collaborator Mathias Oechslin entitled "Behavioral, neuro-functional and neuro-anatomical correlates of experience dependant music perception" (FNS 100014_125050). This research project investigates brain adaptations in correlation with changes of behavior in young adults with varying musical experience, anticipating gradual changes in behavior, brain functioning and brain structure with degree of musical aptitude. In this frame, I did the data collection of hippocampus volumes and analyzed the results in correlation with a literature research on the subject
Aberrations of the point spread function of a multimode fiber
We investigate the point spread function of a multimode fiber. The distortion
of the focal spot created on the fiber output facet is studied for a variety of
the parameters. We develop a theoretical model of wavefront shaping through a
multimode fiber and use it to confirm our experimental results and analyze the
nature of the focal distortions. We show that aberration-free imaging with a
large field of view can be achieved by using an appropriate number of segments
on the spatial light modulator during the wavefront-shaping procedure. The
results describe aberration limits for imaging with multimode fibers as in,
e.g., microendoscopy.Comment: 10 pages, 6 figure
Robust Lasso-Zero for sparse corruption and model selection with missing covariates
We propose Robust Lasso-Zero, an extension of the Lasso-Zero methodology
[Descloux and Sardy, 2018], initially introduced for sparse linear models, to
the sparse corruptions problem. We give theoretical guarantees on the sign
recovery of the parameters for a slightly simplified version of the estimator,
called Thresholded Justice Pursuit. The use of Robust Lasso-Zero is showcased
for variable selection with missing values in the covariates. In addition to
not requiring the specification of a model for the covariates, nor estimating
their covariance matrix or the noise variance, the method has the great
advantage of handling missing not-at random values without specifying a
parametric model. Numerical experiments and a medical application underline the
relevance of Robust Lasso-Zero in such a context with few available
competitors. The method is easy to use and implemented in the R library lass0
Modelling and mathematical results arising from ferromagnetic problems
In this article, we investigate the equations of magnetostatics for a configuration where a ferromagnetic material occupies a bounded domain and is surrounded by vacuum. Furthermore, the ferromagnetic law takes the form i.e., the magnetizing field H and the magnetic induction B are collinear, but the relative permeability µr is allowed to depend on the modulus of H. We prove the well-posedness of the magnetostatic problem under suitable convexity assumptions, and the convergence of several iterative methods, both for the original problem set in the Beppo-Levi space W 1(ℝ3), and for a finite-dimensional approximation. The theoretical results are illustrated by numerical examples, which capture the known physical phenomen
Faunal response to benthic and hyporheic sedimentation varies with direction of vertical hydrological exchange
1. Sedimentation and clogging of benthic and hyporheic zone substrates is increasingly being recognised as one of the greatest threats to the ecological integrity of riverine ecosystems globally. This ex-situ study examined the influence of sedimentation (benthic and hyporheic) and pattern of hydrological exchange on the vertical distribution of the freshwater shrimp Gammarus pulex within the experimental substrates of running water mesocosms. 2. Six sediment treatments representing a continuum from a clean gravel substratum through to heavy sediment loading of both benthic and hyporheic substrates were used to examine the distribution of G. pulex in relation to the direction of hydrological exchange (downwelling, upwelling and no exchange). 3. The vertical distribution of fauna varied significantly for both sediment treatment and pattern of hydrological exchange. There was a significant interaction between the two effects indicating that the effect of sedimentation varied depending on the pattern of vertical hydrological exchange
Stratégie de protection à sélectivité totale pour réseaux MTDC
International audienceLa mise en place de réseaux à courant continu de grande taille en Europe est un objectif plausible dans un futur proche compte tenu de l'évolution du mix énergétique. En effet, de grands sites décentralisés de production d'énergies renouvelables vont progressivement apparaître (ex : fermes éoliennes offshores, centrales de production photovoltaïque, etc.). Avec les convertisseurs de type VSC, il est techniquement possible d'assembler plusieurs liaisons HVDC en une structure en réseau. Ainsi, un tel réseau permettra le transit d'une grande quantité de puissance, de l'ordre de plusieurs gigawatts, en courant continu, entre les différentes stations de conversion qui le composent. La protection d'un tel ouvrage est par conséquent un point critique et indispensable. En effet, en cas de défaut dans la partie à courant continu et au vue des puissances qui transitent, il est primordial de réduire au maximum les conséquences liées à l'apparition de ce défaut. Si plusieurs gigawatts sont échangés dans le réseau à courant continu, il est risqué pour la stabilité du (ou des) réseau(x) AC extérieur(s) de stopper l'ensemble de ce transit. C'est pour cela que des stratégies de protection rapides, efficaces et sélectives doivent être mises en œuvre. Cet article propose une revue des principales contraintes liées à la protection des réseaux à courant continu qui sont intrinsèques au courant continu, des différentes stratégies de protection qui peuvent être appliquées à un tel réseau et des principaux types de disjoncteurs à courant continu. Les différentes durées de fonctionnement de la détection et des disjoncteurs sont à comparer avec le temps critique d'élimination des défauts du réseau MTDC. Mots-clés—Disjoncteur à courant continu HVDC, Plan de protection, Réseau MTDC, Station de conversion, Sélectivité, Temps critique d'élimination des défauts.</p
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