Objective methods for assessing perceptual image quality traditionally attempted to quantify the visibility of errors (differences) between a distorted image and a reference image using a variety of known properties of the human visual system. Under the assumption that human visual perception is highly adapted for extracting structural information from a scene, we introduce an alternative complementary framework for quality assessment based on the degradation of structural information. As a specific example of this concept, we develop a structural similarity index and demonstrate its promise through a set of intuitive examples, as well as comparison to both subjective ratings and state-of-the-art objective methods on a database of images compressed with JPEG and JPEG2000. A MATLAB implementation of the proposed algorithm is available online at http://www.cns.nyu.edu//spl sim/lcv/ssim/.

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Image quality assessment: from error visibility to structural similarity

抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Introduction to a Transient World. Fourier Kingdom. Discrete Revolution. Time Meets Frequency. Frames. Wavelet Zoom. Wavelet Bases. Wavelet Packet and Local Cosine Bases. An Approximation Tour. Estimations are Approximations. Transform Coding. Appendix A: Mathematical Complements. Appendix B: Software Toolboxes.

http://ahvazdownload.persiangig.com/document/article/39.pdf

A wavelet tour of signal processing

A general non-parametric technique is proposed for the analysis of a complex multimodal feature space and to delineate arbitrarily shaped clusters in it. The basic computational module of the technique is an old pattern recognition procedure: the mean shift. For discrete data, we prove the convergence of a recursive mean shift procedure to the nearest stationary point of the underlying density function and, thus, its utility in detecting the modes of the density. The relation of the mean shift procedure to the Nadaraya-Watson estimator from kernel regression and the robust M-estimators; of location is also established. Algorithms for two low-level vision tasks discontinuity-preserving smoothing and image segmentation - are described as applications. In these algorithms, the only user-set parameter is the resolution of the analysis, and either gray-level or color images are accepted as input. Extensive experimental results illustrate their excellent performance.

Mean shift: a robust approach toward feature space analysis

Publisher Summary This chapter focuses on the modern notion of short-term memory, called working memory. Working memory refers to the temporary maintenance of information that was just experienced or just retrieved from long-term memory but no longer exists in the external environment. These internal representations are short-lived, but can be maintained for longer periods of time through active rehearsal strategies, and can be subjected to various operations that manipulate the information in such a way that makes it useful for goal-directed behavior. Working memory is a system that is critically important in cognition and seems necessary in the course of performing many other cognitive functions, such as reasoning, language comprehension, planning, and spatial processing. This chapter demonstrates the functional importance of dopamine to working memory function in several ways. Elucidation of the cognitive and neural mechanisms underlying human working memory is an important focus of cognitive neuroscience and neurology for much of the past decade. One conclusion that arises from research is that working memory, a faculty that enables temporary storage and manipulation of information in the service of behavioral goals, can be viewed as neither a unitary, nor a dedicated system. Data from numerous neuropsychological and neurophysiological studies in animals and humans demonstrates that a network of brain regions, including the prefrontal cortex, is critical for the active maintenance of internal representations.

Chapter 11 Working memory

Purpose To compare the effects of purported cognitive enhancing dietary bioactive ingredients on subjective and objective measures of cognitive and motor performance during a first-person shooter video game. Methods Using a placebo-controlled crossover design, nine healthy men (23.4±5.7 yr, 178.9±5.8cm, 86.0±17.1kg) completed four 20-minute gaming sessions designed to assess cognitive, motor, and perceptual skills via artificial intelligence-driven battery of tasks (Aim Lab). Participants ingested either a placebo (PL), caffeine (CAFF), or caffeine + methylliberine (Dynamine™) + theacrine (TeaCrine®) (CMT). Before and after each gaming session participants rated various feelings of affect. Data were analyzed using mixed factorial ANOVA, bootstrapping post-hoc tests with 95% confidence intervals, and effect sizes. Results Compared to PL, self-assessed performance was significantly increased in CMT vs. PL (p=0.035) and self-assessed jitteriness was increased by CAFF vs. PL (p=0.043). CMT was associated with a greater improvement of participants’ visuo-spatial working memory from baseline vs. PL (p=0.04) and CAFF (p=0.033). CAFF had a greater decrease in reaction time for false alarms (indicating diminished cognitive control) from baseline vs. PL (p=0.002) and CMT (p=0.001) and a greater increase for time on target tracking vs. PL (p=0.008) and CMT (p=0.047). Compared to PL, CMT was associated with a greater decrease in median kill time (indicating improved speed) (p=0.017). Compared to PL, systolic blood pressure was significantly increased by CAFF (p=0.025) and CMT (p=0.020) but remained within normal limits. Conclusions Acute CMT supplementation improved cognitive and motor abilities in recreational gamers. The addition of theacrine and methylliberine to caffeine may lessen some undesirable effects of isolated caffeine ingestion on cognitive control and jitteriness.

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Effects of TeaCrine® (theacrine), Dynamine™ (methylliberine), and caffeine on gamer psychomotor performance in a first-person shooter video game scenario

FMRI cortical activity predicts pattern-detection performance

Neural basis of stereo dkpth perceffion measured with fMRI

[PDF]  [Full Text] , February 1, 2006; 95 (2): 591-592. J Neurophysiol Z. Kourtzi Adaptation to Firstand Second-Order Patterns in Human Visual Cortex" Textures of Natural Images in the Human Brain. Focus on "Orientation-Selective [PDF]  [Full Text]  [Abstract] , December 20, 2006; 26 (51): 13128-13142. J. Neurosci. J. Larsson and D. J. Heeger Two Retinotopic Visual Areas in Human Lateral Occipital Cortex [PDF]  [Full Text]  [Abstract] , February 1, 2007; 97 (2): 1319-1325. J Neurophysiol H. Ashida, A. Lingnau, M. B. Wall and A. T. Smith Motion fMRI Adaptation Reveals Separate Mechanisms for First-Order and Second-Order [PDF]  [Full Text]  [Abstract] , February 28, 2007; 27 (9): 2186-2195. J. Neurosci. L. Montaser-Kouhsari, M. S. Landy, D. J. Heeger and J. Larsson Orientation-Selective Adaptation to Illusory Contours in Human Visual Cortex

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Second-Order Patterns in Human Visual Cortex Orientation-Selective Adaptation to First- and

Adaptation is the process that changes a neuron's response based on recent inputs. In the traditional model, a neuron's state of adaptation depends on the recent input to that neuron alone, whereas in a recently introduced model (Hebbian normalization), adaptation depends on the structure of neural correlated firing. In particular, increased response products between pairs of neurons leads to increased mutual suppression. We test a psychophysical prediction of this model: adaptation should depend on 2nd-order statistics of input stimuli. That is, if two stimuli excite two distinct sub-populations of neurons, then presenting those stimuli simultaneously during adaptation should strengthen mutual suppression between those subpopulations. We confirm this prediction in two experiments. In the first, pairing two gratings synchronously during adaptation (i.e., a plaid) rather than asynchronously (interleaving the two gratings in time) leads to increased effectiveness of one pattern for masking the other. In the second, pairing the gratings in a center-surround configuration results in reduced apparent contrast for the central grating when paired with the same surround (as compared with a condition in which the central grating appears with a different surround at test than during adaptation). These results are consistent with the prediction that an increase in response covariance leads to greater mutual suppression between neurons. This effect is detectable both at threshold (masking) and well above threshold (apparent contrast).

David J. Heeger

Papers

Effects of TeaCrine® (theacrine), Dynamine™ (methylliberine), and caffeine on gamer psychomotor performance in a first-person shooter video game scenario

FMRI cortical activity predicts pattern-detection performance

Neural basis of stereo dkpth perceffion measured with fMRI

Second-Order Patterns in Human Visual Cortex Orientation-Selective Adaptation to First- and

Contingent adaptation in masking and surround suppression