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Mouse models are widely used in studies of various forms of transcranial electric stimulation (TES). However, there is limited knowledge of the electric field distribution induced by TES in mice, and computational models to estimate this distribution are lacking. This study examines the electric field and current density distribution in the mouse brain induced by TES. We created a high-resolution...
This study examines the characteristics of the electric field (E-field) induced in the brain by electroconvulsive therapy (ECT) and magnetic seizure therapy (MST). The electric field induced by five ECT electrode configurations (bilateral, bifrontal, right unilateral, focal electrically administered seizure therapy, and frontomedial) as well as an MST coil configuration (circular) was computed in...
An epiretinal prosthesis aims to restore functional vision in patients suffering from retinal degeneration caused by diseases such as Retinitis Pigmentosa (RP) and Age-Related Macular Degeneration (AMD). These diseases result in the loss of photoreceptors but bipolar, amacrine and ganglion cells survive at high rates and can be electrically activate to produce the sensation of light. Continuous application...
We investigated the morphological and electrochemical properties of an explanted laser-machined 32 channel electrocorticogram (ECoG) electrode array made of platinum-iridium and silicone rubber. It was connected to a wireless brain-computer interface (BCI) and implanted in a sheep for more than 15 months. Recordings and stimulations of cortical activity were conducted over the whole period on a regularly...
Regenerative peripheral nerve interfaces (RPNIs) are for signal transfer between peripheral nerves inside the body to controllers for motorized prosthetics external to the body. Within the residual limb of an amputee, surgical construction of a RPNI connects a remaining peripheral nerve and spare muscle. Nerve signals become concentrated within the RPNI. Currently metal electrodes implanted on the...
We describe for the first time the design, implementation, and testing of a telemetry controlled simultaneous stimulation and recording device (SRD) to deliver chronic intercortical microstimulation (ICMS) to physiologically identified sites in rat somatosensory cortex (SI) and test hypotheses that chronic ICMS strengthens interhemispheric pathways and leads to functional reorganization in the enhanced...
This paper presents a power-efficient modular wireless platform which has been designed for prototyping and pre-clinical evaluations of neural recording implants. This Kit for Designing Implants (KDI) is separated in function specific modules of 34×34mm which can be assembled as needed. Five modules have been designed and optimized for ultra-low power consumption and a protective casing has been designed...
Electrode arrays used in neural recording and stimulation applications must be implanted carefully to minimize damage to the underlying tissue. A device has been designed to improve a surgeon's control over implantation parameters including depth, insertion velocity, and insertion force. The device has been designed to operate without contacting tissue and to respond to tissue movements in real time...
In neuroscience optogenetics was established as common research method. However, the devices used for opto-genetical stimulation, so called optrodes, are often made of stiff materials which lead to cell damage. We investigated the suitability of the epoxy based polymers SU-8, EpoClad and EpoCore for the fabrication of bendable thin-film waveguides. With the integration of such waveguides into neural...
In preparing a wireless cortical stimulator for use in the Intracortical Visual Prosthesis (ICVP) project at the Illinois Institute of Technology (IIT), an accelerated environmental stress test is being performed on prototype stimulator modules. Stimulator devices, containing a custom application specific integrated circuit (ASIC), and encapsulated with PDMS, were soaked in an autoclave chamber at...
We report a novel method to fabricate chronic neural interfaces with the intent to combine the reliability and lifetime of bulk metal electrodes, with the miniaturization and mechanical flexibility of thin-film polymer microelectrode arrays. 10 μm thick platinum discs were laser cut from a foil into the shape of individual electrodes, and coated with gold on the backside. The discs were bonded to...
This paper reports a method of making optical probes for optogenetics-based deep brain optical stimulation using SU-8, which effectively increases light coupling efficiency, has excellent mechanical stiffness, and reduces fabrication complexity. By mounting microscale LEDs (μLEDs) at the tip of a SU-8 probe and directly inserting the light source into deep brain regions, attenuation caused by light...
Transcranial direct current stimulation (tDCS) has been used to affect the excitability of neurons within the cerebral cortex. Improvements in motor learning have been found in multiple studies when tDCS was applied to the motor cortex during or before task learning is performed. The application of tDCS to motor imagery, a cognitive task showing activation in similar areas to motor execution, has...
Brain is an electrochemical system and recent studies suggest simultaneous measurement of interrelated brain's electrical and neurochemical activity may lead to better understanding of brain function in addition to developing optimal neural prosthetics. By exploiting opamp Time-sharing technique to minimized power dissipation and silicon area, we have fabricated a power efficient implantable CMOS...
We present an electronic cortical neuron incorporating dynamic spike threshold and active dendritic properties. The circuit is simulated using a carbon nanotube field-effect transistor SPICE model. We demonstrate that our neuron has lower spike threshold for coincident synaptic inputs; however when the synaptic inputs are not in synchrony, it requires larger depolarization to evoke the neuron to fire...
Intracortical microelectrodes can be used to treat various neurological disorders given their capabilities to interface with single or multiple populations of neurons. However, most of these penetrating devices have been reported to fail over time, within weeks to months, putatively due to the foreign body response (FBR) which persistently aggravates the surrounding brain tissues. A number of studies...
Neuronal networks cultured on microelectrode arrays (MEAs) have been utilized as biosensors that can detect all or nothing extracellular action potentials, or spikes. Coating the microelectrodes with carbon nanotubes (CNTs), either pristine or conjugated with a conductive polymer, has been previously reported to improve extracellular recordings presumably via reduction in microelectrode impedance...
Knowledge of the bio-impedance and its equivalent circuit model at the electrode-electrolyte/tissue interface is important in the application of functional electrical stimulation. Impedance can be used as a merit to evaluate the proximity between electrodes and targeted tissues. Understanding the equivalent circuit parameters of the electrode can further be leveraged to set a safe boundary for stimulus...
Iridium oxide has been widely used in neural recording and stimulation due to its good stability and large charge storage capacity (CSC). In general, the iridium oxide film used in the electrophysiological application can be grouped into three principal classifications: sputtering iridium oxide film (SIROF), activated iridium oxide film (AIROF) and electrodeposited iridium oxide film (EIROF). Although...
Micro-electrocorticography (μECoG) displays advantages over traditional invasive methods. The μECoG electrode can record neural activity with high spatial-temporal resolution and it can reduce implantation side effects (e.g. vascular and local-neuronal damage, tissue encapsulation, infection). In this study, we propose a printable transparent μECoG electrode for optogenetic applications by using ultrasonic...
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