Akito Ishihara

Electrical interfacing between neurons and electronics via vertically integrated sub-4 μm-diameter silicon probe arrays fabricated by vapor–liquid–solid growth

We report here a technique for use in electrical interfaces between neurons and microelectronics, using vertically integrated silicon probe arrays with diameters of 2-3.5 microm and lengths of 60-120 microm. Silicon probe arrays can be fabricated by selective vapor-liquid-solid (VLS) growth. A doped n-type silicon probe with the resistance of 1 k Omega has an electrical impedance of less than 10 M Omega in physiological saline. After inserting the probe arrays into the retina of a carp (Cyrpinus carpio), we conducted electrical recording of neural signals, using the probes to measure light-evoked electrical neural signals. We determined that recorded signals represented local field potentials of the retina (electroretinogram (ERG)). The VLS-probe can provide minimally invasive neural recording/stimulation capabilities at high spatial resolution for fundamental studies of nervous systems. In addition, the probe arrays can be integrated with microelectronics; therefore, these probes make it possible to construct interfaces between neurons and microelectronics in advanced neuroscience applications.

Enlarged gold-tipped silicon microprobe arrays and signal compensation for multi-site electroretinogram recordings in the isolated carp retina.

In order to record multi-site electroretinogram (ERG) responses in isolated carp retinae, we utilized three-dimensional (3D), extracellular, 3.5-μm-diameter silicon (Si) probe arrays fabricated by the selective vapor-liquid-solid (VLS) growth method. Neural recordings with the Si microprobe exhibit low signal-to-noise (S/N) ratios of recorded responses due to the high-electrical-impedance characteristics of the small recording area at the probe tip. To increase the S/N ratio, we designed and fabricated enlarged gold (Au) tipped Si microprobes (10-μm-diameter Au tip and 3.5-μm-diameter probe body). In addition, we demonstrated that the signal attenuation and phase delay of ERG responses recorded via the Si probe can be compensated by the inverse filtering method. We conclude that the reduction of probe impedance and the compensation of recorded signals are useful approaches to obtain distortion-free recording of neural signals with high-impedance microelectrodes.

Three-dimensional multichannel Si microprobe electrode array chip for analysis of the nervous system

This paper reports on a sensor chip device including a needle-like penetrating microprobe electrode array for simultaneous analysis of neurons in tissue. The probe array was fabricated on a Si substrate by selective epitaxial Si growth, is a few microns in diameter similar to the dimensions of the neurons with low invasiveness and low tissue damage. Using standard IC process followed by the probe growth, the probe array can be fabricated on IC signal processors improving the performance of the electrode chip. Neural signals were recorded from a carp retina with the Si microprobes.

A Next Generation Modeling Environment PLATO: Platform for Collaborative Brain System Modeling

To understand the details of brain function, a large scale system model that reflects anatomical and neurophysiological characteristics needs to be implemented. Though numerous computational models of different brain areas have been proposed, these integration for the development of a large scale model have not yet been accomplished because these models were described by different programming languages, and mostly because they used different data formats. This paper introduces a platform for a collaborative brain system modeling (PLATO) where one can construct computational models using several programming languages and connect them at the I/O level with a common data format. As an example, a whole visual system model including eye movement, eye optics, retinal network and visual cortex is being developed. Preliminary results demonstrate that the integrated model successfully simulates the signal processing flow at the different stages of visual system.

Neural recording with low-invasive Si microprobe array

Reported here is Si microprobe electrode array, developed for using in the recording of neurons in the tissue. The probe array can be fabricated on IC chip, using standard IC process followed by a selective Si probe growth. In this work, the Si probes with 2-4 /spl mu/m in diameter were fabricated. The probe array could provide low-invasiveness and low damage to neurons in the neural electrode penetration. The resistance of the probe was 1 k/spl Omega/, and the impedance, measured in saline, was less than 500 k/spl Omega/, at 1 kHz. Neural recording was carried out using the retina of a carp (Cyrpinus carpio), and light-evoked neural responses of the retina were recorded with the Si microprobe electrodes.

Simulation platform: cloud-computing meets computational neuroscience

Computational models and theoretical tools are essential components in computational neuroscience. A number of models and tools have been developed and registered at various online databases such as ModelDB and J-Node Platforms. Yet, the reuse of such resources still remains quite difficult. For example, to carry out a computer simulation of a model, we have to download the program from the database, extract, read instructions, compile if the program is written in a general programming language such as C, install the appropriate neural simulator if it is written for a simulator such as GENESIS, NEURON, and NEST, and finally we may be ready to do it, if no problems occurs during all the setup mentioned above. How can we avoid this hustle? As a solution of it, we introduce a cloud-based system for online computer simulation called Simulation Platform. Simulation Platform is a cloud of virtual machines running GNU/Linux. On a virtual machine, various software including developer tools such as compilers and libraries, popular neural simulators, and scientific software such as Gnuplot, R and Octave, are pre-installed. When a user posts a request, a virtual machine is assigned to the user, and the simulation starts on that machine. The user can remotely access the virtual machine through a web browser and carries out the simulation interactively (a screenshot is shown in Fig. ​Fig.1).1). There is no need to install any software. It only requires a web browser. Therefore, Simulation Platform provides an ubiquitous computing environment for computational neuroscience research so as to free neuroscientists from tedious computer administration tasks and allow them to solely concentrate on their science. A demo site is open at http://sf4.sim.neuroinf.jp/~tyam/cns11/. Figure 1 A screenshot of a web browser during a computer simulation.

Multisite field potential recording from retina via vapor-liquid-solid grown silicon probe array

We report in-vitro multisite field potential recordings from fish retina using a vertically integrated silicon (Si) microprobe array. Eight active channels of the enlarged probe-head “Kokeshi (Japanese dolls)” type Si probe enabled multisite electrical recordings of retinal responses (electroretinograms (ERGs)) to white light stimuli. The ERG a- and b-waves were obtained at each probe, and the result suggests the capability of the Si probe array for use in further investigations of spatio-temporal property of ERGs.

1709 Ionic current model of retinal bipolar cells

1710 A POSSIBLE MOLECULAR MECHANISM OF L-THREGDOPS ACTION ON OCULAR DOMINANCE PLASTICITY. NOBUKO MJATAGA=~, TSUYOSHI SHIOMITSLFJ, FUMIHIKO FUKAMAUCHI’, KAZUYUKl IMAMURA2,: AND YASUYOSHI WATANABE?? ‘Med. Res. Inst.. Tokvo Med. and Dent. Univ., Tokvo, 101. %bFemtomole Biorecoznition Proiect. IRDC Osaka 565, %st. of Neurosci.. Osaka Biosci. Inst., Osaka 565, Japan. L-threo-3,4Dlhydroxyphenylserine (L-threo-DOPS) is an exogenous precursor of I-noradrenaline. Our previous study showed that L-threo-DOPS could reduce proportion of binocular cells (Binocularity ~0.4) in aplastic visual cortex of adult cats when monocular deprivation was performed concomitantly with chronic drug administration for one month. It is reported that expression of immediate early genes such as zif 268, cfos and tissue-type plasminogen activator (tPA) may play an important role in activity dependent regulation of neuronal plasticity. In this study, we examined whether L-threo-DOPS changes expression of these genes in the rat visual cortex. Using Northern blot analysis, we found that the expression of zif 268 mRNA was reduced to 5096 of control level within 6 hours after a single administration of L-threo-DOPS (100 mg/kg, i.p.) and benserazide (1 mg/kg, i.p.). No significant decrease in zif mRNA expression was observed in control animals which were injected only with benserazide, a peripheral aromatic amino acid decarboxylase inhibitor. Although c-fos mRNA expression was not detectable in either control animals or L-threo-DOPS injected animals, it was found that Fos like immunoreactivity was significantly decreased in the visual cortex by L-threo-DOPS injection. On the other hand, tPA mRNA expression was increased twice within 6 hours after L-threo-DOPS injection. Taken together with a fact that an infusion of plasminogen activator inhibitor-I partially suppressed ocular dominance plasticity in kitten visual cortex, it is suggested that Lthreo-DOPS may regulate ocular dominance plasticity via tPA gene regulation.