Visuomotor transformations underlying hunting behavior in zebrafish

Visuomotor circuits filter visual information and determine whether or not to engage downstream motor modules to produce behavioral outputs. However, the circuit mechanisms that mediate and link perception of salient stimuli to execution of an adaptive response are poorly understood. We combined a virtual hunting assay for tethered larval zebrafish with two-photon functional calcium imaging to simultaneously monitor neuronal activity in the optic tectum during naturalistic behavior. Hunting responses showed mixed selectivity for combinations of visual features, specifically stimulus size, speed, and contrast polarity. We identified a subset of tectal neurons with similar highly selective tuning, which show non-linear mixed selectivity for visual features and are likely to mediate the perceptual recognition of prey. By comparing neural dynamics in the optic tectum during response versus non-response trials, we discovered premotor population activity that specifically preceded initiation of hunting behavior and exhibited anatomical localization that correlated with motor variables. In summary, the optic tectum contains non-linear mixed selectivity neurons that are likely to mediate reliable detection of ethologically relevant sensory stimuli. Recruitment of small tectal assemblies appears to link perception to action by providing the premotor commands that release hunting responses. These findings allow us to propose a model circuit for the visuomotor transformations underlying a natural behavior

Sprawling cities are rapidly encroaching on Earth's biodiversity

[Extract] One of the most important demographic events of the past half-century is the dramatic growth of urban areas worldwide. Growing cities, like insatiable amoebas, tend to engulf and devour their surrounding lands, often at the expense of biodiversity

Whole-field visual motion drives swimming in larval zebrafish via a stochastic process

Caudo-rostral whole-field visual motion elicits forward locomotion in many organisms, including larval zebrafish. Here, we investigate the dependence on the latency to initiate this forward swimming as a function of the speed of the visual motion. We show that latency is highly dependent on speed for slow speeds ( 1.5 s, which is much longer than neuronal transduction processes. What mechanisms underlie these long latencies? We propose two alternative, biologically inspired models that could account for this latency to initiate swimming: an integrate and fire model, which is history dependent, and a stochastic Poisson model, which has no history dependence. We use these models to predict the behavior of larvae when presented with whole-field motion of varying speed and find that the stochastic process shows better agreement with the experimental data. Finally, we discuss possible neuronal implementations of these models

Rerouting a major Indonesian mining road to spare nature and reduce development costs

Road-infrastructure projects are expanding rapidly worldwide while penetrating into previously undisturbed forests. In Sumatra, Indonesia, a planned 88-km-long mining road for transporting coal would imperil the Harapan Forest, the island's largest surviving tract of lowland rainforest. Such roads often lead to increased forest encroachment and illegal logging, fires, poaching, and mining. To evaluate the potential impact of the proposed road, we first manually mapped all existing roads inside and around the Harapan Forest using remote-sensing imagery. We then calculated the expected increase in forest loss from three proposed mining-road routes using a metric based on travel-time mapping. Finally, we used least-cost-path analyses to identify new routes for the road that would minimize forest disruption and road-construction costs. We found that road density inside and nearby the Harapan Forest is already 3-4 times higher than official data sources indicate. Based on our analyses, each of the three proposed mining-road routes would lead to 3,000-4,300 ha of additional forest loss from human encroachment plus another 424 ha lost from road construction itself. We propose new routes for the mining road that would result in up to 3,321 ha less forest loss with markedly lower construction costs than any other planned route. We recommend approaches such as ours, using least-cost-path analysis, to minimize the environmental and financial costs of major development projects

Comparison of Coulomb Blockade Thermometers with the International Temperature Scale PLTS-2000

The operation of the primary Coulomb blockade thermometer (CBT) is based on a measurement of bias voltage dependent conductance of arrays of tunnel junctions between normal metal electrodes. Here we report on a comparison of a CBT with a high accuracy realization of the PLTS-2000 temperature scale in the range from 0.008 K to 0.65 K. An overall agreement of about 1% was found for temperatures above 0.25 K. For lower temperatures increasing differences are caused by thermalization problems which are accounted for by numerical calculations based on electron-phonon decoupling.Comment: 6 pages, 5 figure

From whole-brain data to functional circuit models: the zebrafish optomotor response

Detailed descriptions of brain-scale sensorimotor circuits underlying vertebrate behavior remain elusive. Recent advances in zebrafish neuroscience offer new opportunities to dissect such circuits via whole-brain imaging, behavioral analysis, functional perturbations, and network modeling. Here, we harness these tools to generate a brain-scale circuit model of the optomotor response, an orienting behavior evoked by visual motion. We show that such motion is processed by diverse neural response types distributed across multiple brain regions. To transform sensory input into action, these regions sequentially integrate eye- and direction-specific sensory streams, refine representations via interhemispheric inhibition, and demix locomotor instructions to independently drive turning and forward swimming. While experiments revealed many neural response types throughout the brain, modeling identified the dimensions of functional connectivity most critical for the behavior. We thus reveal how distributed neurons collaborate to generate behavior and illustrate a paradigm for distilling functional circuit models from whole-brain data

Associations of social processing abilities with psychosocial stress sensitivity

Through the long-term activation of the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis, chronic psychosocial stress can compromise mental and bodily health. Psychosocial stress is determined by the perception of social interactions as ego-threatening, and thus strongly influenced by individual social processing capacities. In the current study, we investigated whether three key components of social processing are linked to how individuals respond to the experience of acute psychosocial stress exposure. Empathy, compassion, and Theory of Mind (ToM) were assessed using a state-of-the-art paradigm, the EmpaToM. Participants (N = 118) also underwent the Trier Social Stress Test (TSST), a standardized psychosocial laboratory stress test. Stress responses were measured in terms of salivary cortisol and alpha-amylase, heart-rate, high-frequency heart-rate variability (HF-HRV), and subjective stress experience. ToM performance correlated with different aspects of the acute psychosocial stress response. More specifically, higher levels of ToM were linked to increased alpha-amylase and reduced HF-HRV sensitivity to stress. Empathy and compassion levels had no influence on stress sensitivity. We conclude that ToM performance has a stable albeit contradictory association with acute psychosocial stress, while empathy and compassion tendencies appear to be largely unrelated. Overall, the relationship between EmpaToM-derived empathy, compassion, and ToM characteristics with stress sensitivity in the TSST is relatively weak

Monitoring Neural Activity with Bioluminescence during Natural Behavior

Existing techniques for monitoring neural activity in awake, freely behaving vertebrates are invasive and difficult to target to genetically identified neurons. We used bioluminescence to non-invasively monitor the activity of genetically specified neurons in freely behaving zebrafish. Transgenic fish with the Ca$^{2+}$-sensitive photoprotein green fluorescent protein (GFP)-Aequorin in most neurons generated large and fast bioluminescent signals that were related to neural activity, neuroluminescence, which could be recorded continuously for many days. To test the limits of this technique, we specifically targeted GFP-Aequorin to the hypocretin-positive neurons of the hypothalamus. We found that neuroluminescence generated by this group of ~20 neurons was associated with periods of increased locomotor activity and identified two classes of neural activity corresponding to distinct swim latencies. Our neuroluminescence assay can report, with high temporal resolution and sensitivity, the activity of small subsets of neurons during unrestrained behavior.Molecular and Cellular Biolog

The Structure and Timescales of Heat Perception in Larval Zebrafish

SummaryAvoiding temperatures outside the physiological range is critical for animal survival, but how temperature dynamics are transformed into behavioral output is largely not understood. Here, we used an infrared laser to challenge freely swimming larval zebrafish with “white noise” heat stimuli and built quantitative models relating external sensory information and internal state to behavioral output. These models revealed that larval zebrafish integrate temperature information over a time-window of 400 ms preceding a swim bout and that swimming is suppressed right after the end of a bout. Our results suggest that larval zebrafish compute both an integral and a derivative across heat in time to guide their next movement. Our models put important constraints on the type of computations that occur in the nervous system and reveal principles of how somatosensory temperature information is processed to guide behavioral decisions such as sensitivity to both absolute levels and changes in stimulation