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ABSTRACT Echolocating big brown bats hunt insects flying along unpredictable paths in front of vegetation. We conducted three psychophysical experiments to investigate how these bats alter their spatial attention when localizing virtual target echoes appearing unpredictably in azimuth and against weak physical clutter. Four bats were trained to detect virtual echoes presented from a 120 deg azimuthal array of six loudspeakers. Within a single trial, echoes could remain in the same position or shift unpredictably to a new one. The bats performed well in stationary trials but were less accurate when targets shifted more peripherally and contralaterally to the original azimuth. They aimed their sonar beams accurately at targets appearing centrally; they were less precise but faster when localizing targets in the periphery, maintaining a more central acoustic gaze with only momentary peripheral shifts. When localizing a shifted target, bats reduced the interpulse intervals between broadcasts and emitted proportionally more sonar sound groups, suggesting increased perceived task difficulty. Weak clutter located closely behind the virtual target reduced accuracy in localizing target shifts, affected the speed of beam aim adjustment, and was associated with an increase in broadcast duration. Interpulse intervals and sonar sound groups were not strongly affected by clutter. Behavioral differences between bats showed the impact of individual problem-solving strategies. These findings demonstrate that the distribution of spatial attention is biased towards the center of the ensonified field of view and is influenced by weak background clutter. 

Collective behavior spans several orders of magnitude of biological organization, from cell colonies to flocks of birds. We used time-resolved tracking of individual glioblastoma cells to investigate collective motion in an ex vivo model of glioblastoma. At the population level, glioblastoma cells display weakly polarized motion in the (directional) velocities of single cells. Unexpectedly, fluctuations in velocities are correlated over distances many times the size of a cell. Correlation lengths scale linearly with the maximum end-to-end length of the population, indicating that they are scale-free and lack a characteristic decay scale other than the size of the system. Last, a data-driven maximum entropy model captures statistical features of the experimental data with only two free parameters: the effective length scale (n_c) and strength (J) of local pairwise interactions between tumor cells. These results show that glioblastoma assemblies exhibit scale-free correlations in the absence of polarization, suggesting that they may be poised near a critical point. 

From bacterial quorum sensing to human language, communication is essential for social interactions. Nematodes produce and sense pheromones to communicate among individuals and respond to environmental changes. These signals are encoded by different types and mixtures of ascarosides, whose modular structures further enhance the diversity of this nematode pheromone language. Interspecific and intraspecific differences in this ascaroside pheromone language have been described previously, but the genetic basis and molecular mechanisms underlying the variation remain largely unknown. Here, we analyzed natural variation in the production of 44 ascarosides across 95 wild Caenorhabditis elegans strains using high-performance liquid chromatography coupled to high-resolution mass spectrometry. We discovered wild strains defective in the production of specific subsets of ascarosides ( e.g. , the aggregation pheromone icas#9) or short- and medium-chain ascarosides, as well as inversely correlated patterns between the production of two major classes of ascarosides. We investigated genetic variants that are significantly associated with the natural differences in the composition of the pheromone bouquet, including rare genetic variants in key enzymes participating in ascaroside biosynthesis, such as the peroxisomal 3-ketoacyl-CoA thiolase, daf-22 , and the carboxylesterase cest-3 . Genome-wide association mappings revealed genomic loci harboring common variants that affect ascaroside profiles. Our study yields a valuable dataset for investigating the genetic mechanisms underlying the evolution of chemical communication.