Stimulus statistics change sounds from near-indiscriminable to hyperdiscriminable

Objects and events in the sensory environment are generally predictable, making most of the energy impinging upon sensory transducers redundant. Given this fact, efficient sensory systems should detect, extract, and exploit predictability in order to optimize sensitivity to less predictable inputs that are, by definition, more informative. Not only are perceptual systems sensitive to changes in physical stimulus properties, but growing evidence reveals sensitivity both to relative predictability of stimuli and to co-occurrence of stimulus attributes within stimuli. Recent results revealed that auditory perception rapidly reorganizes to efficiently capture covariance among stimulus attributes. Acoustic properties per se were perceptually abandoned, and sounds were instead processed relative to patterns of cooccurrence. Here, we show that listeners\u27 ability to distinguish sounds from one another is driven primarily by the extent to which they are consistent or inconsistent with patterns of covariation among stimulus attributes and, to a lesser extent, whether they are heard frequently or infrequently. When sounds were heard frequently and deviated minimally from the prevailing pattern of covariance among attributes, they were poorly discriminated from one another. In stark contrast, when sounds were heard rarely and markedly violated the pattern of covariance, they became hyperdiscriminable with discrimination performance beyond apparent limits of the auditory system. Plausible cortical candidates underlying these dramatic changes in perceptual organization are discussed. These findings support efficient coding of stimulus statistical structure as a model for both perceptual and neural organization. © 2016 Stilp, Kluender. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Arkansas\u27 Timber Resource: Yesterday, Today, and Tomorrow

Demand for forest products continues to rise. Arkansas provides about 4% of the U.S. total forest production and about 12% of the south central region production. Questions exist about the ability of current forest resources to completely meet anticipated future demand. In 1985, the U.S. Forest Service and the Arkansas Timber Study Committee began to analyze the existing forest base to determine whether future demand could be met from the current forest, or if not, what management changes were needed to help meet future demand. In 1985, Arkansas forests covered approximately 48% of the total land area of the state. However, the forest land base has changed drastically over the last 20 years. Projections show that changes in forest acreage, ownership, and management types will continue for the next 40 years. Greatest changes in land ownership will occur in the nonindustrial private forest (NIPF) landowner sector. Forest industry lands will show the greatest changes in timber type. Public forest ownerships will continue to be a significant part of the state\u27s total resource base, but will not undergo the significant changes of other sectors. This paper discusses these trends and the reasons for changes that are occurring

Arkansas\u27 Incendiary Wildfire Record: 1983-1987

All wildfire reports from lands protected by the Arkansas Forestry Commission for the calendar years 1983 through 1987 were studied. The number of wildfires steadily increased from 2,185 in 1983 to 4,150 in 1987, burning a total of 27,146 hectares in 1987. Incendiarism on forested lands in 1987 comprised 77% of the total fires and 84% of the area burned. Incendiarism was responsible for 40% of all fires and 60% of the area burned in 1983, but increased to 54% of all fires and 69% of the area burned in 1987. In 1987, 80% of all incendiary fires on industry lands were started by local residents. Most incendiary fires occurred on Class 3 (52%) and Class-2 (27%) fire-danger class-days. More incendiary fires (64%) occurred during the spring fire season (January through June). The general public reported 66% the non-incendiary fires, but only 56% of the incendiary-caused fires. Implications of these findings for wildfire prevention programs are discussed

Establishment of a robust single axis of cell polarity by coupling multiple positive feedback loops

Establishment of cell polarity-or symmetry breaking-relies on local accumulation of polarity regulators. Although simple positive feedback is sufficient to drive symmetry breaking, it is highly sensitive to stochastic fluctuations typical for living cells. Here, by integrating mathematical modelling with quantitative experimental validations, we show that in the yeast Saccharomyces cerevisiae a combination of actin- and guanine nucleotide dissociation inhibitor-dependent recycling of the central polarity regulator Cdc42 is needed to establish robust cell polarity at a single site during yeast budding. The guanine nucleotide dissociation inhibitor pathway consistently generates a single-polarization site, but requires Cdc42 to cycle rapidly between its active and inactive form, and is therefore sensitive to perturbations of the GTPase cycle. Conversely, actin-mediated recycling of Cdc42 induces robust symmetry breaking but cannot restrict polarization to a single site. Our results demonstrate how cells optimize symmetry breaking through coupling between multiple feedback loops

X-ray white beam topography of self-organized domains in flux-grown BaTiO3 single crystals

The phenomenon of self-organization of domains into a “square-net pattern” in single-crystal, flux-grown BaTiO3 several degrees below the ferroelectric to paraelectric phase transition was investigated using in situ synchrotron x-ray topography. The tetragonal distortion of the crystal was determined by measuring the angular separation between the diffraction images received from 90° a and c domains in the projection topographs, and shows a rapid decrease towards 110 °C, the onset temperature for self-organization. The onset of self-organization is accompanied by bending of the {100} lattice planes parallel to the crystal surface, which produces a strain that persists up to and beyond the Curie temperature, where the crystal becomes cubic and the self-organized domains disappear. At the Curie point, the bending angle α100=8.1(±0.3)mrad is at a maximum and corresponds to the radius of curvature of the surface being 16.3(±0.6) mm

Efficient Coding and Statistically Optimal Weighting of Covariance among Acoustic Attributes in Novel Sounds

To the extent that sensorineural systems are efficient, redundancy should be extracted to optimize transmission of information, but perceptual evidence for this has been limited. Stilp and colleagues recently reported efficient coding of robust correlation (r = .97) among complex acoustic attributes (attack/decay, spectral shape) in novel sounds. Discrimination of sounds orthogonal to the correlation was initially inferior but later comparable to that of sounds obeying the correlation. These effects were attenuated for less-correlated stimuli (r = .54) for reasons that are unclear. Here, statistical properties of correlation among acoustic attributes essential for perceptual organization are investigated. Overall, simple strength of the principal correlation is inadequate to predict listener performance. Initial superiority of discrimination for statistically consistent sound pairs was relatively insensitive to decreased physical acoustic/psychoacoustic range of evidence supporting the correlation, and to more frequent presentations of the same orthogonal test pairs. However, increased range supporting an orthogonal dimension has substantial effects upon perceptual organization. Connectionist simulations and Eigenvalues from closed-form calculations of principal components analysis (PCA) reveal that perceptual organization is near-optimally weighted to shared versus unshared covariance in experienced sound distributions. Implications of reduced perceptual dimensionality for speech perception and plausible neural substrates are discussed

Real-Time Contrast Enhancement to Improve Speech Recognition

An algorithm that operates in real-time to enhance the salient features of speech is described and its efficacy is evaluated. The Contrast Enhancement (CE) algorithm implements dynamic compressive gain and lateral inhibitory sidebands across channels in a modified winner-take-all circuit, which together produce a form of suppression that sharpens the dynamic spectrum. Normal-hearing listeners identified spectrally smeared consonants (VCVs) and vowels (hVds) in quiet and in noise. Consonant and vowel identification, especially in noise, were improved by the processing. The amount of improvement did not depend on the degree of spectral smearing or talker characteristics. For consonants, when results were analyzed according to phonetic feature, the most consistent improvement was for place of articulation. This is encouraging for hearing aid applications because confusions between consonants differing in place are a persistent problem for listeners with sensorineural hearing loss