Cortical neural prostheses require chronically implanted small-area microelectrode arrays that simultaneously record and stimulate neural activity. It is necessary to develop new materials with low interface impedance and large charge transfer capacity for this application and we explore the use of conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) for the same. We subjected PEDOT coated electrodes to voltage cycling between -0.6 and 0.8 V, 24 h continuous biphasic stimulation at 3 mC/cm² and accelerated aging for four weeks. Characterization was performed using cyclic voltammetry, electrochemical impedance spectroscopy, and voltage transient measurements. We found that PEDOT coated electrodes showed a charge injection limit 15 times higher than Platinum Iridium (PtIr) electrodes and electroplated Iridium Oxide (IrOx) electrodes when using constant current stimulation at zero voltage bias. In vivo chronic testing of microelectrode arrays implanted in rat cortex revealed that PEDOT coated electrodes show higher signal-to-noise recordings and superior charge injection compared to PtIr electrodes.

Summary Brown adipose tissue (BAT) possesses the inherent ability to dissipate metabolic energy as heat through uncoupled mitochondrial respiration. An essential component of the mitochondrial electron transport chain is coenzyme Q (CoQ). While cells mostly synthesize CoQ endogenously, exogenous supplementation with CoQ has been successful as a therapy for patients with CoQ deficiency. However, which tissues depend on exogenous CoQ uptake as well as the mechanism by which CoQ is taken up by cells and the role of this process in BAT function is not well understood. Here we report that the scavenger receptor CD36 drives the uptake of CoQ by BAT and is required for normal BAT function. BAT from mice lacking CD36 displays CoQ deficiency, impaired CoQ uptake, hypertrophy, altered lipid metabolism, mitochondrial dysfunction, and defective non-shivering thermogenesis. Together, these data reveal an important new role for the systemic transport of CoQ to BAT and its function in thermogenesis.

There is growing interest in intracortical microstimulation as a means of providing sensory input in neuroprosthetic systems. We believe that precisely controlling the timing and parameters of stimulation in closed loop can significantly improve the efficacy of this technique. Here, we present a system for closed-loop microstimulation in awake rodents chronically implanted with multielectrode arrays. The system interfaces with existing commercial recording and stimulating hardware. Using custom-made hardware, we can stimulate and record from electrodes on the same implanted array and significantly reduce the stimulation artifact. Stimulation sequences can either be preprogrammed or triggered by neural or behavioral events. Specifically, this system can provide feedback stimulation in response to action potentials or features in the local field potential recorded on any of the electrodes within 15 ms. It can also trigger stimulation based on behavioral events, such as real-time tracking of rat whiskers captured with high-speed video. We believe that this system, which can be recreated easily, will help to significantly refine the technique of intracortical microstimulation and advance the field of neuroprostheses.

Cortical microstimulation has been proposed as a method to deliver sensory percepts to circumvent damaged sensory receptors or pathways. However, much of perception involves the active movement of sensory organs and the integration of information across sensory and motor modalities. The efficacy of cortical microstimulation in such an active sensing paradigm has not been demonstrated. We report a novel behavioral paradigm which delivers microstimulation in real-time based on a rat's movements and show that rats can perform sensorimotor integration with electrically delivered stimuli. Using a real-time whisker tracking system, we delivered microstimulation in barrel cortex of actively whisking rats when their whisker crossed a particular spatial location which defined the target. Rats learned to integrate microstimulation cues with their knowledge of whisker position to infer target location along the rostro-caudal axis in less than 200 ms. In a separate experiment, we found that rats trained to respond to cortical microstimulation responded similarly to whisker deflections while ignoring auditory distracters, suggesting that barrel cortex stimulation may be perceptually similar to somatosensory stimuli. This ability to deliver sensory percepts using cortical microstimulation in an active sensing system might have significant implications for the development of sensorimotor neuroprostheses.