Recently, various methods have emerged for sub-Nyquist sampling and reconstruction of signals with finite rate of innovation (FRI). These methods seek to sample parametric signals at close to their information rate and later reconstruct the parameters of interest. Some proposed reconstruction algorithms are based on annihilating filters and root-finding.Stochastic methods based on Gibbs sampling were subsequently proposed with the intent of improving robustness to noise, but these may run too slowly for some real-time applications. We present a fast maximum-likelihood-based deterministic greedy algorithm, IterML, for reconstructing FRI signals from noisy samples. We show in simulation that it achieves comparable or better performance than previous algorithms at a much lower computational cost. We also uncover a fundamental flaw in the application of MMSE (minimum mean squared error) estimation, a technique employed by some existing methods, to the problem in question.

He BD, Wein A, Varshney LR, Kusuma J, Richardson AG, Srinivasan L. Generalized analog thresholding for spike acquisition at ultralow sampling rates.

Various recursive Bayesian filters based on reach state equations (RSE) have been proposed to convert neural signals into reaching movements in brain-machine interfaces. When the target is known, RSE produce exquisitely smooth trajectories relative to the random walk prior in the basic Kalman filter. More realistically, the target is unknown, and gaze analysis or other side information is expected to provide a discrete set of potential targets. In anticipation of this scenario, various groups have implemented RSE-based mixture (hybrid) models, which define a discrete random variable to represent target identity. While principled, this approach sacrifices the smoothness of RSE with known targets. This paper combines empirical spiking data from primary motor cortex and mathematical analysis to explain this loss in performance. We focus on angular velocity as a meaningful and convenient measure of smoothness. Our results demonstrate that angular velocity in the trajectory is approximately proportional to change in target probability. The constant of proportionality equals the difference in heading between parallel filters from the two most probable targets, suggesting a smoothness benefit to more narrowly spaced targets. Simulation confirms that measures to smooth the data likelihood also improve the smoothness of hybrid trajectories, including increased ensemble size and uniformity in preferred directions. We speculate that closed-loop training or neuronal subset selection could be used to shape the user's tuning curves towards this end.

Acting as sentinels capable of quickly organizing a secondary immune response upon pathogen challenge, resident memory CD8 T (TRM) populations are initially primed by microenvironment cues and APC licensing following acute infection of peripheral tissues. Despite their capacity for heterologous protection against influenza virus (flu) challenge, scant knowledge exists as to factors necessary to establish and maintain airway and lung parenchymal (LP) CD8 TRM cells. In contrast to mechanisms described for other tissues, lung CD8 TRM cell establishment required cognate antigen recognition once cells were recruited to the lung by local inflammation. Furthermore, this combination of local antigen and inflammation formed long-lasting TRM populations in the LP and airways that highly express the chemokine receptor CXCR6 and adhesion molecule CD49a. During a primary intranasal (IN) flu infection, CXCR6 is preferentially expressed on virus-specific CD8 T cells in the airways and LP by day 7 post-infection. Selectively, LP CD8 TRM cells highly express CXCR6, while systemically circulating flu-specific cells achieve only an intermediate expression level. Finally, use of mixed bone marrow chimeras show that wild-type virus-specific memory CD8 T cells predominate over CXCR6-/- cells in the airway and LP after IN infection with Sendai or flu virus. Thus, our data show that local antigen and inflammation coupled with CXCR6 expression is key to establish CD8 TRM cells in the LP and airways.