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• Mg 2 B 2 O 5 whisker helps to reduce the cost of reinforced composites as compared to other whiskers. • Different basic preparation methods and growth mechanisms for the production of Mg 2 B 2 O 5 whisker are discussed. • Mg 2 B 2 O 5 whisker is effectively improved the mechanical, friction materials and reinforcing composite materials. • The effects of surface modification of Mg 2 B 2 O 5 whisker on alloys and polymers are discussed. Magnesium borate (Mg 2 B 2 O 5) whiskers are highly regarded as a promising inorganic reinforcing material due to their availability, ease of preparation, and remarkable reinforcing effect. The main objective of this article is to examine the properties of Mg 2 B 2 O 5 whiskers and to encourage researchers to utilize them, thereby enhancing the characteristics of various composites in a cost–effective manner. Six production methods of Mg 2 B 2 O 5 whiskers are addressed, and based on these methods, different growth mechanisms of Mg 2 B 2 O 5 whiskers, including liquid–solid, solid–liquid–solid, vapor–solid, and vapor–liquid–solid mechanisms, are analyzed and summarized. As reinforcing materials, Mg 2 B 2 O 5 whiskers are widely employed in alloys and polymers, effectively enhancing the physical and chemical properties of the resulting whisker–reinforced composites, including mechanical, friction and wear resistance, and flame retardancy properties. Furthermore, the impact of surface modification of Mg 2 B 2 O 5 whiskers on the properties of composites was explored. The cost–effectiveness, favorable properties, and wide availability of Mg 2 B 2 O 5 whiskers make them excellent potential materials for numerous applications, and the article provides an analysis and forecasts the future development direction and prospects of Mg 2 B 2 O 5 whiskers. [Display omitted] [ABSTRACT FROM AUTHOR]

Photoreduction of CO 2 to valuable fuels provides a promising strategy for managing the global carbon balance using renewable solar energy, yet the design of active, cost-effective, highly selective, and stable CO 2 reduction photocatalysts remains a big challenge. Herein, we report a novel SiOC aerogel photocatalyst synthesized by a simple one-step sol-gel process, combined with the supercritical drying technique and heat treatment processes. The resulting SiOC aerogel exhibits a large BET specific area with typical hierarchical structures, which is responsible for the enhanced photocatalytic activity. In addition, the formation mechanism of the SiOC whisker aerogel is revealed in this study. The optimized SiOC aerogel exhibits CH 4 and CO evolution activity of 5.8 and 20.5 μmol/g under simulated sunlight irradiation, respectively, without any additional co-catalyst or sacrificial agent, which is 6.4 and 3.9 times higher than those of the pristine SiC aerogel. The density functional theory (DFT) calculation confirms that the resulting SiOC aerogel can effectively adsorb and activate CO 2 and H 2 O molecules on the catalyst surface. The Gibbs free energy diagram further verifies the superior performance of the resulting SiOC aerogel over the pristine SiC and SiO 2 cluster via the rate-determining step calculations. The high efficiency of CO 2 reduction can be attributed to the structural merits and the electronic structures modulation, which greatly achieves fast separation and transfer of charge carriers. The work paves an insight into the rational design of photocatalysts toward simultaneously facilitating carrier separation and CO 2 activation from aerogel-based porous materials. • A novel highly efficient SiOC aerogel for CO 2 photoreduction reaction (CRR) is developed. • The SiOC aerogel displays greatly enhanced CRR activity as compared with the reported works. • The formation mechanism of the SiC whisker within the SiOC aerogel is revealed. • The density functional theory calculations are carried out for revealing the CRR mechanism. [ABSTRACT FROM AUTHOR]

A series of nanopillar compression tests were performed on tungsten as a function of temperature using in situ transmission electron microscopy with localized laser heating. Surface oxidation was observed to form on the pillars and grow in thickness with increasing temperature. Deformation between 850 °C and 1120 °C is facilitated by long-range diffusional transport from the tungsten pillar onto adjacent regions of the Y2O3-stabilized ZrO2 indenter. The constraint imposed by the surface oxidation is hypothesized to underly this mechanism for localized plasticity, which is generally the so-called whisker growth mechanism. The results are discussed in context of the tungsten fuzz growth mechanism in He plasma-facing environments. The two processes exhibit similar morphological features and the conditions under which fuzz evolves appear to satisfy the conditions necessary to induce whisker growth.

Studies using functional magnetic resonance imaging assume that hemodynamic responses have roughly linear relationships with underlying neural activity. However, to accurately investigate the neurovascular transfer function and compare its variability across brain regions, it is necessary to obtain full-field imaging of both electrophysiological and hemodynamic responses under various stimulus conditions with superior spatiotemporal resolution. Optical imaging combined with voltage-sensitive dye (VSD) and intrinsic signals (IS) is a powerful tool to address this issue. We performed VSD and IS imaging in the primary (S1) and secondary (S2) somatosensory cortices of rats to obtain optical maps of whisker-evoked responses. There were characteristic differences in sensory responses between the S1 and S2 cortices: VSD imaging revealed more localized excitatory and stronger inhibitory neural activity in S1 than in S2. IS imaging revealed stronger metabolic responses in S1 than in S2. We calculated the degree of response to compare the sensory responses between cortical regions and found that the ratio of the degree of response of S2 to S1 was similar, irrespective of whether the ratio was determined by VSD or IS imaging. These results suggest that neurovascular coupling does not vary between the S1 and S2 cortices.

Fly ash is a by-product from burning of coal. Utilization of fly ash by carbothermic reduction is an effective way to recover aluminum, silicon, and iron to enhance product-added value. This work is focused on the phase transformation of Al2O3, SiO2 and Fe2O3 during carbothermic reduction of fly ash in air. A comparative analysis of carbothermic reduction of fly ash in air and in nitrogen was made. Thermodynamics analysis was performed to illustrate the possible reactions for residue and condensate. X-ray diffraction (XRD), scanning electronic microscope (SEM), and energy dispersive spectrometry (EDS) were employed to characterize the phase composition, surface morphology, and microstructure of the reduced products. Results show that Fe3Si and Fe2Si appear sequentially with increasing of temperature. Al5O6N is an intermediate compound. Residue of Al9FeSi3, Al, and Si, and condensate of SiC, AlN and C are obtained. β-SiAlON was not found in the residue. Nitrogen is involved in the reduction of Al2O3 but not in the reduction of SiO2 and Fe2O3. Carbothermic reduction of fly ash in air did not behave the same as fly ash in nitrogen.

Haptic perception synthesizes touch with proprioception, the sense of body position. Humans and mice alike experience rich active touch of the face. Because most facial muscles lack proprioceptor endings, the sensory basis of facial proprioception remains unsolved. Facial proprioception may instead rely on mechanoreceptors that encode both touch and self-motion. In rodents, whisker mechanoreceptors provide a signal that informs the brain about whisker position. Whisking involves coordinated orofacial movements, so mechanoreceptors innervating facial regions other than whiskers could also provide information about whisking. To define all sources of sensory information about whisking available to the brain, we recorded spikes from mechanoreceptors innervating diverse parts of the face. Whisker motion was encoded best by whisker mechanoreceptors, but also by those innervating whisker pad hairy skin and supraorbital vibrissae. Redundant self-motion responses may provide the brain with a stable proprioceptive signal despite mechanical perturbations during active touch.

We present a cost-effective, compact foot-print, and open-source Raspberry Pi-based widefield imaging system. The compact nature allows the system to be used for close-proximity dual-brain cortical mesoscale functional-imaging to simultaneously observe activity in two head-fixed animals in a staged social touch-like interaction. We provide all schematics, code, and protocols for a rail system where head-fixed mice are brought together to a distance where the macrovibrissae of each mouse make contact. Cortical neuronal functional signals (GCaMP6s; genetically encoded Ca 2+ sensor) were recorded from both mice simultaneously before, during, and after the social contact period. When the mice were together, we observed bouts of mutual whisking and cross-mouse correlated cortical activity across the cortex. Correlations were not observed in trial-shuffled mouse pairs, suggesting that correlated activity was specific to individual interactions. Whisking-related cortical signals were observed during the period where mice were together (closest contact). The effects of social stimulus presentation extend outside of regions associated with mutual touch and have global synchronizing effects on cortical activity., Competing Interests: The authors declare no competing financial interests., (Copyright © 2023 Michelson et al.)

Understanding neural function requires quantification of the sensory signals that an animal's brain evolved to interpret. These signals in turn depend on the morphology and mechanics of the animal's sensory structures. Although the house mouse (Mus musculus) is one of the most common model species used in neuroscience, the spatial arrangement of its facial sensors has not yet been quantified. To address this gap, the present study quantifies the facial morphology of the mouse, with a particular focus on the geometry of its vibrissae (whiskers). The study develops equations that establish relationships between the three-dimensional (3D) locations of whisker basepoints, whisker geometry (arclength, curvature) and the 3D angles at which the whiskers emerge from the face. Additionally, the positions of facial sensory organs are quantified relative to bregma-lambda. Comparisons with the Norway rat (Rattus norvegicus) indicate that when normalized for head size, the whiskers of these two species have similar spacing density. The rostral-caudal distances between facial landmarks of the rat are a factor of ∼2.0 greater than the mouse, while the scale of bilateral distances is larger and more variable. We interpret these data to suggest that the larger size of rats compared with mice is a derived (apomorphic) trait. As rodents are increasingly important models in behavioral neuroscience, the morphological model developed here will help researchers generate naturalistic, multimodal patterns of stimulation for neurophysiological experiments and allow the generation of synthetic datasets and simulations to close the loop between brain, body and environment., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2023. Published by The Company of Biologists Ltd.)

The superior colliculus (SC) is an essential structure for the control of eye movements. In rodents, the SC is also considered to play an important role in whisking behavior, in which animals actively move their vibrissae (mechanosensors) to gather tactile information about the space around them during exploration. We investigated how the SC contributes to vibrissal movement control. We found that when the SC was unilaterally lesioned, the resting position of the vibrissae shifted backward on the side contralateral to the lesion. The unilateral SC lesion also induced an increase in the whisking amplitude on the contralateral side. To explore the anatomical basis for SC involvement in vibrissal movement control, we then quantitatively evaluated axonal projections from the SC to the brainstem using neuronal labeling with a virus vector. Neurons of the SC mainly sent axons to the contralateral side in the lower brainstem. We found that the facial nucleus received input directly from the SC, and that the descending projections from the SC also reached the intermediate reticular formation and pre-Bötzinger complex, which are both considered to contain neural oscillators generating rhythmic movements of the vibrissae. Together, these results indicate the existence of a neural circuit in which the SC modulates vibrissal movements mainly on the contralateral side, via direct connections to motoneurons, and via indirect connections including the central pattern generators.

• Barrel cells exhibit multiwhisker receptive fields. • Source of multiwhisker whisker barrel responses is controversial. • This study evaluates feedforward mechanisms for multiwhisker responses. • A realistic model shows feedforward mechanisms can explain much empirical data. There is substantial anatomical segregation in the organization of the rodent barrel system – each whisker on the mystacial pad sends input to TC cells within a dedicated thalamic barreloid, which in turn innervates a corresponding cortical barrel, and RS cells within a barrel respond primarily to deflections of the corresponding whisker at the beginning of the dedicated transmission line (the principal whisker, PW). However, it is also well-established that barrel cells exhibit multiwhisker receptive fields (RFs), and display lower amplitude, longer latency responses to deflections of non-PWs (or adjacent whiskers, AWs). There is considerable controversy regarding the origin of such multiwhisker RFs; three possibilities include: (i) TC cells within a barreloid respond to multiple whiskers, and barrel RS cells simply inherit multiwhisker responses from their aligned barreloid; (ii) TC cells respond only to the PW, but individual barreloids innervate multiple barrels; (iii) multiwhisker responses of barrel cells arise from lateral corticocortical (barrel-to-barrel) synaptic transmission. Ablation studies attempting to pinpoint the source of RS cell AW responses are often contradictory (though experimental work tends to suggest possibilities (i) or (iii) to be most plausible), and hence it is important to carefully evaluate these hypotheses in terms of available physiological data on barreloid and barrel response dynamics. In this work, I employ a biologically detailed model of the rat barrel cortex to evaluate possibility (i) , and I show that, within the model, hypothesis (i) is capable of explaining a broad range of the available physiological data on responses to single (PW or AW) deflections and paired whisker deflections (AW deflection followed by PW deflection), as well as the dependence of such responses on the angular direction of whisker deflection. In particular, the model shows that barrel RS cells can exhibit AW direction tuning despite the fact that barreloid to barrel wiring has no systematic dependence on the AW direction preference of TC cells. Future modeling work will examine the other possibilities for the generation of multiwhisker RS cell RFs, and compare and contrast the different possible mechanisms within the context of available experimental data. [ABSTRACT FROM AUTHOR]

In this study, composite ceramics with tunable electromagnetic properties were developed based on SiC-Si 3 N 4 hybrids. First, SiC-Si 3 N 4 whisker preforms with various SiC whisker (SiC w) concentrations were prepared by the nitridation of Si in SiC w -Si powder compacts. The in-situ -grown Si 3 N 4 whiskers (Si 3 N 4w) were dispersed uniformly in the voids inside the interconnected network formed by SiC w. The whisker reinforcements effectively toughened the SiBCN matrix through interface debonding, crack deflection and whisker pullout mechanisms. The electromagnetic properties of the composite ceramics can be tuned by adjusting the composition of (SiC-Si 3 N 4) w preforms. The composite ceramic with 31.9 vol% SiC w exhibited the broadest effective absorption bandwidth (EAB) of 2.9 GHz in X band. Furthermore, a multilayer radar absorbing structure (RAS) composed of ceramic composites with gradient electromagnetic parameters was constructed to further improve the absorption properties. By adjusting the structure of the RAS, the resulting EAB of the RAS covered the entire X band. • SiC and Si 3 N 4 whiskers formed reinforcement preforms with wave absorbing ability. • SiC and Si 3 N 4 whiskers effectively toughened the composite ceramics. • Adjusting SiC concentration tunes electromagnetic properties of the composites. • A multilayer radar absorbing structure realized improved broadband absorption. [ABSTRACT FROM AUTHOR]

Hybrid copper matrix composites reinforced by TiB whiskers and TiB 2 particles were fabricated by in situ mixing casting in combination with rolling and annealing. During turbulent mixing and copper mold casting processes, the in situ reactions carried out completely, and the macrosegregation of reinforcements in the composites was overcome efficiently. By controlling the rolling and annealing parameters, unfavorable casting defects, including "chain-type" reinforcement clusters and shrinkage porosities that formed during the end stage of solidification, were eliminated. Accordingly, the uniform distribution of hybrid reinforcements in the as-annealed composites provided good comprehensive performance. Compared to the 2.6 wt%TiB 2p /Cu composite, the (1.0 wt%TiB 2p -0.9 wt%TiB w)/Cu hybrid composite exhibited both higher strength (492 MPa) and higher electrical conductivity (85.5% International Annealed Copper Standard). Therefore, the hybrid effect in the copper matrix composites can be explained by the fact that a better strengthening effect was achieved by adding less hybrid reinforcement, which helped maintain the electrical conductivity at a relatively high level. • TiB whiskers and TiB 2 particles distribute uniformly in copper matrix. • The strength of composites is improved by adding less hybrid reinforcement. • Low hybrid reinforcement concentration leads to a high electrical conductivity. • A positive hybrid effect is achieved in comprehensive properties of CMCs. [ABSTRACT FROM AUTHOR]

Rodents are the most commonly studied model system in neuroscience, but surprisingly few studies investigate the natural sensory stimuli that rodent nervous systems evolved to interpret. Even fewer studies examine neural responses to these natural stimuli. Decades of research have investigated the rat vibrissal (whisker) system in the context of direct touch and tactile stimulation, but recent work has shown that rats also use their whiskers to help detect and localize airflow. The present study investigates the neural basis for this ability as dictated by the mechanical response of whiskers to airflow. Mechanical experiments show that a whisker’s vibration magnitude depends on airspeed and the intrinsic shape of the whisker. Surprisingly, the direction of the whisker’s vibration changes as a function of airflow speed: vibrations transition from parallel to perpendicular with respect to the airflow as airspeed increases. Recordings from primary sensory trigeminal ganglion neurons show that these neurons exhibit responses consistent with those that would be predicted from direct touch. Trigeminal neuron firing rate increases with airspeed, is modulated by the orientation of the whisker relative to the airflow, and is influenced by the whisker’s resonant frequencies. We develop a simple model to describe how a population of neurons could leverage mechanical relationships to decode both airspeed and direction. These results open new avenues for studying vibrissotactile regions of the brain in the context of evolutionarily important airflow-sensing behaviors and olfactory search. Although this study used only female rats, all results are expected to generalize to male rats. [ABSTRACT FROM AUTHOR]

Background: Nerve reconstructive surgery induces a transient loss and a prolonged and a gradual return of sensory inputs to the brain. It is unknown whether, following this massive peripheral denervation, the brain will experience a prolonged period of severe, intrinsic dysfunction. Objective: We aim to investigate the mechanisms of return of processing function in cortical neurons. Methods: We used the whisker model in rats to evaluate the functional recovery in the somatosensory cortex after a nerve reconstruction surgery. Multi-unit recording in the barrel cortex was performed in lightly anesthetized rats while their whiskers were stimulated by a whisker stimulator. Results: We observed a loss of neuronal responses to whisker stimulation 1 week after surgery, which started to recover 2 weeks after surgery. Following the surgery, only 11.8% of units had principle whiskers (PWs) returned to their original status while 17.7% had PWs different from their original status, indicating the effect of aberrant reinnervation on the whisker response map. Conclusions: Robust neuronal responses to sensory stimulation even when only sparse sensory inputs are available in the early recovery phase. During this phase, aberrant reinnervation induces disorganized whisker tuning, a finding that might be account for the hypoesthesia and paresthesia during early recovery after nerve reconstruction. [ABSTRACT FROM AUTHOR]

Highlights • Hydroxyapatite whiskers (HAWs) were prepared by hydrothermal method. • Mg2+, Zn2+ and Sr2+ were tried to incorporate into HAWs. • Morphological and structural properties of cation-incorporated samples were analysed. • Sr2+ and low concentration of Mg2+ showed least inhibition effect on HAWs formation. Abstract The feasibility of incorporating high (M/M+Ca = 16 mol. %) and low (M/M+Ca = 4.76 mol. %) concentrations of Mg2+, Zn2+ and Sr2+, as divalent cations with interesting biological properties, into the structure of well-known bioceramic: hydroxyapatite (HA) was carefully assessed. An established hydrothermal synthesis method was employed for preparation of HA in whisker-like morphology. Consequently, the possibility of synthesizing HA whiskers (HAWs) with cationic substitutions and effects of the introduced ions on morphology, structure and composition of HA products were evaluated. Almost, all the cation-substituted preparations could maintain the apatite phase, while the decrease in crystallite size and crystallinity was obvious. Lattice parameters (a, c) of the hexagonal system of HA were also affected in accordance with the type and amount of substituting cation. Zn2+ and high amounts of Mg2+ dramatically inhibited formation of whisker-like apatite and promoted formation of a mixture of hexagonal prism-like and flaky bundles, or hexagonal and multifaceted morphologies, respectively. However, Sr2+ exhibited minimum inhibitory effect on HAWs formation. Therefore, Sr- and Mg-substituted (low concentration of Mg) HAWs could be prepared for their potential biomedical applications. [ABSTRACT FROM AUTHOR]

Recent work has quantified the geometric parameters of individual rat vibrissae (whiskers) and developed equations that describe how these parameters vary as a function of row and column position across the array. This characterization included a detailed quantification of whisker base diameter and arc length as well as the geometry of the whisker medulla. The present study now uses these equations for whisker geometry to quantify several properties of the whisker that govern its mechanical behavior. We first show that the average density of a whisker is lower in its proximal region than in its distal region. This density variation appears to be largely attributable to the presence of the whisker cuticle rather than the medulla. The density variation has very little effect on the center of mass of the whisker. We next show that the presence of the medulla decreases the deflection of the whisker under its own weight and also decreases its mass moment of inertia while sacrificing <1% stiffness at the whisker base compared with a solid whisker. Finally, we quantify two dimensionless parameters across the array. First, the deflection-to-length ratio decreases from caudal to rostral: caudal whiskers are longer but deflect more under their own weight. Second, the nondimensionalized radius of gyration is approximately constant across the array, which may simplify control of whisking by the intrinsic muscles. We anticipate that future work will exploit the mechanical properties computed in the present study to improve simulations of the mechanosensory signals associated with vibrissotactile exploratory behavior. NEW & NOTEWORTHY The mechanical signals transmitted by a whisker depend critically on its geometry. We used measurements of whisker geometry and mass to quantify the center of mass, mass moment of inertia, radius of gyration, and deflection under gravity of the whisker. We describe how variations in these quantities across the array could enhance sensing behaviors while reducing energy costs and simplifying whisking control. Most importantly, we provide derivations for these quantities for use in future simulation work. [ABSTRACT FROM AUTHOR]

Alaskan seals are found in remote and sometimes inaccessible locations, making it difficult to collect time‐series information. This study explores a novel method to examine temporal changes in diet and physiological status of ringed (Pusa hispida), spotted (Phoca largha), and harbor (Phoca vitulina) seals using cortisol concentrations and δ15N and δ13C stable isotopes (SIs) measured in serial sections of whiskers. As whiskers grow, whisker tissue is deposited sequentially making these measurements temporally aligned. Whisker cortisol presented in a distinct pattern with elevated concentrations at the root section followed by a curvilinear decline moving toward the tip of most whiskers. Comparing SIs at the root to the rest of the whiskers, δ13C values were slightly lower in ringed and harbor seal whiskers and δ15N values were slightly higher in harbor seal whiskers. The data were modeled controlling for the observed trends in cortisol concentrations and further associations between cortisol concentrations and SIs were detected in spotted and harbor seal whiskers. Additional research examining the source and stability of whisker cortisol is warranted. However, the methods presented here demonstrate that whiskers could prove valuable to gather long‐term and naturally aligned dietary and physiological information. [ABSTRACT FROM AUTHOR]

Metallic whiskers of pure lead (Pb) have been observed in the solder of several types of transistors. The conditions that lead to these whiskers were evaluated, including characterization of the whisker lengths and whisker density as a function of time and temperature. The potential cause and impact they would have on the reliability of electronics has been investigated. Based on these results, it is hypothesized that these whiskers may be caused by the relief of residual stresses that are created during the evolution of Au-In and/or Au-Pb intermetallic compounds or, possibly, by a decomposition of the AuPb3 phase. Due to their small size, the Pb whiskers that were observed were considered to not be a reliability concern, but similar or larger Pb whiskers could cause electrical failure in some applications. [ABSTRACT FROM AUTHOR]

Abstract Ammonium aluminum carbonate hydroxide (AACH) whiskers prepared by hydrothermal technique were employed as precursor material for development of porous alumina. After compaction of AACH whiskers at 8 bars, calcination was performed at 650 °C followed by sintering at different temperatures. The sintered samples were characterized by XRD, FTIR, SEM and mercury intrusion porosimetry. Mechanical strength was determined by compression testing. At sintering temperatures of 1200 °C to 1400 °C, the % age porosity was around 80%. At 1500 °C, the percentage porosity decreased to 71%. The as-prepared AACH consisted of bundles of whiskers with diameters as thick as 0.7 µm, while an individual whisker had a diameter of about 100 nm with an aspect ratio of about 33. A two-phase mixture consisting of θ- and α-alumina was obtained at 1100 °C, while at 1200 °C and above, single phase α-alumina was formed. θ-alumina retained the bundle-like morphology. However, transformation to α-alumina was accompanied by formation of bead-like morphology. These beads were joined together through necks/stems within the whiskers as well as across the parallel-lying whiskers. These necks grew at 1300 °C to form aggregates with smooth surfaces. At 1400 °C, these aggregates started joining with each other by neck formation and at 1500 °C, a three-dimensional network was formed. For sintering temperatures of up to 1400 °C, pores with sizes around 260 nm were very stable. At 1500 °C, significant pore growth took place along with an overall densification. Therefore, number of pores with sizes of around 260 nm decreased and those with sizes around 10 µm, 1 µm and 5 nm increased. The compression strength of samples sintered at 1100 °C to 1300 °C was in the range of 3.4–4.3 MPa. At 1400 °C, the strength increased to 5.2 MPa, while at 1500 °C, it jumped to 10.8 MPa due to the formation of three-dimensional network. [ABSTRACT FROM AUTHOR]

Since sensory systems operate with a finite quantity of processing resources, an animal would benefit from prioritizing processing of sensory stimuli within a time window that is expected to provide key information. This behavioral manifestation of such prioritization is known as attention. Here, we investigate attention with temporal cueing and its neuronal correlates in the rat primary vibrissal somatosensory (vS1) cortex. Rats were trained in a simple whisker vibration detection task. A vibration was presented at one of two spatial locations (left or right), sometimes after an unknown time interval and sometimes after receiving an auditory cue. The auditory cue provided temporal but not spatial information about the vibration. We found that for all rats ( n = 6), the auditory cue consistently enhanced detection of the vibration stimulus. Neuronal activity in vS1 cortex reflected the observed behavioral enhancement from temporal cueing with single units responded differentially to the whisker vibration stimulus when it was temporally predicted by the auditory cue, exhibiting an enhanced signal-to-noise ratio. Our findings indicate that rats are capable of prioritizing processing within a specified time window and provide evidence that the primary sensory cortex may participate in the temporal allocation of resources. NEW & NOTEWORTHY We demonstrate a novel paradigm of temporal cueing in rats. In a two-alternative whisker detection task, an auditory cue provided information about the timing of the stimulus but not the correct choice. In the presence of cue, detection was faster and more accurate, and neuronal activity from the primary somatosensory cortex revealed enhanced representation of vibrations. These results thus establish the rat as an alternative model organism to primates for studying temporal attention. [ABSTRACT FROM AUTHOR]

Behavioral adaptation is a prerequisite for survival in a constantly changing sensory environment, but the underlying strategies and relevant variables driving adaptive behavior are not well understood. Many learning models and neural theories consider probabilistic computations as an efficient way to solve a variety of tasks, especially if uncertainty is involved. Although this suggests a possible role for probabilistic inference and expectation in adaptive behaviors, there is little if any evidence of this relationship experimentally. Here, we investigated adaptive behavior in the rat model by using a well controlled behavioral paradigm within a psychophysical framework to predict and quantify changes in performance of animals trained on a simple whisker-based detection task. The sensory environment of the task was changed by transforming the probabilistic distribution ofwhisker deflection amplitudes systematically while measuring the animal's detection performance and corresponding rate of accumulated reward. We show that the psychometric function deviates significantly and reversibly depending on the probabilistic distribution of stimuli. This change in performance relates to accumulating a constant reward count across trials, yet it is exempt from changes in reward volume. Our simple model of reward accumulation captures the observed change in psychometric sensitivity and predicts a strategy seeking to maintain reward expectation across trials in the face of the changing stimulus distribution. We conclude that rats are able maintain a constant payoff under changing sensory conditions by flexibly adjusting their behavioral strategy. Our findings suggest the existence of an internal probabilistic model that facilitates behavioral adaptation when sensory demands change. [ABSTRACT FROM AUTHOR]

Whisker formation in tin films is a mode of stress relaxation, but the exact conditions causing them are yet to be established. In this work, a three-dimensional full-field chemo-thermo-mechanically coupled crystal plasticity simulation of thermally strained tin films was performed to evaluate the stress evolution and connect it to the redistribution of vacancies. Spatial heterogeneity in the hydrostatic stress along the grain boundary network (that served as the primary conduit for mass transport) was observed, which became more homogeneous towards the film surface. Normal and shear tractions on the columnar grain boundaries were evaluated as they might be crucial to breaking of the oxide layer (formed on the film surface) especially when inclined grain boundaries are present. With such an advanced multi-physics framework, several crystallographic and geometrical factors influencing whisker formation can be analyzed thereby leading to a better understanding of the factors modulating the nucleation and growth of such whiskers. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Novel mullite-bonded SiC whisker/SiC matrix composite is designed and prepared. • The oxidation kinetics is systematically investigated. • The aspect ratio of SiC whiskers increases after morphology modification. • Triple-layered SiC–SiO 2 –Al 2 O 3 raw materials are prepared via a coating process. • The toughening mechanisms of the new composite are discussed. Abstract A novel mullite-bonded SiC-whisker-reinforced SiC matrix composite (SiCw/SiC, SiC whisker-to-SiC powder mass ratio of 1:9) was designed and successfully prepared. Before preparing the composite, the inexpensive lab-made SiCw was first modified by an oxidation/leaching process and then coated with Al 2 O 3. The kinetics results indicate that the oxidation process can be described by improved shrinking-cylinder models. The aspect ratio of SiCw improved after modification. Subsequently, raw materials with a SiC–SiO 2 –Al 2 O 3 triple-layered structure were obtained after the Al 2 O 3 -coating process and used as feedstocks during the subsequent hot-pressing sintering. Finally, the characterization of the composites indicates that the mullite-bonded sample performs better (relative density of 93.8 ± 1.4%, flexural strength of 533.3 ± 18.2 MPa, fracture toughness of 13.6 ± 2.1 MPa m1/2, and Vickers hardness of 20.6 ± 2.5 GPa) than the reference sample without the mullite interface. The improved toughness could essentially be attributed to the moderately strong interface bonding and effective load transfer effects of the mullite interface. [ABSTRACT FROM AUTHOR]

The superior colliculus (SC) is an essential structure for the control of eye movements. In rodents, the SC is also considered to play an important role in whisking behavior, in which animals actively move their vibrissae (mechanosensors) to gather tactile information about the space around them during exploration. We investigated how the SC contributes to vibrissal movement control. We found that when the SC was unilaterally lesioned, the resting position of the vibrissae shifted backward on the side contralateral to the lesion. The unilateral SC lesion also induced an increase in the whisking amplitude on the contralateral side. To explore the anatomical basis for SC involvement in vibrissal movement control, we then quantitatively evaluated axonal projections from the SC to the brainstem using neuronal labeling with a virus vector. Neurons of the SC mainly sent axons to the contralateral side in the lower brainstem. We found that the facial nucleus received input directly from the SC, and that the descending projections from the SC also reached the intermediate reticular formation and pre-Bötzinger complex, which are both considered to contain neural oscillators generating rhythmic movements of the vibrissae. Together, these results indicate the existence of a neural circuit in which the SC modulates vibrissal movements mainly on the contralateral side, via direct connections to motoneurons, and via indirect connections including the central pattern generators. [ABSTRACT FROM AUTHOR]

Bodies change continuously, but we do not know if and how these changes affect somatosensory cortex. We address this issue in the whisker-barrel-cortex-pathway. We ask how outgrowing whiskers are mapped onto layer 4 barrel neuron responses. Half of whisker follicles contained dual whiskers, a shorter presumably outgrowing whisker (referred to as young whisker) and a longer one (referred to as old whisker). Young whiskers were much thinner than old ones but were inserted more deeply into the whisker follicle. Both whiskers were embedded in one outer root sheath surrounded by a common set of afferent nerve fibers. We juxtacellularly identified layer 4 barrel neurons representing dual whiskers with variable whisker length differences in anesthetized rats. Strength and latency of neuronal responses were strongly correlated for deflections of young and old whiskers but were not correlated with whisker length. The direction preferences of young and old whiskers were more similar than expected by chance. Old whiskers evoked marginally stronger and slightly shorter latency spike and local field potential responses than young whiskers. Our data suggest a conservative rewiring mechanism, which connects young whiskers to existing peripheral sensors. The fact that layer 4 barrel neurons retain their response properties is remarkable given the different length, thickness, and insertion depth of young and old whiskers. Retention of cortical response properties might be related to the placement of young and old whisker in one common outer root sheath and may contribute to perceptual stability across whisker replacement. [ABSTRACT FROM AUTHOR]

The effect of indium doping on whisker mitigation in tin electroplated on copper has been investigated. Whisker growth studies show that indium addition to Sn effectively mitigates whisker growth. Cross-section images showed predominantly columnar grains in the thin film. X-ray photoelectron spectroscopy studies of the oxide revealed a mixture of In2O3 and SnO2, along with a stoichiometrically defective oxide that can serve as a vacancy source at the metal-oxide interface. In addition, Auger electron spectroscopy showed In segregation at the grain boundaries as well as In enrichment just below the oxide layer. Cyclic voltammetry tests showed that the anodic behavior of the thin films exhibits active/passive transition where the passive current increases significantly upon doping Sn with In. We interpret these surface-related results in terms of a less tenacious oxide that permits reduction of in-plane compressive residual stress, thereby minimizing the driving force for whisker formation and growth. [ABSTRACT FROM AUTHOR]

During reward-based learning tasks, animals make orofacial movements that globally influence brain activity at the timings of reward expectation and acquisition. These orofacial movements are not explicitly instructed and typically appear along with goal-directed behaviors. Here, we show that reinforcing optogenetic stimulation of dopamine neurons in the ventral tegmental area (oDAS) in mice is sufficient to induce orofacial movements in the whiskers and nose without accompanying goal-directed behaviors. Pavlovian conditioning with a sensory cue and oDAS elicited cue-locked and oDAS-aligned orofacial movements, which were distinguishable by a machine-learning model. Inhibition or knockout of dopamine D1 receptors in the nucleus accumbens inhibited oDAS-induced motion but spared cue-locked motion, suggesting differential regulation of these two types of orofacial motions. In contrast, inactivation of the whisker primary motor cortex (wM1) abolished both types of orofacial movements. We found specific neuronal populations in wM1 representing either oDAS-aligned or cue-locked whisker movements. Notably, optogenetic stimulation of wM1 neurons successfully replicated these two types of movements. Our results thus suggest that accumbal D1-receptor-dependent and -independent neuronal signals converge in the wM1 for facilitating distinct uninstructed orofacial movements during a reward-based learning task. [Display omitted] • Optogenetic stimulation of VTA-DA neurons (oDAS) elicits orofacial movement • Cue-oDAS association induces distinct cue-locked and oDAS-aligned orofacial actions • Accumbal D1Rs mediate oDAS-aligned, but not cue-locked, motion • Different neuronal signals converge in wM1, triggering unique orofacial movements Investigating how mice display differential orofacial movements during reward anticipation and acquisition, Li and Nakano et al. highlight the pivotal role of the whisker primary motor cortex. It channels distinct neuronal signals—some via the mesolimbic dopamine pathway, others bypassing it—to facilitate unique orofacial actions. [ABSTRACT FROM AUTHOR]