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Background: According to current taxonomy only three out of 27 Sinohimalayan leaf warbler species (Phylloscopidae) are considered genetically uniform across their entire breeding range along the Southeastern margin of the Qinghai-Tibetan Plateau, the Buff-barred Warbler (Phylloscopus pulcher) being one of them. Because marked differentiation among Himalayan and Chinese populations has been recently demonstrated for a number of Phylloscopus species (or sister species) we investigated the intraspecific variation of a mitochondrial gene, songs and morphology of P. pulcher in a phylogeographic approach.
Methods: We sequenced a fragment of the mitochondrial cytochrome b, reconstructed haplotype networks and analyzed DNA polymorphism among Himalayan and Chinese populations. We measured time and frequency parameters of two distinct song types and analyzed among population-differentiation in a principal component analysis and a discriminant analysis. We also compared measurements of body size dimensions taken from museum specimens.
Results: The mitochondrial haplotype network (cytb) was divided into two distinct clusters corresponding to geographic origin of samples. Pairwise genetic distances among Himalayan and Chinese mtDNA lineages account for 1.3% which coincides with Pleistocene lineage separation at roughly 650,000 years ago. Genetic diversity is slightly higher in the Chinese part of the species’ range with respect to haplotype and nucleotide diversity while the less diversified Himalayan population lineage shows signs of recent range expansion. The vocal repertoire of P. pulcher comprises two distinct verse types that are combined with short interspersed click notes to long continuous song displays. Trill verse types showed significant differences among regions in almost all measured frequency and time parameters: Chinese males displayed more rapid and more broad-banded trills at a lower pitch. In contrast, warbling verse types showed a distinctively different structure among regions: Himalayan songs consisted of repeated syllables while Chinese songs comprised repetitions of single, long and strongly modulated elements. Subtle morphological differences among specimens from the two study regions could only be confirmed for plumage coloration but not for metric characters.
Conclusions: Based on the genetic and bioacoustic distinctiveness of Chinese Buff-barred Warbler populations, we recommend that the name Phylloscopus pulcher vegetus Bangs, 1913 should be re-validated for this taxon.
The locus coeruleus (LC) contains the majority of central noradrenergic neurons sending wide projections throughout the entire CNS. The LC is considered to be essential for multiple key brain functions including arousal, attention and adaptive stress responses as well as higher cognitive functions and memory. Electrophysiological studies of LC neurons have identified several characteristic functional features such as low-frequency pacemaker activity with broad action potentials, transient high-frequency burst discharges in response to salient stimuli and an apparently homogeneous inhibition of firing by activation of somatodendritic α2 autoreceptors (α2AR). While stress-mediated plasticity of the α2AR response has been described, it is currently unclear whether different LC neurons projecting to distinct axonal targets display differences in α2AR function. Using fluorescent beads-mediated retrograde tracing in adult C57Bl6/N mice, we compared the anatomical distributions and functional in vitro properties of identified LC neurons projecting either to medial prefrontal cortex, hippocampus or cerebellum. The functional in vitro analysis of LC neurons confirmed their mostly uniform functional properties regarding action potential generation and pacemaker firing. However, we identified significant differences in tonic and evoked α2AR-mediated responses. While hippocampal-projecting LC neurons were partially inhibited by endogenous levels of norepinephrine and almost completely silenced by application of saturating concentrations of the α2 agonist clonidine, prefrontal-projecting LC neurons were not affected by endogenous levels of norepinephrine and only partially inhibited by saturating concentrations of clonidine. Thus, we identified a limited α2AR control of electrical activity for prefrontal-projecting LC neurons indicative of functional heterogeneity in the LC-noradrenergic system.
Beitrag zur Kenntnis der Wasserinsektenfauna Nordwest-Hessens : 1. Köcherfliegen (Trichoptera)
(1992)
Context information supports serial dependence of multiple visual objects across memory episodes
(2020)
Serial dependence is thought to promote perceptual stability by compensating for small changes of an object’s appearance across memory episodes. So far, it has been studied in situations that comprised only a single object. The question of how we selectively create temporal stability of several objects remains unsolved. In a memory task, objects can be differentiated by their to-be-memorized feature (content) as well as accompanying discriminative features (context). We test whether congruent context features, in addition to content similarity, support serial dependence. In four experiments, we observe a stronger serial dependence between objects that share the same context features across trials. Apparently, the binding of content and context features is not erased but rather carried over to the subsequent memory episode. As this reflects temporal dependencies in natural settings, our findings reveal a mechanism that integrates corresponding content and context features to support stable representations of individualized objects over time.
Context information supports serial dependence of multiple visual objects across memory episodes
(2019)
Visual perception operates in an object-based manner, by integrating associated features via attention. Working memory allows a flexible access to a limited number of currently relevant objects, even when they are occluded or physically no longer present. Recently, it has been shown that we compensate for small changes of an object’s feature over memory episodes, which can support its perceptual stability. This phenomenon was termed ‘serial dependence’ and has mostly been studied in situations that comprised only a single relevant object. However, since we are typically confronted with situations where several objects have to be perceived and held in working memory, the central question of how we selectively create temporal stability of several objects has remained unsolved. As different objects can be distinguished by their accompanying context features, like their color or temporal position, we tested whether serial dependence is supported by the congruence of context features across memory episodes. Specifically, we asked participants to remember the motion directions of two sequentially presented colored dot fields per trial. At the end of a trial one motion direction was cued for continuous report either by its color (Experiment 1) or serial position (Experiment 2). We observed serial dependence, i.e., an attractive bias of currently toward previously memorized objects, between current and past motion directions that was clearly enhanced when items had the same color or serial position across trials. This bias was particularly pronounced for the context feature that was used for cueing and for the target of the previous trial. Together, these findings demonstrate that coding of current object representations depends on previous representations, especially when they share similar content and context features. Apparently the binding of content and context features is not completely erased after a memory episode, but it is carried over to subsequent episodes. As this reflects temporal dependencies in natural settings, the present findings reveal a mechanism that integrates corresponding bundles of content and context features to support stable representations of individualized objects over time.
Objective: Research on visual working memory has shown that individual stimulus features are processed in both specialized sensory regions and higher cortical areas. Much less evidence exists for auditory working memory. Here, a main distinction has been proposed between the processing of spatial and non-spatial sound features. Our aim was to examine feature-specific activation patterns in auditory working memory.
Methods: We collected fMRI data while 28 healthy adults performed an auditory delayed match-to-sample task. Stimuli were abstract sounds characterized by both spatial and non-spatial information, i.e., interaural time delay and central frequency, respectively. In separate recording blocks, subjects had to memorize either the spatial or non-spatial feature, which had to be compared with a probe sound presented after a short delay. We performed both univariate and multivariate comparisons between spatial and non-spatial task blocks.
Results: Processing of spatial sound features elicited a higher activity in a small cluster in the superior parietal lobe than did sound pattern processing, whereas there was no significant activation difference for the opposite contrast. The multivariate analysis was applied using a whole-brain searchlight approach to identify feature-selective processing. The task-relevant auditory feature could be decoded from multiple brain regions including the auditory cortex, posterior temporal cortex, middle occipital gyrus, and extended parietal and frontal regions.
Conclusion: In summary, the lack of large univariate activation differences between spatial and non-spatial processing could be attributable to the identical stimulation in both tasks. In contrast, the whole-brain multivariate analysis identified feature-specific activation patterns in widespread cortical regions. This suggests that areas beyond the auditory dorsal and ventral streams contribute to working memory processing of auditory stimulus features.
Abiotic and biological aspects of spring biotopcs in the Paleozoic Rhenish shield und the Hessian sandstone plate (Hesse, Germany) were compnred. Springs in the Rhenish shield have fluctuating discharges with a risk of drying out in summer, and high ranges of water temperature. In contrast, springs in the sandstone area have well-balanced discharge and temperature regimes. The bioiogical aspect of this study investigates general questions of community structure and examples of autecological adaptation of life cycles. The spring community composition is characterized in tems of environmental factors and trophic relationships in the water column und in the adjacent limnic-terrestrial interface. Lifecycle adaptations of Synagapetus are typical for inhabitants of springs with unstable discharge regimes. Its eggs are resistant to drought and the larvae possess ventilation mechanisms which are efficient even in periods of low discharge. As an example, the life-cycles of several Apataniinae are discussed in the context of adaptation to cold springs, and their embryonic development is compared to those of eurytopic Trichoptera. Finally, synecological aspects of the spatial and temporal distributions of several Trichoptera species, as recorded in emergence traps, are described. Closely related species show more or less strong niche separation.
Songs in passerine birds are important for territory defense and mating. Speciation rates in oscine passerines are so high, due to cultural evolution, that this bird lineage makes up half of the extant bird species. Leaf warblers are a speciose Old-World passerine family of limited morphological differentiation, so that songs are even more important for species delimitation. We took 16 sonographic traits from song recordings of 80 leaf warbler taxa and correlated them with 15 potentially explanatory variables, pairwise, and in linear models. Based on a well-resolved molecular phylogeny of the same taxa, all pairwise correlations were corrected for relatedness with phylogenetically independent contrasts and phylogenetic generalized linear models were used. We found a phylogenetic signal for most song traits, but a strong one only for the duration of the longest and of the shortest element, which are presumably inherited instead of learned. Body size of a leaf warbler species is a constraint on song frequencies independent of phylogeny. At least in this study, habitat density had only marginal impact on song features, which even disappeared through phylogenetic correction. Maybe most leaf warblers avoid the deterioration through sound propagation in dense vegetation by singing from exposed perches. Latitudinal (and longitudinal) extension of the breeding ranges was correlated with most song features, especially verse duration (longer polewards and westwards) and complexity (lower polewards). Climate niche or expansion history might explain these correlations. The number of different element types per verse decreases with elevation, possibly due to fewer resources and congeneric species at higher elevations.
Due to an increasing awareness of the potential hazardousness of air pollutants, new laws, rules and guidelines have recently been implemented globally. In this respect, numerous studies have addressed traffic-related exposure to particulate matter using stationary technology so far. By contrast, only few studies used the advanced technology of mobile exposure analysis. The Mobile Air Quality Study (MAQS) addresses the issue of air pollutant exposure by combining advanced high-granularity spatial-temporal analysis with vehicle-mounted, person-mounted and roadside sensors. The MAQS-platform will be used by international collaborators in order 1) to assess air pollutant exposure in relation to road structure, 2) to assess air pollutant exposure in relation to traffic density, 3) to assess air pollutant exposure in relation to weather conditions, 4) to compare exposure within vehicles between front and back seat (children) positions, and 5) to evaluate "traffic zone"- exposure in relation to non-"traffic zone"-exposure. Primarily, the MAQS-platform will focus on particulate matter. With the establishment of advanced mobile analysis tools, it is planed to extend the analysis to other pollutants including including NO2, SO2, nanoparticles, and ozone.
Knowledge about the biogeographic affinities of the world’s tropical forests helps to better understand regional differences in forest structure, diversity, composition, and dynamics. Such understanding will enable anticipation of region-specific responses to global environmental change. Modern phylogenies, in combination with broad coverage of species inventory data, now allow for global biogeographic analyses that take species evolutionary distance into account. Here we present a classification of the world’s tropical forests based on their phylogenetic similarity. We identify five principal floristic regions and their floristic relationships: (i) Indo-Pacific, (ii) Subtropical, (iii) African, (iv) American, and (v) Dry forests. Our results do not support the traditional neo- versus paleotropical forest division but instead separate the combined American and African forests from their Indo-Pacific counterparts. We also find indications for the existence of a global dry forest region, with representatives in America, Africa, Madagascar, and India. Additionally, a northern-hemisphere Subtropical forest region was identified with representatives in Asia and America, providing support for a link between Asian and American northern-hemisphere forests.