Biology subjects

Wolf, F.

Publications and source records attributed to Wolf, F..

32 records · Page 2Linked to original sources

bioRxiv2021

Deforestation projections imply range-wide population decline for critically endangered Bornean orangutan

Assessing where wildlife populations are at risk from future habitat loss is particularly important for land-use planning and avoiding biodiversity declines. Combining projections of future deforestation with species density information provides an improved way to anticipate such declines. Using the endemic and critically endangered Bornean orangutan (Pongo pygmaeus) as a case study we applied a spatio-temporally explicit deforestation model to forest loss data from 2001-2017 and projected future impacts on orangutans to the 2030s. Our projections point to continued deforestation across the island, amounting to a loss of forest habitat for 26,200 (CI: 19,500-34,000) orangutans. Populations currently persisting in forests gazetted for industrial timber and oil palm concessions, or unprotected forests outside of concessions, were projected to experience the worst losses within the next 15 years, amounting to 15,400 (CI: 12,000-20,500) individuals. Lowland forests with high orangutan densities in West and Central Kalimantan were also projected to be at high risk from deforestation, irrespective of land-use. In contrast, most protected areas and logging concessions currently harboring orangutans will continue to face low levels of deforestation. Our business-as-usual projections indicate the importance of protected areas, efforts to prevent the conversion of logged forests for the survival of highly vulnerable wildlife, and protecting orangutan habitat in plantation landscapes. The modeling framework could be expanded to other species with available density or occurrence data. Our findings highlight that species conservation should not only attempt to act on the current situation, but also be adapt to changes in drivers to be effective.

ecology↗

bioRxiv2021

Ultrafast population coding and axo-somatic compartmentalization

Populations of cortical neurons respond to common input within a millisecond. Morphological features and active ion channel properties were suggested to contribute to this astonishing processing speed. Here we report an exhaustive study of ultrafast population coding for varying axon initial segment (AIS) location, soma size, and axonal current properties. In particular, we studied their impact on two experimentally observed features 1) precise action potential timing, manifested in a wide-bandwidth dynamic gain, and 2) high-frequency boost under slowly fluctuating correlated input. While the density of axonal channels and their distance from the soma had a very small impact on bandwidth, it could be moderately improved by increasing soma size. When the voltage sensitivity of axonal currents was increased we observed ultrafast coding and high-frequency boost. We conclude that these computationally relevant features are strongly dependent on axonal ion channels voltage sensitivity, but not their number or exact location. We point out that ion channel properties, unlike dendrite size, can undergo rapid physiological modification, suggesting that the temporal accuracy of neuronal population encoding could be dynamically regulated. Our results are in line with recent experimental findings in AIS pathologies and establish a framework to study structure-function relations in AIS molecular design.

neuroscience↗

bioRxiv2021

Shared and unique properties of place cells in anterior cingulate cortex and hippocampus

Hippocampal sharp-wave ripples (SWRs) and the associated replay of neuronal sequences are well-established as the primary physiological substrates for memory consolidation. While the local transformations they induce within the hippocampus are well-characterized, their impact on the downstream cortical representations remains unknown. Here, we identify a distinct functional class of neurons in the anterior cingulate cortex "spatial context cells" that emerge through the multi-day integration of discrete hippocampal inputs. Using closed-loop disruption of SWRs and longitudinal calcium imaging, we demonstrate that formation of this global spatial framework depends on SWRs during offline periods. Whereas standard cortical place maps remain intact following SWR disruption, the emergence of spatial context cells is selectively abolished. These cells preferentially express c-Fos, identifying them as constituents of the cortical memory engram, and exhibit broad receptive fields that develop through an experience-dependent process of field convergence. Collectively, these findings establish SWR-mediated replay as a computational bridge transforming high-resolution, fragmented hippocampal spatial codes into generalized, stable cortical schemas. This work reveals a bifurcated consolidation process, identifying SWR-dependent synaptic remodeling as a fundamental mechanism for the ontogeny of remote memory.

neuroscience↗

bioRxiv2020

Environmental enrichment enhances precision and remodeling speed of synaptic nanoarchitecture revealed by crosstalk free two-color in vivo STED nanoscopy

Synaptic plasticity underlies long-lasting structural and functional changes to brain circuitry and its experience-dependent remodeling can be fundamentally enhanced by environmental enrichment. It is unknown, however, whether and how environmental enrichment alters the morphology and dynamics of individual synapses. Here, we present a virtually crosstalk free, two-color in vivo STED microscope to simultaneously superresolve the dynamics of endogenous PSD95 of the post-synaptic density and spine geometry. With environmental enrichment, the size distributions of PSD95 and spine head sizes were sharper than in controls, indicating that synaptic strength is set more precisely with environmental enrichment. Spine head geometry and PSD95 assemblies were highly dynamic but their changes correlated only mildly. With environmental enrichment, the topography of the PSD95 nanoorganization was more dynamic; changes in size were smaller than in mice housed in standard cages and depended linearly on their original size. Thus, two-color in vivo time-lapse imaging of synaptic nanoorganization uncovers a unique synaptic nanoplasticity associated with the enhanced learning capabilities under environmental enrichment.

neuroscience↗

bioRxiv2020

Chronic in vivo STED nanoscopy uncovers multiple drivers of shape volatility in stable cortical spines

Excitatory synapses on dendritic spines of pyramidal neurons are considered a central memory locus. To foster both continuous adaption as well as the storage of long-term information, spines need to be plastic and stable at the same time. Here we advanced in vivo STED nanoscopy to superresolve distinct features of dendritic spines (head size, neck length and width) in mouse neocortex for up to one month. While LTP-dependent changes predict highly correlated modifications of spine geometry, we find both, uncorrelated dynamics, as well as correlated changes, indicating multiple independent drivers of spine remodeling. The magnitude of this remodeling suggests substantial fluctuations in synaptic strength, and is exaggerated in a mouse model of neurodegeneration. Despite this high degree of volatility, all spine features also exhibit persistent components that are maintained over long periods of time. Thus, at the nanoscale, stable dendritic spines exhibit a delicate balance of stability and volatility.

neuroscience↗

bioRxiv2020

Global trends in biodiversity and ecosystem services from 1900 to 2050

Despite the scientific consensus on the extinction crisis and its anthropogenic origin, the quantification of historical trends and of future scenarios of biodiversity and ecosystem services has been limited, due to the lack of inter-model comparisons and harmonized scenarios. Here, we present a multi-model analysis to assess the impacts of land-use and climate change from 1900 to 2050. During the 20th century provisioning services increased, but biodiversity and regulating services decreased. Similar trade-offs are projected for the coming decades, but they may be attenuated in a sustainability scenario. Future biodiversity loss from land-use change is projected to keep up with historical rates or reduce slightly, whereas losses due to climate change are projected to increase greatly. Renewed efforts are needed by governments to meet the 2050 vision of the Convention on Biological Diversity. One Sentence SummaryDevelopment pathways exist that allow for a reduction of the rates of biodiversity loss from land-use change and improvement in regulating services but climate change poses an increasing challenge.

ecology↗

bioRxiv2019

Background correlations selectively boost the gamma-sensitivity of cortical GABAergic neurons

Fast oscillations in cortical circuits critically depend on GABAergic interneurons. Which interneuron types and populations can drive different cortical rhythms, however, remains unresolved and may depend on brain state. Here, we measured the sensitivity of different GABAergic interneurons in prefrontal cortex under conditions mimicking distinct brain states. While fast-spiking neurons always exhibited a wide bandwidth of around 400 Hz, the response properties of spike-frequency adapting interneurons switched with the background inputs statistics. Slowly fluctuating background activity, as typical for sleep or quiet wakefulness, dramatically boosted the neurons sensitivity to gamma- and ripple-frequencies. A novel time-resolved dynamic gain analysis revealed rapid sensitivity modulations that enable neurons to periodically boost gamma oscillations and ripples during specific phases of ongoing low-frequency oscillations. This mechanism presumably contributes substantially to cross-frequency coupling and predicts these prefrontal interneurons to be exquisitely sensitive to high-frequency ripples, especially during brain states characterized by slow rhythms.

neuroscience↗

bioRxiv2019

Profiling cellular diversity in sponges informs animal cell type and nervous system evolution

The evolutionary origin of metazoan cell types such as neurons, muscles, digestive, and immune cells, remains unsolved. Using whole-body single-cell RNA sequencing in a sponge, an animal without nervous system and musculature, we identify 18 distinct cell types comprising four major families. This includes nitric-oxide sensitive contractile cells, digestive cells active in macropinocytosis, and a family of amoeboid-neuroid cells involved in innate immunity. We uncover presynaptic genes in an amoeboid-neuroid cell type, and postsynaptic genes in digestive choanocytes, suggesting asymmetric and targeted communication. Corroborating this, long neurite-like extensions from neuroid cells directly contact and enwrap choanocyte microvillar collars. Our data indicate a link between neuroid and immune functions in sponges, and suggest that a primordial neuro-immune system cleared intruders and controlled ciliary beating for feeding.

developmental biology↗

bioRxiv2019

Localized calcium accumulations prime synapses for phagocyte removal in cortical neuroinflammation

Cortical pathology contributes to chronic cognitive impairment of patients suffering from the neuroinflammatory disease multiple sclerosis (MS). How such gray matter inflammation affects neuronal structure and function is not well understood. Here we use functional and structural in vivo imaging in a mouse model of cortical MS to demonstrate that bouts of cortical inflammation disrupt cortical circuit activity coincident with a widespread but transient loss of dendritic spines. Spines destined for removal show a local calcium accumulation and are subsequently removed by invading macrophages and activated microglia. Targeting phagocyte activation with a new antagonist of the colony-stimulating factor 1 receptor prevents cortical synapse loss. Overall, our study identifies synapse loss as a key pathological feature of inflammatory gray matter lesions that is amenable to immunomodulatory therapy.\n\nHIGHLIGHTSO_LIWidespread, but transient loss of synapses in inflammatory lesions and beyond\nC_LIO_LIReversible impairment of neuronal firing and circuit function in the inflamed cortex\nC_LIO_LICalcium dyshomeostasis of single spines precedes swift synapse loss\nC_LIO_LIPhagocyte-mediated spine pruning as targetable mechanism of synapse loss\nC_LI

neuroscience↗

bioRxiv2018

Emergence and suppression of cooperation by action visibility in transparent games

Real-world agents, such as humans, animals and robots, observe each other during interactions and choose their own actions taking the partners ongoing behaviour into account. Yet, classical game theory assumes that players act either strictly sequentially or strictly simultaneously (without knowing the choices of each other). To account for action visibility and provide a more realistic model of interactions under time constraints, we introduce a new game-theoretic setting called transparent game, where each player has a certain probability to observe the choice of the partner before deciding on its own action. Using evolutionary simulations, we demonstrate that even a small probability of seeing the partners choice before ones own decision substantially changes evolutionary successful strategies. Action visibility enhances cooperation in a Bach-or-Stravinsky game, but disrupts cooperation in a more competitive iterated Prisoners Dilemma. In both games, strategies based on the "Win-stay, lose-shift" and "Tit-for-tat" principles are predominant for moderate transparency, while for high transparency strategies of "Leader-Follower" type emerge. Our results have implications for studies of human and animal social behaviour, especially for the analysis of dyadic and group interactions.

evolutionary biology↗

bioRxiv2018

Automated Segmentation of Epithelial Tissue Using Cycle-Consistent Generative Adversarial Networks

A central problem in biomedical imaging is the automated segmentation of images for further quantitative analysis. Recently, fully convolutional neural networks, such as the U-Net, were applied successfully in a variety of segmentation tasks. A downside of this approach is the requirement for a large amount of well-prepared training samples, consisting of image - ground truth mask pairs. Since training data must be created by hand for each experiment, this task can be very costly and time-consuming. Here, we present a segmentation method based on cycle consistent generative adversarial networks, which can be trained even in absence of prepared image - mask pairs. We show that it successfully performs image segmentation tasks on samples with substantial defects and even generalizes well to different tissue types.

bioinformatics↗

bioRxiv2018

Optochemical control of cell contractility at single cell resolution during tissue morphogenesis

AbstractsThe spatial and temporal dynamics of cell contractility plays a key role in tissue morphogenesis, wound healing and cancer invasion. Here we report a simple, single cell resolution, optochemical method to induce reversible minute-scale cell contractions in vivo during morphogenesis. We employed the photolabile Ca2+ chelator o-nitrophenyl EGTA to induce bursts of intracellular free Ca2+ by laser photolysis. Ca2+ bursts appear within seconds and are restricted to individual target cells. Cell contraction reliably followed within a minute, to about half of the cross-sectional area. Increased Ca2+ levels and contraction were reversible and the target cells further participated in tissue morphogenesis. Cell contractions are paralleled with non-muscle myosin-II accumulation in the apico-medial cortex, indicating that Ca2+ bursts trigger non-muscle myosin II activation. Our approach can be easily adapted to many experimental systems and species, as no specific genetic elements are required and a widely used reagent is employed.

developmental biology↗

bioRxiv2018

Using imaging photoplethysmography for heart rate estimation in non-human primates

For humans and for non-human primates heart rate is a reliable indicator of an individuals current physiological state, with applications ranging from health checks to experimental studies of cognitive and emotional state. In humans, changes in the optical properties of the skin tissue correlated with cardiac cycles (imaging photoplethysmogram, iPPG) allow non-contact estimation of heart rate by its proxy, pulse rate. Yet, there is no established simple and non-invasive technique for pulse rate measurements in awake and behaving animals. Using iPPG, we here demonstrate that pulse rate in rhesus monkeys can be accurately estimated from facial videos. We computed iPPGs from seven color facial videos of three awake head-stabilized rhesus monkeys. Pulse rate estimated from iPPGs was in good agreement with reference data from a pulse-oximeter with error of pulse rate estimation below 5% for 82% of all epochs, and below 10% for 98% of the epochs. We conclude that iPPG allows non-invasive and non-contact estimation of pulse rate in non-human primates, which is useful for physiological studies and can be used toward welfare-assessment of non-human primates in research.

bioengineering↗

bioRxiv2017

Statistical Mechanics Of Phase Space Partitioning In Large-Scale Spiking Neuron Circuits

Synaptic interactions structure the phase space of the dynamics of neural circuits and constrain neural computation. Understanding how requires methods that handle those discrete interactions, yet few exist. Recently, it was discovered that even random networks exhibit dynamics that partitions the phase space into numerous attractor basins. Here we utilize this phenomenon to develop theory for the geometry of phase space partitioning in spiking neural circuits. We find basin boundaries structuring the phase space are pre-images of spike-time collision events. Formulating a statistical theory of spike-time collision events, we derive expressions for the rate of divergence of neighboring basins and for their size distribution. This theory reveals that the typical basin diameter grows with inhibitory coupling strength and shrinks with the rate of spike events. Our study provides an analytical and generalizable approach for dissecting how connectivity, coupling strength, single neuron dynamics and population activity shape the phase space geometry of spiking circuits.

biophysics↗