SUMMARY Responses of neurons in early visual cortex change little with training, and appear insufficient to account for perceptual learning. Behavioral performance, however, relies on population activity, and the accuracy of a population code is constrained by correlated noise among neurons. We tested whether training changes interneuronal correlations in the dorsal medial superior temporal area, which is involved in multisensory heading perception. Pairs of single units were recorded simultaneously in two groups of subjects: animals trained extensively in a heading discrimination task, and “naïve” animals that performed a passive fixation task. Correlated noise was significantly weaker in trained versus naïve animals, which might be expected to improve coding efficiency. However, we show that the observed uniform reduction in noise correlations leads to little change in population coding efficiency when all neurons are decoded. Thus, global changes in correlated noise among sensory neurons may be insufficient to account for perceptual learning.

Experimental and numerical results concerning solid particle motion in a plane wake are presented that demonstrate the importance of large-scale vortex structures in self-organizing dispersion processes. Previous studies have demonstrated that a time scale ratio involving the aerodynamic response time of the particles and a characteristic time of the vortex structures is an important parameter for indicating the qualitative and quantitative nature of the dispersion process. A stretching and folding mechanism associated with vortex development and merging interactions has been suggested as a description for characterizing particle dispersion in plane mixing layers at intermediate time scale ratios. For plane wakes where large-scale vortex mergers rarely occur, a highly organized particle dispersion process focuses intermediate time scale ratio particles along the boundaries of the large-scale vortices. The fractal correlation dimension associated with chaotic systems is found to be a useful parameter for quantifying the relative organization of the dispersion patterns as a function of the particle time scale ratio.

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Abstract--This paper presents a discrete sliding mode control (DSMC) scheme for a series-series compensated wireless power transfer (WPT) system to achieve fast maximum energy efficiency (MEE) tracking and output voltage regulation. The power transmitter of the adopted WPT system comprises a DC/AC converter, which incorporates the hill-climbing-search-based phase angle control in achieving minimum input current injection from its DC source, thereby attaining minimum input power operation. The power receiver comprises a buck-boost converter that emulates an optimal load value, following the MEE point determined by the DSMC scheme. With this WPT system, no direct communication means is required between the transmitter and the receiver. Therefore, the implementation cost of this system is potentially lower and annoying communication delays which deteriorate control performance are absent. Both the simulation and experiment results show that this WPT system displays better dynamic regulation of the output voltage during MEE tracking when it is controlled by DSMC, as compared to that controlled by the conventional discrete proportional-integral (PI) control. Such an improvement prevents the load from sustaining undesirable overshoot/undershoot during transient states.Index Terms--Discrete sliding mode control (DSMC), series-series compensated wireless power transfer (WPT) system, maximum energy efficiency (MEE), hill-climbing-search-based phase angle control, dynamic performance.

Human perception of speed declines with age. Much of the decline is probably mediated by changes in the middle temporal (MT) area, an extrastriate area whose neural activity is linked to the perception of speed. In the present study, we used random-dot patterns to study the effects of aging on speed-tuning curves in cortical area MT of macaque visual cortex. Our results provide evidence for a significant degradation of speed selectivity in MT. Cells in old animals preferred lower speeds than did those in young animals. Response modulation and discriminative capacity for speed in old monkeys were also significantly weaker than those in young ones. Concurrently, MT cells in old monkeys showed increased baseline responses, peak responses and response variability, and these changes were accompanied by decreased signal-to-noise ratios. We also found that speed discrimination thresholds in old animals were higher than in young ones. The foregoing neural changes may mediate the declines in visual motion perception that occur during senescence.

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In this paper, a two-layer adaptive Differential Evolution (ADE) algorithm is adopted to monitor the parameters of the receiving resonators and the mutual inductances of series-series (SS)-compensated wireless power transfer (WPT) systems. By only measuring the primary coils' voltages and currents, the proposed monitoring method can be applied for multiple-coil SS-compensated WPT systems without any feedback signals from the receivers. Compared to the conventional monitoring method based on the Genetic Algorithm (GA), which may find local optimal solutions by the manually tuned parameters of the mutation rate, the crossover rate, and the generations, the proposed method based on the two-layer ADE can always find global optimal solutions by the automatically tuned parameters of the differential weight, the crossover rate, and the generations. Experimental results validate that the ADE and the proposed two-layer ADE can monitor the parameters of both two-and three-coil SS-compensated WPT systems more steadily and accurately than the conventional GA. Additionally, the proposed two-layer ADE is verified to monitor the parameters of three-coil SS-compensated WPT systems with three different arrangements more accurately than the ADE.