Evolution of a stream ecosystem in recently deglaciated terrain

Climate change and associated glacial recession create new stream habitat that leads to the assembly of new riverine communities through primary succession. However, there are still very few studies of the patterns and processes of community assembly during primary succession for stream ecosystems. We illustrate the rapidity with which biotic communities can colonize and establish in recently formed streams by examining Stonefly Creek in Glacier Bay, Alaska (USA), which began to emerge from a remnant glacial ice mass between 1976 and 1979. By 2002, 57 macroinvertebrate and 27 microcrustacea species had become established. Within 10 years of the stream's formation, pink salmon and Dolly Varden charr colonized, followed by other fish species, including juvenile red and silver salmon, Coast Range sculpin, and sticklebacks. Stable-isotope analyses indicate that marine-derived nitrogen from the decay of salmon carcasses was substantially assimilated within the aquatic food web by 2004. The findings from Stonefly Creek are compared with those from a long-term study of a similarly formed but older stream (12 km to the northeast) to examine possible similarities in macroinvertebrate community and biological trait composition between streams at similar stages of development. Macroinvertebrate community assembly appears to have been initially strongly deterministic owing to low water temperature associated with remnant ice masses. In contrast, microcrustacean community assembly appears to have been more stochastic. However, as stream age and water temperature increased, macroinvertebrate colonization was also more stochastic, and taxonomic similarity between Stonefly Creek and a stream at the same stage of development was,<50%. However the most abundant taxa were similar, and functional diversity of the two communities was almost identical. Tolerance is suggested as the major mechanism of community assembly. The rapidity with which salmonids and invertebrate communities have become established across an entire watershed has implications for the conservation of biodiversity in freshwater habitats

Intraoperative electrocortical stimulation of Brodman area 4: a 10-year analysis of 255 cases

BACKGROUND: Brain tumor surgery is limited by the risk of postoperative neurological deficits. Intraoperative neurophysiological examination techniques, which are based on the electrical excitability of the human brain cortex, are thus still indispensable for surgery in eloquent areas such as the primary motor cortex (Brodman Area 4). METHODS: This study analyzed the data obtained from a total of 255 cerebral interventions for lesions with direct contact to (121) or immediately adjacent to (134) Brodman Area 4 in order to optimize stimulation parameters and to search for direct correlation between intraoperative potential changes and specific surgical maneuvers when using monopolar cortex stimulation (MCS) for electrocortical mapping and continuous intraoperative neurophysiological monitoring. RESULTS: Compound muscle action potentials (CMAPs) were recorded from the thenar muscles and forearm flexors in accordance with the large representational area of the hand and forearm in Brodman Area 4. By optimizing the stimulation parameters in two steps (step 1: stimulation frequency and step 2: train sequence) MCS was successful in 91% (232/255) of the cases. Statistical analysis of the parameters latency, potential width and amplitude showed spontaneous latency prolongations and abrupt amplitude reductions as a reliable warning signal for direct involvement of the motor cortex or motor pathways. CONCLUSION: MCS must be considered a stimulation technique that enables reliable qualitative analysis of the recorded potentials, which may thus be regarded as directly predictive. Nevertheless, like other intraoperative neurophysiological examination techniques, MCS has technical, anatomical and neurophysiological limitations. A variety of surgical and non-surgical influences can be reason for false positive or false negative measurements

Grasping isoluminant stimuli

We used a virtual reality setup to let participants grasp discs, which differed in luminance, chromaticity and size. Current theories on perception and action propose a division of labor in the brain into a color proficient perception pathway and a less color-capable action pathway. In this study, we addressed the question whether isoluminant stimuli, which provide only a chromatic but no luminance contrast for action planning, are harder to grasp than stimuli providing luminance contrast or both kinds of contrast. Although we found that grasps of isoluminant stimuli had a slightly steeper slope relating the maximum grip aperture to disc size, all other measures of grip quality were unaffected. Overall, our results do not support the view that isoluminance of stimulus and background impedes the planning of a grasping movement

Behavioral modeling of human choices reveals dissociable effects of physical effort and temporal delay on reward devaluation

There has been considerable interest from the fields of biology, economics, psychology, and ecology about how decision costs decrease the value of rewarding outcomes. For example, formal descriptions of how reward value changes with increasing temporal delays allow for quantifying individual decision preferences, as in animal species populating different habitats, or normal and clinical human populations. Strikingly, it remains largely unclear how humans evaluate rewards when these are tied to energetic costs, despite the surge of interest in the neural basis of effort-guided decision-making and the prevalence of disorders showing a diminished willingness to exert effort (e.g., depression). One common assumption is that effort discounts reward in a similar way to delay. Here we challenge this assumption by formally comparing competing hypotheses about effort and delay discounting. We used a design specifically optimized to compare discounting behavior for both effort and delay over a wide range of decision costs (Experiment 1). We then additionally characterized the profile of effort discounting free of model assumptions (Experiment 2). Contrary to previous reports, in both experiments effort costs devalued reward in a manner opposite to delay, with small devaluations for lower efforts, and progressively larger devaluations for higher effort-levels (concave shape). Bayesian model comparison confirmed that delay-choices were best predicted by a hyperbolic model, with the largest reward devaluations occurring at shorter delays. In contrast, an altogether different relationship was observed for effort-choices, which were best described by a model of inverse sigmoidal shape that is initially concave. Our results provide a novel characterization of human effort discounting behavior and its first dissociation from delay discounting. This enables accurate modelling of cost-benefit decisions, a prerequisite for the investigation of the neural underpinnings of effort-guided choice and for understanding the deficits in clinical disorders characterized by behavioral inactivity

Anthropic resource exploitation and use of the territory at the onset of social complexity in the Neolithic-Chalcolithic Western Pyrenees: a multi-isotope approach

Carbon (δ13C) and nitrogen (δ15N) stable isotope analyses from bone collagen provide information about the dietary protein input, while strontium isotopes (87Sr/86Sr) from tooth enamel give us data about provenance and potential territorial mobility of past populations. To date, isotopic results on the prehistory of the Western Pyrenees are scarce. In this article, we report human and faunal values of the mentioned isotopes from the Early-Middle Neolithic site of Fuente Hoz (Anuntzeta) and the Late Neolithic/Early Chalcolithic site of Kurtzebide (Letona, Zigoitia). The main objectives of this work are to analyze the dietary and territorial mobility patterns of these populations. Furthermore, as an additional aim, we will try to discuss social ranking based on the isotope data and existing literature on this topic in the region of study. Our results show that, based on the bioavailable Sr values, both purported local and non-local humans were buried together at the sites. Additionally, they suggest similar resource consumption based on C3 terrestrial resources (i.e. ovicaprids, bovids, and suids) as the main part of the protein input. Overall, this study sheds light on how individuals from different backgrounds were still buried together and shared the same dietary lifestyle at a time in the Prehistory of Iberia when social complexities started to appear

Towards reconciling structure and function in the nuclear pore complex

The spatial separation between the cytoplasm and the cell nucleus necessitates the continuous exchange of macromolecular cargo across the double-membraned nuclear envelope. Being the only passageway in and out of the nucleus, the nuclear pore complex (NPC) has the principal function of regulating the high throughput of nucleocytoplasmic transport in a highly selective manner so as to maintain cellular order and function. Here, we present a retrospective review of the evidence that has led to the current understanding of both NPC structure and function. Looking towards the future, we contemplate on how various outstanding effects and nanoscopic characteristics ought to be addressed, with the goal of reconciling structure and function into a single unified picture of the NPC

Developmental malformation of the corpus callosum: a review of typical callosal development and examples of developmental disorders with callosal involvement

This review provides an overview of the involvement of the corpus callosum (CC) in a variety of developmental disorders that are currently defined exclusively by genetics, developmental insult, and/or behavior. I begin with a general review of CC development, connectivity, and function, followed by discussion of the research methods typically utilized to study the callosum. The bulk of the review concentrates on specific developmental disorders, beginning with agenesis of the corpus callosum (AgCC)—the only condition diagnosed exclusively by callosal anatomy. This is followed by a review of several genetic disorders that commonly result in social impairments and/or psychopathology similar to AgCC (neurofibromatosis-1, Turner syndrome, 22q11.2 deletion syndrome, Williams yndrome, and fragile X) and two forms of prenatal injury (premature birth, fetal alcohol syndrome) known to impact callosal development. Finally, I examine callosal involvement in several common developmental disorders defined exclusively by behavioral patterns (developmental language delay, dyslexia, attention-deficit hyperactive disorder, autism spectrum disorders, and Tourette syndrome)

Assessing Arboreal Adaptations of Bird Antecedents: Testing the Ecological Setting of the Origin of the Avian Flight Stroke

The origin of avian flight is a classic macroevolutionary transition with research spanning over a century. Two competing models explaining this locomotory transition have been discussed for decades: ground up versus trees down. Although it is impossible to directly test either of these theories, it is possible to test one of the requirements for the trees-down model, that of an arboreal paravian. We test for arboreality in non-avian theropods and early birds with comparisons to extant avian, mammalian, and reptilian scansors and climbers using a comprehensive set of morphological characters. Non-avian theropods, including the small, feathered deinonychosaurs, and Archaeopteryx, consistently and significantly cluster with fully terrestrial extant mammals and ground-based birds, such as ratites. Basal birds, more advanced than Archaeopteryx, cluster with extant perching ground-foraging birds. Evolutionary trends immediately prior to the origin of birds indicate skeletal adaptations opposite that expected for arboreal climbers. Results reject an arboreal capacity for the avian stem lineage, thus lending no support for the trees-down model. Support for a fully terrestrial ecology and origin of the avian flight stroke has broad implications for the origin of powered flight for this clade. A terrestrial origin for the avian flight stroke challenges the need for an intermediate gliding phase, presents the best resolved series of the evolution of vertebrate powered flight, and may differ fundamentally from the origin of bat and pterosaur flight, whose antecedents have been postulated to have been arboreal and gliding

Consensus Paper: Cerebellum and Social Cognition.

The traditional view on the cerebellum is that it controls motor behavior. Although recent work has revealed that the cerebellum supports also nonmotor functions such as cognition and affect, only during the last 5 years it has become evident that the cerebellum also plays an important social role. This role is evident in social cognition based on interpreting goal-directed actions through the movements of individuals (social "mirroring") which is very close to its original role in motor learning, as well as in social understanding of other individuals' mental state, such as their intentions, beliefs, past behaviors, future aspirations, and personality traits (social "mentalizing"). Most of this mentalizing role is supported by the posterior cerebellum (e.g., Crus I and II). The most dominant hypothesis is that the cerebellum assists in learning and understanding social action sequences, and so facilitates social cognition by supporting optimal predictions about imminent or future social interaction and cooperation. This consensus paper brings together experts from different fields to discuss recent efforts in understanding the role of the cerebellum in social cognition, and the understanding of social behaviors and mental states by others, its effect on clinical impairments such as cerebellar ataxia and autism spectrum disorder, and how the cerebellum can become a potential target for noninvasive brain stimulation as a therapeutic intervention. We report on the most recent empirical findings and techniques for understanding and manipulating cerebellar circuits in humans. Cerebellar circuitry appears now as a key structure to elucidate social interactions