Microdevices for studies of cultured neural networks

A cultured network has the advantages that the network is two-dimensional and easily observed, that the biochemical environment can be controlled, and that conventional electrodes as well as extracellular electrodes incorporated into the cultured substrate can be used to selectively stimulate and record from individual neurons in the network. It is possible to study small numbers of connected neurons, from a few to hundreds. This talk will describe two techniques, the multielectrode array and the silicon neurochip, and their application to long-term communication with a network by means of simultaneous recording or stimulation of many neurons

Moving live dissociated neurons with an optical tweezer

The use of an optical tweezer for moving dissociated neurons was studied. The main features of the tweezers are outlined as well as the general principles of its operation. Infrared beams at 980 and 1064 nm were used, focused so as to make a trap for holding neurons and moving them. Absorption by cells at those wavelengths is very small. Experiments were done to evaluate nonsticky substrate coatings, from which neurons could be easily lifted with the tweezers. The maximum speed of cell movement as a function of laser power was determined. Detailed studies of the damage to cells as a function of beam intensity and time of exposure were made. The 980 nm beam was much less destructive, for reasons that are not understood, and could be used to safely move cells through distances of millimeters in times of seconds. An illustrative application of the use of the tweezers to load neurons without damage into plastic cages on a glass substrate was presented. The conclusion is that optical tweezers are an accessible and practical tool for helping to establish neuron cultures of cells placed in specific locations

A long-term in vitro silicon-based microelectrode-neuron connection

A novel method for long-term recording and simulation applicable to cultured neurons has been developed. Silicon-based microelectrodes have been fabricated using integrated-circuit technology and micromachining. The chronic connection is made by positioning the tip of the `diving-board electrode' into contact with the top of the cell body. The electrode support structure is then glued to the bottom of the culture dish. Two-way electrical connections to Helisoma B19 neurons have been maintained for up to four days. This capability makes it possible to conduct experiments that are not practical using conventional techniques

The concept of God and man in Augustine, Aquinas, and Maimonides

Thesis (M.A.)--Boston University, 196

Interview with Jerome Pine

An interview in four sessions, October-November 2001, with Jerome Pine, neuroscientist and physics professor in the Division of Physics, Mathematics, and Astronomy. Recalls graduate school at Cornell (MS with Philip Morrison, PhD, 1956, with Kenneth Greisen); instructorship 1956-62 at Stanford Linear Accelerator Center; arrival at Caltech as associate professor in 1963. Member of Caltech high-energy physics user group at SLAC and Fermilab; early involvement in science education; takes up neuroscience; 1978-79 sabbatical, Washington University Medical School with W. Maxwell Cowan; neurobiology workshop, Woods Hole, summer 1978; summer course with John Nicholls, Cold Spring Harbor, 1979; invents multi-electrode device to record action potentials from cultured neurons; sets up Pinelab; prevalence of physicists in neurobiology. Recalls graduate students; discusses his neurobiology course. 1987-88 sabbatical in U.K. at Medical Research Council Laboratory with Dennis Bray and Kings College-Chelsea on science assessment in schools; NSF grant to study science assessment in elementary schools. Works on elementary-school science education with James M. Bower in Pasadena school district; with Bower and Jennifer Yuré, visits Mesa, AZ, school district. Pilot program, Field School, later expansion; partnership with Apple; establishment of Project SEED (Science for Early Educational Development). Involvement of Georges Charpak; program in France. Establishment of CAPSI (Caltech Precollege Science Initiative); developing content modules for teacher education; grant from NSF Centers for Teacher Enhancement. His innovations in Caltech undergraduate physics; two-track Physics 1 course; take-home physics kits. Freshman seminars; teaching atomic physics to juniors. Caltech’s lack of interest in CAPSI; CAPSI’s research division; Caltech’s promotion of student diversity; Lee Browne’s minority-students program. Concludes by discussing spread of his science-education programs to Colombia, Estonia, and Sweden

An extremely rich repertoire of bursting patterns during the development of cortical cultures

BACKGROUND: We have collected a comprehensive set of multi-unit data on dissociated cortical cultures. Previous studies of the development of the electrical activity of dissociated cultures of cortical neurons each focused on limited aspects of its dynamics, and were often based on small numbers of observed cultures. We followed 58 cultures of different densities – 3000 to 50,000 neurons on areas of 30 to 75 mm(2 )– growing on multi-electrode arrays (MEAs) during the first five weeks of their development. RESULTS: Plating density had a profound effect on development. While the aggregate spike detection rate scaled linearly with density, as expected from the number of cells in proximity to electrodes, dense cultures started to exhibit bursting behavior earlier in development than sparser cultures. Analysis of responses to electrical stimulation suggests that axonal outgrowth likewise occurred faster in dense cultures. After two weeks, the network activity was dominated by population bursts in most cultures. In contrast to previous reports, development continued with changing burst patterns throughout the observation period. Burst patterns were extremely varied, with inter-burst intervals between 1 and 300 s, different amounts of temporal clustering of bursts, and different firing rate profiles during bursts. During certain stages of development bursts were organized into tight clusters with highly conserved internal structure. CONCLUSION: Dissociated cultures of cortical cells exhibited a much richer repertoire of activity patterns than previously reported. Except for the very sparsest cultures, all cultures exhibited globally synchronized bursts, but bursting patterns changed over the course of development, and varied considerably between preparations. This emphasizes the importance of using multiple preparations – not just multiple cultures from one preparation – in any study involving neuronal cultures. These results are based on 963 half-hour-long recordings. To encourage further investigation of the rich range of behaviors exhibited by cortical cells in vitro, we are making the data available to other researchers, together with Matlab code to facilitate access

Neural Transplant Staining with DiI and Vital Imaging by 2-Photon Laser-Scanning Microscopy

We are developing a multielectrode silicon neuroprobe for maintaining a long-term, specific, two-way electrical interface with nervous tissue. Our approach involves trapping a neuron (from an embryonic rat hippocampus) in a small well with a stimulation/ recording electrode at its base. The well is covered with a grillwork through which the neuron\u27s processes are allowed to grow, making synaptic contact with the host tissue, in our case a cultured slice from a rat hippocampus. Each neuroprobe can accommodate 15 neurons, one per well. As a first step in studying neurite outgrowth from the neuroprobe, it was necessary to develop new staining techniques so that neurites from the probe neurons can be distinguished from those belonging to the host, without interference from non-specific background staining. We virtually eliminated background staining through a number of innovations involving dye solubility, cell washing, and debris removal. We also reduced photobleaching and phototoxicity, and enhanced imaging depth by using a 2-photon laser-scanning microscope. We focused on using the popular membrane dye, DiI, however a number of other membrane dyes were shown to provide clear images of neural processes using pulsed illumination at 900 nm. These techniques will be useful to others wishing to follow over time the growth of neurons in culture or after transplantation in vivo, in a non-destructive way

Scattering of 200-Mev positrons by electrons

Scattering of positrons by electrons has been investigated by bombarding a beryllium target with 200-Mev positrons and observing the recoil electrons in a diffusion cloud chamber located behind the target. The cloud chamber was in a magnetic field which permitted the yield of recoil electrons to be measured as a function of their energy W. The experiment covered the range 88<~W<~200 Mev. The positron beam also traversed the cloud chamber and the total number of incident positrons was determined by track-counting. The total electron yield for 88<~W<~200 Mev is (113±9)% below that predicted by the first-order Bhabha theory. This difference cannot be interpreted until radiative corrections to the theory have been evaluated. A calculation of these corrections which is valid for the conditions of this experiment is not available. The shape of the electron energy spectrum is in good agreement with the Bhabha theory, and inconsistent with the theory if annihilation terms are omitted