The cognitive significance of resonating neurons in the cerebral cortex

Most neural fibers of the cerebral cortex engage in electric signaling, but one particular fiber, the apical dendrite of the pyramidal neuron, specializes in electric resonating. This dendrite extends upward from somas of pyramidal neurons, the most numerous neurons of the cortex. The apical dendrite is embedded in a recurrent corticothalamic circuit that induces surges of electric current to move repeatedly down the dendrite. Narrow bandwidths of surge frequency (resonating) enable cortical circuits to use specific carrier frequencies, which isolate the processing of those circuits from other circuits. Resonating greatly enhances the intensity and duration of electrical activity of a neuron over a narrow frequency range, which underlies attention in its various modes. Within the minicolumn, separation of the central resonating circuit from the surrounding signal processing network separates “having” subjective impressions from “thinking about” them. Resonating neurons in the insular cortex apparently underlie cognitive impressions of feelings.     

Dendrite growth velocity in the undercooled melt of glass forming Ni50Zr50 compound

Glass-forming Ni₅₀Zr₅₀ intermetallic compound is containerless undercooled and solidified using electrostatic levitation. Large undercoolings up to ?T = 300 K are achieved. The dendrite growth velocity of the congruently melting alloy is measured as a function of undercooling using a high-speed camera technique. The experimental data is analysed within a sharp interface theory. It is found that the driving force of crystallisation is controlling the growth kinetics at ?T < 250 K but at larger undercoolings the growth kinetics is progressively controlled by atomic diffusion. This leads to a slowing down of the growth velocity. The maximum velocity and the temperature at which the maximum occurs (T_max) are inferred from the dendrite growth velocity – undercooling relation. The relation of the temperature T_max and the glass temperature fits into a general classification scheme for glass-forming systems. The kinetic and thermal undercooling terms are calculated within dendrite growth theory as a function of the total undercooling. At ?T > 126 K, the kinetic undercooling dominates and increases rapidly with the undercooling ?T. The maximum prefactor of the kinetic undercooling is plotted vs. the reciprocal temperature. Its temperature dependence is discussed.     

Faceting of a rough solid–liquid interface of a metal induced by forced convection

The solid–liquid interface of metallic systems of small entropy of fusion is characterized by a rough interface and dendritic morphology. In contrast, systems of high entropy of fusion like semimetals and semiconductors show smooth interfaces and facetted interfaces. The present work demonstrates that, in an undercooled melt of a metal–metalloid alloy Ni₂B of intermediate entropy of fusion, a transition from a rough to a smooth interface is induced by forced convection of the melt. Electrostatic levitation is used to container-less undercool droplets in a quiescent state with no convection while electromagnetic levitation (EML) is used to undercool droplets with forced convection. The growth velocity of the solid phase is monitored as a function of undercooling by a high-speed video camera. The data are analysed within dendrite growth theory. In the case of EML, a transition from a rough to a smooth interface is indicated during dendrite growth in the undercooled melt. This is confirmed by facetted microstructures of samples solidified upon undercooling by EML. Hopper-like crystals are formed like in non-metals as bismuth, halite and ice.     

Layer and regional effects of environmental enrichment on the pyramidal neuron morphology of the rat

The environmental enrichment (EE) paradigm is widely used to study experience-dependent brain plasticity. Several studies have investigated functional and anatomical EE effects. However, as EE effects are different according to cerebral region, cortical layer, dendritic field and morphological index considered, a univocal characterization of neuronal morphological changes following rearing in enriched environments is lacking.Aim of the present study was to characterize in the rat the effects of EE on the neuronal morphology of frontal and parietal cortical regions, the main target areas of the stimulation provided by the paradigm. Male Wistar rats were housed in an enriched environment for 3.5 months from the 21st postnatal day. For the morphological analysis, biotinylated dextran amine (BDA)-labeled pyramidal neurons were selected from frontal (M1–M2) and parietal (S1–S2) cortical layers III and V. Apical and basal dendritic branching and spines were analyzed using the Sholl method.Results showed that EE increased branching and spines in both layers of frontal cortex, but had a greater effect on apical arborization. In parietal cortex, EE significantly affected branching and spines in layer III but not layer V neurons, in which only a tendency to be influenced by the rearing conditions was observed in basal arborization.It is hypothesized that these multifaceted morphological EE effects are connected to the heavy involvement of a sensory-motor circuit engaged in the guidance of voluntary action and in motor learning activated by EE stimulation.     

Atom vacancies at a screw dislocation core in SrTiO3

A screw dislocation in strontium titanate has been studied taking benefit of negative spherical aberration-imaging in a spherical aberration-corrected transmission electron microscope. The core structure of the dislocation is atomically resolved with respect to both cation and oxygen columns by the inclusion of the central core area. The dislocation core is characterized by a helical distortion of the lattice planes, which leads, in particular, to azimuthally elongated image dots associated with individual atomic columns close to the core centre. The atomic coordination in the dislocation core is identified and a high density of atom vacancies is revealed for a Ti–O column at the core.     

Effect of thermoelectric magnetic force on the array of dendrites during directional solidification of Al–Cu alloys in a high magnetic field

By eliminating the effect of the magnetic moment arising from the magnetic crystalline anisotropy, the effect of the thermoelectric magnetic force on the array of dendrites during directional solidification of Al–35?wt%Cu and Al-40?wt%Cu alloys in a high magnetic field has been investigated experimentally. The results indicate that the dendrite array is essentially destroyed, a result that could have general significance for understanding the processes involved in the solidification of alloys in a magnetic field.     

High magnetic field induction of the formation of twinned dendrites during directional solidification of Al–4.5wt%Cu alloy

It is reported that the application of a high magnetic field is capable of inducing the formation of twinned dendrites during directional solidification of Al–4.5wt%Cu alloy. Numerical results reveal that a unidirectional thermoelectric magnetic force acts on tilted dendrites during directional solidification under a magnetic field. This force should be responsible for the formation of twinned dendrites. The work may initiate a new method for inducing twinned dendrites in Al-based alloys via an applied high magnetic field during directional solidification.