Biology subjects

Vatsyayan, R.

Publications and source records attributed to Vatsyayan, R..

6 recordsLinked to original sources

bioRxiv2026

A Thin Film Transistor Backplane for Scalable Chronic Neural Interfaces

Scaling neural interfaces to ever-higher channel counts has accelerated rapidly with advances in thin-film fabrication, lithography, and connectorization, enabling passive arrays to reach thousands of channels and chart credible pathways to much larger formats. Integrating active electronics directly at the sensing sites offers a complementary route to higher channel density by reducing the number of interconnects required to access large arrays. Here we introduce a monolithic flexible thin-film integrated circuit platform for active neural sensing, inspired by active-matrix display technology. The system integrates dual-gate amorphous indium gallium zinc oxide transistors on polyimide substrates to implement in-pixel transconductance amplification and row-column time-division multiplexing, improving scability for high-channel-count applications. Co-optimization of device architecture, contact engineering, and a hybrid ceramic-polymer thin-film encapsulation yields stable operation with projected lifetimes exceeding 38 years under accelerated aging. In acute and chronic in vivo rat studies, the platform exhibits negligible thermal burden, robust sensory-evoked recordings, and stable functionality over 30 days despite tissue encapsulation. These results establish display-inspired flexible thin-film electronics as a scalable building block for next-generation neural interfaces.

bioengineering↗

bioRxiv2026

Adaptive Charge Modulation Enables Focal, Selective Spinal Cord Stimulation

Clinical neuromodulation primarily employs near-field low frequency electrical stimulation to activate neurons in the immediate vicinity of the electrode. We introduce Adaptive Charge Modulation (ACM), a spatiotemporal, charge-balanced stimulation strategy that focuses activation at deep tissue sites distant from the stimulating contacts. We apply ACM to stimulate deep regions of the spinal cord, distant from dorsal root entry zones which are preferentially activated during low frequency stimulation (LFS). ACM applies multipolar, biphasic rectangular pulses to exceed activation thresholds in deeper neuronal populations, with reduced surface activation, potentially due to high-frequency suppression of neural activity. In epidural spinal cord stimulation in rats, ACM achieved single-muscle selectivity among fourteen monitored muscles with minimal co-activation of other muscles. Using simultaneous, high spatiotemporal resolution, 2,112-channel brain-spine recordings, we characterized the response latencies and pathways consistent with focal recruitment at depth. We observed chronic stability of the electrode and ACM in freely behaving animals over 68 days post-implantation. By enabling focal activation with epidural surface electrodes, ACM may expand the reach and precision of neuromodulation and neural interfaces.

bioengineering↗

bioRxiv2025

Stimulation with ECoG electrodes modulates cortical activity and sensory processing in the awake mouse brain

Electrical stimulation has been widely used to probe neural network properties and treat dysfunction. Electrocorticography (ECoG) electrodes, long used for activity monitoring, can also stimulate the brain in a minimally invasive and chronic manner. However, how cortical surface electrical stimulation impacts cortical network activity remains poorly understood. Using in vivo calcium imaging in the awake mouse brain with chronically implanted ECoG electrodes, we measured how electrical stimulation modulates the activity of visual cortical neurons, including during concurrent visual stimulation. We found that cortical surface electrical stimulation initially activates L2/3 neurons followed by prolonged inhibition lasting seconds after stimulation. Electrical stimulation suppresses the activity of neurons at their preferred grating orientation but enhances their responses to non-preferred visual stimuli, thereby reducing sensory feature selectivity. By measuring how electrical stimulation modulates the activity of inhibitory neuron subtypes including PV, SST, and NDNF interneurons, we propose a circuit model in which L1 NDNF interneurons are strongly activated by cortical electrical stimulation and, in turn, inhibit L2/3 excitatory neurons and PV interneurons through volume transmission of GABA.

neuroscience↗

bioRxiv2025

Towards individualized deep brain stimulation: A stereoencephalography-based workflow for unbiased neurostimulation target identification

ObjectivesDeep brain stimulation (DBS) is increasingly being used to treat a variety of neuropsychiatric conditions, many of which exhibit idiosyncratic symptom presentations and neural correlates across individuals. Thus, we have utilized inpatient stereoelectroencephalography (sEEG) to identify personalized therapeutic stimulation sites for chronic implantation of DBS. Informed by our experience, we have developed a statistics-driven framework for stimulation testing to identify therapeutic targets. Materials and MethodsFourteen participants (major depressive disorder = 6, chronic pain = 6, obsessive-compulsive disorder = 2) underwent inpatient testing using sEEG and symptom monitoring to identify personalized stimulation targets for subsequent DBS implantation. We present a structured approach to this sEEG testing, integrating a Stimulation Testing Decision Tree with power analysis and effect size considerations to inform adequately powered results to detect therapeutic stimulation sites with statistical rigor. ResultsEffect sizes (Hedges g) of stimulation-induced symptom score changes ranged from -1.5 to +2.39. The standard deviation of sham trial responses was a strong predictor of stimulation response variability, as confirmed by a leave-one-out cross-validated linear regression (R2 = 0.67, permutation p<0.001). Thus, early sham trial data could be used to estimate the variability of stimulation responses for power analysis calculations. We show that approximately 10 sham trials were needed to robustly estimate sham variability. Power analysis (using a paired-t test) showed that for effect sizes [≥] 1.1, roughly 10 trials should be used per stimulation site for sufficiently powered results. ConclusionsThe presented workflow is adaptable to multiple indications and is specifically designed to overcome key challenges experienced during stimulation site testing. Through incorporating sham trials, effect size calculations, and tolerability testing, the described approach can be used to identify personalized and clinically efficacious stimulation sites.

neuroscience↗

bioRxiv2024

Graphene-polymer Nanofibers Enable Optically Induced Electrical Maturation in Stem Cell-Derived Cardiomyocytes and Brain Organoids

Human pluripotent stem cell (hPSC)-derived electrically excitable cells provide a unique window into development, but they remain electrically immature partially due to the lack of chronic stimulation. Here, we fabricated electrospun polymer nanofibers containing light-reactive reduced graphene oxide (rGO) as part of a new classes of on-demand, electrically active biomaterials to enhance cell function. Fiber size, stiffness, and electrical conductivity varied with rGO concentration, which impacted hPSC-derived cardiomyocyte and neuron responses; with acute light stimulation, cardiomyocytes exhibited increased, synchronous calcium handling, and neurons showed more calcium peaks with higher frequency. Chronic, repetitive nanofiber light stimulation caused brain organoids to become increasingly electrically active and to activate photoreceptor pathways. This work outlines a tunable method where electrical cell functions can be titrated with rGO fibers and light stimulation, and it suggests that repetitive light stimulation may provide a novel method for retinal differentiation. HIGHLIGHTSO_LIElectrospun graphene-polymer nanofibers electrically respond to light stimulation C_LIO_LILight reactive graphene nanofibers stimulate electrically excitable cells in real-time C_LIO_LIStem cell-derived cardiomyocytes and neurons on nanofibers functionally improve C_LIO_LILight-training of brain organoids induces retinal and excitable neuron maturation C_LI

bioengineering↗

bioRxiv2022

Flexible, Scalable, High Channel Count Stereo-Electrode for Recording in the Human Brain

Over the past decade, stereotactically placed electrodes have become the gold standard for deep brain recording and stimulation for a wide variety of neurological and psychiatric diseases. Current electrodes, however, are limited in their spatial resolution and ability to record from small populations of neurons, let alone individual neurons. Here, we report on a novel, reconfigurable, monolithically integrated human-grade flexible depth electrode capable of recording from up to 128 channels and able to record at a depth of 10 cm in brain tissue. This thin, stylet-guided depth electrode is capable of recording local field potentials and single unit neuronal activity (action potentials), validated across species. This device represents a major new advance in manufacturing and design approaches which extends the capabilities of a mainstay technology in clinical neurology. One-Sentence SummaryA human-grade thin-film depth electrode offers new opportunities in spatial and temporal resolution for recording brain activity.

neuroscience↗