Cross-modal facilitation of auditory discrimination in a frog.

Stimulation in one sensory modality can affect perception in a separate modality, resulting in diverse effects including illusions in humans. This can also result in cross-modal facilitation, a process where sensory performance in one modality is improved by stimulation in another modality. For instance, a simple sound can improve performance in a visual task in both humans and cats. However, the range of contexts and underlying mechanisms that evoke such facilitation effects remain poorly understood. Here, we demonstrated cross-modal stimulation in wild-caught túngara frogs, a species with well-studied acoustic preferences in females. We first identified that a combined visual and seismic cue (vocal sac movement and water ripple) was behaviourally relevant for females choosing between two courtship calls in a phonotaxis assay. We then found that this combined cross-modal stimulus rescued a species-typical acoustic preference in the presence of background noise that otherwise abolished the preference. These results highlight how cross-modal stimulation can prime attention in receivers to improve performance during decision-making. With this, we provide the foundation for future work uncovering the processes and conditions that promote cross-modal facilitation effects.

Evolutionary and Allometric Insights into Anuran Auditory Sensitivity and Morphology.

As species change through evolutionary time, the neurological and morphological structures that underlie behavioral systems typically remain coordinated. This is especially important for communication systems, in which these structures must remain coordinated both within and between senders and receivers for successful information transfer. The acoustic communication of anurans ("frogs") offers an excellent system to ask when and how such coordination is maintained, and to allow researchers to dissociate allometric effects from independent correlated evolution. Anurans constitute one of the most speciose groups of vocalizing vertebrates, and females typically rely on vocalizations to localize males for reproduction. Here, we compile and compare data on various aspects of auditory morphology, hearing sensitivity, and call-dominant frequency across 81 species of anurans. We find robust, phylogenetically independent scaling effects of body size for all features measured. Furthermore, after accounting for body size, we find preliminary evidence that morphological evolution beyond allometry can correlate with hearing sensitivity and dominant frequency. These data provide foundational results regarding constraints imposed by body size on communication systems and motivate further data collection and analysis using comparative approaches across the numerous anuran species.

Systematic shifts in scaling behavior based on organizational strategy in universities.

To build better theories of cities, companies, and other social institutions such as universities, requires that we understand the tradeoffs and complementarities that exist between their core functions, and that we understand bounds to their growth. Scaling theory has been a powerful tool for addressing such questions in diverse physical, biological and urban systems, revealing systematic quantitative regularities between size and function. Here we apply scaling theory to the social sciences, taking a synoptic view of an entire class of institutions. The United States higher education system serves as an ideal case study, since it includes over 5,800 institutions with shared broad objectives, but ranges in strategy from vocational training to the production of novel research, contains public, nonprofit and for-profit models, and spans sizes from 10 to roughly 100,000 enrolled students. We show that, like organisms, ecosystems and cities, universities and colleges scale in a surprisingly systematic fashion following simple power-law behavior. Comparing seven commonly accepted sectors of higher education organizations, we find distinct regimes of scaling between a school's total enrollment and its expenditures, revenues, graduation rates and economic added value. Our results quantify how each sector leverages specific economies of scale to address distinct priorities. Taken together, the scaling of features within a sector along with the shifts in scaling across sectors implies that there are generic mechanisms and constraints shared by all sectors, which lead to tradeoffs between their different societal functions and roles. We highlight the strong complementarity between public and private research universities, and community and state colleges, that all display superlinear returns to scale. In contrast to the scaling of biological systems, our results highlight that much of the observed scaling behavior is modulated by the particular strategies of organizations rather than an immutable set of constraints.

Covariation among multimodal components in the courtship display of the túngara frog.

Communication systems often include a variety of components, including those that span modalities, which may facilitate detection and decision-making. For example, female túngara frogs and fringe-lipped bats generally rely on acoustic mating signals to find male túngara frogs in a mating or foraging context, respectively. However, two additional cues (vocal sac inflation and water ripples) can enhance detection and choice behavior. To date, we do not know the natural variation and covariation of these three components. To address this, we made detailed recordings of calling males, including call amplitude, vocal sac volume and water ripple height, in 54 frogs (2430 calls). We found that all three measures correlated, with the strongest association between the vocal sac volume and call amplitude. We also found that multimodal models predicted the mass of calling males better than unimodal models. These results demonstrate how multimodal components of a communication system relate to each other and provide an important foundation for future studies on how receivers integrate and compare complex displays.

Complex sensory environments alter mate choice outcomes.

Noise is a common problem in animal communication. We know little, however, about how animals communicate in the presence of noise using multimodal signals. Multimodal signals are hypothesised to be favoured by evolution because they increase the efficacy of detection and discrimination in noisy environments. We tested the hypothesis that female túngara frogs' responses to attractive male advertisement calls are improved in noise when a visual signal component is added to the available choices. We tested this at two levels of decision complexity (two and three choices). In a two-choice test, the presence of noise did not reduce female preferences for attractive calls. The visual component of a calling male, associated with an unattractive call, also did not reduce preference for attractive calls in the absence of noise. In the presence of noise, however, females were more likely to choose an unattractive call coupled with the visual component. In three-choice tests, the presence of noise alone reduced female responses to attractive calls and this was not strongly affected by the presence or absence of visual components. The responses in these experiments fail to support the multimodal signal efficacy hypothesis. Instead, the data suggest that audio-visual perception and cognitive processing, related to mate choice decisions, are dependent on the complexity of the sensory scene.

Behavioral and neural auditory thresholds in a frog.

Vocalizations play a critical role in mate recognition and mate choice in a number of taxa, especially, but not limited to, orthopterans, frogs, and birds. But receivers can only recognize and prefer sounds that they can hear. Thus a fundamental question linking neurobiology and sexual selection asks-what is the threshold for detecting acoustic sexual displays? In this study, we use 3 methods to assess such thresholds in túngara frogs: behavioral responses, auditory brainstem responses, and multiunit electrophysiological recordings from the midbrain. We show that thresholds are lowest for multiunit recordings (ca. 45 dB SPL), and then for behavioral responses (ca. 61 dB SPL), with auditory brainstem responses exhibiting the highest thresholds (ca. 71 dB SPL). We discuss why these estimates differ and why, as with other studies, it is unlikely that they should be the same. Although all of these studies estimate thresholds they are not measuring the same thresholds; behavioral thresholds are based on signal salience whereas the 2 neural assays estimate physiological thresholds. All 3 estimates, however, make it clear that to have an appreciation for detection and salience of acoustic signals we must listen to those signals through the ears of the receivers.

Aerodigestive and communicative behaviors in anencephalic and hydranencephalic infants.

The aerodigestive and communicative behaviors of anencephalic and hydranencephalic patients are assessed from literature sources and are compared with documented neural structures present in the brainstem, subcortical, and cortical regions of the brain. Much of the data analyzed corroborate previous neurological studies, which focus on central pattern generators and development in model organisms. However, findings suggest that further research is necessary to determine which components of these systems support these behaviors. A low reporting rate of behavior in tandem with pathology is observed throughout the literature. More data pairing behavior and pathology is recommended, both in the interest of understanding the relationship between neural structures and functions, and to provide clinicians with more information about a patient's signs and symptoms. Potential clinical practices are recommended to increase documentation about patients within this population.

The sentence wrap-up dogma.

Current sentence processing research has focused on early effects of the on-line incremental processes that are performed at each word or constituent during processing. However, less attention has been devoted to what happens at the end of the clause or sentence. More specifically, over the last decade and a half, a lot of effort has been put into avoiding measuring event-related brain potentials (ERPs) at the final word of a sentence, because of the possible effects of sentence wrap-up. This article reviews the evidence on how and when sentence wrap-up impacts behavioral and ERP results. Even though the end of the sentence is associated with a positive-going ERP wave, thus far this effect has not been associated with any factors hypothesized to affect wrap-up. In addition, ERP responses to violations have not been affected by this positivity. "Sentence-final" negativities reported in the literature are not unique to sentence final positions, nor do they obscure or distort ERP effects associated with linguistic manipulations. Finally, the empirical evidence used to argue that sentence-final ERPs are different from those recorded at sentence-medial positions is weak at most. Measuring ERPs at sentence-final positions is therefore certainly not to be avoided at all costs, especially not in cases where the structure of the language under investigation requires it. More importantly, researchers should follow rigorous method in their experimental design, avoid decision tasks which may induce ERP confounds, and ensure all other possible explanations for results are considered. Although this article is directed at a particular dogma from a particular literature, this review shows that it is important to reassess what is regarded as "general knowledge" from time to time.

Perceived Synchrony of Frog Multimodal Signal Components Is Influenced by Content and Order.

Multimodal signaling is common in communication systems. Depending on the species, individual signal components may be produced synchronously as a result of physiological constraint (fixed) or each component may be produced independently (fluid) in time. For animals that rely on fixed signals, a basic prediction is that asynchrony between the components should degrade the perception of signal salience, reducing receiver response. Male túngara frogs, Physalaemus pustulosus, produce a fixed multisensory courtship signal by vocalizing with two call components (whines and chucks) and inflating a vocal sac (visual component). Using a robotic frog, we tested female responses to variation in the temporal arrangement between acoustic and visual components. When the visual component lagged a complex call (whine + chuck), females largely rejected this asynchronous multisensory signal in favor of the complex call absent the visual cue. When the chuck component was removed from one call, but the robofrog inflation lagged the complex call, females responded strongly to the asynchronous multimodal signal. When the chuck component was removed from both calls, females reversed preference and responded positively to the asynchronous multisensory signal. When the visual component preceded the call, females responded as often to the multimodal signal as to the call alone. These data show that asynchrony of a normally fixed signal does reduce receiver responsiveness. The magnitude and overall response, however, depend on specific temporal interactions between the acoustic and visual components. The sensitivity of túngara frogs to lagging visual cues, but not leading ones, and the influence of acoustic signal content on the perception of visual asynchrony is similar to those reported in human psychophysics literature. Virtually all acoustically communicating animals must conduct auditory scene analyses and identify the source of signals. Our data suggest that some basic audiovisual neural integration processes may be at work in the vertebrate brain.

Sensory Biology: How Female Treefrogs Pick Mates at a Noisy Party.

A recent study has found that, despite strong acoustic masking from background noise, female treefrogs are able to select among individual males advertising for mates by taking advantage of small, periodic decreases in the overall noise structure.

Risks of multimodal signaling: bat predators attend to dynamic motion in frog sexual displays.

Many sexual displays contain multiple components that are received through a variety of sensory modalities. Primary and secondary signal components can interact to induce novel receiver responses and become targets of sexual selection as complex signals. However, predators can also use these complex signals for prey assessment, which may limit the evolution of elaborate sexual signals. We tested whether a multimodal sexual display of the male túngara frog (Physalaemus pustulosus) increases predation risk from the fringe-lipped bat (Trachops cirrhosus) when compared with a unimodal display. We gave bats a choice to attack one of two frog models: a model with a vocal sac moving in synchrony with a mating call (multisensory cue), or a control model with the call but no vocal sac movement (unimodal cue). Bats preferred to attack the model associated with the multimodal display. Furthermore, we determined that bats perceive the vocal sac using echolocation rather than visual cues. Our data illustrate the costs associated with multimodal signaling and that sexual and natural selection pressures on the same trait are not always mediated through the same sensory modalities. These data are important when considering the role of environmental fluctuations on signal evolution as different sensory modalities will be differentially affected.

Crossmodal comparisons of signal components allow for relative-distance assessment.

Animals have multiple senses through which they detect their surroundings and often integrate sensory information across different modalities to generate perceptions. Animal communication, likewise, often consists of signals containing stimuli processed by different senses. Stimuli with different physical forms (i.e., from different sensory modalities) travel at different speeds. As a consequence, multimodal stimuli simultaneously emitted at a source can arrive at a receiver at different times. Such differences in arrival time can provide unique information about the distance to the source. Male túngara frogs (Physalaemus pustulosus) call from ponds to attract females and to repel males. Production of the sound incidentally creates ripples on the water surface, providing a multimodal cue. We tested whether male frogs attend to distance-dependent cues created by a calling rival and whether their response depends on crossmodal comparisons. In a first experiment, we showed distance-dependent changes in vocal behavior: males responded more strongly with decreasing distance to a mimicked rival. In a second experiment, we showed that males can discriminate between relatively near and far rivals by using a combination of unimodal cues, specifically amplitude changes of sound and water waves, as well as crossmodal differences in arrival time. Our data reveal that animals can compare the arrival time of simultaneously emitted multimodal cues to obtain information on relative distance to a source. We speculate that communicative benefits from crossmodal comparison may have been an important driver of the evolution of elaborate multimodal displays.

Comprehension of marked pronouns in Spanish and English: object anaphors cross-linguistically.

Previous research on pronoun resolution has identified several individual factors that are deemed to be important for resolving reference. In this paper, we argue that of these factors, as tested here, plausibility is the most important, but interacts with form markedness and structural parallelism. We investigated how listeners resolved object pronouns that were ambiguous in the sense of having more than one possible antecedent. We manipulated the form of the anaphoric expression in terms of accentuation (English: Experiments 1a and 2a) and morphology (Spanish: Experiments 1b and 2b). We looked at sentences where both antecedents were equally plausible, or where only one of the antecedents was plausible. Listeners generally resolved toward the (parallel) grammatical object of the previous clause. When the pronouns were marked due to accentuation (English) or use of specific morphology (Spanish), preference switched to the alternative antecedent, the grammatical subject of the previous clause. In contrast, when one of the two antecedents was a much more plausible antecedent than the other, antecedent choice was almost wholly dictated by plausibility, although reference form prominence did significantly attenuate the strength of the preference.

Robots in the service of animal behavior.

As reading fiction can challenge us to better understand fact, using fake animals can sometimes serve as our best solution to understanding the behavior of real animals. The use of dummies, doppelgangers, fakes, and physical models have served to elicit behaviors in animal experiments since the early history of behavior studies, and, more recently, robotic animals have been employed by researchers to further coax behaviors from their study subjects. Here, we review the use of robots in the service of animal behavior, and describe in detail the production and use of one type of robot - "faux" frogs - to test female responses to multisensory courtship signals. The túngara frog (Physalaemus pustulosus) has been a study subject for investigating multimodal signaling, and we discuss the benefits and drawbacks of using the faux frogs we have designed, with the larger aim of inspiring other scientists to consider the appropriate application of physical models and robots in their research.

Multimodal signal variation in space and time: how important is matching a signal with its signaler?

Multimodal signals (acoustic+visual) are known to be used by many anuran amphibians during courtship displays. The relative degree to which each signal component influences female mate choice, however, remains poorly understood. In this study we used a robotic frog with an inflating vocal sac and acoustic playbacks to document responses of female túngara frogs to unimodal signal components (acoustic and visual). We then tested female responses to a synchronous multimodal signal. Finally, we tested the influence of spatial and temporal variation between signal components for female attraction. Females failed to approach the isolated visual cue of the robotic frog and they showed a significant preference for the call over the spatially separate robotic frog. When presented with a call that was temporally synchronous with the vocal sac inflation of the robotic frog, females did not show a significant preference for this over the call alone; when presented with a call that was temporally asynchronous with vocal sac inflation of the robotic frog, females discriminated strongly against the asynchronous multimodal signal in favor of the call alone. Our data suggest that although the visual cue is neither necessary nor sufficient for attraction, it can strongly modulate mate choice if females perceive a temporal disjunction relative to the primary acoustic signal.

Radiographic and clinical evaluation of single-tooth Biolok implants: a 5-year study.

PURPOSE: The purpose of this prospective clinical and radiographic study was to evaluate Biolok implants used for single-tooth replacement during 5 years of function. MATERIALS AND METHODS: Thirty-nine patients received Biolok implants for single-tooth replacement. Clinical and radiographic recordings were made at baseline (placement of restoration) and at 1, 3, and 5 years. Plaque Index (PI), Gingival Index (GI), and clinical attachment level were the clinical parameters recorded. Clinical attachment level was measured using a customized probing template and a standard pressure electronic probe. Bone level changes were measured from standardized radiographs. Clinical attachment level and bone level were recorded to the nearest 0.1 mm. Correlations between clinical attachment level, bone level, PI, and GI were evaluated. RESULTS: The cumulative survival rate was 97.4% (38 of 39 implants). The mean clinical attachment level change over 5 years was a loss of 0.17+/-0.23 mm. Significant correlations between clinical attachment level change and PI were found at 3 and 5 years (P < .015). Significant correlations between clinical attachment level change and GI were not found (P >.05). Mean bone loss was 0.83+/-0.03 mm from baseline to 1 year, 0.26+/-0.03 mm from 1 year to 3 years, and 0.14+/-0.04 mm from 3 to 5 years. Significant correlations between bone level changes and PI or GI were not found (P > .05). DISCUSSION: Over a 5-year evaluation period, the bone levels and clinical attachment levels were stable. These results were consistent with other studies of single-tooth implants. CONCLUSIONS: After 5 years of function, the results suggest that Biolok implants can be successfully used for single-tooth replacement.

An esthetic technique to fill screw-retained fixed prostheses.

Currently, many composite materials have been used in the filling of access openings for screw-retained implant prosthesis. The main disadvantage of these materials is the compromise in esthetics that they place on the implant crown. An additional disadvantage is leakage of bacterial contaminants around traditional light-cured composites placed in the screw access hole. This article introduces a technique that uses opaqueing composites and the expansion properties of panacea (Zeza Inc, Chester, NY) resin to help remedy these problems. The fabrication of the silicone obturator is explained in previous literature. By following this technique, the dentist can use resin to decrease microleakage and opaqueing composite to improve esthetics.

Separating the effects of intra- and interspecific age-structured interactions in an experimental fish assemblage.

We documented patterns of age-structured biotic interactions in four mesocosm experiments with an assemblage of three species of co-occurring fishes from the Florida Everglades, the eastern mosquitofish (Gambusia holbrooki), sailfin molly (Poecilia latipinna), and bluefin killifish (Lucania goodei). These species were chosen based on their high abundance and overlapping diets. Juvenile mosquitofish and sailfin mollies, at a range of densities matching field estimates, were maintained in the presence of adult mosquitofish, sailfin mollies, and bluefin killifish to test for effects of competition and predation on juvenile survival and growth. The mesocosms held 1,200 l of water and all conditions were set to simulate those in Shark River Slough, Everglades National Park (ENP), USA. We placed floating mats of periphyton and bladderwort in each tank in standard volumes that matched field values to provide cover and to introduce invertebrate prey. Of 15 possible intra- and interspecific age-structured interactions, we found 7 to be present at the densities of these fish found in Shark River Slough marshes. Predation by adult mosquitofish on juvenile fish, including conspecifics, was the strongest effect observed. We also observed growth limitation in mosquitofish and sailfin molly juveniles from intra- and interspecific competition. When maintained at high densities, juvenile mosquitofish changed their diets to include more cladocerans and fewer chironomid larvae relative to low densities. We estimated size-specific gape limitation by adult mosquitofish when consuming juvenile mosquitofish and sailfin mollies. At high field densities, intraspecific competition might prolong the time period when juveniles are vulnerable to predation by adult mosquitofish. These results suggest that path analysis, or other techniques used to document food-web interactions, must include age-specific roles of these fishes.