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Molecular dynamics study on anisotropic water cluster formation in polyethylene: A fundamental perspective on water tree initiation
The microscopic mechanisms of water tree inception in polymeric insulating materials remain a critical challenge for high-voltage engineering. In this study, molecular dynamics simulations were employed to investigate the structural and kinetic responses of water nanoclusters in a polyethylene matrix to external electric fields (0 and 2 V/nm). We demonstrate a fundamental disparity between ion-free pure water and ion-containing (Na+ and SO42−) clusters. In pure water systems, external fields induce macroscopic elongation along the field direction, accompanied by a reduction in the activation energy for hydrogen-bond dissociation. This field-induced dynamic softening kinetically facilitates continuous structural reorganization. Conversely, in ion-containing systems, the intense Coulombic attraction of the ions forms an electrostatically locked “hydration core.” This core exhibits an anomalously high activation energy that remains robustly intact even under 2 V/nm fields, causing kinematic freezing of the cluster’s morphology. These findings suggest that while pure water possesses the kinetic flexibility to undergo one-dimensional anisotropic growth under electrical stress, ionic impurities act as stable, non-deformable aggregation centers. Such contrasting dynamic behaviors provide a fundamental perspective on the initial cluster stabilization and directional elongation processes associated with water tree initiation.
A scheme to transform extracellular matrices into source and sink modes engulfing cancerous cells
The frequency dependent dielectric property of biological tissues plays a pivotal role in deciphering the intricacies of electromagnetic field cancer cell interaction and propels new therapeutics in the domain of electrotherapy. This study investigates a theoretical and computational approach to study the propagation of electromagnetic fields in a multilayered tissue model consisting of extracellular matrix (ECM), phospholipid bilayer, and intracellular media. The targeted delivery and accumulation of nanoparticles (NPs) of aspect ratio ∼100 in the ECM transform it into source and sink modes due to the distribution of electric field lines in the ECM region. Nanoparticles induce localized heating due to the increased specific absorption rate to achieve a steady-state temperature rise of 55°C within the first half cycle of the EM field and thermal diffusion and cooling in the refractory period of the EM field. The temperature variation instigates cell death (apoptosis) through localized hyperthermia. The duration of EM field application to achieve hyperthermia is inversely proportional to the frequency of the applied electric field and the concentration of the nanoparticles in the ECM. In the frequency range of a few tens of kHz such as 20 − 40 kHz and NP ECM concentration in the range 50%−100%, hyperthermia-triggered optimum apoptosis yield can be achieved in the time scale of ∼ 41.33–10.25 h. In the sub-kHz frequency of ∼50 Hz, hyperthermia application time increases to ∼20 months. However, in the very low frequency regime, the source–sink oscillations are progressively suppressed and the system transitions to a diffusion-dominated regime, while preserving the inverse frequency–NP relationship.
Anisotropic thermal transport and thermoelectric properties of hexagonal LiSr <i>X</i> ( <i>X</i> = As, Sb, Bi)
Hexagonal LiSrX (X = As, Sb, Bi) compounds exhibit intrinsically low lattice thermal conductivity and promising thermoelectric transport properties due to their layered crystal structures and strong phonon anharmonicity. In this work, we systematically investigate their thermal and electronic transport behaviors using first-principles calculations combined with anharmonic phonon and Boltzmann transport theories. The results demonstrate that all three compounds possess excellent dynamical, thermodynamic, and mechanical stability over a wide temperature range. The lattice thermal conductivity is dominated by low- to mid-frequency acoustic phonons and exhibits pronounced crystallographic anisotropy. As the X atom evolves from As to Bi, phonon softening and enhanced fourth-order anharmonicity significantly suppress the lattice thermal conductivity. Electronic structure calculations reveal that all compounds are direct-bandgap semiconductors with favorable n-type transport characteristics, including high carrier mobility and enhanced power factors. Among them, LiSrBi achieves the best thermoelectric performance with a maximum ZT value of approximately 1.0 at 800 K. Our results further show that the synergistic interplay among weak interatomic bonding, layered structural anisotropy, and anharmonic phonon dynamics governs the thermal transport behavior and thermoelectric performance of this material family. These findings provide useful insights for the design of high-performance layered thermoelectric materials.
Spectral evolution and real-space topological classification in a non-Hermitian Aubry–André–Harper model with quasiperiodic on-site potential
We present a systematic numerical study of the one-dimensional non-Hermitian Aubry–André–Harper model, which incorporates asymmetric nonreciprocal hopping and a quasiperiodic on-site potential. Using exact diagonalization, we investigate the interplay between the non-Hermitian skin effect driven by nonreciprocal hopping and Anderson localization induced by quasiperiodic disorder. We first analyze the evolution of the complex energy spectrum as the quasiperiodic potential strength V is tuned, revealing four characteristic stages: a fully closed point-gap topological loop in the complex plane, the onset of band splitting, the rupture of the topological loop into independent sub-loops, and the full collapse of the spectrum onto the real axis. We then construct detailed two-dimensional localization phase diagrams based on the average inverse participation ratio, demonstrating that nonreciprocal hopping enriches the phase structure of the standard Hermitian AAH model by introducing left-skin and right-skin topological phases alongside the extended metallic and Anderson insulating phases. Finally, we compute the real-space winding number under twisted boundary conditions and map out the complete topological phase diagram, clearly delineating regions with winding numbers W = +1, W = −1, and W = 0. Our results provide a comprehensive numerical characterization of the competition between quasiperiodic disorder and non-Hermitian nonreciprocity.
A data-driven framework for band-structure optimization and valley-topological control in phononic crystals
Band-structure characteristics in phononic crystals are highly sensitive to structural variations and strong multi-parameter coupling, necessitating dense sampling to effectively explore the design space. However, exhaustive searches are computationally prohibitive when using traditional simulations. To address this challenge, a Multilayer Perceptron (MLP) based surrogate model was developed and integrated with particle swarm optimization for efficient optimization of the valley-related branch separation. Its performance was benchmarked against convolutional neural network and support vector machine models. Additionally, unit-cell rotation was introduced as a key degree of freedom, allowing data-driven optimization and topological regulation to be incorporated into a unified design framework. The results demonstrated that the MLP model outperformed the comparative models in both prediction accuracy and convergence behavior, achieving a mean squared error of 6.54 × 10−5. Simultaneously, the trained MLP achieved a per-configuration speedup of approximately 8 × 104 times compared to finite element method simulations. The optimized valley-related branch separation had a width of 16 229 Hz, with lower and upper frequency bounds of 7349 and 23 578 Hz, respectively, along the Γ–K–M–Γ path. Further analysis revealed that rotational modulation induces band-structure reconstruction, generating valley-dependent edge states with controllable topological phase transitions and enabling robust propagation of interface states within the constructed heterostructure, even under complex structural perturbations. Overall, this work achieved an effective integration of data-driven design and physical mechanism regulation, providing a unified and scalable framework for the topological optimization of phononic crystal structures.
Influence of pre-existing negative surface charges on secondary electron emission avalanche evolution in vacuum surface flashover of spacecraft
Surface charging of dielectric materials is commonly observed in spacecraft under complex space environments. The accumulated charges on dielectric surfaces can modify the local electric-field distribution and subsequently affect secondary electron emission avalanche (SEEA), which plays a critical role in vacuum surface flashover. However, the influence mechanism of pre-existing surface charges formed before discharge initiation on the subsequent SEEA evolution remains insufficiently understood. In this work, a 2-spatial- and 3-velocity-dimensional particle-in-cell model is employed to investigate the effect of pre-existing negative surface charges near the cathode on vacuum surface flashover development. Different levels of localized negative surface charge densities are introduced as initial charging states, and their effects on electron emission, avalanche evolution, surface charge accumulation, and electric-field redistribution are systematically analyzed. The results demonstrate that the pre-existing charge of dielectric surfaces can strongly regulate subsequent vacuum flashover behavior, providing new insights into the coupling mechanism between surface charging and SEEA development in spacecraft and vacuum insulation systems.
Electro-thermal and mechanical simulations of laser annealing perovskite films
Conventional thermal annealing of oxide thin films (&gt;600 °C) often induces interfacial diffusion and substrate degradation, compromising structural integrity. Nanosecond pulsed laser annealing (ns-PLA) circumvents these limitations by enabling ultrafast, localized energy deposition with minimal thermal load. However, the fundamental mechanisms governing film–substrate interactions under ns-PLA remain unclear due to the complex interplay of electromagnetic, thermal, and mechanical processes, including light–matter interactions, transient heat transfer, and stress–strain dynamics from differential thermal expansion. To address this, we present a fully coupled electro-thermo-mechanical finite element model of ns-PLA. Our model integrates Maxwell's equations in the frequency domain, transient heat transfer, and thermoelastic stress analysis. For a 3 ns, 40 mJ cm−2 pulse, simulations reveal that electromagnetic interference localizes absorption near the LaNiO3/SrTiO3 interface, deviating from Beer–Lambert predictions. Peak temperatures exceed 1100 °C, with vertical thermal gradients of ∼109 K m−1, accelerating diffusion and epitaxial ordering by three orders of magnitude compared to furnace annealing. The thermoelastic response generates transient stresses of several gigapascals, exhibiting a distinct tensile–compressive distribution across the interface. Our findings emphasize the necessity of multiphysics coupling for accurately describing ns-PLA and provide quantitative insights into stress generation during epitaxial crystallization. This work advances the understanding of non-equilibrium phenomena in oxide heterostructures and establishes ns-PLA as a versatile tool for probing and controlling such processes at the nanoscale.
Interfacial Failure and Self‐Healing in Solid‐State Batteries
ABSTRACT Solid‐state batteries hold great promise for simultaneously improving energy density and intrinsic safety. However, their practical application is severely impeded by interfacial instabilities arising from coupled mechanical, chemical, and electrochemical degradation during cycling, ultimately resulting in rapid performance decay. Although conventional strategies, such as interfacial coatings or electrode structural optimization, have partially improved electrochemical performance, their inherently static nature renders them ill‐equipped to adapt to the continuous and dynamic evolution of interfacial damage during long‐term operation. To address these persistent challenges, dynamic interfacial self‐healing has emerged as a compelling strategy for developing highly durable and stable solid‐state batteries. In this review, we first discuss the origins and evolution of mechanical, chemical, and electrochemical failures at the interface, highlighting their intricate interplay. Recent progress in self‐healing strategies, including physical flow, chemical restoration, external stimuli, and electric fields was subsequently analyzed to solve specific interfacial failure behavior. Perspectives on the emerging strategies and key challenges for achieving high self‐healing efficiency were provided in the end. The development of self‐healing mechanisms presents a highly viable route toward the realization of robust, low‐pressure solid‐state batteries.
Molecular Bridge Overcomes Carrier Transport Limitations for High‐Efficiency Quantum Dot Photovoltaic
ABSTRACT Metal halide perovskite quantum dots (QDs) are promising candidates for next‐generation photovoltaic devices; however, their practical performance is largely limited by inefficient charge transport between neighboring QDs. To address this issue, we designed and synthesized a series of conjugated functional molecules, Mono‐OMe, Bi‐OMe, and Tetra‐OMe, featuring varying numbers of anchoring sites to tailor the interfaces within solid QD films. The π‐conjugated backbone promotes efficient charge transport between QDs, while multidentate anchoring groups enhance QD surface passivation. Systematic experimental characterizations reveal that higher denticity leads to more effective enhancements of the QD/organic heterointerfaces. In particular, the rationally designed tetradentate molecular bridge Tetra‐OMe forms more robust coordination with perovskite QDs, effectively passivating surface defects and promoting charge transport between adjacent QDs. As a result, molecularly bridged QD‐based solar cells achieve high‐power conversion efficiencies (PCEs) of 17.71% for wide‐bandgap CsPbI 3 and 19.06% (certified 18.72%) for narrow‐bandgap FAPbI 3 perovskite QDs, representing state‐of‐the‐art performance in QD photovoltaics.
Topological Frustration of Ångström‐Confined Water for Stable Aqueous Zinc‐Ion Batteries
ABSTRACT Despite extensive efforts to regulate water activity in hydrogel electrolytes for aqueous zinc‐ion batteries (AZIBs), current strategies are insufficient to impose spatial constraints on water molecules and prevent the self‐assembly of bulk water networks. Herein, we report a quasi‐solid hybrid electrolyte (HM) by integrating polyacrylamide with a rigid inorganic montmorillonite (MMT) framework that imposes strong ångström confinement on interlayer water molecules. Such spatial confinement restricts the volume required to assemble a bulk three‐dimensional tetrahedral hydrogen‐bond network. Concurrently, polar Si‐O bonds on the MMT surface chemically anchor water molecules in a one‐hydrogen‐down configuration, inducing symmetry breaking and topological frustration. Consequently, Grotthuss‐type proton transport and water autoionization are suppressed. This molecular‐level regulation mitigates water‐induced parasitic reactions and byproduct accumulation, ensuring a reversible Zn/electrolyte interface. As a result, the assembled Zn||NH 4 V 4 O 10 full cell achieves stable cycling for over 800 cycles at 1 A g −1 . By shifting the electrolyte design toward ångström topological engineering, this work establishes a promising paradigm for suppressing water‐induced parasitic reactions in high‐performance AZIBs.
Space‐Time‐Frequency Information Metasurface and Its Application in Electromagnetic Environment Sensing
ABSTRACT The advancement of 6G communications, Internet of Things, and electronic warfare systems toward higher frequencies, wider bandwidths, and multi‐scenario cooperation has imposed increasingly stringent demands on real‐time and high‐precision electromagnetic field sensing. However, the efficiency‐complexity trade‐off persists as a critical bottleneck for conventional sensing approaches in the space, time and space‐time domains. To address this problem, we propose a space‐time‐frequency information metasurface and investigate its applications in electromagnetic environment sensing. By incorporating differentiated frequency‐shift digital coding into meta‐atoms, different meta‐atoms will modulate distinct characteristic frequencies independently, resulting in a space‐time‐frequency coding strategy. The joint coding strategy enables efficient decoupling and parallel extraction of atom‐level electromagnetic signals in frequency domain under a single radio‐frequency reception channel, significantly reducing the system complexity and hardware costs. This method extends the modulation dimensions of information metasurface to the space‐time‐frequency coding, and may pave a new pathway for high‐dimensional electromagnetic signal processing and sensing systems.
TESCLA: A Fully Soft Electromagnetic Linear Actuator With Continuous Bending Enabled by Liquid‐Metal Solenoids
ABSTRACT Linear actuators are widely employed in robots and wearable devices due to their capability of directly generating linear motion. Although soft actuators and flexible linear actuators have been developed to enable effective operation in various configurations, they are still constrained by a limited actuation range and a discrete bending, which restricts their achievable workspace and curvatures. Here, we propose a tubular electromagnetic soft conformal linear actuator (TESCLA) exerting thrust force over a large actuation stroke with continuous bending. The actuator operates under both a straight configuration and a conformal deformation to the surrounding environment, leveraging the softness of liquid‐metal solenoids (soft stator) and compliant magnetic composites (soft mover). The synchronous actuation strategy allows the actuator to produce controllable bidirectional electromagnetic thrust by applying an electric current to the soft stator. In addition, the step position is estimated by measuring inductance variance of the soft solenoids resulting from the displacement of the soft mover. The design of the actuator components is evaluated through numerical simulations to determine an effective configuration, considering performance characteristics such as thrust force, minimum step size, and sensing resolution. By utilizing the functionalities of the proposed actuator, biomimetic robotic applications and a wearable haptic device were demonstrated.
Nondestructive Integration of Laser‐Induced Biomass Graphene for Sustainable Wearable Electronics
ABSTRACT Laser‐induced graphene (LIG) circuits hold significant promise for wearable electronics due to their excellent chemical stability and biocompatibility. However, fossil‐derived aromatic precursors are challenged by limited availability and environmental burden, and high energy laser processing damages substrates and hinders separation. Here, we propose a nondestructive strategy that integrates rapid heat dissipation and stress‐free pattern transfer based on a botanical lignin‐based precursor. Guided by the ReaxFF molecular dynamics simulation on the decomposition and reconstruction processes, lignin‐derived LIG circuits with high‐ordered structure and sheet resistance as low as 15 Ω sq −1 are obtained, and allow for complete integration onto a wide range of polymers, including those with ultrathin (20 µm), low‐modulus (69 kPa), and low‐melting‐point (84°C) profiles previously inaccessible. Leveraging the above platforms, six flexible devices irradiating light, electron, and thermal sensing applications are constructed, demonstrating its universality. Last but not the least, lignin offers high biosynthetic yield, closed‐loop recyclability, and excellent biodegradability, achieving an approximately 90% reduction in environmental footprint compared to fossil‐based alternatives.
Coherent Solid–Solution Interface With Near‐Zero Lattice Mismatch Enables Stable Zinc Anodes
ABSTRACT Aqueous Zn‐ion batteries (AZIBs) are attractive for large‐scale energy storage owing to their high theoretical capacity, intrinsic safety, and low cost. However, interfacial instability of Zn metal remains a major obstacle, leading to dendritic growth, parasitic reactions, and rapid capacity decay. Here, we introduce a coherent solid–solution interface (SSI) strategy with near‐zero lattice mismatch to stabilize the Zn metal anode. The in situ formed SSI exhibits a lattice mismatch of only 0.11% with Zn, enabling coherent Zn growth and suppressing detrimental side reactions. Combined experimental and theoretical analyses reveal that the SSI reduces interfacial polarization, suppresses HER, and promotes uniform lattice‐aligned dense Zn deposition. As a result, SSI‐Zn delivers stable Zn||Zn symmetric cell cycling for over 9100 h (1 year and 18 days) and achieves Zn||Cu asymmetric cell performance with a Coulombic efficiency (CE) of 99.9% over 10 000 cycles. In full cell configurations, Zn||AC cells and Zn||I 2 cells operate stably for over 120 000 cycles and 17 000 cycles, respectively, with average CE (ACE) values of 99.6% and 99.99%. Furthermore, an anode‐free Zn||Br pouch cell operates stably at an areal capacity of 5 mAh cm −2 with 99.4% ACE, achieving a practical energy density of 61 Wh kg −1 . By coupling near‐zero lattice mismatch with interfacial stabilization, this work demonstrates coherent interface engineering as a promising strategy toward high‐energy and long‐lifespan AZIBs.
Advancing 1.84 eV Wide‐Bandgap Perovskite Photovoltaics Beyond 20% via Single‐Facet‐Oriented Self‐Assembled Molecules
ABSTRACT Uncontrolled crystal growth and structural heterogeneity in solution‐processed self‐assembled molecules (SAMs) remain major limitations for efficient interfacial charge transport. Herein, we report a dipole‐engineered molecular strategy to regulate SAMs crystallization through the rational design of fluorinated benzimidazole‐carboxylic acid (BzIm‐COOH) derivatives (1F‐COOH, 2F‐COOH, and 3F‐COOH). Co‐assembly of these molecules with the parent SAMs induces strong electrostatic and dipole‐dipole interactions that direct crystal growth along the (100) facet, converting the SAMs layer from a polyfaceted, disordered morphology into a highly oriented architecture. Among them, 3F‐COOH, possessing the largest molecular dipole moment, exhibits the most pronounced facet‐directing capability. In addition to structural regulation, the BzIm‐COOH molecules optimize the interfacial energetics at the hole‐transport‐layer/perovskite junction, enabling more efficient hole extraction. Meanwhile, strong chemical interactions between 3F‐COOH and the perovskite precursor regulate crystallization kinetics and passivate interfacial defects. Consequently, wide‐bandgap (1.84 eV) PSCs incorporating 3F‐COOH deliver a champion efficiency of 20.16% (certified 19.25%) with markedly improved operational stability (90.38% after 600 h). The strategy further enables 26.75% perovskite/organic tandem devices and extends to 1.67 eV perovskite devices (23.56%) and perovskite/silicon tandems (32.34%, certified 31.54%). This work establishes dipole‐engineered molecular engineering as a powerful approach for directing SAMs crystallography and optimizing charge‐selective interfaces.
Low‐Dimensional V–VI van der Waals Compound Photodetectors
ABSTRACT This review for the first time provides a comprehensive overview on the low‐dimensional V–VI van der Waals compounds‐based photodetectors. It begins with the fundamental physical mechanisms for photodetection and the properties of various V–VI van der Waals compounds. Then, the preparation methods for producing low‐dimensional V–VI compounds have been presented. Following this, various photodetectors based on low‐dimensional V–VI compounds with distinct characteristics have been epitomized by categorizing them into trivial semiconductors and non‐trivial topological insulators. Subsequently, photodetectors built of V–VI compounds based heterostructures have been introduced, elaborating on the collaborative benefits enabled by heterostructuring. In the end, the future directions of this burgeoning domain have been proposed. On the whole, this review presents a full landscape of low‐dimensional V–VI van der Waals compound photodetectors, underscoring alternative paradigms for the implementation of the next generation of advanced optoelectronic devices and systems.
Reclaiming Reactive Oxygen Species With Taurine/Peroxytaurine Redox Couple for Achieving Ultra‐Long‐Term Cycle Stability in 4.8 V Li‐Rich Layered Oxide Cathodes
ABSTRACT Li‐rich Mn‐based layered oxides (LRMOs) are essential cathode materials for higher energy densities in batteries. Nevertheless, the release of reactive oxygen species (ROS) at high voltages, accompanied by the migration of surface oxygen vacancies and transition metal ions, results in continuous electrolyte decomposition, irreversible phase transition, and nanovoids formation within bulk materials. These processes significantly shorten cycle life of batteries and limit practical applications. Herein, inspired by biological properties of taurine (TA) in scavenging ROS, we propose a straightforward cathode additive strategy by employing TA to effectively interact with ROS, thereby generating a reversible TA/peroxotaurine redox couple. This innovative mechanism enables efficient recycling of ROS, which in turn inhibits continuous electrolyte decomposition, O 2 release, and nanovoid formation. Furthermore, the derived high‐quality cathode electrolyte interphase layer, which is rich in inorganic components and thinner in structure, stabilizes the layered structure while ensuring efficient Li + transport kinetics. Consequently, the modified LRMO demonstrates an exceptional initial Coulombic efficiency of 89% (vs. 81% for LRMO), and a splendid capacity retention of 92% at 1C after 400 cycles (vs. 68% for LRMO). Additionally, the pouch cell paired with graphite anodes exhibits superior capacity retention of 78% after 1000 ultra‐long cycles at 1/3C.
Analog Tensor Processing With Carbon Nanotube In‐Memory Matrix Multiplications for Edge Computer Vision Acceleration
ABSTRACT Computer vision requires intense tensor operations, primarily matrix multiplications, imposing substantial computation demands. Using hardware such as GPU and ASICs for acceleration offers a viable solution. Their application at edge, however, can be constrained by complexity in the computing architecture and incompatibility with analog systems. Here, we prototype an analog tensor core based on carbon nanotube charge‐trapping nonvolatile memory for edge computer vision acceleration. The memory, exhibiting ∼100 linear, symmetric analog weights with fast programming (500 ns) and data processing (1 Mbit/s), enables in‐memory matrix multiplications, facilitating compact tensor core design and operation of vectors and scalars in visual tasks. As demonstrations, the analog tensor core proves three‐dimensional (3D) spatial transformation with an error of <2.81% and edge detection with a signal‐to‐noise ratio of >22 dB, underpinning its potential for accelerating computer vision tasks in, for example, autonomous driving, VR/AR, robot navigation, and industrial automation. Proof‐of‐concept simulation achieves viewfield distortion correction and edge detection of street view fisheye captures by parallel single‐layer tensor processing using our analog tensor core in large scales.
The role of the locus coeruleus in eye movements during perceptual decision making
The locus coeruleus (LC) is the primary source of norepinephrine in the brain and has been implicated in the processes of attention, arousal, and perceptual decision making. Although prior work has linked transient LC activation to both sensory stimulus processing and motor processing, the precise contribution of LC to the distinct sensory and motor components of perceptual decisions remains unclear. Here, we recorded the spiking activity of single LC neurons in rhesus macaques (1 male, 1 female) while they performed a visual two-alternative forced-choice change detection task with a saccadic report, designed to cleanly dissociate sensory and motor contributions to LC activity. We found that the large majority of recorded neurons showed robust increases in response tightly locked to the choice saccade, while only a small fraction showed significant responses to the visual stimuli. Saccade-aligned LC responses did not vary with behavioral outcome, perceptual difficulty, reaction time, or session-wide fluctuations in perceptual sensitivity and criterion, indicating that LC motor-related signals were dissociated from perceptual performance. Together, these results demonstrated the existence of a subpopulation of LC neurons whose activity was tightly coupled to oculomotor output across both voluntary and involuntary eye movements during perceptual decision making, but were independent of perceptual decision accuracy. Our findings support a role for LC in facilitating motor preparation and execution in response to behaviorally significant sensory events. Significance Statement The locus coeruleus has been implicated as a main source of changes in the state of the brain through its brain-wide neuromodulatory inputs. We recorded from this deep brain structure during a task that helped separately assess how it contributes to sensory signals and eye movements to report a decision. We found that the locus coeruleus has activity consistent with a role in facilitating motor preparation relevant to perceptual decisions.
Stage-dependent effects of “too little and too much” medial prefrontal activity on reversal learning in rats: functional inhibition impairs early, whereas neural disinhibition impairs late reversals
Schizophrenia is associated with prefrontal cortex dysfunction, including neural disinhibition (reduced GABAergic inhibition) and hypoactivation (‘hypofrontality’), alongside impaired reversal learning. However, evidence implicating prefrontal regions, including the rodent medial PFC (mPFC), in reversal learning is mixed. mPFC involvement may scale with demand for mPFC-dependent attention and cognitive control to overcome prepotent responses and to learn that reward contingencies can reverse, which is highest during early reversals. We therefore hypothesized that (1) the mPFC is required for early reversal learning but less important when reversal proficiency is high during late reversals. Furthermore, mPFC disinhibition may impair cognitive performance by causing circuit-level disruption outside the mPFC. Therefore, we hypothesized that (2) even when the mPFC is not required, mPFC disinhibition may impair reversal performance. To test hypotheses (1) and (2), we first examined the effect of mPFC functional inhibition and disinhibition, by microinfusion of the GABA-A receptor agonist muscimol and antagonist picrotoxin, on early reversals (reversals 1-3) versus late reversals (reversal 5 onwards) on a 2-lever discrimination task in adult male rats. mPFC functional inhibition by muscimol impaired only early reversals, increasing perseveration and impairing lose-shift behavior at reversal 2. In contrast, mPFC disinhibition by picrotoxin impaired late reversals, reducing lose-shift and win-stay behavior. Using chemogenetic mPFC disinhibition (hM4Di-mediated inhibition of GABAergic neurons), we further tested hypothesis (2). Similar to mPFC picrotoxin, chemogenetic mPFC disinhibition impaired late reversals, primarily disrupting win-stay behavior. Our findings suggest that reduced and disinhibited mPFC activity impair distinct aspects of reversal learning. Significance statement Schizophrenia is associated with reduced activation (“hypofrontality”) and neural disinhibition (reduced GABAergic inhibition) within the prefrontal cortex (PFC). However, it is not clear if and how these distinct aspects of prefrontal dysfunction contribute to impaired reversal learning, a key feature of the cognitive inflexibility characterizing schizophrenia. Here, we combined bi-directional manipulations of prefrontal GABAergic inhibition with testing of reversal learning in rats. Increasing prefrontal functional inhibition (i.e., reducing prefrontal activation) selectively impaired early reversals, enhancing perseveration and reducing lose-shift behavior, whereas prefrontal disinhibition disrupted late reversals, impairing both lose-shift and win-stay behavior. Our findings suggest that reduced activation and disinhibition of PFC disrupt distinct aspects of reversal learning, by distinct mechanisms.