Theoretical evaluation of a four-band fiber-optic radiometer

A theoretical simulation of a four-band fiber-optic radiometric technique is presented. This is a technique for remote, noncontact temperature measurement of a sample near room temperature, under conditions of unknown emissivity and ambient temperature. A realistic setup of a broadband IR detector, a set of three filters, an IR fiber, and a MATLAB software package for the calculations, is simulated in two steps: a calibration process and a measurement process. The results of the simulation show the limitations and advantages of the four-band radiometric technique and show the expected resolution of the sample temperature and emissivity and of the ambient temperature measurement. The theoretical resolution of the sample temperature measured by the four-band radiometric setup comes close to the resolution achieved in an equivalent single-band radiometric setup. The four-band method has an additional advantage of making it possible to calculate values of emissivity and ambient temperature.     

Learning and generalization with the information bottleneck

The Information Bottleneck is an information theoretic framework that finds concise representations for an ‘input’ random variable that are as relevant as possible for an ‘output’ random variable. This framework has been used successfully in various supervised and unsupervised applications. However, its learning theoretic properties and justification remained unclear as it differs from standard learning models in several crucial aspects, primarily its explicit reliance on the joint input–output distribution. In practice, an empirical plug-in estimate of the underlying distribution has been used, so far without any finite sample performance guarantees. In this paper we present several formal results that address these difficulties. We prove several finite sample bounds, which show that the information bottleneck can provide concise representations with good generalization, based on smaller sample sizes than needed to estimate the underlying distribution. The bounds are non-uniform and adaptive to the complexity of the specific model chosen. Based on these results, we also present a preliminary analysis on the possibility of analyzing the information bottleneck method as a learning algorithm in the familiar performance-complexity tradeoff framework. In addition, we formally describe the connection between the information bottleneck and minimal sufficient statistics.     

Efficiency of GSR detection of information with repeated presentation of series of stimuli in two motivational states.

Investigated the possibility of reducing errors in the detection of information using the GSR by employing a longer interrogation with repetitions of the same critical item. 2 groups of 58 undergraduates were tested: the 1st was tested under instructions intended to arouse high motivation to beat the machine; the other was tested under low motivation to beat the machine. It was possible to reduce errors in information detection through a simple combination of GSRs obtained from 10 repetitions of the same interrogation sequence. Motivation did not produce any noticeable effect on the efficiency of detection of information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanism of age-related differences in frequency discrimination with backward masking: Speed of processing or stimulus persistence?

In Exp 1, frequency-discrimination thresholds were estimated in a 2-interval, forced-choice, backward masking procedure with a masker acoustically dissimilar to the targets. Young Ss were more efficient in escaping the effects of masking than were their elderly counterparts. In Exp 2, young and elderly Ss performed the same task, with a masker acoustically similar to the targets and with a target-dissimilar masker. Under target-similar masking and at short target–masker intervals, the elderly demonstrated significant improvement, reaching the level of performance of the young, whereas under the target-dissimilar masker, the age-related differences were restored. Both age-related slowing of information processing and increase in stimulus persistance can account for the results of Exp 1, but only increased stimulus persistence explains the results of Exp 2. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vascular health and longitudinal changes in brain and cognition in middle-aged and older adults.

The impact of vascular health on the relations between structural brain changes and cognition was assessed in a longitudinal study of 46 adults, 23 of whom remained healthy for 5 years and 23 of whom had hypertension at baseline or acquired vascular problems during follow-up. At both measurement occasions, the volume of white matter hyperintensities (WMH) and regional brain volumes correlated with age. In 5 years, WMH volume more than doubled in the vascular risk group but did not increase in healthy participants. The frontal lobes had the highest WMH load at baseline and follow-up; the parietal WMH showed the greatest rate of expansion. In the vascular risk group, systolic blood pressure at follow-up correlated with posterior WMH volume. The fastest cortical shrinkage was observed in the prefrontal cortex and the hippocampus. Fluid intelligence correlated with WMH burden and declined along with faster WMH progression. In the vascular risk group, WMH progression and shrinkage of the fusiform cortex correlated with decline in working memory. Thus, poor vascular health contributes to age-related declines in brain and cognition, and some of the age-related declines may be limited to persons with elevated vascular risk. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transport phenomena in the human nasal cavity: a computational model

Development and growth of V1 begins during embryogenesis and continues postnatally. The growth of V1 has direct implications on the organization of features such as the retinotopic map and the pattern of visual cortical columns. We have examined the postnatal growth and two-dimensional shape of V1 in macaque monkeys, cats, and rats. The perimeter, area, and anterior-posterior length of V1 were measured from unfolded and flattened sections from neonatal and adult animals from each of these species. Although there were substantial differences in the overall amount of postnatal growth, from 18% in macaque monkeys to more than 100% in cats, in all three species the shape of V1 did not change during development. Thus, growth of the mammalian visual cortex is well described as an isotropic expansion, so the layout of the global features, such as the arrangement of ocular dominance columns and the retinotopic map, does not need to change during development. Furthermore, quantification of the shape confirms the observations that there is a similar, egg-like oval shape to the visual cortex of these mammalian species.     

Multivariate information bottleneck

The information bottleneck (IB) method is an unsupervised model independent data organization technique. Given a joint distribution, p(X, Y), this method constructs a new variable, T, that extracts partitions, or clusters, over the values of X that are informative about Y. Algorithms that are motivated by the IB method have already been applied to text classification, gene expression, neural code, and spectral analysis. Here, we introduce a general principled framework for multivariate extensions of the IB method. This allows us to consider multiple systems of data partitions that are interrelated. Our approach utilizes Bayesian networks for specifying the systems of clusters and which information terms should be maintained. We show that this construction provides insights about bottleneck variations and enables us to characterize the solutions of these variations. We also present four different algorithmic approaches that allow us to construct solutions in practice and apply them to several real-world problems.     

Neuroanatomical and cognitive mediators of age-related differences in episodic memory.

Aging is associated with declines in episodic memory. In this study, the authors used a path analysis framework to explore the mediating role of differences in brain structure, executive functions, and processing speed in age-related differences in episodic memory. Measures of regional brain volume (prefrontal gray and white matter, caudate, hippocampus, visual cortex), executive functions (working memory, inhibitory control, task switching, temporal processing), processing speed, and episodic memory were obtained in a sample of young and older adults. As expected, age was linked to reduction in regional brain volumes and cognitive performance. Moreover, neural and cognitive factors completely mediated age differences in episodic memory. Whereas hippocampal shrinkage directly affected episodic memory, prefrontal volumetric reductions influenced episodic memory via limitations in working memory and inhibitory control. Age-related slowing predicted reduced efficiency in temporal processing, working memory, and inhibitory control. Lastly, poorer temporal processing directly affected episodic memory. No direct effects of age on episodic memory remained once these factors were taken into account. These analyses highlight the value of a multivariate approach with the understanding of complex relationships in cognitive and brain aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative deficit in recognition memory in a lifespan sample of healthy adults.

Advanced age is associated with decrements in episodic memory, which are more pronounced in memory for associations than for individual items. The associative deficit hypothesis (ADH) states that age differences in recognition memory reflect difficulty in binding components of a memory episode and retrieving bound units. To date, ADH has received support only in studies of extreme age groups, and the influence of sex, education, and health on age-related associative deficit is unknown. We address those issues using a verbal paired-associate yes–no recognition paradigm on a lifespan sample of 278 healthy, well-educated adults. In accord with the ADH, greater age was associated with lower hit and greater false alarm rates and more liberal response bias on associative recognition tests. Women outperformed men on recognition of items and associations, but among normotensive participants, women outperformed men only on memory for associations and not on item recognition. Thus, although supporting ADH in a large lifespan sample of healthy adults, the findings indicate that the effect may be partially driven by an age-related increase in liberal bias in recognition of associations. Sex differences and health factors may modify the associative deficit regardless of age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)