EEG correlates of tactile perception abnormalities in children with autism spectrum disorder

The aim of the investigation was to study the changes in EEG power and behavioral responses to C-tactile stimulation in typically developing (TD) children and children with autism spectrum disorder (ASD). Materials and Methods. EEG to manually delivered tactile stimuli was recorded for 79 children (ASD=39, TD=40) aged 5 to 10 years. CARS scores were obtained for each participant immediately before the recording session. The study involved recording resting EEG in eyes open condition within 1–2 min and collecting EEG response to tactile stimuli delivered pseudo-randomly for 3 experimental conditions (stroking with a soft brush, stroking with a harsh brush, and stimulation with a spiked roller delivered to the outer side of right forearm, stroking velocity was within 2–5 cm/s). Behavioral responses obtained by video recording during the experiment were assessed and coded. Behavioral responses were classified into 5 patterns: 1) signs of relaxation (facial gesture and body posture); 2) signs of resistance, attempts to withdraw the hand; 3) negative emotions, crying, shouting; 4) positive emotions, smile, laughter; 5) looking at the hand being stimulated. EEG power in 18 narrow frequency bands with a bandwidth of 1 Hz in a range of 2–20 Hz was analyzed. Results. The study revealed two types of response to tactile stimulation. The first type was not specific for particular tactile stimulation type, was accompanied by an increase in beta power (16–20 Hz) mainly in the left hemisphere and was more common in children with ASD. The second type of response was accompanied by an increase in frontal theta power (4–6 Hz) due to C-tactile system stimulation with a soft brush and was observed only in the TD children. The first type of response was accompanied by negative emotions and attempts to withdraw the hand, while the second type was characterized by relaxation. Conclusion. The response of children with ASD to all types of tactile stimulation accompanied by an increase in beta power can be associated with both hypersensitivity and stress reaction of these children to the experimental situation. Selective response to C-tactile stimulation accompanied by an increase in frontal theta power has been found in the control group (TD) only. The results of this study can be useful for better understanding of hypersensitivity in children with ASD and gaining insight into the mechanisms of the disease

Pseudogap in a thin film of a conventional superconductor

A superconducting state is characterized by the gap in the electronic density of states which vanishes at the superconducting transition temperature Tc. It was discovered that in high temperature superconductors a noticeable depression in the density of states still remains even at temperatures above Tc; this feature being called pseudogap. Here we show that a pseudogap exists in a conventional superconductor: ultrathin titanium nitride films over a wide range of temperatures above Tc. Our study reveals that this pseudogap state is induced by superconducting fluctuations and favored by two-dimensionality and by the proximity to the transition to the insulating state. A general character of the observed phenomenon provides a powerful tool to discriminate between fluctuations as the origin of the pseudogap state, and other contributions in the layered high temperature superconductor compounds.Comment: 26 pages, 4 figure

Keldysh technique and non-linear sigma-model: basic principles and applications

The purpose of this review is to provide a comprehensive pedagogical introduction into Keldysh technique for interacting out-of-equilibrium fermionic and bosonic systems. The emphasis is placed on a functional integral representation of underlying microscopic models. A large part of the review is devoted to derivation and applications of the non-linear sigma-model for disordered metals and superconductors. We discuss such topics as transport properties, mesoscopic effects, counting statistics, interaction corrections, kinetic equation, etc. The sections devoted to disordered superconductors include Usadel equation, fluctuation corrections, time-dependent Ginzburg-Landau theory, proximity and Josephson effects, etc. (This review is a substantial extension of arXiv:cond-mat/0412296.)Comment: Review: 103 pages, 19 figure

Retrograde traffic in the biosynthetic-secretory route

In the biosynthetic-secretory route from the rough endoplasmic reticulum, across the pre-Golgi intermediate compartments, the Golgi apparatus stacks, trans Golgi network, and post-Golgi organelles, anterograde transport is accompanied and counterbalanced by retrograde traffic of both membranes and contents. In the physiologic dynamics of cells, retrograde flow is necessary for retrieval of molecules that escaped from their compartments of function, for keeping the compartments’ balances, and maintenance of the functional integrities of organelles and compartments along the secretory route, for repeated use of molecules, and molecule repair. Internalized molecules may be transported in retrograde direction along certain sections of the secretory route, and compartments and machineries of the secretory pathway may be misused by toxins. An important example is the toxin of Shigella dysenteriae, which has been shown to travel from the cell surface across endosomes, and the Golgi apparatus en route to the endoplasmic reticulum, and the cytosol, where it exerts its deleterious effects. Most importantly in medical research, knowledge about the retrograde cellular pathways is increasingly being utilized for the development of strategies for targeted delivery of drugs to the interior of cells. Multiple details about the molecular transport machineries involved in retrograde traffic are known; a high number of the molecular constituents have been characterized, and the complicated fine structural architectures of the compartments involved become more and more visible. However, multiple contradictions exist, and already established traffic models again are in question by contradictory results obtained with diverse cell systems, and/or different techniques. Additional problems arise by the fact that the conditions used in the experimental protocols frequently do not reflect the physiologic situations of the cells. Regular and pathologic situations often are intermingled, and experimental treatments by themselves change cell organizations. This review addresses physiologic and pathologic situations, tries to correlate results obtained by different cell biologic techniques, and asks questions, which may be the basis and starting point for further investigations

Failure of Mott’s formula for the thermopower in carbon nanotubes

This is the author accepted manuscript.Well-known Mott’s formula links the thermoelectric power characterized by the Seebeck coefficient to conductivity. We calculate analytically the thermoelectric current and Seebeck coefficient in one-dimensional systems and show that, while the prediction of Mott’s formula is valid for Dirac fermions, it is misleading for the carriers having a parabolic dispersion. We apply the developed formalism to metallic single wall carbon nanotubes and obtain a nontrivial nonmonotonic dependence of the Seebeck coefficient on the chemical potential. We emphasize that, in contrast to Mott’s formula, the classical Kelvin’s formula that links thermoelectric power to the temperature derivative of the chemical potential is perfectly valid in carbon nanotubes in the ballistic regime. Interestingly, however, the Kelvin’s formula fails in two- and three-dimensional systems in the ballistic regime