Biology subjects

Dayeh, S. A.

Publications and source records attributed to Dayeh, S. A..

8 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↗

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↗

bioRxiv2024

Modular Phoneme Processing in Human Superior Temporal Gyrus

Modular organization is fundamental to cortical processing, but its presence is human association cortex is unknown. We characterized phoneme processing with 128-1024 channel micro-arrays at 50-200m pitch on superior temporal gyrus of 7 patients. High gamma responses were highly correlated within [~]1.7mm diameter modules, sharply delineated from adjacent modules with distinct time-courses and phoneme-selectivity. We suggest that receptive language cortex may be organized in discrete processing modules.

neuroscience↗

bioRxiv2023

The Brain Electroencephalogram Microdisplay for Precision Neurosurgery

Brain surgeries are among the most delicate clinical procedures and must be performed with the most technologically robust and advanced tools. When such surgical procedures are performed in functionally critical regions of the brain, functional mapping is applied as a standard practice that involves direct coordinated interactions between the neurosurgeon and the clinical neurology electrophysiology team. However, information flow during these interactions is commonly verbal as well as time consuming which in turn increases the duration and cost of the surgery, possibly compromising the patient outcomes. Additionally, the grids that measure brain activity and identify the boundaries of pathological versus functional brain regions suffer from low resolution (3-10 mm contact to contact spacing) with limited conformity to the brain surface. Here, we introduce a brain intracranial electroencephalogram microdisplay (Brain-iEEG-microdisplay) which conforms to the brain to measure the brain activity and display changes in near real-time (40 Hz refresh rate) on the surface of the brain in the surgical field. We used scalable engineered gallium nitride (GaN) substrates with 6" diameter to fabricate, encapsulate, and release free-standing arrays of up to 2048 GaN light emitting diodes (LEDs) in polyimide substrates. We then laminated the LED arrays on the back of micro-electrocorticography (ECoG) platinum nanorod grids (PtNRGrids) and developed hardware and software to perform near real-time intracranial EEG analysis and activation of light patterns that correspond to specific cortical activities. Using the Brain-iEEG-microdisplay, we precisely ideFSntified and displayed important cortical landmarks and pharmacologically induced pathological activities. In the rat model, we identified and displayed individual cortical columns corresponding to individual whiskers and the near real-time evolution of epileptic discharges. In the pig animal model, we demonstrated near real-time mapping and display of cortical functional boundaries using somatosensory evoked potentials (SSEP) and display of responses to direct electrical stimulation (DES) from the surface or within the brain tissue. Using a dual-color Brain-iEEG-microdisplay, we demonstrated co-registration of the functional cortical boundaries with one color and displayed the evolution of electrical potentials associated with epileptiform activity with another color. The Brain-iEEG-microdisplay holds the promise of increasing the efficiency of diagnosis and possibly surgical treatment, thereby reducing the cost and improving patient outcomes which would mark a major advancement in neurosurgery. These advances can also be translated to broader applications in neuro-oncology and neurophysiology. One Sentence SummaryA brain intracranial electroencephalogram microdisplay (Brain-iEEG-microdisplay) measures and displays real-time brain activity in the surgical field.

neuroscience↗

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↗

bioRxiv2019

Microscale physiological events on the human cortical surface detected with PEDOT:PSS Electrodes

Despite ongoing advancements in our understanding of the local single-cellular and network-level activity of neuronal populations in the human brain, extraordinarily little is known about their intermediate microscale local circuit dynamics. Here, we utilized ultrahigh density microelectrode arrays and a rare opportunity to perform intracranial recordings across multiple cortical areas in human participants to discover three distinct classes of cortical activity that are not locked to ongoing natural brain rhythmic activity. The first included fast waveforms similar to extracellular single unit activity. The other two types were discrete events with slower waveform dynamics and were found preferentially in upper layers of the grey matter. They were also observed in rodents, non-human primates, and semi-chronic recordings in humans via laminar and Utah array microelectrodes. The rates of all three events were selectively modulated by auditory and electrical stimuli, pharmacological manipulation, and cold saline application and had small causal co-occurrences. These results suggest that with the proper combination of high resolution microelectrodes and analytic techniques it is possible to capture neuronal dynamics that lay between somatic action potentials and aggregate population activity and that understanding these intermediate microscale dynamics may reveal important details of the full circuit behavior in human cognition.

neuroscience↗