The developmental pattern of stimulus and response interference in a color-object Stroop task: an ERP study

Background

Several studies have shown that Stroop interference is stronger in children than in adults. However, in a standard Stroop paradigm, stimulus interference and response interference are confounded. The purpose of the present study was to determine whether interference at the stimulus level and the response level are subject to distinct maturational patterns across childhood. Three groups of children (6–7 year-olds, 8–9 year-olds, and 10–12 year-olds) and a group of adults performed a manual Color-Object Stroop designed to disentangle stimulus interference and response interference. This was accomplished by comparing three trial types. In congruent (C) trials there was no interference. In stimulus incongruent (SI) trials there was only stimulus interference. In response incongruent (RI) trials there was stimulus interference and response interference. Stimulus interference and response interference were measured by a comparison of SI with C, and RI with SI trials, respectively. Event-related potentials (ERPs) were measured to study the temporal dynamics of these processes of interference.

Results

There was no behavioral evidence for stimulus interference in any of the groups, but in 6–7 year-old children ERPs in the SI condition in comparison with the C condition showed an occipital P1-reduction (80–140 ms) and a widely distributed amplitude enhancement of a negative component followed by an amplitude reduction of a positive component (400–560 ms). For response interference, all groups showed a comparable reaction time (RT) delay, but children made more errors than adults. ERPs in the RI condition in comparison with the SI condition showed an amplitude reduction of a positive component over lateral parietal (-occipital) sites in 10–12 year-olds and adults (300–540 ms), and a widely distributed amplitude enhancement of a positive component in all age groups (680–960 ms). The size of the enhancement correlated positively with the RT response interference effect.

Conclusion

Although processes of stimulus interference control as measured with the color-object Stroop task seem to reach mature levels relatively early in childhood (6–7 years), development of response interference control appears to continue into late adolescence as 10–12 year-olds were still more susceptible to errors of response interference than adults.     

On a Kinetic Fitzhugh–Nagumo Model of Neuronal Network

We investigate existence and uniqueness of solutions of a McKean–Vlasov evolution PDE representing the macroscopic behaviour of interacting Fitzhugh–Nagumo neurons. This equation is hypoelliptic, nonlocal and has unbounded coefficients. We prove existence of a solution to the evolution equation and non trivial stationary solutions. Moreover, we demonstrate uniqueness of the stationary solution in the weakly nonlinear regime. Eventually, using a semigroup factorisation method, we show exponential nonlinear stability in the small connectivity regime.     

Challenging the absence of observable hydrogens in the assignment of absolute configurations by NMR: application to chiral primary alcohols

The absolute configuration of beta-chiral primary alcohols devoid of observable hydrogens on one of the beta-substituents at the asymmetric carbon (L(1)/L(2)) can be determined by comparison of the (1)H NMR of their (R)- and (S)-9-AMA ester derivatives and analysis of the Deltadelta(RS) for the L substituent and the Cbeta-H.     

The Stereochemistry of 1,2,3‐Triols Revealed by 1H NMR Spectroscopy: Principles and Applications

The conformational compositions of the tris(α‐methoxy‐α‐phenylacetic acid) ester derivatives of 1,2,3‐prim,sec,sec‐triols are presented. These conformations have been determined by theoretical and experimental data (i.e., energy‐ and chemical‐shift calculations, circular dichroism (CD) experiments, coupling‐constant analysis, enantioselective deuteration experiments, and low‐temperature NMR spectroscopic studies). A detailed analysis of the anisotropic effects due to the most significant conformers in the ¹H NMR spectra supported the correlation between the ¹H NMR spectra (Δδ^RS value of H(3′) and |Δ(Δδ^RS)| parameters) and the absolute configuration of the substrate. The study also allows the identification of the pro‐R and pro‐S methylene protons from their vicinal coupling constants and relative chemical shifts.     

A theoretical investigation of the nonrigid six-coordinate compounds [Mo(R)F5], [W(R)F5], and related compounds

Density functional calculations for [M(CH3)F5], [M(CF3)F5], [M(CH3S)F5], and [M(CF3S)F5] (M=Mo, W) show that they are expected to be nonrigid molecules, with energy barriers for the octahedral-trigonal-prismatic interchange as low as 7.2 kJ mol(-1). The ground state for the CH3- and CF3- compounds is trigonal prismatic, for the CH3S- and CF3S- compounds, (distorted) octahedral. All calculated compounds [M(C6F5)nF(6-n)] (M=Mo, W) have a trigonal-prismatic ground state, whereas the situation for [M(C6H5)nF(6-n)] (M=Mo, W) is more complex.     

Role of barium(II) in the determination of the absolute configuration of chiral amines by 1H NMR spectroscopy

The assignment of the absolute configuration of alpha-chiral primary amines by complexation of their MPA derivatives with Ba2+ and NMR analysis of the changes generated is presented. All that is required is (a) the derivatization of the amine of unknown configuration with one enantiomer of the auxiliary reagent (MPA), either (R) or (S)-alpha-methoxyphenylacetic acid, (b) the recording of the 1H NMR spectrum of the resulting amide in MeCN-d3, (c) the addition of Ba(ClO4)2 to the NMR tube, and (d) the recording of a second spectrum after a few minutes of shaking. The above steps take a few minutes and are followed by an analysis of the shifts (measured as Deltadelta(Ba)) produced on the L1 and L2 substituents of the amine by the addition of Ba2+ and their comparison with those expected from the conformational changes produced by the complexation. The conformational changes initiated by complexation have been subjected to NMR and CD studies, which showed that the formation of the complex shifts the equilibrium from an antiperiplanar (AP) to a synperiplanar (SP) form, leading to an increase of the shielding by the phenyl group of MPA of the substituent of the amine located on the same side. In addition, theoretical calculations [density functional theory (DFT)] provide further support for the formation, structure, and stability of the complexes. The general applicability of this method and the trustworthiness of the resulting configurational assignment were guaranteed with a series of amines of known absolute configuration and varied structures, used as test compounds. The method proposed is simple, fast, and inexpensive, and it requires a very small amount of sample, only one derivatization, and the recording of just two 1H NMR spectra at room temperature. A graphical guide to simplify the application of this method is included.     

Lab-in-a-tube: ultracompact components for on-chip capture and detection of individual micro-/nanoorganisms

A review of present and future on-chip rolled-up devices, which can be used to develop lab-in-a-tube total analysis systems, is presented. Lab-in-a-tube is the integration of numerous rolled-up components into a single device constituting a microsystem of hundreds/thousands of independent units on a chip, each individually capable of sorting, detecting and analyzing singular organisms. Such a system allows for a scale-down of biosensing systems, while at the same time increasing the data collection through a large, smart array of individual biosensors. A close look at these ultracompact components which have been developed over the past decade is given. Methods for the capture of biomaterial are laid out and progress of cell culturing in three-dimensional scaffolding is detailed. Rolled-up optical sensors based on photoluminescence, optomechanics, optofluidics and metamaterials are presented. Magnetic sensors are introduced as well as electrical components including heating, energy storage and resistor devices.     

Collective motion of microspheres in suspensions observed by phase-mode dynamic ultrasound scattering technique

Compared with a nano-sized particle, dynamics of a micron-sized particle in a liquid is often associated with sedimentation (or floating) due to its relatively large mass. The motion of more than two particles is dominated by the hydrodynamic interactions, which are known to persist over a fairly long range, e.g., several millimeters, in suspensions. The particle size may be obtained from the dynamic ultrasound scattering (DSS) technique by the analysis of velocity fluctuations, whose origin is believed to take root in the particle-number fluctuations among temporally formed domains involving collective motion of particles with a certain cut-off length. In this study, such collective particle motion in highly turbid solutions was visualized by means of the phase-mode DSS technique with a single element transducer. Quantitative agreement between the velocity fluctuations obtained by the phase- and conventional amplitude-mode analyses was confirmed, followed by examination of the concentration and the particle size dependences on the dynamic structures induced by the long-ranged interactions. It was found that the phase mode-DSS was a promising method to evaluate the time-dependent structures of the micro-particles in highly turbid suspensions.     

Mass transfer in shell-core inorganic TIP1 ion exchanger

The ion exchange processes of (OAc^–) and (OAc^–) proceeding in shell-core inorganic ion exchanger Ti (HPO₄)₂·1/2H₂O has been studied and the diffusion equation whose boundary conditions are satisfied by a shell-core model was solved. Based on the equation solved and experimental data, the diffusion coefficients corresponding to the exchange process (OAc^–) and Li⁺–H⁺ (OAc^–) at 17°C are found to be 7.7×10^–9 and 6.2×10^–8 cm² s^–1 and the activation energies 3.4×10⁴ and 5.0×10³ J mol^–1, respectively. Compared to the gel type of styrene-divinylbenzene strong acid exchanger with 20% cross linking, it can be concluded that the rate of or exchange is 3.5 times faster than that in the organic exchanger.TIP was obtained from the Salt Lake Institute of the Academy of Science of China.