Coevolution of visual signals and eye morphology in Polistes paper wasps

To be effective, signals must propagate through the environment and be detected by receivers. As a result, signal form evolves in response to both the constraints imposed by the transmission environment and receiver perceptual abilities. Little work has examined the extent to which signals may act as selective forces on receiver sensory systems to improve the efficacy of communication. If receivers benefit from accurate signal assessment, selection could favour sensory organs that improve discrimination of established signals. Here, we provide evidence that visual resolution coevolves with visual signals in Polistes wasps. Multiple Polistes species have variable facial patterns that function as social signals, whereas other species lack visual signals. Analysis of 19 Polistes species shows that maximum eye facet size is positively associated with both eye size and presence of visual signals. Relatively larger facets within the eye''s acute zone improve resolution of small images, such as wasp facial signals. Therefore, sensory systems may evolve to optimize signal assessment. Sensory adaptations to facilitate signal detection may represent an overlooked area of the evolution of animal communication.     

Particle deposition and sensory drive

The mutualism between chemical cues emitted into the air and variations in how primates respond to them using olfaction has demonstrated aspects of species‐specific adaptations. Building on this mutualism we can look at particle deposition as another means to understanding how various environments may have elicited biological changes that enable efficient communication. Research on particle movement and deposition within the nasal cavity is largely based on questions about health as it relates to drug delivery systems and overall olfactory function in modern humans. With increased access to 3D models and the use of computational fluid dynamic analysis, researchers have been able to simulate site‐specific deposition, to determine what particles are making it through the nasal cavity to the main olfactory epithelium, which ultimately leads to processing in the olfactory bulb. Here we discuss particle deposition research, sensory drive and their potential applications to evolutionary anthropology.     

A dead giveaway: Foraging vultures and other avian scavengers respond to auditory cues

Carrion represents an unpredictable and widely distributed primary food source for vultures and other avian scavengers. Avian scavengers in African savanna ecosystems are reported to rely exclusively on visual stimuli to locate carcasses. However, carnivores’ predation of large mammalian herbivores and subsequent competition for access to the carcass can result in considerable noise, often audible over long distances and for prolonged periods. Vultures and other avian scavengers may therefore detect and respond to these auditory cues, as do the mammalian carnivores alongside which vultures have coevolved, but this has not been investigated to date. Working in the Serengeti ecosystem, Tanzania, we used diurnal auditory broadcasts to simulate predation and competitive carnivore feeding interactions. Based on the current understanding of avian scavenger ecology, we hypothesized that avian responses to call‐in stations would be evoked exclusively by visual, rather than auditory, cues. We therefore predicted that (a) the arrival of avian scavengers at call‐in stations should be preceded and facilitated by mammalian carnivores and that (b) the arrival of avian scavengers would be positively correlated with the number of mammalian scavengers present, which would increase detectability. We recorded 482 birds during 122 separate playback events. In 22% of these instances, avian scavengers arrived first, ruling out responses based exclusively on visual observations of mammalian carnivores, thereby contradicting our first prediction. Furthermore, the first avian arrivals at survey sessions were inversely related to the number of hyenas and jackals present, contradicting our second prediction. Since no bait or carcasses were used during the experiments, these responses are indicative of the birds’ ability to detect and respond to audio stimuli. Our findings challenge the current consensus of sensory perception and foraging in these species and provide evidence that avian scavengers have the ability to use sound to locate food resources.     

Portrait of visual cortical circuits for generating neural oscillation dynamics

The mouse primary visual cortex (V1) has emerged as a classical system to study neural circuit mechanisms underlying visual function and plasticity. A variety of efferent-afferent neuronal connections exists within the V1 and between the V1 and higher visual cortical areas or thalamic nuclei, indicating that the V1 system is more than a mere receiver in information processing. Sensory representations in the V1 are dynamically correlated with neural activity oscillations that are distributed across different cortical layers in an input-dependent manner. Circuits consisting of excitatory pyramidal cells (PCs) and inhibitory interneurons (INs) are the basis for generating neural oscillations. In general, INs are clustered with their adjacent PCs to form specific microcircuits that gate or filter the neural information. The interaction between these two cell populations has to be coordinated within a local circuit in order to preserve neural coding schemes and maintain excitation–inhibition (E–I) balance. Phasic alternations of the E–I balance can dynamically regulate temporal rhythms of neural oscillation. Accumulating experimental evidence suggests that the two major sub-types of INs, parvalbumin-expressing (PV⁺) cells and somatostatin-expressing (SOM⁺) INs, are active in controlling slow and fast oscillations, respectively, in the mouse V1. The review summarizes recent experimental findings on elucidating cellular or circuitry mechanisms for the generation of neural oscillations with distinct rhythms in either developing or matured mouse V1, mainly focusing on visual relaying circuits and distinct local inhibitory circuits.     

Microscale grooves regulate maturation development of hPSC-CMs by the transient receptor potential channels (TRP channels)

The use of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) is limited in drug discovery and cardiac disease mechanism studies due to cell immaturity. Micro-scaled grooves can promote the maturation of cardiomyocytes by aligning them in order, but the mechanism of cardiomyocytes alignment has not been studied. From the level of calcium activity, gene expression and cell morphology, we verified that the W20H5 grooves can effectively promote the maturation of cardiomyocytes. The transient receptor potential channels (TRP channels) also play an important role in the maturation and development of cardiomyocytes. These findings support the engineered hPSC-CMs as a powerful model to study cardiac disease mechanism and partly mimic the myocardial morphological development. The important role of the TRP channels in the maturation and development of myocardium is first revealed.     

Comparison between touchscreen operant chambers and water maze to detect early prefrontal dysfunction in mice

The relative lack of sensitive and clinically valid tests of rodent behavior might be one of the reasons for the limited success of the clinical translation of preclinical Alzheimer's disease (AD) research findings. There is a general interest in innovative behavioral methodology, and protocols have been proposed for touchscreen operant chambers that might be superior to existing cognitive assessment methods. We assessed and analyzed touchscreen performance in several novel ways to examine the possible occurrence of early signs of prefrontal (PFC) functional decline in the APP/PS1 mouse model of AD. Touchscreen learning performance was compared between APP/PS1-21 mice and wildtype littermates on a C57BL/6J background at 3, 6 and 12 months of age in parallel to the assessment of spatial learning, memory and cognitive flexibility in the Morris water maze (MWM). We found that older mice generally needed more training sessions to complete the touchscreen protocol than younger ones. Older mice also displayed defects in MWM working memory performance, but touchscreen protocols detected functional changes beginning at 3 months of age. Histological changes in PFC of APP/PS1 mice indeed occurred as early as 3 months. Our results suggest that touchscreen operant protocols are more sensitive to PFC dysfunction, which is of relevance to the use of these tasks and devices in preclinical AD research and experimental pharmacology.