Multimodal in vivo brain electrophysiology with integrated glass microelectrodes

An Opto-electrophysiology Neural Probe with Photoelectric Artifact-Free for Advanced Single-Neuron Analysis

Opto-electrophysiology neural probes targeting single-cell levels offer an important avenue for elucidating the intrinsic mechanisms of the nervous system using different physical quantities, representing a significant future direction for brain-computer interface (BCI) devices. However, the highly integrated structure poses significant challenges to fabrication processes and the presence of photoelectric artifacts complicates the extraction and analysis of target signals. Here, we propose a highly miniaturized and integrated opto-electrophysiology neural probe for electrical recording and optical stimulation at the single-cell/subcellular level. The design of a total internal reflection layer addresses the photoelectric artifacts that are more pronounced in single-cell devices compared to conventional implantable BCI devices. Finite element simulations and electrical signal tests demonstrate that the opto-electrophysiology neural probe eliminates the photoelectric artifacts in the time domain, which represents a significant breakthrough for optoelectrical integrated BCI devices. Our proposed opto-electrophysiology neural probe holds substantial potential for promoting the development of in vivo BCI devices and developing advanced therapeutic strategies for neurological disorders.

A Soft-Fiber Bioelectronic Device with Axon-Like Architecture Enables Reliable Neural Recording In Vivo under Vigorous Activities

Implantable neural devices that record neurons in various states, including static states, light activities such as walking, and vigorous activities such as running, offer opportunities for understanding brain functions and dysfunctions. However, recording neurons under vigorous activities remains a long-standing challenge because it leads to intense brain deformation. Thus, three key requirements are needed simultaneously for neural devices, that is, low modulus, low specific interfacial impedance, and high electrical conductivity, to realize stable device/brain interfaces and high-quality transmission of neural signals. However, they always contradict each other in current material strategies. Here, a soft fiber neural device capable of stably tracking individual neurons in the deep brain of medium-sized animals under vigorous activity is reported. Inspired by the axon architecture, this fiber neural device is constructed with a conductive gel fiber possessing a network-in-liquid structure using conjugated polymers and liquid matrices and then insulated with soft fluorine rubber. This strategy reconciles the contradictions and simultaneously confers the fiber neural device with low modulus (300 kPa), low specific impedance (579 kΩ µm2), and high electrical conductivity (32 700 S m-1) - ≈1-3 times higher than hydrogels. Stable single-unit spike tracking in running cats, which promises new opportunities for neuroscience is demonstrated.

Multifunctional microelectronic fibers enable wireless modulation of gut and brain neural circuits

Progress in understanding brain-viscera interoceptive signaling is hindered by a dearth of implantable devices suitable for probing both brain and peripheral organ neurophysiology during behavior. Here we describe multifunctional neural interfaces that combine the scalability and mechanical versatility of thermally drawn polymer-based fibers with the sophistication of microelectronic chips for organs as diverse as the brain and the gut. Our approach uses meters-long continuous fibers that can integrate light sources, electrodes, thermal sensors and microfluidic channels in a miniature footprint. Paired with custom-fabricated control modules, the fibers wirelessly deliver light for optogenetics and transfer data for physiological recording. We validate this technology by modulating the mesolimbic reward pathway in the mouse brain. We then apply the fibers in the anatomically challenging intestinal lumen and demonstrate wireless control of sensory epithelial cells that guide feeding behaviors. Finally, we show that optogenetic stimulation of vagal afferents from the intestinal lumen is sufficient to evoke a reward phenotype in untethered mice.

In situ self-referenced intracellular two-electrode system for enhanced accuracy in single-cell analysis

Since the emergence of single-cell electroanalysis, the two-electrode system has become the predominant electrochemical system for real-time behavioral analysis of single-cell and multicellular populations. However, due to the transmembrane placement of the two electrodes, cellular activities can be interrupted by the transmembrane potentials, and the test results are susceptible to influences from factors such as intracellular solution, membrane, and bulk solution. These limitations impede the advancement of single-cell analysis. Here, we propose a highly miniaturized and integrated in situ self-referenced intracellular two-electrode system (IS-SRITES), wherein both the working and reference electrodes are positioned inside the cell. Additionally, we demonstrated the stability (0.28 mV/h) of the solid-contact in situ Ag/AgCl reference electrode and the ability of the system to conduct standard electrochemical testing in a wide pH range (pH 6.0-8.0). Cell experiments confirmed the non-destructive performance of the electrode system towards cells and its capacity for real-time monitoring of intra- and extracellular pH values. Moreover, through equivalent circuits, finite element simulations, and drug delivery experiments, we illustrated that the IS-SRITES can yield more accurate test results and exhibit enhanced resistance to interference from the extracellular environment. Our proposed system holds the potential to enable the precise detection of intracellular substances and optimize the existing model of the electrode system for intracellular signal detection, thereby spearheading advancements in single-cell analysis.

Enzymatic Galvanic Redox Potentiometry for In Vivo Biosensing

Redox potentiometry has emerged as a new platform for in vivo sensing, with improved neuronal compatibility and strong tolerance against sensitivity variation caused by protein fouling. Although enzymes show great possibilities in the fabrication of selective redox potentiometry, the fabrication of an enzyme electrode to output open-circuit voltage (EOC) with fast response remains challenging. Herein, we report a concept of novel enzymatic galvanic redox potentiometry (GRP) with improved time response coupling the merits of the high selectivity of enzyme electrodes with the excellent biocompatibility and reliability of GRP sensors. With a glucose biosensor as an illustration, we use flavin adenine dinucleotide-dependent glucose dehydrogenase as the recognition element and carbon black as the potential relay station to improve the response time. We find that the enzymatic GRP biosensor rapidly responds to glucose with a good linear relationship between EOC and the logarithm of glucose concentration within a range from 100 μM to 2.65 mM. The GRP biosensor shows high selectivity over O2 and coexisting neurochemicals, good reversibility, and sensitivity and can in vivo monitor glucose dynamics in rat brain. We believe that this study will pave a new platform for the in vivo potentiometric biosensing of chemical events with high reliability.

Construction of a Flexible Optogenetic Device for Multisite and Multiregional Optical Stimulation Through Flexible µ-LED Displays on the Cerebral Cortex

Precisely delivering light to multiple locations in biological tissue is crucial for advancing multiregional optogenetics in neuroscience research. However, conventional implantable devices typically have rigid geometries and limited light sources, allowing only single or dual probe placement with fixed spacing. Here, a fully flexible optogenetic device with multiple thin-film microscale light-emitting diode (µ-LED) displays scattering from a central controller is presented. Each display is heterogeneously integrated with thin-film 5 × 10 µ-LEDs and five optical fibers 125 µm in diameter to achieve cellular-scale spatial resolution. Meanwhile, the device boasts a compact, flexible circuit capable of multichannel configuration and wireless transmission, with an overall weight of 1.31 g, enabling wireless, real-time neuromodulation of freely moving rats. Characterization results and finite element analysis have demonstrated excellent optical properties and mechanical stability, while cytotoxicity tests further ensure the biocompatibility of the device for implantable applications. Behavior studies under optogenetic modulation indicate great promise for wirelessly modulating neural functions in freely moving animals. The device with multisite and multiregional optogenetic modulation capability offers a comprehensive platform to advance both fundamental neuroscience studies and potential applications in brain-computer interfaces.

Fast Reconfigurable Electrode Array Based on Titanium Oxide for Localized Stimulation of Cultured Neural Network

Planar microelectrode arrays have become standard tools for in vitro neural-network analysis. However, these predefined micropatterned devices lack adaptability to target-specific cells within a cultured network. Herein, we fabricated a reconfigurable TiO₂ electrode array with an anatase-brookite bicrystalline polymorphous mesoporous layer. Because of its selective absorption of ultraviolet (UV) light and corresponding photoconductivity, TiO₂ electrode array was identified as a promising tool for high-resolution light-addressing. The TiO₂ film was used as a semitransparent semiconductor with a high R_off/R_on ratio of 10⁵ and a fast response time of 400 ms. In addition, the effect of UV radiation on the resistance of the TiO₂ film over 30 d in an aqueous environment was analyzed, with the film exhibiting high stability. An arbitrary UV pattern was applied to a reconfigurable TiO₂ electrode using a digital micromirror device (DMD), affording highly localized neural stimulation at the single-cell level. The reconfigurable TiO₂ electrode with a patterned indium tin oxide (ITO) substrate enabled the independent connection of up to 60 points with external stimulators and signal recorders. We believe this technique would be helpful for electrophysiological research requiring the analysis of cell and neural-network features using a highly localized neural interface.

An integrated perspective for the diagnosis and therapy of neurodevelopmental disorders - From an engineering point of view

Neurodevelopmental disorders (NDDs) are complex conditions with largely unknown pathophysiology. While many NDD symptoms are familiar, the cause of these disorders remains unclear and may involve a combination of genetic, biological, psychosocial, and environmental risk factors. Current diagnosis relies heavily on behaviorally defined criteria, which may be biased by the clinical team's professional and cultural expectations, thus a push for new biological-based biomarkers for NDDs diagnosis is underway. Emerging new research technologies offer an unprecedented view into the electrical, chemical, and physiological activity in the brain and with further development in humans may provide clinically relevant diagnoses. These could also be extended to new treatment options, which can start to address the underlying physiological issues. When combined with current speech, language, occupational therapy, and pharmacological treatment these could greatly improve patient outcomes. The current review will discuss the latest technologies that are being used or may be used for NDDs diagnosis and treatment. The aim is to provide an inspiring and forward-looking view for future research in the field.

In Vivo Penetrating Microelectrodes for Brain Electrophysiology

In recent decades, microelectrodes have been widely used in neuroscience to understand the mechanisms behind brain functions, as well as the relationship between neural activity and behavior, perception and cognition. However, the recording of neuronal activity over a long period of time is limited for various reasons. In this review, we briefly consider the types of penetrating chronic microelectrodes, as well as the conductive and insulating materials for microelectrode manufacturing. Additionally, we consider the effects of penetrating microelectrode implantation on brain tissue. In conclusion, we review recent advances in the field of in vivo microelectrodes.

Robotic multi-probe single-actuator inchworm neural microdrive

A wide range of techniques in neuroscience involve placing individual probes at precise locations in the brain. However, large-scale measurement and manipulation of the brain using such methods have been severely limited by the inability to miniaturize systems for probe positioning. Here, we present a fundamentally new, remote-controlled micropositioning approach composed of novel phase-change material-filled resistive heater micro-grippers arranged in an inchworm motor configuration. The microscopic dimensions, stability, gentle gripping action, individual electronic control, and high packing density of the grippers allow micrometer-precision independent positioning of many arbitrarily shaped probes using a single piezo actuator. This multi-probe single-actuator design significantly reduces the size and weight and allows for potential automation of microdrives. We demonstrate accurate placement of multiple electrodes into the rat hippocampus in vivo in acute and chronic preparations. Our robotic microdrive technology should therefore enable the scaling up of many types of multi-probe applications in neuroscience and other fields.

Optically Triggering and Monitoring Single-Cell-Level Metabolism Using Ormosil-Decorated Ultrathin Fibers

The integration of biological components and artificial devices requires a bio-machine interface that can simultaneously trigger and monitor the activities in biosystems. Herein, we use an organically modified silicate (ormosil) composite coating containing a light-responsive nanocapsule and a fluorescent bioprobe for reactive oxygen species (ROS) to decorate ultrathin optical fibers, namely, ormosil-decorated ultrathin fibers (OD-UFs), and demonstrate that these OD-UFs can optically trigger and monitor the intracellular metabolism activities in living cells. The sizes and shapes of UF tips were finely controlled to match the dimension and mechanical properties of living cells. The increased elasticity of the ormosil coating of OD-UFs reduces possible mechanical damage during the cell membrane penetration. The light-responsive nanocapsule was physically absorbed on the surface of the ormosil coating and could release a stimulant to trigger the metabolism activities in cells upon the guided laser through OD-UFs. The fluorescent bioprobe was covalently linked with the ormosil matrix for monitoring the intracellular ROS generation, which was verified by the in vitro experiments on the microdroplets of a hydrogen peroxide solution. Finally, we found that the living cells could maintain most of their viability after being inserted with OD-UFs, and the intracellular metabolism activities were successfully triggered and monitored at the single-cell level. The OD-UF provides a new platform for the investigation of intracellular behaviors for drug stimulations and represents a new proof of concept for a bio-machine interface based on the optical and chemical activities of organic functional molecules.

From End to End: Gaining, Sorting, and Employing High-Density Neural Single Unit Recordings

The meaning behind neural single unit activity has constantly been a challenge, so it will persist in the foreseeable future. As one of the most sourced strategies, detecting neural activity in high-resolution neural sensor recordings and then attributing them to their corresponding source neurons correctly, namely the process of spike sorting, has been prevailing so far. Support from ever-improving recording techniques and sophisticated algorithms for extracting worthwhile information and abundance in clustering procedures turned spike sorting into an indispensable tool in electrophysiological analysis. This review attempts to illustrate that in all stages of spike sorting algorithms, the past 5 years innovations' brought about concepts, results, and questions worth sharing with even the non-expert user community. By thoroughly inspecting latest innovations in the field of neural sensors, recording procedures, and various spike sorting strategies, a skeletonization of relevant knowledge lays here, with an initiative to get one step closer to the original objective: deciphering and building in the sense of neural transcript.

jULIEs: nanostructured polytrodes for low traumatic extracellular recordings and stimulation in the mammalian brain

Objective Extracellular microelectrode techniques are the most widely used approach to interrogate neuronal populations. Regardless of the manufacturing method, damage to the vasculature and circuit function during probe insertion remains a concern. Reducing the footprint of the penetrating probes is a potential solution to this issue. However, coupling to the extracellular signals requires careful surface engineering. Approach Here, we show that continuously drawn SiO2-insulated ultra-microelectrode fibres offer an attractive substrate to address these challenges. Individual fibres can be fabricated to >10m continuous stretches and a selection of diameters below 30 µm with a low resistance (<100 Ω/m), continuous metal core of <10 µm and atomically flat smooth shank surfaces. To optimize the properties of the miniaturised electrode-tissue interface, we electrodeposit rough Au structures followed by ~20nm IrOx film by electrodeposition resulting in reduction of the interfacial impedance to <500kΩ at 1 kHz. Main results We demonstrate that these ultra-low impedance electrodes (jULIEs) can record and stimulate single and multi-unit activity with minimal tissue disturbance and exceptional signal-to-noise ratio in both superficial (~40µm) and deep (~6mm) structures of the mouse brain. We further show that sensor modifications are stable and probe manufacturing is reproducible. Significance Minimally perturbing bidirectional neural interfacing can reveal circuit function in the mammalian brain in vivo.

Deep Learning for Voltammetric Sensing in a Living Animal Brain

Numerous neurochemicals have been implicated in the modulation of brain function, making them appealing analytes for sensors and diagnostics. However, it is a grand challenge to selectively measure multiple neurochemicals simultaneously in vivo because of their great variations in concentrations, dynamic nature, and composition. Herein, we present a deep learning-based voltammetric sensing platform for the highly selective and simultaneous analysis of three neurochemicals in a living animal brain. The system features a carbon fiber electrode capable of capturing the mixed dynamics of a neurotransmitter, neuromodulator, and ions. Then a powerful deep neural network is employed to resolve individual chemical and spatial-temporal information. With this, a single electrochemical measurement reveals an interplaying concentration changes of dopamine, ascorbate, and ions in living rat brain, which is unobtainable with existing analytical methodologies. Our strategy provides a powerful means to expedite research in neuroscience and empower sensing-aided diagnostic applications.

Animal models of developmental dyslexia: Where we are and what we are missing

Developmental dyslexia (DD) is a complex neurodevelopmental disorder and the most common learning disability among both school-aged children and across languages. Recently, sensory and cognitive mechanisms have been reported to be potential endophenotypes (EPs) for DD, and nine DD-candidate genes have been identified. Animal models have been used to investigate the etiopathological pathways that underlie the development of complex traits, as they enable the effects of genetic and/or environmental manipulations to be evaluated. Animal research designs have also been linked to cutting-edge clinical research questions by capitalizing on the use of EPs. For the present scoping review, we reviewed previous studies of murine models investigating the effects of DD-candidate genes. Moreover, we highlighted the use of animal models as an innovative way to unravel new insights behind the pathophysiology of reading (dis)ability and to assess cutting-edge preclinical models.

AgRP neurons: Regulators of feeding, energy expenditure, and behavior

Neurons in the hypothalamic arcuate nucleus (ARC) that express agouti-related peptide (AgRP) govern a critical aspect of survival: the drive to eat. Equally important to survival is the timing at which food is consumed-seeking or eating food to alleviate hunger in the face of a more pressing threat, like the risk of predation, is clearly maladaptive. To ensure optimal prioritization of behaviors within a given environment, therefore, AgRP neurons must integrate signals of internal need states with contextual environmental cues. In this state-of-the-art review, we highlight recent advances that extend our understanding of AgRP neurons, including the neural circuits they engage to regulate feeding, energy expenditure, and behavior. We also discuss key findings that illustrate how both classical feedback and anticipatory feedforward signals regulate this neuronal population and how the integration of these signals may be disrupted in states of energy excess. Finally, we examine both technical and conceptual challenges facing the field moving forward.

Automated microscope-independent fluorescence-guided micropipette

Glass micropipette electrodes are commonly used to provide high resolution recordings of neurons. Although it is the gold standard for single cell recordings, it is highly dependent on the skill of the electrophysiologist. Here, we demonstrate a method of guiding micropipette electrodes to neurons by collecting fluorescence at the aperture, using an intra-electrode tapered optical fiber. The use of a tapered fiber for excitation and collection of fluorescence at the micropipette tip couples the feedback mechanism directly to the distance between the target and electrode. In this study, intra-electrode tapered optical fibers provide a targeted robotic approach to labeled neurons that is independent of microscopy.

SHYBRID: A Graphical Tool for Generating Hybrid Ground-Truth Spiking Data for Evaluating Spike Sorting Performance

Spike sorting is the process of retrieving the spike times of individual neurons that are present in an extracellular neural recording. Over the last decades, many spike sorting algorithms have been published. In an effort to guide a user towards a specific spike sorting algorithm, given a specific recording setting (i.e., brain region and recording device), we provide an open-source graphical tool for the generation of hybrid ground-truth data in Python. Hybrid ground-truth data is a data-driven modelling paradigm in which spikes from a single unit are moved to a different location on the recording probe, thereby generating a virtual unit of which the spike times are known. The tool enables a user to efficiently generate hybrid ground-truth datasets and make informed decisions between spike sorting algorithms, fine-tune the algorithm parameters towards the used recording setting, or get a deeper understanding of those algorithms.

Cellular Classes in the Human Brain Revealed In Vivo by Heartbeat-Related Modulation of the Extracellular Action Potential Waveform

Determining cell types is critical for understanding neural circuits but remains elusive in the living human brain. Current approaches discriminate units into putative cell classes using features of the extracellular action potential (EAP); in absence of ground truth data, this remains a problematic procedure. We find that EAPs in deep structures of the brain exhibit robust and systematic variability during the cardiac cycle. These cardiac-related features refine neural classification. We use these features to link bio-realistic models generated from in vitro human whole-cell recordings of morphologically classified neurons to in vivo recordings. We differentiate aspiny inhibitory and spiny excitatory human hippocampal neurons and, in a second stage, demonstrate that cardiac-motion features reveal two types of spiny neurons with distinct intrinsic electrophysiological properties and phase-locking characteristics to endogenous oscillations. This multi-modal approach markedly improves cell classification in humans, offers interpretable cell classes, and is applicable to other brain areas and species.

Emerging intraoral biosensors

Biomedical devices that involved continuous and real-time health-care monitoring have drawn much attention in modern medicine, of which skin electronics and implantable devices are widely investigated. Skin electronics are characterized for their non-invasive access to the physiological signals, and implantable devices are superior at the diagnosis and therapy integration. Despite the significant progress achieved, many gaps remain to be explored to provide a more comprehensive overview of human health. As the connecting point of the outer environment and human systems, the oral cavity contains many unique biomarkers that are absent in skin or inner organs, and hence, this could become a promising alternative locus for designing health-care monitoring devices. In this review, we outline the status of the oral cavity during the communication of the environment and human systems and compare the intraoral devices with skin electronics and implantable devices from the biophysical and biochemical aspects. We further summarize the established diagnosis database and technologies that could be adopted to design intraoral biosensors. Finally, the challenges and potential opportunities for intraoral biosensors are discussed. Intraoral biosensors could become an important complement for existing biomedical devices to constitute a more reliable health-care monitoring system.

Bioinspired Materials for In Vivo Bioelectronic Neural Interfaces

The success of in vivo neural interfaces relies on their long-term stability and large scale in interrogating and manipulating neural activity after implantation. Conventional neural probes, owing to their limited spatiotemporal resolution and scale, face challenges for studying the massive, interconnected neural network in its native state. In this review, we argue that taking inspiration from biology will unlock the next generation of in vivo bioelectronic neural interfaces. Reducing the feature sizes of bioelectronic neural interfaces to mimic those of neurons enables high spatial resolution and multiplexity. Additionally, chronic stability at the device-tissue interface is realized by matching the mechanical properties of bioelectronic neural interfaces to those of the endogenous tissue. Further, modeling the design of neural interfaces after the endogenous topology of the neural circuitry enables new insights into the connectivity and dynamics of the brain. Lastly, functionalization of neural probe surfaces with coatings inspired by biology leads to enhanced tissue acceptance over extended timescales. Bioinspired neural interfaces will facilitate future developments in neuroscience studies and neurological treatments by leveraging bidirectional information transfer and integrating neuromorphic computing elements.

Galvanic Redox Potentiometry Based Microelectrode Array for Synchronous Ascorbate and Single-Unit Recordings in Rat Brain

Neuronal communication relies on cooperation between the chemical and electrical patterns of neurons. Thus, techniques for illustrating the linkage of the neurochemical events and action potentials with high temporal and spatial resolution is imperative to gain a comprehensive understanding of the intricacies of brain function. Herein, we integrate galvanic redox potentiometry (GRP) and electrophysiological recording onto a 16-site Au microelectrode array (MEA), one of which is for indicating the ascorbate concentration while the others for single-unit activity assessment. The electrochemical probing site was modified with single-walled carbon nanotubes to promote electron-transfer kinetics of ascorbate at low overpotential so as to enlarge the driving force for the spontaneous ascorbate/O₂ cell reaction. The resulting GRP-based MEA outputs open-circuit potential that is in a linear relationship with the logarithmic ascorbate concentration and exhibits high selectivity against a set of coexisting electroactive species. Furthermore, no reciprocal interference between the two recording systems is observed during concurrent GRP sensing of ascorbate and single-unit recording in a rat brain. In vivo feasibility of the GRP-based MEA is demonstrated by synchronous real-time measurement of ascorbate release and electrical activity from multiple neuronal populations during spreading depression. Our GRP-based MEA sensor creates new opportunities to realize high-throughput screening or mapping of neurochemical patterns in a larger dimension and correlate them to neuron functions across a spatial scale.

Flexible, diamond-based microelectrodes fabricated using the diamond growth side for neural sensing

Diamond possesses many favorable properties for biochemical sensors, including biocompatibility, chemical inertness, resistance to biofouling, an extremely wide potential window, and low double-layer capacitance. The hardness of diamond, however, has hindered its applications in neural implants due to the mechanical property mismatch between diamond and soft nervous tissues. Here, we present a flexible, diamond-based microelectrode probe consisting of multichannel boron-doped polycrystalline diamond (BDD) microelectrodes on a soft Parylene C substrate. We developed and optimized a wafer-scale fabrication approach that allows the use of the growth side of the BDD thin film as the sensing surface. Compared to the nucleation surface, the BDD growth side exhibited a rougher morphology, a higher sp ³ content, a wider water potential window, and a lower background current. The dopamine (DA) sensing capability of the BDD growth surface electrodes was validated in a 1.0 mM DA solution, which shows better sensitivity and stability than the BDD nucleation surface electrodes. The results of these comparative studies suggest that using the BDD growth surface for making implantable microelectrodes has significant advantages in terms of the sensitivity, selectivity, and stability of a neural implant. Furthermore, we validated the functionality of the BDD growth side electrodes for neural recordings both in vitro and in vivo. The biocompatibility of the microcrystalline diamond film was also assessed in vitro using rat cortical neuron cultures.

Frequency Modulated Parametric Oscillation for Antenna Powered Wireless Transmission of Voltage Sensing Signals

Wireless transmission of voltage signals are particularly useful for sensors embedded inside a closed environment where long-term operation without internal batteries is desirable. For this purpose, voltage tuning resonators can be used, because their voltage-dependent frequency responses can be contactlessly characterized by loop antennas connected to the output and input ports of a network analyzer. However, such passive sensors have limited remote detectability and temporal resolution, especially for smaller frequency shifts that would require repetitive averaging for acceptable measurement accuracy. To overcome these limitations, a double frequency parametric resonator is inductively coupled with a voltage tuning resonator to convert resonance frequency shifts of the passive sensor into frequency encoded oscillation signals that can be instantaneously detected over larger distance separations. This antenna powered FM transmitter has a compact design to achieve good voltage sensitivity and linearity, making it potentially useful for multiple applications from PH sensing to electrophysiological recording.

Methods for single-cell recording and labeling in vivo

Targeting individual neurons in vivo is a key method to study the role of single cell types within local and brain-wide microcircuits. While novel technological developments now permit assessing activity from large number of cells simultaneously, there is currently no better solution than glass micropipettes to relate the physiology and morphology of single-cells. Sharp intracellular, juxtacellular, loose-patch and whole-cell approaches are some of the configurations used to record and label individual neurons. Here, we review procedures to establish successful electrophysiological recordings in vivo followed by appropriate labeling for post hoc morphological analysis. We provide operational recommendations for optimizing each configuration and a generic framework for functional, neurochemical and morphological identification of the different cell-types in a given region. Finally, we highlight emerging approaches that are challenging our current paradigms for single-cell recording and labeling in the living brain.