Generation of Locomotor-Like Activity in the Isolated Rat Spinal Cord Using Intraspinal Electrical Microstimulation Driven by a Digital Neuromorphic CPG.

Neural prostheses based on electrical microstimulation offer promising perspectives to restore functions following lesions of the central nervous system (CNS). They require the identification of appropriate stimulation sites and the coordination of their activation to achieve the restoration of functional activity. On the long term, a challenging perspective is to control microstimulation by artificial neural networks hybridized to the living tissue. Regarding the use of this strategy to restore locomotor activity in the spinal cord, to date, there has been no proof of principle of such hybrid approach driving intraspinal microstimulation (ISMS). Here, we address a first step toward this goal in the neonatal rat spinal cord isolated ex vivo, which can display locomotor-like activity while offering an easy access to intraspinal circuitry. Microelectrode arrays were inserted in the lumbar region to determine appropriate stimulation sites to elicit elementary bursting patterns on bilateral L2/L5 ventral roots. Two intraspinal sites were identified at L1 level, one on each side of the spinal cord laterally from the midline and approximately at a median position dorso-ventrally. An artificial CPG implemented on digital integrated circuit (FPGA) was built to generate alternating activity and was hybridized to the living spinal cord to drive electrical microstimulation on these two identified sites. Using this strategy, sustained left-right and flexor-extensor alternating activity on bilateral L2/L5 ventral roots could be generated in either whole or thoracically transected spinal cords. These results are a first step toward hybrid artificial/biological solutions based on electrical microstimulation for the restoration of lost function in the injured CNS.

BioMEA: a versatile high-density 3D microelectrode array system using integrated electronics.

Microelectrode arrays (MEAs) offer a powerful tool to both record activity and deliver electrical microstimulations to neural networks either in vitro or in vivo. Microelectronics microfabrication technologies now allow building high-density MEAs containing several hundreds of microelectrodes. However, dense arrays of 3D micro-needle electrodes, providing closer contact with the neural tissue than planar electrodes, are not achievable using conventional isotropic etching processes. Moreover, increasing the number of electrodes using conventional electronics is difficult to achieve into compact devices addressing all channels independently for simultaneous recording and stimulation. Here, we present a full modular and versatile 256-channel MEA system based on integrated electronics. First, transparent high-density arrays of 3D-shaped microelectrodes were realized by deep reactive ion etching techniques of a silicon substrate reported on glass. This approach allowed achieving high electrode aspect ratios, and different shapes of tip electrodes. Next, we developed a dedicated analog 64-channel Application Specific Integrated Circuit (ASIC) including one amplification stage and one current generator per channel, and analog output multiplexing. A full modular system, called BIOMEA, has been designed, allowing connecting different types of MEAs (64, 128, or 256 electrodes) to different numbers of ASICs for simultaneous recording and/or stimulation on all channels. Finally, this system has been validated experimentally by recording and electrically eliciting low-amplitude spontaneous rhythmic activity (both LFPs and spikes) in the developing mouse CNS. The availability of high-density MEA systems with integrated electronics will offer new possibilities for both in vitro and in vivo studies of large neural networks.

Laparoscopic gastropexy for the treatment of gastric volvulus associated with wandering spleen.

A 2.5-year-old boy was referred to the emergency room for a sudden onset of diffuse and increasing abdominal pain with lethargy, abdominal distension, and vomiting, all in the past 24 hours. A plain abdominal X-ray showed gastric distension. Two liters of gastric contents were evacuated by suction. The abdominal sonogram showed an unusual position of the spleen in the left-lower quadrant, with no splenic ischemia. The diagnosis of gastric volvulus associated with a wandering spleen was then evoked. Laparoscopic exploration revealed a nonischemic spleen, absence of normal supporting ligaments for the spleen, and gastric distension with flaccid gastric walls. The spleen was then easily moved in the left-under quadrant. A parietal peritoneal posterolateral incision was made, opposite the large gastric curve, up to the diaphragm (7 cm). This delimitated a sharp demarcation zone between the two edges of the incised peritoneum. The stomach was fixed to the peritoneal incision, covering and anchoring the spleen in a good position. Recovery was uneventful, and an abdominal sonogram performed 4 years after the surgery shows a viable spleen in its correct location. The rarity of gastric volvulus associated with a wandering spleen and its fast clinical improvement with medical treatment often delays the diagnosis and the surgical treatment. Laparoscopy in this case has a dual relevance: diagnosis and therapeutic management (splenectomy or gastropexy). Laparoscopic gastropexy for the treatment of gastric volvulus associated with a wandering spleen is an easy procedure and combines the advantages of all the surgical techniques previously described.