Large-scale multielectrode recording and stimulation of neural activity

Large circuits of neurons are employed by the brain to encode and process information. How this encoding and processing is carried out is one of the central questions in neuroscience. Since individual neurons communicate with each other through electrical signals (action potentials), the recording of neural activity with arrays of extracellular electrodes is uniquely suited for the investigation of this question. Such recordings provide the combination of the best spatial (individual neurons) and temporal (individual action-potentials) resolutions compared to other large-scale imaging methods. Electrical stimulation of neural activity in turn has two very important applications: it enhances our understanding of neural circuits by allowing active interactions with them, and it is a basis for a large variety of neural prosthetic devices. Until recently, the state-of-the-art in neural activity recording systems consisted of several dozen electrodes with inter-electrode spacing ranging from tens to hundreds of microns. Using silicon microstrip detector expertise acquired in the field of high-energy physics, we created a unique neural activity readout and stimulation framework that consists of high-density electrode arrays, multi-channel custom-designed integrated circuits, a data acquisition system, and data-processing software. Using this framework we developed a number of neural readout and stimulation systems: (1) a 512-electrode system for recording the simultaneous activity of as many as hundreds of neurons, (2) a 61-electrode system for electrical stimulation and readout of neural activity in retinas and brain-tissue slices, and (3) a system with telemetry capabilities for recording neural activity in the intact brain of awake, naturally behaving animals. We will report on these systems, their various applications to the field of neurobiology, and novel scientific results obtained with some of them. We will also outline future directions

Large-scale imaging of retinal output activity

A system is being developed to study how the retina processes, encodes and communicates information about the visual world to the brain. It will image the activity of retinal output neurons over a region of live retina approaching that used for significant neural computation in the visual cortex. A prototype system consisting of 61 microelectrodes, covering an area of 0.17 mm(2), is described, including some first results with monkey retina. The plans and status for a system with 512 microelectrodes, covering an area of 1.7 mm(2), are also given

Large-area microelectrode arrays for recording of neural signals

To understand the neural code, that the retina uses to communicate the visual scene to the brain, large-area microelectrode arrays are needed to record retinal signals simultaneously from many recording sites. This will give a valuable insight into how large biological neural networks (such as the brain) process information, and may also be important in the development of a retinal prosthesis as a potential cure for some forms of blindness. We have used the transparent conductor indium tin oxide to fabricated electrode arrays with approximately 500 electrodes spaced at 60 μm. The fabrication procedures include photolithography, electron-beam lithography, chemical etching and reactive-ion etching. These arrays have been tested electrically using impedance measurements over the range of frequencies important when recording extracellular action potentials (0.1-100kHz). The data has been compared to a circuit model of the electrode/electrolyte interface. One type of array (512 electrodes) behaves as theory would dictate and exhibits an impedance of 200 kΩ at 1kHz. The other array (519 electrodes) has an impedance of 350 kΩ at this frequency, which is higher than predicted by the models. This can perhaps be attributed to the difference in fabrication techniques. The 512-electrode array has been coupled to low-noise amplification circuitry and has recorded signals from a variety of retinal tissues. Example in vitro recordings are shown here

What does the eye tell the brain?: Development of a system for the large-scale recording of retinal output activity

A multielectrode array system has been developed to study how the retina processes and encodes visual images. This system can simultaneously record the extracellular electrical activity from hundreds of retinal output neurons as a dynamic visual image is focused on the input neurons. The retinal output signals detected can be correlated with the visual input to study the neural code used by the eye to send information about the visual world to the brain. The system consists of the following components: 1) a 32 16 rectangular array of 512 planar microelectrodes with a sensitive area of 1.7 mm2 ; the electrode spacing is 60 m and the electrode diameter is 5 m (hexagonal arrays with 519 electrodes are under development); 2) eight 64-channel custom-designed integrated circuits to platinize the electrodes and ac couple the signals; 3) eight 64-channel integrated circuits to amplify, band-pass filter, and analog multiplex the signals; 4) a data acquisition system; and 5) data processing software. This paper will describe the design of the system, the experimental and data analysis techniques, and some first results with live retina. The system is based on techniques and expertise acquired in the development of silicon microstrip detectors for high-energy physics experiments

Properties and application of a multichannel integrated circuit for low-artifact, patterned electrical stimulation of neural tissue

Modern multielectrode array (MEA) systems can record the neuronal activity from thousands of electrodes, but their ability to provide spatio-temporal patterns of electrical stimulation is very limited. Furthermore, the stimulus-related artifacts significantly limit the ability to record the neuronal responses to the stimulation. To address these issues, we designed a multichannel integrated circuit for a patterned MEA-based electrical stimulation and evaluated its performance in experiments with isolated mouse and rat retina. The Stimchip includes 64 independent stimulation channels. Each channel comprises an internal digital-to-analogue converter that can be configured as a current or voltage source. The shape of the stimulation waveform is defined independently for each channel by the real-time data stream. In addition, each channel is equipped with circuitry for reduction of the stimulus artifact. Main results. Using a high-density MEA stimulation/recording system, we effectively stimulated individual retinal ganglion cells (RGCs) and recorded the neuronal responses with minimal distortion, even on the stimulating electrodes. We independently stimulated a population of RGCs in rat retina, and using a complex spatio-temporal pattern of electrical stimulation pulses, we replicated visually evoked spiking activity of a subset of these cells with high fidelity. Significance. Compared with current state-of-the-art MEA systems, the Stimchip is able to stimulate neuronal cells with much more complex sequences of electrical pulses and with significantly reduced artifacts. This opens up new possibilities for studies of neuronal responses to electrical stimulation, both in the context of neuroscience research and in the development of neuroprosthetic devices

Fiber optic sensors in the ATLAS Inner Detector

A prototype system of Fiber Optic Sensors (FOS) for the accurate measurement of temperature and relative humidity, has been installed inside the Inner Detector volume of the ATLAS experiment at the LHC. The goal is to evaluate the behavior of the technology against radiation effects, and possibly to assess its suitability for future collider experiments, starting from HL-LHC. It follows the description of the work that has led to the choice of the sensors, their testing and calibration in the laboratory, their successive installation and operation in ATLAS, and the development of the data acquisition chain. The first results on performance are reported

Use of diamond sensors for a high-flux, high-rate X-ray pass-through diagnostic.

X-ray free-electron lasers (XFELs) deliver pulses of coherent X-rays on the femtosecond time scale, with potentially high repetition rates. While XFELs provide high peak intensities, both the intensity and the centroid of the beam fluctuate strongly on a pulse-to-pulse basis, motivating high-rate beam diagnostics that operate over a large dynamic range. The fast drift velocity, low X-ray absorption and high radiation tolerance properties of chemical vapour deposition diamonds make these crystals a promising candidate material for developing a fast (multi-GHz) pass-through diagnostic for the next generation of XFELs. A new approach to the design of a diamond sensor signal path is presented, along with associated characterization studies performed in the XPP endstation of the LINAC Coherent Light Source (LCLS) at SLAC. Qualitative charge collection profiles (collected charge versus time) are presented and compared with those from a commercially available detector. Quantitative results on the charge collection efficiency and signal collection times are presented over a range of approximately four orders of magnitude in the generated electron-hole plasma density

Fiber optic sensors in the ATLAS Inner Detector

A prototype system of Fiber Optic Sensors (FOS) for the accurate measurement of temperature and relative humidity, has been installed inside the Inner Detector volume of the ATLAS experiment at the LHC. The goal is to evaluate the behavior of the technology against radiation effects, and possibly to assess its suitability for future collider experiments, starting from HL-LHC. It follows the description of the work that has led to the choice of the sensors, their testing and calibration in the laboratory, their successive installation and operation in ATLAS, and the development of the data acquisition chain. The first results on performance are reported

The barrel modules of the ATLAS semiconductor tracker

This paper describes the silicon microstrip modules in the barrel section of the SemiConductor Tracker (SCT) of the ATLAS experiment at the CERN Large Hadron Collider (LHC). The module requirements, components and assembly techniques are given, as well as first results of the module performance on the fully assembled barrels that make up the detector being installed in the ATLAS experiment

Design and performance of the ABCD3TA ASIC for readout of silicon strip detectors in the ATLAS semiconductor tracker

The ABCD3TA is a 128-channel ASIC with binary architecture for the readout of silicon strip particle detectors in the Semiconductor Tracker of the ATLAS experiment at the Large Hadron Collider (LHC). The chip comprises fast front-end and amplitude discriminator circuits using bipolar devices, a binary pipeline for first level trigger latency, a second level derandomising buffer and data compression circuitry based on CMOS devices. It has been designed and fabricated in a BiCMOS radiation resistant process. Extensive testing of the ABCD3TA chips assembled into detector modules show that the design meets the specifications and maintains the required performance after irradiation up to a total ionising dose of 10 Mrad and a 1-MeV neutron equivalent fluence of 2×1014 n/cm2, corresponding to 10 years of operation of the LHC at its design luminosity. Wafer screening and quality assurance procedures have been developed and implemented in large volume production to ensure that the chips assembled into modules meet the rigorous acceptance criteria.</p