Neuronal signal detecting and stimulating circuit array for monolithic integrated MEA

A neuronal signal detecting circuit and a neuronal signal stimulating circuit designed for a monolithic integrated MEA（micro-electrode array） system are described. As a basic cell of the circuits, an OPA（ operational amplifier） is designed with low power, low noise, small size and high gain. The detecting circuit has a chip area of 290 μm × 400 μm, a power dissipation of 2.02 mW, an equivalent input noise of 17.72 nV/ Hz, a gain of 60. 5 dB, and an output voltage from - 2. 48 to ＋ 2. 5 V. The stimulating circuit has a chip area of 130 μm × 290 μm, a power dissipation of 740 μW, and an output voltage from - 2. 5 to 2. 04 V. The parameters show that two circuits are suitable for a monolithic integrated MEA system. The detecting circuit and MEA have been fabricated. The test results show that the detecting circuit works well.

Preparation of Electrode Array by Electrochemical Etching Based on FEM

Process technology of multiple cylindrical micro-pins by wire-electrical discharge machining （wire-EDM） and electrochemical etching was presented. A row of rectangular micro-columns were machined by wire-EDM and then machined into cylindrical shape by electrochemical etching. However, the shape of the multiple electrodes and the consistent sizes of the electrodes row are not easy to be controlled. In the electrochemical process, the shape of the cathode electrode determines the current density distribution on the anode and so the forming of multiple electrodes. This paper proposes a finite element method （FEM） to accurately optimize the electrode profile. The microelectrodes row with uniformity diameters with size from hundreds micrometers to several decades could be fabricated, and mathematical model controlling the shape and diameter of multiple microelectrodes was provided. Furthermore, a good agreement between experimental and theoretical results was confirmed.

N-methyl-D-aspartate (NMDA) mediates vascular relaxation via nitric oxide (NO) in rats but not in mice

Amperometric studies have indicated that substance P as well as NMDA stimulates release of NO in rat aortic rings. These data have been confirmed by functional observations of vaso-relaxant action of NMDA within noradrenaline pre-contracted aortic rings, supporting the presence of NMDA receptor in rat aortic rings. It is known that the enzyme endothelial NO synthase (eNOS) mediates vasodilatation not only in rats, but also in C57BL6 mice aortic ring, indicating that in this blood vessel NO is the endogenous endothelium-derived vasodilator. In this work, amperometry together with specifically nitrites insensitive micro-biosensors have been applied to examine the effect of NMDA and substance P upon NO release in rat and in two strains of mice aortic rings. The electrochemical data monitored demonstrate that NMDA mediates vascular relaxation via NO in rats but not in mice. These results are supported by functional data, therefore they suggest that NMDA receptors are “not responding” within these experimental conditions in mice aortic rings.

GABA_A Receptor Activity Suppresses the Transition from Interictal to Ictal Epileptiform Discharges in Juvenile Mouse Hippocampus

Exploring the transition from inter-ictal to ictal epileptiform discharges(IDs) and how GABAAreceptormediated action affects the onset of IDs will enrich our understanding of epileptogenesis and epilepsy treatment.We used Mg2+-free artificial cerebrospinal fluid(ACSF) to induce epileptiform discharges in juvenile mouse hippocampal slices and used a micro-electrode array to record the discharges. After the slices were exposed to Mg2+-free ACSF for 10 min–20 min, synchronous recurrent seizurelike events were recorded across the slices, and each event evolved from inter-ictal epileptiform discharges(IIDs) to pre-ictal epileptiform discharges(PIDs), and then to IDs.During the transition from IIDs to PIDs, the duration of discharges increased and the inter-discharge interval decreased. After adding 3 lmol/L of the GABAAreceptor agonist muscimol, PIDs and IDs disappeared, and IIDs remained. Further, the application of 10 lmol/L muscimol abolished all the epileptiform discharges. When the GABAAreceptor antagonist bicuculline was applied at 10 lmol/L, IIDs and PIDs disappeared, and IDs remained at decreased intervals. These results indicated that there are dynamic changes in the hippocampal network preceding the onset of IDs, and GABAAreceptor activity suppresses the transition from IIDs to IDs in juvenile mouse hippocampus.

To Explore High Magnetoelectrochemical Chirality

Cu films were electrodeposited under a magnetic field of 5 T on the Pt disc electrodes with diameters of 3 mm ~ 25 μm.Such magnetoelectrodeposited(MED) Cu films were employed as an electrode,and cyclic voltammograms were measured for the electrochemical reactions of an amino acid of alanine.Chiral behavior was observed as oxidation current difference between the enantiomers.Clear magnetoelectrochemical chirality was observed on the micro-disk electrode and on the kinetic-controlled electrode process of alanine.The chiral response was durable for more than 10 cycles of the consecutive voltammetric measurements of the enantiomers.

A multi-channel analog IC for in vitro neural recording

Recent work in the field ofneurophysiology has demonstrated that, by observing the firing characteristic of action potentials （AP） and the exchange pattern of signals between neurons, it is possible to reveal the nature of ＂memory＂ and ＂thinking＂ and help humans to understand how the brain works. To address these needs, we developed a prototype fully integrated circuit （IC） with micro-electrode array （MEA） for neural recording. In this scheme, the microelectrode array is composed by 64 detection electrodes and 2 reference electrodes. The proposed IC consists of 8 recording channels with an area of 5 x 5 mm2. Each channel can operate independently to process the neural signal by amplifying, filtering, etc. The chip is fabricated in 0.5-#m CMOS technology. The simulated and measured results show the system provides an effective device for recording feeble signal such as neural signals.