Peripheral auditory processing changes seasonally in Gambel’s white-crowned sparrow

Song in oscine birds is a learned behavior that plays important roles in breeding. Pronounced seasonal differences in song behavior and in the morphology and physiology of the neural circuit underlying song production are well documented in many songbird species. Androgenic and estrogenic hormones largely mediate these seasonal changes. Although much work has focused on the hormonal mechanisms underlying seasonal plasticity in songbird vocal production, relatively less work has investigated seasonal and hormonal effects on songbird auditory processing, particularly at a peripheral level. We addressed this issue in Gambel’s white-crowned sparrow (Zonotrichia leucophrys gambelii), a highly seasonal breeder. Photoperiod and hormone levels were manipulated in the laboratory to simulate natural breeding and non-breeding conditions. Peripheral auditory function was assessed by measuring the auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAEs) of males and females in both conditions. Birds exposed to breeding-like conditions demonstrated elevated thresholds and prolonged peak latencies when compared with birds housed under non-breeding-like conditions. There were no changes in DPOAEs, however, which indicates that the seasonal differences in ABRs do not arise from changes in hair cell function. These results suggest that seasons and hormones impact auditory processing as well as vocal production in wild songbirds.     

Individual recognition through olfactory–auditory matching in lemurs

Individual recognition can be facilitated by creating representations of familiar individuals, whereby information from signals in multiple sensory modalities become linked. Many vertebrate species use auditory–visual matching to recognize familiar conspecifics and heterospecifics, but we currently do not know whether representations of familiar individuals incorporate information from other modalities. Ring-tailed lemurs (Lemur catta) are highly visual, but also communicate via scents and vocalizations. To investigate the role of olfactory signals in multisensory recognition, we tested whether lemurs can recognize familiar individuals through matching scents and vocalizations. We presented lemurs with female scents that were paired with the contact call either of the female whose scent was presented or of another familiar female from the same social group. When the scent and the vocalization came from the same individual versus from different individuals, females showed greater interest in the scents, and males showed greater interest in both the scents and the vocalizations, suggesting that lemurs can recognize familiar females via olfactory–auditory matching. Because identity signals in lemur scents and vocalizations are produced by different effectors and often encountered at different times (uncoupled in space and time), this matching suggests lemurs form multisensory representations through a newly recognized sensory integration underlying individual recognition.     

Integration of sensory and motor processing underlying social behaviour in túngara frogs

Social decision making involves the perception and processing of social stimuli, the subsequent evaluation of that information in the context of the individual's internal and external milieus to produce a decision, and then culminates in behavioural output informed by that decision. We examined brain networks in an anuran communication system that relies on acoustic signals to guide simple, stereotyped motor output. We used egr-1 mRNA expression to measure neural activation in male túngara frogs, Physalaemus pustulosus, following exposure to conspecific and heterospecific calls that evoke competitive or aggressive behaviour. We found that acoustically driven activation in auditory brainstem nuclei is transformed into activation related to sensory-motor interactions in the diencephalon, followed by motor-related activation in the telencephalon. Furthermore, under baseline conditions, brain nuclei typically have correlated egr-1 mRNA levels within brain divisions. Hearing conspecific advertisement calls increases correlations between anatomically distant brain divisions; no such effect was observed in response to calls that elicit aggressive behaviour. Neural correlates of social decision making thus take multiple forms: (i) a progressive shift from sensory to motor encoding from lower to higher stages of neural processing and (ii) the emergence of correlated activation patterns among sensory and motor regions in response to behaviourally relevant social cues.     

He hears,she hears: Are there sex differences in auditory processing?

Songbirds learn individually unique songs through vocal imitation and use them in courtship and territorial displays. Previous work has identified a forebrain auditory area, the caudomedial nidopallium (NCM), that appears specialized for discriminating and remembering conspecific vocalizations. In zebra finches (ZFs), only males produce learned vocalizations, but both sexes process these and other signals. This study assessed sex differences in auditory processing by recording extracellular multiunit activity at multiple sites within NCM. Juvenile female ZFs (n = 46) were reared in individual isolation and artificially tutored with song. In adulthood, songs were played back to assess auditory responses, stimulus‐specific adaptation, neural bias for conspecific song, and memory for the tutor's song, as well as recently heard songs. In a subset of females (n = 36), estradiol (E2) levels were manipulated to test the contribution of E2, known to be synthesized in the brain, to auditory responses. Untreated females (n = 10) showed significant differences in response magnitude and stimulus‐specific adaptation compared to males reared in the same paradigm (n = 9). In hormone‐manipulated females, E2 augmentation facilitated the memory for recently heard songs in adulthood, but neither E2 augmentation (n = 15) nor E2 synthesis blockade (n = 9) affected tutor song memory or the neural bias for conspecific song. The results demonstrate subtle sex differences in processing communication signals, and show that E2 levels in female songbirds can affect the memory for songs of potential suitors, thus contributing to the process of mate selection. The results also have potential relevance to clinical interventions that manipulate E2 in human patients. © 2014 Wiley Periodicals, Inc. Develop Neurobiol 75: 302–314, 2015     

Are you looking at me? Accuracy in processing line-of-sight in Turner syndrome.

The behavioural phenotype of women with Turner syndrome (X-monosomy, 45,X) is poorly understood, but includes reports of some social development anomalies. With this in mind, accuracy of direction of gaze detection was investigated in women with Turner syndrome. Two simple experimental tasks were used to test the prediction that the ability to ascertain gaze direction from face photographs showing small lateral angular gaze deviations would be impaired in this syndrome, compared with a control population of men and women. The prediction was confirmed and was found to affect both the detection of egocentric gaze from the eyes (''is the face looking at me?'') and the detection of allocentric gaze, where the eyes in a photographed face inspected one of a number of locations of attention (''where is she looking?''). We suggest that dosage-sensitive X-linked genes contribute to the development of gaze-monitoring abilities.     

Molecular interference in antibody–antigen interaction studied with magnetic force immunoassay

1. Download : Download full-size image

     

An ecological perspective of allelochemical interference in land–water interface communities

Allelochemical interactions among aquatic macrophytes and between macrophytes and attached microbial assemblages (epiphyton) influence a number of ecological processes. The ecological importance of these interactions, however, is poorly understood; we hypothesize that paucity has resulted, in part, from (1) a narrow focus on exploration for herbicidal plant products from aquatic macrophytes, (2) the difficulties in distinguishing resource competition from allelopathic interference, and (3) a predominance of approaching aquatic allelopathy from a terrestrial perspective. Based upon recent thorough investigations of allelopathy among aquatic vascular plants, chemical compounds that influence competitive interactions among littoral organisms are amphiphilic compounds that tend to remain near the producing organism (e.g., polyphenolic compounds and volatile fatty acids). Production of these compounds may be influenced by relative availability of nutrients (particularly phosphorus and nitrogen), inorganic carbon, and light. Macrophyte strategies of clonal reproduction, in an effort to persist in these highly productive and competitive habitats, have contributed to reduced reliance upon sexual reproduction that is correlated with allelopathic autotoxicity among several dominant wetland plant species. Although few studies document the importance of allelochemical interactions in the wetland and littoral zones of aquatic ecosystems, abundant evidence supports the potential for significant effects on competition and community structure; effects of altered nutrient ratios and availability on plant chemical composition; and resultant effects on trophic interactions, particularly suppression of herbivory, competitive attached algae and cyanobacteria, and heterotrophic utilization of organic matter by bacteria and fungi.     

Genotype–phenotype correlation in long QT syndrome families

Heterogeneity in clinical manifestations is a well-known feature in Long QT Syndrome (LQTS). The extent of this phenomenon became evident in families wherein both symptomatic and asymptomatic family members are reported. The study hence warrants genetic testing and/or screening of family members of LQTS probands for risk stratification and prediction.Of the 46 families screened, 18 probands revealed novel variations/compound heterozygosity in the gene/s screened. Families 1–4 revealed probands carrying novel variations in KCNQ1 gene along with compound heterozygosity of risk genotypes of the SCN5A, KCNE1 and NPPA gene/s polymorphisms screened. It was also observed that families- 5, 6 and 7 were typical cases of “anticipation” in which both mother and child were diagnosed with congenital LQTS (cLQTS). Families- 16 and 17 represented aLQTS probands with variations in IKs and INa encoding genes. First degree relatives (FDRs) carrying the same haplotype as the proband were also identified which may help in predictive testing and management of LQTS. Most of the probands exhibiting a family history were found to be genetic compounds which clearly points to the role of cardiac genes and their modifiers in a recessive fashion in LQTS manifestation.     

Recurrent V1–V2 interaction in early visual boundary processing

A majority of cortical areas are connected via feedforward and feedback fiber projections. In feedforward pathways we mainly observe stages of feature detection and integration. The computational role of the descending pathways at different stages of processing remains mainly unknown. Based on empirical findings we suggest that the top-down feedback pathways subserve a context-dependent gain control mechanism. We propose a new computational model for recurrent contour processing in which normalized activities of orientation selective contrast cells are fed forward to the next processing stage. There, the arrangement of input activation is matched against local patterns of contour shape. The resulting activities are subsequently fed back to the previous stage to locally enhance those initial measurements that are consistent with the top-down generated responses. In all, we suggest a computational theory for recurrent processing in the visual cortex in which the significance of local measurements is evaluated on the basis of a broader visual context that is represented in terms of contour code patterns. The model serves as a framework to link physiological with perceptual data gathered in psychophysical experiments. It handles a variety of perceptual phenomena, such as the local grouping of fragmented shape outline, texture surround and density effects, and the interpolation of illusory contours. Received: 28 October 1998 / Accepted in revised form: 19 March 1999     

Predator interference emerging from trophotaxis in predator–prey systems: An individual-based approach

An individual-based model describing predator–prey interactions within a closed rectangular habitat was developed to study how different assumptions about the individual movements lead to the emergence at the population level of various kinds of prey- and predator-dependence in the spatially aggregated trophic function.In addition to random walk, both species are capable of directional movement, i.e., the model accounts for the predator prey-taxis and evasion of predators by prey individuals. The taxis stimulus of each species is the odour of the other species, which is distributed continuously in space. Spatial behaviour of individuals is determined by the specific response to the odour gradient and the tendency to maintain the taxis velocity.In order to facilitate the assessment of the trophic function, the model allows removing the effect of demographic density variations on the predator ration, keeping population sizes constant.Analyzing the dependence of the trophic function with the average predator density, we found that, depending on the intensity of taxis, the predator population exhibits various degrees of interference, from very low to very high values. In particular, a moderate taxis generates distinct levels of interference including the ratio-dependent case. The letter maximizes the average consumption rate.A new generalized function containing ratio-dependence and prey-dependence as special cases, at high and low population abundances, is suggested. This trophic function fits the simulated data better than the Hassell–Varley–Holling expression does.     

Revealing the role of predator interference in a predator–prey system with disease in prey population

Predation on a species subjected to an infectious disease can affect both the infection level and the population dynamics. There is an ongoing debate about the act of managing disease in natural populations through predation. Recent theoretical and empirical evidence shows that predation on infected populations can have both positive and negative influences on disease in prey populations. Here, we present a predator–prey system where the prey population is subjected to an infectious disease to explore the impact of predator on disease dynamics. Specifically, we investigate how the interference among predators affects the dynamics and structure of the predator–prey community. We perform a detailed numerical bifurcation analysis and find an unusually large variety of complex dynamics, such as, bistability, torus and chaos, in the presence of predators. We show that, depending on the strength of interference among predators, predators enhance or control disease outbreaks and population persistence. Moreover, the presence of multistable regimes makes the system very sensitive to perturbations and facilitates a number of regime shifts. Since, the habitat structure and the choice of predators deeply influence the interference among predators, thus before applying predators to control disease in prey populations or applying predator control strategy for wildlife management, it is essential to carefully investigate how these predators interact with each other in that specific habitat; otherwise it may lead to ecological disaster.