Abdul-Karim et al. IEEE Trans. Image Processing MS Word XP 1 Automatic Selection of Parameters for Vessel/Neurite Segmentation Algorithms

Abstract — An automated method is presented for selecting optimal parameter settings for vessel/neurite segmentation algorithms using the minimum description length principle and a recursive random search algorithm. It trades off a probabilistic measure of image-content coverage, against its conciseness. It enables non-expert users to select parameter settings objectively, without knowledge of underlying algorithms, broadening the applicability of the segmentation algorithm, and delivering higher morphometric accuracy. It enables adaptation of parameters across batches of images. It simplifies the user interface to just one optional parameter, and reduces the cost of technical support. Finally, the method is modular, extensible, and amenable to parallel computation. The method is applied to 223 images of human retinas and cultured neurons, from four different sources, using a single segmentation algorithm with 8 parameters. Improvements in segmentation quality compared to default settings using 1000 iterations ranged from 4.7 – 21%. Paired t-tests showed that improvements are statistically significant (p < 0.0005). Most of the improvement occurred in the first 44 iterations. Improvements in descriptio

Optical Monitoring of Neural Network Connectivity Using FM1-43-Evoked Activity from Focal Stimulation of Microelectrode Arrays

This work was supported by the International Collaboration Program NBS-ERC/KOSEF (S.J.K) and by the National Institute of Biomedical Imaging and Bioengineering under Agreement Number R21-EB007782 (M.R.H)

Synaptic Connectivity of a Low Density Patterned Neuronal Network Produced on the Poly-L-Lysine Stamped Microelectrode Array

Rectangular networks of rat hippocampal neurons have been produced on microelectrode arrays (MEAs). The crossing points of networks were located at the recording electrode sites by aligned microcontact printing (muCP) technique. Polydimethysiloxane (PDMS) stamp was fabricated to print fine poly-L-lysine (PLL) patterns of 2 mum-width lines for neurites and 20 mum-diameter circles for cell bodies. Different densities of neurons were applied on the PLL-stamped MEAs to find how a low density of neurons still has the functional connectivity. From the neural network applied with a density of 200 cells/mm2 , we could observe signal propagation among spontaneous activities. Electrical responses were also evoked by 200 muA current pulse stimulation with 50 mus pulse width. Immunocytostaining was employed to identify dendrites, synapses, and nuclei in the patterned neurons.This work was supported by the International Collaboration Program, NBS-ERC(Nano Bioelectronics and Systems Research Center)/KOSEF(Korea Science and Engineering Foundation) and NIH, NS-044287, NSF, ECS-9876771

Identification of synaptic activities in microelectrode array-based neural networks

The Microelectrode Arrays (MEAs) have been used for several decades to investigate neuronal networks in vitro. In most of the studies, the neuronal networks have been studied statistically due to complexity of cultured neuronal networks. However, in order to understand the behaviours of neuronal networks dynamically, the identification of synaptic activities of individual neurons is crucial. In this study, we observed individual synaptic activities by utilizing low density neuronal networks arranged orthogonally on MEAs.This work was supported by the International Collaboration Program, NBS-ERC (Nano Bioelectronics and Systems Engineering Research Center)/ KOSEF (Korea Science and Engineering Foundation) and NIH, NS-044287, NSF, ECS-9876771

Modulation of Cultured Neural Networks Using Neurotrophin Release

Polyacrylamide and poly(ethylene glycol) diacrylate hydrogels were synthesized and characterized for use as drug release and substrates for neuron cell culture. Protein release kinetics was determined by incorporating bovine serum albumin (BSA) into hydrogels during polymerization. To determine if hydrogel incorporation and release affect bioactivity, alkaline phosphatase was incorporated into hydrogels and a released enzyme activity determined using the fluorescence-based ELF-97 assay. Hydrogels were then used to deliver a brain-derived neurotrophic factor (BDNF) from hydrogels polymerized over planar microelectrode arrays (MEAs). Primary hippocampal neurons were cultured on both control and neurotrophin-containing hydrogel-coated MEAs. The effect of released BDNF on neurite length and process arborization was investigated using automated image analysis. An increased spontaneous activity as a response to the released BDNF was recorded from the neurons cultured on the top of hydrogel layers. These results demonstrate that proteins of biological interest can be incorporated into hydrogels to modulate development and function of cultured neural networks. These results also set the stage for development of hydrogel-coated neural prosthetic devices for local delivery of various biologically active molecules.This work was supported by the International Collaboration Program, Nano Bioelectronics and Systems Engineering Research Center/Korea Science and Engineering Foundation (R11-2000-075-00002-0), by the Nanobiotechnology Center (NBTC), an STC Program of the National Science Foundation under agreement no. ECS-9876771, the National Institutes of Health under agreement no. R01-NS044287 (WS) and by the National Institute of Biomedical Imaging and Bioengineering under agreement no. R21EB007782 (MRH). The computational image analysiswas supported by the Center for Subsurface Sensing and Imaging Systems (NSF EEC- 9986821). The authors acknowledge use of the Wadsworth Center Advanced Light Microscopy & Image Analysis Core Facility. They would also like to thank Shirley Madewell and Adriana Verschoor for critical review of the manuscript

Low-density neuronal networks cultured using patterned poly-l-lysine on microelectrode arrays

Synaptic activity recorded from low-density networks of cultured rat hippocampal neurons was monitored using microelectrode arrays (MEAs). Neuronal networks were patterned with poly-l-lysine (PLL) using microcontact printing ( CP). Polydimethysiloxane (PDMS) stamps were fabricated with relief structures resulting in patterns of 2 m-wide lines for directing process growth and 20 m-diameter circles for cell soma attachment. These circles were aligned to electrode sites. Different densities of neurons were plated in order to assess the minimal neuron density required for development of an active network. Spontaneous activity was observed at 10–14 days in networks using neuron densities as low as 200 cells/mm2. Immunocytochemistry demonstrated the distribution of dendrites along the lines and the location of foci of the presynaptic protein, synaptophysin, on neuron somas and dendrites. Scanning electron microscopy demonstrated that single fluorescent tracks contained multiple processes. Evoked responses of selected portions of the networks were produced by stimulation of specific electrode sites. In addition, the neuronal excitability of the network was increased by the bath application of high K+ (10–12 mM). Application of DNQX, an AMPA antagonist, blocked all spontaneous activity, suggesting that the activity is excitatory and mediated through glutamate receptors.This work was supported by the International Collaboration Program, NBS-ERC (Nano Bioelectronics and Systems Engineering Research Center)/KOSEF(Korea Science and Engineering Foundation) and NIH, R01NS-044287, NSF, ECS-9876771. Authors also appreciate help from T.H. Lee and J.K. Lee for assistance in the fabrication of MEAs and stamp masters