Incorporating Prediction in Models for Two-Dimensional Smooth Pursuit

A predictive component can contribute to the command signal for smooth pursuit. This is readily demonstrated by the fact that low frequency sinusoidal target motion can be tracked with zero time delay or even with a small lead. The objective of this study was to characterize the predictive contributions to pursuit tracking more precisely by developing analytical models for predictive smooth pursuit. Subjects tracked a small target moving in two dimensions. In the simplest case, the periodic target motion was composed of the sums of two sinusoidal motions (SS), along both the horizontal and the vertical axes. Motions following the same or similar paths, but having a richer spectral composition, were produced by having the target follow the same path but at a constant speed (CS), and by combining the horizontal SS velocity with the vertical CS velocity and vice versa. Several different quantitative models were evaluated. The predictive contribution to the eye tracking command signal could be modeled as a low-pass filtered target acceleration signal with a time delay. This predictive signal, when combined with retinal image velocity at the same time delay, as in classical models for the initiation of pursuit, gave a good fit to the data. The weighting of the predictive acceleration component was different in different experimental conditions, being largest when target motion was simplest, following the SS velocity profiles

Reinserting physiology into cardiac mapping using omnipolar electrograms

Unipolar electrograms are voltage signals that reflect time-varying extracellular currents. Bipolar electrograms provide differential extracellular voltages along an axis and resemble a local directional derivative. Both are based on the fundamental concept of electric fields in tissues. Omnipolar electrograms are derived from a clique, a group of nearby electrodes that generate bipolar signals from multiple directions. They are electrode and catheter-orientation independent. • Omnipolar electrograms provide wavefront characteristics, such as amplitude, timing, direction, and speed, in physiologically relevant directions located at the center of the electrode clique. This enables determinations of a maximal bipolar voltage amplitude termed OT Vmax, the generalization of peak-to-peak in the presence of directionality, and is not affected by catheter orientation and is less sensitive to electrode distance for small cliques. • Specialized catheters and three-dimensional mapping system software enable omnipolar electrograms and derived quantities to be generated and displayed in real-time. • Omnipolar electrograms during atrial fibrillation are significantly less influenced by directional factors, allowing for robust and consistent substrate assessment. • Mapping the ventricles using an equispaced electrode grid catheter and omnipolar electrograms can provide reliable substrate assessment within infarcted and noninfarcted regions of the ventricles to aid in determining ablation targets, such as a lesion gap or an isthmus

Physiological assessment of ventricular myocardial voltage using omnipolar electrograms

Background Characterization of myocardial health by bipolar electrograms are critical for ventricular tachycardia therapy. Dependence of bipolar electrograms on electrode orientation may reduce reliability of voltage assessment along the plane of arrhythmic myocardial substrate. Hence, we sought to evaluate voltage assessment from orientation‐independent omnipolar electrograms. Methods and Results We mapped the ventricular epicardium of 5 isolated hearts from each species—healthy rabbits, healthy pigs, and diseased humans—under paced conditions. We derived bipolar electrograms and voltage peak‐to‐peak (Vpps) along 2 bipolar electrode orientations (horizontal and vertical). We derived omnipolar electrograms and Vpps using omnipolar electrogram methodology. Voltage maps were created for both bipoles and omnipole. Electrode orientation affects the bipolar voltage map with an average absolute difference between horizontal and vertical of 0.25±0.18 mV in humans. Vpps provide larger absolute values than horizontal and vertical bipolar Vpps by 1.6 and 1.4 mV, respectively, in humans. Bipolar electrograms with the largest Vpps from either along horizontal or vertical orientation are highly correlated with omnipolar electrograms and with Vpps values (0.97±0.08 and 0.94±0.08, respectively). Vpps values are more consistent than bipoles, in both beat‐by‐beat (CoV, 0.28±0.19 versus 0.08±0.13 in human hearts) and rhythm changes (0.55±0.21 versus 0.40±0.20 in porcine hearts). Conclusions Omnipoles provide physiologically relevant and consistent voltages that are along the maximal bipolar direction on the plane of the myocardium

Plasma fibronectin supports neuronal survival and reduces brain injury following transient focal cerebral ischemia but is not essential for skin-wound healing and hemostasis.

Fibronectin performs essential roles in embryonic development and is prominently expressed during tissue repair. Two forms of fibronectin have been Identified: plasma fibronectin (pFn), which Is expressed by hepatocytes and secreted In soluble form into plasma; and cellular fibronectin (cFn), an insoluble form expressed locally by fibroblasts and other cell types and deposited and assembled into the extracellular matrix. To investigate the role of pFn in vivo, we generated pfn-deficient adult mice using Cre-loxP conditional gene-knockout technology. Here we show that pfn-deficient mice show increased neuronal apoptosis and larger Infarction areas following transient focal cerebral ischemia. However, pFn is dispensable for skin-wound healing and hemostasis