Testing multiple pathways for impacts of the non-native Black-headed Weaver Ploceus melanocephalus on native birds in Iberia in the early phase of invasion

Not all non-native species have strong negative impacts on native species. It is desirable to assess whether a non-native species will have a negative impact at an early stage in the invasion process, when management options such as eradication are still available. Although it may be difficult to detect early impacts of non-native species, it is necessary to ensure that management decisions can be based on case-specific scientific evidence. We assess the impacts of a non-native bird, the Black-headed Weaver Ploceus melanocephalus, at an early stage in its invasion of the Iberian Peninsula. To do this we identify potential pathways by which competition for shared resources by Black-headed Weavers could lead to population declines in two ecologically similar native species, and generate hypotheses to test for evidence of competition along these pathways. Black-headed Weavers could potentially impact native species by displacing them from nesting habitat, or by reducing habitat quality. We found no evidence for either potential competition pathway, suggesting that Black-headed Weavers do not currently compete with the two native species. However, it is possible that mechanisms that currently allow coexistence may not operate once Black-headed Weavers reach higher population densities or different habitats

Bridging consent: from toll bridges to lift bridges?

<p>Abstract</p> <p>Background</p> <p>The ability to share human biological samples, associated data and results across disease-specific and population-based human research biobanks is becoming increasingly important for research into disease development and translation. Although informed consent often does not anticipate such cross-domain sharing, it is important to examine its plausibility. The purpose of this study was to explore the feasibility of bridging consent between disease-specific and population-based research. Comparative analyses of 1) current ethical and legal frameworks governing consent and 2) informed consent models found in disease-specific and population-based research were conducted.</p> <p>Discussion</p> <p>Ethical and legal frameworks governing consent dissuade cross-domain data sharing. Paradoxically, analysis of consent models for disease-specific and population-based research reveals such a high degree of similarity that bridging consent could be possible if additional information regarding bridging was incorporated into consent forms. We submit that bridging of consent could be supported if current trends endorsing a new interpretation of consent are adopted. To illustrate this we sketch potential bridging consent scenarios.</p> <p>Summary</p> <p>A bridging consent, respectful of the spirit of initial consent, is feasible and would require only small changes to the content of consents currently being used. Under a bridging consent approach, the initial data and samples collection can serve an identified research project as well as contribute to the creation of a resource for a range of other projects.</p

Proceedings of the ... Conference on Scientific Research in the National Parks. --

Mode of access: Internet.Vols. for 1976- sponsored by the National Park Service and the American Institute of Biological Sciences

Visuomotor velocity transformations for visually guided manual tracking

To achieve accurate visually guided arm movements the brain transforms visual input into appropriate motor commands for the arm. For reaches towards static targets this transformation accounts for the complete 3D eye-head-shoulder geometry. However, position and velocity signals are processed by different neural pathways. Therefore, we ask whether a similar visuomotor transformation is also performed for velocity signals. To address this question, we designed a model describing the complete visuomotor transformation geometry for pointing, accounting for 3D eye-in-head and head-on-shoulder rotations and translations. The model predicted compensation for (1) head roll and resulting counter-roll eye movements and (2) for false ocular torsion generated by a misalignment between the retinal and spatial coordinates during oblique gaze positions. We tested these predictions on human subjects that performed manual tracking movements towards moving targets in darkness under different eye and head positions. To test prediction 1, subjects first had to roll their head towards either shoulder. Then, they pointed to the central target, which started moving Is later either to the left or right with an angular vertical component of -10, 0 or 10 deg. Subjects had to track the moving target with their hand while maintaining fixation. Testing prediction 2 was similar, but now the head was maintained in an upright position and subjects instead fixated oblique targets while the same tracking task was carried out. We measured eye, hand and head movements and computed arm velocity during the open-loop period (first 200 ms after movement onset). This initial movement direction was then compared to the model predictions to check whether the 3D eye-head-shoulder geometry was fully, partially or not at all taken into account in the visuomotor transformation. First results suggest that for manual tracking movements, the brain accounts for this complete geometry.Anglai

Transforming retinal velocity into 3D motor coordinates for pursuit eye movements

Saccade planning requires a geometric transformation between the retinal stimulus position and the desired motor plan to acquire the target. This reference frame transformation problem has, however, never been considered for velocity signals. Therefore we asked whether a separate 3D visuomotor transformation of velocity signals was theoretically required by modeling the underlying geometry. We used quaternions to model the 3D eye-in-head geometry. Our model predicted that a visuomotor velocity transformation would require extra-retinal 3D eye-in-head position to convert the retinal velocity input into spatially accurate behavior and includes three different components; (1) the same retinal velocity results in different eye rotation axes depending on eye-in-head position, (2) false torsion due to off-axes eye positions must be compensated for and (3) ocular torsion (e.g. due to the VOR) must be accounted for. To test these predictions, subjects were required either to pursue a moving target viewed under different vertical (prediction 1) or oblique (prediction 2) eye positions, or viewed under different head roll angles generating VOR-induced eye torsion (prediction 3). We measured 3D eye and head orientation and analyzed the openloop gaze pursuit response, i.e. the first 100ms after pursuit onset. We then compared the observed pursuit response to the predictions of the model: if no transformation was performed, pursuit direction should best correlate with the retinal target movement direction; a complete 3D velocity transformation would be reflected in spatially accurate pursuit. We found that for all 3 predictions, the direction of pursuit initiation was spatially accurate and did not follow the retinal (no transformation) hypothesis. This suggests that the brain performs a complete 3D visuomotor velocity transformation for smooth pursuit eye movements that is different from the previously described visuomotor transformation of position signals for saccades.Anglai

Compensation for smooth eye and head movements by gaze saccades during head-unrestrained tracking

Gaze orientationis generally performed using combined eye and head movements. It has been shown in head fixed conditions that smooth eye movements occurring during the saccade latency period are compensated for if the brain has enough time to integrate eye velocity [2,3,4]. Here, we asked whether this was the same when the head was free to move. Subjects sat in front of a 1-m distant tangential screen. They were instructed to pursue a sinusoidal target (Frequency [0.6 to 1.2 Hz]) moving along a straight line in 2D (Orientation [0 to 360 degrees ] and amplitude [20 to 25 degrees ] randomly chosen). 2.2-3.8s after target motion onset, a second target was briefly flashed at a random position on the screen. The position of both eyes was recorded by a video-based recording device (200 Hz), head position was recorded by active infrared marker tracking (200 Hz) and gaze orientation was reconstructed. We analyzed how the orienting gaze shift towards the flash was programmed and how these saccades compensated for the smooth gaze displacement [SGD] during the latency period. Multiple regression analysis showed that gaze saccades were programmed using position error at flash time [PE] and an estimation of SGD. Both the smooth eye (90%) and head displacement (75%) were used in programming the saccade. In conclusion, we propose that the gaze control system uses a similar mechanism to program head restrained and head unrestrained saccades. Eye and head displacements during the saccade latency period were integrated to compensate for intervening eye and head movements.Anglai

Emission Modelling for Supervised ECG Segmentation using Finite Differences

The segmentation of ECG signals into P waves, QRS complexes, T waves and baselines is an important practical problem for physicians diagnosing cardiac diseases. The duration of the signal and the number of beats to segment are often too large for a manual annotation, so that automatic segmentation is a challenging and useful tool. State-of-the-art algorithms use hidden Markov models with wavelet transform encoding and represent the ECG in multidimensional spaces using Gaussian mixtures models. The main problem of this approach is its computational cost due to the number of free parameters, the choice of the wavelet transform parameters and the high failure rate of the EM algorithm. In this work, we propose an alternative emission encoding for hidden Markov models using both the ECG signal and its derivative in order to better model the dynamics of the signal in a lower dimensional space. We show that this method achieves similar performances with much less model parameters and is less subject to failures.Anglai