Effects of noise from functional magnetic resonance imaging on auditory event-related potentials in working memory task

The effects of functional magnetic resonance imaging (fMRI) acoustic noise were investigated on the parameters of event-related responses (ERPs) elicited during auditory matching-to-sample location and pitch working memory tasks. Stimuli were tones with varying location (left or right) and frequency (high or low). Subjects were instructed to memorize and compare either the locations or frequencies of the stimuli with each other. Tape-recorded fMRI acoustic noise was presented in half of the experimental blocks. The fMRI noise considerably enhanced the P1 component, reduced the amplitude and increased the latency of the N1, shortened the latency of the N2, and enhanced the amplitude of the P3 in both tasks. The N1 amplitude was higher in the location than pitch task in both noise and no-noise blocks, whereas the task-related N1 latency difference was present in the no-noise blocks only. Although the task-related differences between spatial and nonspatial auditory responses were partially preserved in noise, the finding that the acoustic gradient noise accompanying functional MR imaging modulated the auditory ERPs implies that the noise may confound the results of auditory fMRI experiments especially when studying higher cognitive processing.     

Cervical transforaminal injection of corticosteroids into a radicular artery: a possible mechanism for spinal cord injury

Spinal cord injury has been recognized as a complication of cervical transforaminal injections, but the mechanism of injury is uncertain. In the course of a transforaminal injection, an observation was made after the initial injection of contrast medium. The contrast medium filled a radicular artery that passed to the spinal cord. The procedure was summarily abandoned, and the patient suffered no ill effects. This case demonstrates that despite using careful and accurate technique, it is possible for material to be injected into a radicular artery. Consequently, inadvertent injection of corticosteroids into a radicular artery may be the mechanism for spinal cord injury following transforaminal injections. This observation warns operators to always perform a test injection of contrast medium, and carefully check for arterial filling using real-time fluoroscopy with digital subtraction.     

Decremental Pulmonary Venous Pulse Propagation: Impact for Catheter Ablation in Focal Atrial Fibrillation

Background: Electrical isolation of pulmonary veins (PV's) is crucial to achieve success in catheter ablation for trigger elimination in focal atrial fibrillation (AF). To guide ostial PV radiofrequency (RF) delivery, it is necessary to identify the electrical breakthrough (EBT) between PV and left atrium. For this purpose, coronary sinus (CS) fixed rate pacing is commonly used. This study evaluated, whether CS extrastimulus pacing is superior in identifying the EBT area as compared to fixed rate pacing. Methods: In 9 patients (51 ± 10 years) undergoing a left sided electrophysiological study for AF ablation, 25 PV's (10 right and 15 left-sided PV's) were mapped using a 4 French fixed-wire catheter with eight 6 mm coiled Platinum electrodes in a distal looped configuration (Revelation Helix, Cardima Inc.). For mapping and ablation the electrode loop was positioned in the PV ostium rectangular to the longitudinal PV axis. EBT area was identified as those electrodes indicating the earliest PV signals during CS pacing. We measured number of EBT electrodes and time between EBT and the latest activated bipoles at the electrode loop during fixed rate and extrastimulus pacing. The reduction of two or more EBT electrodes was defined as a significant benefit in EBT identification. Results: In 22 of 25 PV's mapped PV potentials could be observed. Performing fixed rate pacing the EBT area was identified in a mean of 4.2 ± 1 electrodes, whereas using extrastimulus pacing, EBT area could be significantly reduced to 2.3 ± 0.8 electrodes. The time between EBT and latest electrode activated increased from 14 ± 7 ms to 22 ± 10 ms indicating an intrapulmonary conduction delay during extrastimulus pacing. In 13 of 22 PV's mapped (59%), extrastimulus pacing was beneficial in the identification of the EBT, as the primary target for RF delivery. Conclusions: CS extrastimulus pacing induces intra-PV decremental conduction properties allowing one to identify a more localised and smaller EBT area as the primary target for RF delivery. Performing PV ablation to treat focal AF, extrastimulus maneouvers allow to unmask the true EBT and thus may help to limit intrapulmonary RF delivery.     

Spike sequences and mean firing rate in rat neocortical neurons in vitro

Properties of neuronal discharges and their interrelationship with mean evoked firing rate (MF) were investigated in detail in the rat somatosensory cortex in vitro. Firing was evoked by 1-min depolarizing current injection (0.1-1.0 nA) into pyramidal neurons (n=93) of layers II/III and V. Spike sequence patterns (SSPs) with consecutive increasing or decreasing interspike intervals were analyzed. SSP rate (change of pattern, 2-50 min(-1)) and the deviations of afterhyperpolarizing potentials (up to 1.5 mV) associated with the SSPs were significantly correlated with MF. The number of transitions in spike frequency was dependent on the MF and showed a biphasic interrelation with a reversible point at 5-8 Hz. All neurons analysed were subdivided into two groups: with depolarizing potential after single spike and without such afterdepolarizing potential. It was found that despite significant differences in electrophysiological properties of the cells from these groups, similar dependency in patterns of their discharges upon MF was observed. A possible role of spike sequence patterns in neocortical rhythmical processes is discussed.     

Quantitative analysis of human immunoregulatory cytokines by electrochemiluminescence method

Quantitative analysis of human immunoregulatory cytokines in physiological media and cell cultures plays an important role in fundamental and clinical research. Here we describe the quantification of interleukin (IL)-2, IL-4, IL-10 and interferon-gamma (IFN-gamma) in human serum and peripheral blood mononuclear cell (PBMC)-conditioned medium by electrochemiluminescence method (ECL). We demonstrate that this approach allows to detect cytokine concentration from 1 pg/ml. The high sensitivity in combination with accuracy and wide range of determined concentration indicates that ECL meets the standards of quantitative analysis of cytokines. Simplicity and short time of procedure, small assay volume and high reproducibility make ECL method competitive in practical use with conventional quantitative methods of cytokine detection.