Journal of neuroscience methods
-
J. Neurosci. Methods · Aug 2007
Determination of cerebrospinal fluid concentrations of arginine and dimethylarginines in patients with subarachnoid haemorrhage.
Elevated cerebrospinal fluid (CSF) concentrations of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase (NOS), are assumed to be related to delayed vasospasm after subarachnoid haemorrhage (SAH). However, data on CSF concentrations of L-arginine, ADMA and its structural isomer symmetric dimethylarginine (SDMA) are very sparse in humans. ⋯ First data of patients with SAH showed that on the day of admission CSF concentration values of L-arginine and ADMA were not significantly different from controls, but increased markedly during the course of the hospital stay. The decrease of the L-arginine to ADMA ratio points to a progressive impairment of the NO production rate in the brain after SAH which is confirmed by a simultaneous decrease in nitrate and nitrite concentrations in CSF.
-
J. Neurosci. Methods · Aug 2007
A CMOS-based microelectrode array for interaction with neuronal cultures.
We report on the system integration of a CMOS chip that is capable of bidirectionally communicating (stimulation and recording) with electrogenic cells such as neurons or cardiomyocytes and that is targeted at investigating electrical signal propagation within cellular networks in vitro. The overall system consists of three major subunits: first, the core component is a 6.5 mm x 6.5 mm CMOS chip, on top of which the cells are cultured. It features 128 bidirectional electrodes, each equipped with dedicated analog filters and amplification stages and a stimulation buffer. ⋯ The response patterns have been successfully classified (83% correct) with respect to the different stimulation patterns. The advantages over current microelectrode arrays, as has been demonstrated in the experiments, include the capability to stimulate (voltage stimulation, 8 bit, 60 kHz) spatio-temporal patterns on arbitrary sets of electrodes and the fast stimulation reset mechanism that allows to record neuronal signals on a stimulating electrode 5 ms after stimulation (instantaneously on all other electrodes). Other advantages of the overall system include the small number of needed electrical connections due to the digital interface and the short latency time that allows to initiate a stimulation less than 2 ms after the detection of an action potential in closed-loop configurations.
-
J. Neurosci. Methods · Jul 2007
Quantifying the isolation quality of extracellularly recorded action potentials.
There have been many approaches to the problem of detection and sorting of extra-cellularly recorded action potentials, but only a few methods actually quantify the quality of this fundamental process. In most cases, the quality assessment is based on the subjective judgment of human observers and the recorded units are divided into "well isolated" or "multi-unit" groups. This subjective evaluation precludes comprehensive assessment of single-unit studies since the most basic parameter, i.e. their data quality, is not explicitly defined. ⋯ To validate these quality measures, we simulate spike detection and sorting errors and show that the scores are good predictors of the frequency of errors. The reliability of the isolation score is further verified by errors implanted in real basal ganglia data and by using different sorting algorithms. We conclude that quantitative measures of spike isolation can be obtained independently of the method used for spike detection and sorting, and recommend their reports in any study based on the activity of single neurons.
-
J. Neurosci. Methods · Jun 2007
Pressure application measurement (PAM): a novel behavioural technique for measuring hypersensitivity in a rat model of joint pain.
Chronic joint pain affects physical well being and can lead to severe psychological and social problems, therefore successful long-term management is highly sought-after. No current behavioural measures of pain used in pre-clinical models mimic the clinical dolorimeter, which provides an objective measure of joint hypersensitivity. In this study we aim to use a novel behavioural readout alongside an established measure to mimic the multifactorial measurements taken in the clinic. ⋯ Both PAM and the incapacitance tester detected a reversal of hypersensitivity 1h post-drug administration. Furthermore, the two readouts were highly correlated, and power analysis indicated that PAM was highly reproducible. In conclusion, PAM provides a novel, accurate behavioural tool for detecting a primary mechanical hypersensitivity in a rat model of chronic inflammatory joint pain.
-
J. Neurosci. Methods · Jun 2007
A simple method for efficient spike detection in multiunit recordings.
A number of spike detection and sorting methods exist and the availability of powerful desktop computers may suggest that the problem of spike detection is solved. However, for portable multi-channel systems, when one takes into account the power consumption limitations, computationally simple methods can be advantageous when compared to more complex algorithms. ⋯ The proposed algorithm can be employed in an analog electronic chip thus eliminating the need for the digitization of the original signal. Consequently, only the times of spike occurrence can be transmitted for further analysis.