Working Memory Cells' Behavior May Be Explained by Cross-Regional Networks with Synaptic Facilitation

Neurons in the cortex exhibit a number of patterns that correlate with working memory. Specifically, averaged across trials of working memory tasks, neurons exhibit different firing rate patterns during the delay of those tasks. These patterns include: 1) persistent fixed-frequency elevated rates above baseline, 2) elevated rates that decay throughout the tasks memory period, 3) rates that accelerate throughout the delay, and 4) patterns of inhibited firing (below baseline) analogous to each of the preceding excitatory patterns. Persistent elevated rate patterns are believed to be the neural correlate of working memory retention and preparation for execution of behavioral/motor responses as required in working memory tasks. Models have proposed that such activity corresponds to stable attractors in cortical neural networks with fixed synaptic weights. However, the variability in patterned behavior and the firing statistics of real neurons across the entire range of those behaviors across and within trials of working memory tasks are typical not reproduced. Here we examine the effect of dynamic synapses and network architectures with multiple cortical areas on the states and dynamics of working memory networks. The analysis indicates that the multiple pattern types exhibited by cells in working memory networks are inherent in networks with dynamic synapses, and that the variability and firing statistics in such networks with distributed architectures agree with that observed in the cortex

Leukocyte telomere length is associated with measures of subclinical atherosclerosis

Aims: Our aim was to test the association of mean leukocyte telomere length (LTL) with ultrasonic measures of subclinical atherosclerosis such as intima-media thickness in the common carotid (IMTcc) and sum of plaque areas (SPA) and with serological markers. Methods and results: Carotid and femoral bifurcations were scanned in 762 general population volunteers (46% men) over 40. Four features were considered: (a) IMTcc, (b) sum plaque areas of carotid plaques (SPAcar), (c) sum plaque area of common femoral plaques (SPAfem) and (d) sum plaque area (SPA - sum of the plaque areas of the largest plaques present in each of both carotid and femoral bifurcations). Mean LTL was determined with a quantitative real-time PCR-based method. IMTcc was strongly associated with mean LTL both before and after correction for traditional risk factors (B = -0.002; 95% CI = -0.004 to -0.00; p=0.014). In sex-specific analysis, the association was stronger in men (p for sex interaction < 0.001). SPAfem was associated with LTL in women before and after correction (B = -0.195; 95% CI = -0.38 to -0.01; p=0.037) (p for sex interaction < 0.001). LTL was also associated with age and sex-adjusted levels of hsCRP (p=0.012), sCD40L (p=0.042), homocysteine (p=0.006), creatinine (p=0.02), ApoA1 (p=0.01), Lp(a) (p=0.04) and HOMA-IR (p=0.008). Conclusions: Our results support the telomere hypothesis and highlight potential differences in the biological mechanisms leading to intima-media thickening and/or plaque formation between vascular beds. They may provide insights into a novel treatment of antisenescence to prevent atherosclerosis

Supervisory control of DC-DC bidirectional converter for advanced aeronautic applications

In this paper, a sliding manifold-based control strategy is used for controlling a bidirectional DC-DC converter for aeronautic applications. The proposed design follows a 2-level strategy, where low-level controllers are designed first, then a high-level supervisor is used for scheduling the low-level controllers. Different from previous approaches, each of the low-level controlled system is a globally exponentially stable closed-loop system, thus resulting into simpler conditions for the stability of the overall system. Moreover, stability of the supervisory strategy is rigorously proved by using a suitable Lyapunov function. Finally, a switching implementation is also considered. The effectiveness and robustness of the proposed strategy is shown by detailed simulations in Matlab/Stateflow/SymPowerSystem