Attention controls multisensory perception via two distinct mechanisms at different levels of the cortical hierarchy

To form a percept of the multisensory world, the brain needs to integrate signals from common sources weighted by their reliabilities and segregate those from independent sources. Previously, we have shown that anterior parietal cortices combine sensory signals into representations that take into account the signals’ causal structure (i.e., common versus independent sources) and their sensory reliabilities as predicted by Bayesian causal inference. The current study asks to what extent and how attentional mechanisms can actively control how sensory signals are combined for perceptual inference. In a pre- and postcueing paradigm, we presented observers with audiovisual signals at variable spatial disparities. Observers were precued to attend to auditory or visual modalities prior to stimulus presentation and postcued to report their perceived auditory or visual location. Combining psychophysics, functional magnetic resonance imaging (fMRI), and Bayesian modelling, we demonstrate that the brain moulds multisensory inference via two distinct mechanisms. Prestimulus attention to vision enhances the reliability and influence of visual inputs on spatial representations in visual and posterior parietal cortices. Poststimulus report determines how parietal cortices flexibly combine sensory estimates into spatial representations consistent with Bayesian causal inference. Our results show that distinct neural mechanisms control how signals are combined for perceptual inference at different levels of the cortical hierarchy.

A combination of psychophysics, computational modelling and fMRI reveals novel insights into how the brain controls the binding of information across the senses, such as the voice and lip movements of a speaker.     

Effects of industrial respirators on breathing pattern at different work levels

The effects of a filtering device and an air-line apparatus on breathing pattern were studied in healthy men with different physical characteristics and work capacity. The subjects comprised nine construction workers aged 35-44, and nine firemen aged 21-35. The construction workers' mean maximal oxygen consumption (VO2max) was 34.5 ml min-1 kg-1, the firemen's 66.9 ml min-1 kg-1. Breathing pattern was analyzed for its components, inspiratory time, expiratory time, breathing frequency, tidal volume, and pulmonary ventilation at rest, during two submaximal treadmill walks when the subjects' absolute work load was equal, and during recovery. Neither the filtering device nor the air-line apparatus had a significant effect on breathing pattern when compared with the control values measured twice with a low-resistance breathing valve. A significantly longer expiratory time, lower breathing frequency, and smaller pulmonary ventilation were found for the firemen with the breathing valve and the industrial respirators. The breathing pattern of the construction workers and the firemen differed, but the alterations were not induced by the use of the filtering device or the air-line apparatus when studied at aerobic work levels up to 60% VO2max.     

Headwater biodiversity among different levels of stream habitat hierarchy

With the current loss of biodiversity and threats to freshwater ecosystems, it is crucial to identify hot-spots of biodiversity and on which spatial scale they can be resolved. Conservation and management of these important ecosystems needs insight into whether most of the regional biodiversity (i.e. γ-diversity) can be found locally (i.e. high α-diversity) or whether it is distributed across the region (i.e. high β-diversity). Biodiversity patterns of benthic macroinvertebrates and diatoms were studied in 30 headwater streams in five Swedish catchments by comparing the relative contribution of α- and β-diversity to γ-diversity between two levels of stream habitat hierarchy (catchment and region level). The relationship between species community structure and local environmental factors was also assessed. Our results show that both α- and β-diversity made a significant contribution to γ-diversity. β-diversity remained relatively constant between the two levels of habitat hierarchy even though local environmental control of the biota decreased from the catchment to the region level. To capture most of headwater γ-diversity, management should therefore target sites that are locally diverse, but at the same time select sites so that β-diversity is maximized. As environmental control of the biota peaked at the catchment level, the conservation of headwater stream diversity is likely to be most effective when management targets environmental conditions across multiple local sites within relatively small catchments.     

Changes in breathing pattern at loads near perceptual threshold at different work levels

Five subjects were tested to determine the threshold for detection of an added resistance to inspiration in three tests, one at rest and two with exercise (mild = 50 W; moderate = 100 W) on a cycle ergometer. Changes in the breathing pattern were examined at added resistances near the perceptual threshold. Added inspiratory resistances with a 50% probability of detection were very variable at rest; they decreased significantly from rest (250 Pa.l-1.s-1) to moderate exercise (98 Pa.l-1.s-1) in four subjects. It is suggested that physical exercise may cause discomfort even when workers wearing a respirator do not have any abnormal sensation during sedentary work. Breathing patterns were compared between resistance loaded and unloaded breathing during each test. Decreases in inspiratory peak flow and acceleration of flow early in inspiration were found in resistance loaded breathing in almost all tests and a tendency for tidal volume to decrease was found during moderate exercise only. The ratios of resistance loaded to unloaded breathing for inspiratory time (ti) and total time (tt) tended to be greater in the detected than in the undetected responses at rest and during mild exercise but not during moderate exercise. This would imply that further prolongation of ti and tt in the detected responses was attributable to conscious or subconscious aspects of the resistance leading responses: however, these adjustments in breathing, which reduce frequency, would be less likely to occur as the work rate increases.     

Cognitive components of regularity processing in the auditory domain

Background

Music-syntactic irregularities often co-occur with the processing of physical irregularities. In this study we constructed chord-sequences such that perceived differences in the cognitive processing between regular and irregular chords could not be due to the sensory processing of acoustic factors like pitch repetition or pitch commonality (the major component of ‘sensory dissonance’).

Methodology/Principal Findings

Two groups of subjects (musicians and nonmusicians) were investigated with electroencephalography (EEG). Irregular chords elicited an early right anterior negativity (ERAN) in the event-related brain potentials (ERPs). The ERAN had a latency of around 180 ms after the onset of the music-syntactically irregular chords, and had maximum amplitude values over right anterior electrode sites.

Conclusions/Significance

Because irregular chords were hardly detectable based on acoustical factors (such as pitch repetition and sensory dissonance), this ERAN effect reflects for the most part cognitive (not sensory) components of regularity-based, music-syntactic processing. Our study represents a methodological advance compared to previous ERP-studies investigating the neural processing of music-syntactically irregular chords.     

Differential growth in plants--a phenomenon that occurs at all levels of organization

Differential growth is a feature of cells, the organs which they construct and the whole plant itself. The control of differential growth at each of these three levels of organization resides in the level lower than that in which it is expressed. Thus, differential growth of cells is regulated by the patterns of intracellular microtubules and cellulose microfibrils of the walls, that of organs by the pattern of growth of their cells, and that of the organism by the relative rates of organ growth. The latter is, in turn, determined an all-pervading system of correlative interactions. Plant hormones by may play a role in each of these regulatory systems.     

Slack length of gastrocnemius medialis and Achilles tendon occurs at different ankle angles

Although muscle–tendon slack length is a crucial parameter used in muscle models, this is one of the most difficult measures to estimate in vivo. The aim of this study was to determine the onset of the rise in tension (i.e., slack length) during passive stretching in both Achilles tendon and gastrocnemius medialis. Muscle and tendon shear elastic modulus was measured by elastography (supersonic shear imaging) during passive plantarflexion (0° and 90° of knee angle, 0° representing knee fully extended, in a random order) in 9 participants. The within-session repeatability of the determined slack length was good at 90° of knee flexion (SEM=3.3° and 2.2° for Achilles tendon and gastrocnemius medialis, respectively) and very good at 0° of knee flexion (SEM=1.9° and 1.9° for Achilles tendon and gastrocnemius medialis, respectively). The slack length of gastrocnemius medialis was obtained at a significantly lower plantarflexed angle than for Achilles tendon at both 0° (P<0.0001; mean difference=19.4±3.8°) and 90° of knee flexion (P<0.0001; mean difference=25.5±7.6°). In conclusion, this study showed that the joint angle at which the tendon falls slack can be experimentally determined using supersonic shear imaging. The slack length of gastrocnemius medialis and Achilles tendon occurred at different joint angles. Although reporting this result is crucial to a better understanding of muscle–tendon interactions, further experimental investigations are required to explain this result.     

The brain selenoproteome: priorities in the hierarchy and different levels of selenium homeostasis in the brain of selenium-deficient rats

The application of radionuclides for the localization of essential trace elements in vivo and the characterization of their binding proteins is a story of intermittently made improvements of the techniques used for their detection. In this study we present the use of neutron activation analysis and different autoradiographic imaging methods including real-time digital autoradiography to reveal new insights in the hierarchy of selenium homeostasis. Selenoproteins containing the essential trace element selenium play important roles in the CNS. Although the CNS does not show the highest selenium concentration in the case of selenium-sufficient supply in comparison with other organs, it shows a high priority for selenium uptake and retention in the case of dietary selenium deficiency. To characterize the hierarchy of selenium supply in the brain, in vivo radiotracer labeling with ⁷⁵Se in rats with different selenium status was combined with autoradiographic detection of ⁷⁵Se in brain tissue sections and ⁷⁵Se-labeled selenoproteins after protein separation by two-dimensional gel electrophoresis. This study demonstrates significant differences in the uptake of ⁷⁵Se into the brain of rats with different selenium status. A brain region-specific uptake pattern of the radiotracer ⁷⁵Se in selenium-deficient rats could be revealed and the CSF was identified as a key part of the brain selenium homeostasis.     

Evolution of cultural traits occurs at similar relative rates in different world regions

A fundamental issue in understanding human diversity is whether or not there are regular patterns and processes involved in cultural change. Theoretical and mathematical models of cultural evolution have been developed and are increasingly being used and assessed in empirical analyses. Here, we test the hypothesis that the rates of change of features of human socio-cultural organization are governed by general rules. One prediction of this hypothesis is that different cultural traits will tend to evolve at similar relative rates in different world regions, despite the unique historical backgrounds of groups inhabiting these regions. We used phylogenetic comparative methods and systematic cross-cultural data to assess how different socio-cultural traits changed in (i) island southeast Asia and the Pacific, and (ii) sub-Saharan Africa. The relative rates of change in these two regions are significantly correlated. Furthermore, cultural traits that are more directly related to external environmental conditions evolve more slowly than traits related to social structures. This is consistent with the idea that a form of purifying selection is acting with greater strength on these more environmentally linked traits. These results suggest that despite contingent historical events and the role of humans as active agents in the historical process, culture does indeed evolve in ways that can be predicted from general principles     

Plasma carnitine and acetyl-carnitine levels at different times of the day

An interest in both biochemical and clinical carnitine investigation has recently developed. A more complete and extensive study is obtained if acetyl-carnitine as well as carnitine are investigated. This research, using an improved and simplified method for carnitine and acetyl-carnitine determination in the same sample (1 ml) without radioisotopic tracer use, investigates if there are the same differences in their plasma levels at different times of the day. The sample was eluted in a chromatographic column (55 X 15 mm) containing Sephadex G-25M with phosphate buffer (25 mmol/l, pH 7.4). The fraction containing acetyl and free carnitine was divided and employed separately for two assays. The carnitine assay uses an enzymatic reaction catalyzed by carnitine acetyl-transferase (CAT) and measurements are carried out spectrophotometrically. The calibration curve shows r = 0.987 and sensitivity at 5 mumol/l (reference plasma values: 38 +/- 3 mumol/l in 9 subjects). The acetyl-carnitine assay is carried out concentrating the sample by lyophilization and then measuring the enzymatic coupled reactions catalyzed by CAT, malate dehydrogenase and citrate synthase fluorimetrically. The calibration curve gives r = 0.991 and sensitivity at 1.4 mumol/l (reference plasma values: 2.8 +/- 0.3 mumol/l in 9 subjects). Both assay methods are measured at the end point. The carnitine and acetyl-carnitine measured in the plasma of 6 normal subjects at different times of the day vary respectively from 28 to 37 mumol/l and from 1.1 to 5.2 mumol/l in agreement with plasma free fatty acid (FFA) variation from 230 to 779 microEq/l.(ABSTRACT TRUNCATED AT 250 WORDS)     

亚热带不同纬度植物群落物种多样性分布规律

我国亚热带气候区植被资源丰富,对其典型植物群落的物种多样性分布随纬度和海拔变化规律的探索是一项非常有意义的研究工作。在亚热带区域按照纬度从高到低分别选取猫儿山、南岭和鼎湖山国家级自然保护区中的四个典型植物群落为研究对象。设立四个1hm²样地,采用国家标准方法调查和监测。通过对样地中胸径大于1cm的所有物种进行种-个体曲线分析,对优势种进行径级分布分析,以及对四个群落进行一系列α多样性和β多样性指数的比较和分析,发现四个植物群落的物种多样性随海拔和纬度变化趋势明显。研究结果显示:(1)海拔的差异对于种-个体的分布起到关键作用,个体数随海拔变化更加明显。纬度从南到北单个体种的出现频率逐渐下降,而单个体种对群落物种多样性的贡献也在低海拔地区更为显著。(2)海拔接近的南岭样地和鼎湖山样地α多样性差异显著:由于所处演替阶段不同,以及鼎湖山样地受到人为干扰大,物种多样性反而低于纬度较高的南岭样地。同一纬度不同海拔的猫儿山两块样地相比较,处于中纬度的红军亭样地α多样性高于海拔偏高的八角田样地。(3)四个群落之间由于生境的差异,物种组成明显不同。纬度和海拔对群落β多样性都有影响。...