Biology subjects

Lopez Ruiz, J. R.

Publications and source records attributed to Lopez Ruiz, J. R..

3 recordsLinked to original sources

bioRxiv2023

A compact, ultrahigh-density headstage with high-fidelity hybrid integration for large-scale deep-brain opto-electrophysiology

Recent neuroscientific research seeks to comprehend the sophisticated deep-brain networks of neural circuits consisting of large scale neuronal ensembles across multiple brain regions. An ideal way to unveil the complex connectome might be stimulating individual neurons with high spatial resolution in a broad range of brain, while seamlessly monitoring the correspondent neuronal activities. Optogenetics is known as a key technology to enable such a goal thanks to its high spatial and temporal selectivity in neuromodulation. Existing silicon probe technologies have been able to partially achieve such a goal by recording broad region of brain activities through multiple electrodes per shank, but those cannot complete perfect coverage due to the limited channel counts for the optogenetic stimulation. Here, we present an high-channel-count optogenetic system with simultaneous 256 recoding and 128 optogenetic stimulation sites, exhibiting the highest channel density ever reported, enabled by a flexible polyimide cable-based hybrid-integration of a low-stimulation-artifact micro-LED ({micro}LED) opto-electrode with a low-power and -noise, area-efficient CMOS interfacing integrated-circuit (IC). The presented optogenetic system provides 256-neuron-size electrodes (11 x 15 {micro}m2) with a 40 {micro}m inter-electrode pitch for high spatial oversampling in recording and 128-soma-size {micro}LEDs (8 x 11 {micro}m2) with a 20 {micro}m inter-LED pitch for single-cell resolution in stimulation, resulting in a vertical span of 640 {micro}m and a horizontal span of 2,100 {micro}m with a total 8 shanks. For versatility in optogenetics-based experiments from small rodents to primates with user-preferable settings, the system base that provides programmability of recording and stimulation parameters and rest of signal processing, such as filtering, digitization, and data transmission including serial peripheral interface (SPI) has also been designed within small area of 23.8 x 28.8 mm2 with only 3.5-gram weight, resulting in the highest channel density both in size (0.56 channels/mm2) and weight (109.71 channels/gram) among the state-of-the-art optogenetics-based neuromodulation systems. To verify the system operation in vivo, a compact optogenetics headstage has been also fabricated. Using the prepared optogenetic headstage, 169 isolated neurons have been observed with various stimulation intensities. The results offered in this article indicate that the presented hybrid integrated ultrahigh-density, high-channel-count headstage can be used to realize the massive-scale in-depth brain studies with optogenetics.

bioengineering↗

bioRxiv2023

Simultaneous Electrophysiology and Optogenetic Perturbation of the Same Neurons in Chronically Implanted Animals using microLED Silicon Probes

Optogenetics are a powerful tool for testing how a neural circuit influences neural activity, cognition, and behavior. Accordingly, the number of studies employing optogenetic perturbation has grown exponentially over the last decade. However, recent studies have highlighted that the impact of optogenetic stimulation/silencing can vary depending on the construct used, the local microcircuit connectivity, extent/power of illumination, and neuron types perturbed. Despite these caveats, the majority of studies employ optogenetics without simultaneously recording neural activity in the circuit that is being perturbed. This dearth of simultaneously recorded neural data is due in part to technical difficulties in combining optogenetics and extracellular electrophysiology. The recent introduction of LED silicon probes, which feature independently controllable miniature LEDs embedded at several levels of each of multiple shanks of silicon probes, provides a tractable method for temporally and spatially precise interrogation of neural circuits. Here, we provide a protocol addressing how to perform chronic recordings using LED probes. This protocol provides a schematic for performing causal and reproducible interrogations of neural circuits and addresses all phases of the recording process: introduction of optogenetic construct, implantation of the LED probe, performing simultaneous optogenetics and electrophysiology in vivo, and post-processing of recorded data. SUMMARYThis method allows a researcher to simultaneously perturb neural activity and record electrophysiological signal from the same neurons with high spatial specificity using silicon probes with integrated LEDs. We outline a procedure detailing all stages of the process for performing reliable LED experiments in chronically implanted rodents.

neuroscience↗

bioRxiv2021

Stress related network activity in the intact adrenal medulla.

The adrenal medulla has long been recognized as playing a critical role in mammalian homeostasis and the stress response. The adrenal medulla is populated by clustered chromaffin cells that secrete epinephrine or norepinephrine along with other peptides into the general bloodstream affecting multiple distant target organs. Although the sympatho-adrenal pathway has been heavily studied, detailed knowledge on the central control and in-situ spatiotemporal responsiveness remains poorly understood. For this work we implemented electrophysiological techniques originally developed to elucidate CNS circuitry to characterize the functional micro-architecture of the adrenal medulla. To achieve this, we continuously monitored the electrical activity inside the adrenal medulla in the living anesthetized rat under basal conditions and under physiological stress. Under basal conditions, chromaffin cells fired action potentials with frequencies between [~]0.2 and 4 Hz. Activity was exclusively driven by sympathetic inputs coming through the splanchnic nerve. Furthermore, chromaffin cells were organized into arrays of independent local networks in which cells fire in a specific order, with latencies from hundreds of microseconds to few milliseconds. Electrical stimulation of the splanchnic nerve evoked the exact same spatiotemporal firing patterns that occurred spontaneously. Induction of hypoglycemic stress by administration of insulin resulted in an increase in the activity of a subset of the chromaffin cell networks. In contrast, respiratory arrest induced by anesthesia overdose resulted in an increase in the activity of the entire adrenal medulla before cessation of all activity when the animal died. The results suggest the differential activation of specific networks inside the adrenal gland depending on the stressor. These results revealed a surprisingly complex electrical organization and circuitry of the adrenal medulla that likely reflects the dynamic nature of its neuroendocrine output during basal conditions and during different types of physiological stress. To our knowledge, these experiments are the first to use multi-electrode arrays in vivo to examine the electrical and functional architecture of any endocrine gland. Significance StatementStress from extrinsic (environmental, psychological) and intrinsic (biological) challenges plays a critical role in disturbing the homeostatic balance. While the bodys responses to stress are designed to ameliorate these imbalances, prolonged and dysregulated stress often drives adverse health consequences in many chronic illnesses. The better understanding of the sympatho-adrenal stress response, will potentially impact and improve the treatment of several stress related illnesses. This work focusses on the study of the functional architecture of the adrenal medulla, a key component in neuronal stress response.

physiology↗