A dual-channel optogenetic stimulator selectively modulates distinct defensive behaviors

Flexible electronic-photonic 3D integration from ultrathin polymer chiplets

The integration of flexible electronics and photonics has the potential to create revolutionary technologies, yet it has been challenging to marry electronic and photonic components on a single polymer device, especially through high-volume manufacturing. Here, we present a robust, chiplet-level heterogeneous integration of polymer-based circuits (CHIP), where several post-fabricated, ultrathin, polymer electronic, and optoelectronic chiplets are vertically bonded into one single chip at room temperature and then shaped into application-specific form factors with monolithic Input/Output (I/O). As a demonstration, we applied this process and developed a flexible 3D-integrated optrode with high-density arrays of microelectrodes for electrical recording and micro light-emitting diodes (μLEDs) for optogenetic stimulation while with unprecedented integration of additional temperature sensors for bio-safe operations and shielding designs for optoelectronic artifact prevention. Besides achieving simple, high-yield, and scalable 3D integration of much-needed functionalities, CHIP also enables double-sided area utilization and miniaturization of connection I/O. Systematic device characterization demonstrated the successfulness of this scheme and also revealed frequency-dependent origins of optoelectronic artifacts in flexible 3D-integrated optrodes. In addition to enabling excellent manufacturability and scalability, we envision CHIP to be generally applicable to numerous polymer-based devices to achieve wide-ranging applications.

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.

In Vivo and 3D Imaging Technique(s) for Spatiotemporal Mapping of Pathological Events in Experimental Model(s) of Spinal Cord Injury

Endothelial damage, astrogliosis, microgliosis, and neuronal degeneration are the most common events after spinal cord injury (SCI). Studies highlighted that studying the spatiotemporal profile of these events might provide a deeper understanding of the pathophysiology of SCI. For imaging of these events, available conventional techniques such as 2-dimensional histology and immunohistochemistry (IHC) are well established and frequently used to visualize and detect the altered expression of the protein of interest involved in these events. However, the technique requires the physical sectioning of the tissue, and results are also open to misinterpretation. Currently, researchers are focusing more attention toward the advanced tools for imaging the spinal cord's various physiological and pathological parameters. The tools include two-photon imaging, light sheet fluorescence microscopy, in vivo imaging system with fluorescent probes, and in vivo chemical and fluorescent protein-expressing viral-tracers. These techniques outperform the limitations associated with conventional techniques in various aspects, such as optical sectioning of tissue, 3D reconstructed imaging, and imaging of particular planes of interest. In addition to this, these techniques are minimally invasive and less time-consuming. In this review, we will discuss the various advanced imaging methodologies that will evolve in the future to explore the fundamental mechanisms after SCI.

Blueprints for measuring natural behavior

Until recently laboratory tasks for studying behavior were highly artificial, simplified, and designed without consideration for the environmental or social context. Although such an approach offers good control over behavior, it does not allow for researching either voluntary responses or individual differences. Importantly for neuroscience studies, the activity of the neural circuits involved in producing unnatural, artificial behavior is variable and hard to predict. In addition, different ensembles may be activated depending on the strategy the animal adopts to deal with the spurious problem. Thus, artificial and simplified tasks based on responses, which do not occur spontaneously entail problems with modeling behavioral impairments and underlying brain deficits. To develop valid models of human disorders we need to test spontaneous behaviors consistently engaging well-defined, evolutionarily conserved neuronal circuits. Such research focuses on behavioral patterns relevant for surviving and thriving under varying environmental conditions, which also enable high reproducibility across different testing settings.

Emerging Optoelectronic Devices Based on Microscale LEDs and Their Use as Implantable Biomedical Applications

Thin-film microscale light-emitting diodes (LEDs) are efficient light sources and their integrated applications offer robust capabilities and potential strategies in biomedical science. By leveraging innovations in the design of optoelectronic semiconductor structures, advanced fabrication techniques, biocompatible encapsulation, remote control circuits, wireless power supply strategies, etc., these emerging applications provide implantable probes that differ from conventional tethering techniques such as optical fibers. This review introduces the recent advancements of thin-film microscale LEDs for biomedical applications, covering the device lift-off and transfer printing fabrication processes and the representative biomedical applications for light stimulation, therapy, and photometric biosensing. Wireless power delivery systems have been outlined and discussed to facilitate the operation of implantable probes. With such wireless, battery-free, and minimally invasive implantable light-source probes, these biomedical applications offer excellent opportunities and instruments for both biomedical sciences research and clinical diagnosis and therapy.

Implantable Micro-Light-Emitting Diode (µLED)-based optogenetic interfaces toward human applications

Optogenetics has received wide attention in biomedical fields because of itsadvantages in temporal precision and spatial resolution. Beyond contributions to important advances in fundamental research, optogenetics is inspiring a shift towards new methods of improving human well-being and treating diseases. Soft, flexible and biocompatible systems using µLEDs as a light source have been introduced to realize brain-compatible optogenetic implants, but there are still many technical challenges to overcome before their human applications. In this review, we address progress in the development of implantable µLED probes and recent achievements in (i) device engineering design, (ii) driving power, (iii) multifunctionality and (iv) closed-loop systems. (v) Expanded optogenetic applications based on remarkable advances in µLED implants will also be discussed.

Functional Organisation of the Mouse Superior Colliculus

The superior colliculus (SC) is a highly conserved area of the mammalian midbrain that is widely implicated in the organisation and control of behaviour. SC receives input from a large number of brain areas, and provides outputs to a large number of areas. The convergence and divergence of anatomical connections with different areas and systems provides challenges for understanding how SC contributes to behaviour. Recent work in mouse has provided large anatomical datasets, and a wealth of new data from experiments that identify and manipulate different cells within SC, and their inputs and outputs, during simple behaviours. These data offer an opportunity to better understand the roles that SC plays in these behaviours. However, some of the observations appear, at first sight, to be contradictory. Here we review this recent work and hypothesise a simple framework which can capture the observations, that requires only a small change to previous models. Specifically, the functional organisation of SC can be explained by supposing that three largely distinct circuits support three largely distinct classes of simple behaviours-arrest, turning towards, and the triggering of escape or capture. These behaviours are hypothesised to be supported by the optic, intermediate and deep layers, respectively.

3D Upconversion Barcodes for Combinatory Wireless Neuromodulation in Behaving Animals

Upconversion techniques offer all-optical wireless alternatives to modulate targeted neurons in behaving animals, but most existing upconversion-based optogenetic devices show prefixed emission that is used to excite just one channelrhodopsin at a restricted brain region. Here, a hierarchical upconversion device is reported to enable spatially selective and combinatory optogenetics in behaving rodent animals. The device assumes a multiarrayed optrode format containing engineered upconversion nanoparticles (UCNPs) to deliver dynamic light palettes as a function of excitation wavelength. Three primary emissions at 477, 540, and 654 nm are selected to match the absorption of different channelrhodopsins. The UCNPs are barcode assembled to multiple nanomachined optical pinholes in a microscale pipette device to allow remotely addressable, spectrum programmable, and spatially selective optical interrogation of complex brain circuits. Using the unique device, the basolateral amygdala and caudoputamen circuits are selectively modulated and the associated fear or anxiety behavior in freely behaving rodents is successfully differentiated. It is believed that the 3D barcode upconversion device would be a great supplement to current optogenetic toolsets and opens up new possibilities for sophisticated neural control.