Prolonged electrical stimulation causes no damage to sacral nerve roots in rabbits

Previous studies have shown that, anode block electrical stimulation of the sacral nerve root can produce physiological urination and reconstruct urinary bladder function in rabbits. However, whether long-term anode block electrical stimulation causes damage to the sacral nerve root re- mains unclear, and needs further investigation. In this study, a complete spinal cord injury model was established in New Zealand white rabbits through T9_10 segment transection. Rabbits were given continuous electrical stimulation for a short period and then chronic stimulation for a longer period. Results showed that compared with normal rabbits, the structure of nerve cells in the anterior sacral nerve roots was unchanged in spinal cord injury rabbits after electrical stimu- lation. There was no significant difference in the expression of apoptosis-related proteins such as Bax, Caspase-3, and Bcl-2. Experimental findings indicate that neurons in the rabbit sacral nerve roots tolerate electrical stimulation, even after long-term anode block electrical stimulation.

A cascade model of information processing and encoding for retinal prosthesis

Retinal prosthesis offers a potential treatment for individuals suffering from photoreceptor degeneration diseases.Establishing biological retinal models and simulating how the biological retina convert incoming light signal into spike trains that can be properly decoded by the brain is a key issue.Some retinal models have been presented,ranking from structural models inspired by the layered architecture to functional models originated from a set of specific physiological phenomena.However,Most of these focus on stimulus image compression,edge detection and reconstruction,but do not generate spike trains corresponding to visual image.In this study,based on stateof-the-art retinal physiological mechanism,including effective visual information extraction,static nonlinear rectification of biological systems and neurons Poisson coding,a cascade model of the retina including the out plexiform layer for information processing and the inner plexiform layer for information encoding was brought forward,which integrates both anatomic connections and functional computations of retina.Using MATLAB software,spike trains corresponding to stimulus image were numerically computed by four steps：linear spatiotemporal filtering,static nonlinear rectification,radial sampling and then Poisson spike generation.The simulated results suggested that such a cascade model could recreate visual information processing and encoding functionalities of the retina,which is helpful in developing artificial retina for the retinally blind.

Decoding brain responses to pixelized images in the primary visual cortex: implications for visual cortical prostheses

Visual cortical prostheses have the potential to restore partial vision. Still limited by the low-resolution visual percepts provided by visual cortical prostheses, implant wearers can currently only ＂see＂ pixelized images, and how to obtain the specific brain responses to different pixelized images in the primary visual cortex（the implant area） is still unknown. We conducted a functional magnetic resonance imaging experiment on normal human participants to investigate the brain activation patterns in response to 18 different pixelized images. There were 100 voxels in the brain activation pattern that were selected from the primary visual cortex, and voxel size was 4 mm × 4 mm × 4 mm. Multi-voxel pattern analysis was used to test if these 18 different brain activation patterns were specific. We chose a Linear Support Vector Machine（LSVM） as the classifier in this study. The results showed that the classification accuracies of different brain activation patterns were significantly above chance level, which suggests that the classifier can successfully distinguish the brain activation patterns. Our results suggest that the specific brain activation patterns to different pixelized images can be obtained in the primary visual cortex using a 4 mm × 4 mm × 4 mm voxel size and a 100-voxel pattern.

In-Vitro and In-Vivo Electrical Characteristics of a Penetrating Microelectrode Array for Optic Nerve Electrical Stimulation

The Chinese C-Sight team aims to restore vision to blind patients by means of stimulating the optic nerve with a penetrating microelectrode array. A biocompatible, implantable microwire array was developed having four platinum-iridium shafts, each 100μm in diameter. This penetrating microwire array is described in this paper, including its fabrication techniques and its in-vitro electrical characteristics. Every set of four shafts was spaced 0.4mm from center to center, comprising two short shafts that were 0.3mm long and two that were 0.9mm long. This design was intended to stimulate ganglion cell axons at different depths within the optic nerve. In-vitro electrochemical impedance testing results showed that the impedance at 1kHz ranged from 8 to 10kΩ at room temperature. The voltage responses of the arrays to current pulse stimulation indicated a charge-injection capacity of 210μC/cm2. Finally, in-vivo acute animal experiments showed that the amplitude of the electrically evoked potentials (EEPs) measured in primary visual cortex could be as large as 100 μV upon direct stimulation of the optic nerve.