Verification of biomechanical methods employed in a comprehensive study of mild traumatic brain injury and the effectiveness of American football helmets

Concussion, or mild traumatic brain injury, occurs in many activities, mostly as a result of the head being accelerated. A comprehensive study has been conducted to understand better the mechanics of the impacts associated with concussion in American football. This study involves a sequence of techniques to analyse and reconstruct many different head impact scenarios. It is important to understand the validity and accuracy of these techniques in order to be able to use the results of the study to improve helmets and helmet standards. Two major categories of potential errors have been investigated. The first category concerns error sources specific to the use of crash test dummy instrumentation (accelerometers) and associated data processing techniques. These are relied upon to establish both linear and angular head acceleration responses. The second category concerns the use of broadcast video data and crash test dummy head-neck-torso systems. These are used to replicate the complex head impact scenarios of whole body collisions that occur on the football field between two living human beings. All acceleration measurement and processing techniques were based on well-established practices and standards. These proved to be reliable and reproducible. Potential errors in the linear accelerations due to electrical or mechanical noise did not exceed 2% for the three different noise sources investigated. Potential errors in the angular accelerations due to noise could be as high as 6.7%, due to error accumulation of multiple linear acceleration measurements. The potential error in the relative impact velocity between colliding heads could be as high as 11%, and was found to be the largest error source in the sequence of techniques to reconstruct the game impacts. Full-scale experiments with complete crash test dummies in staged head impacts showed maximum errors of 17% for resultant linear accelerations and 25% for resultant angular accelerations.     

Birds respond similarly to taxidermic models and live cuckoos <Emphasis Type="Italic">Cuculus canorus</Emphasis>

Stuffed birds are widely used in research for identifying effects of predators and nest parasites on bird behaviour, studying levels of aggression and the size of territories. However, the fact that these models do not move or vocalize may question the results of such studies and open them to criticism. One solution would be to determine how the results of research using stuffed dummies correlate with the response of wild animals to enemies under the same environmental conditions. In a first attempt, we examined the correlation between the intensity of mobbing of a dummy cuckoo Cuculus canorus and interactions with live cuckoos in the field during the breeding season in western Poland. A total of 39 bird species mobbed cuckoo dummies; all 39 were found to attack live cuckoos, while 24 species (61.5%) did so during experiments using a dummy. The number of individual birds involved in mobbing a dummy was positively correlated with the number of individuals attacking real cuckoos in the same areas, even when the most commonly mobbing species, the barn swallow Hirundo rustica, was excluded from the analyses. However, we did not find significant differences in frequency of mobbing behaviour depending on cuckoo behaviour described as flight or sitting, or calling rather than remaining quiet. Therefore, we conclude that the use of a dummy for studying mobbing of hosts and non-hosts of the cuckoo provide results that are similar to those made in response to the behaviour of live hosts.     

Innate Flower Recognition in Bumblebees (Bombus terrestris,B. lucorum; Apidae): Optical Signals from Stamens as Landing Reaction Releasers

Innate behavioural reactions in bumblebees were observed in flower dummy experiments. In a previous paper, it was shown that the approach of flower-naive, untrained bumblebees toward flower dummies is released by colour signals, i.e. a gradient of spectral purity. The bumblebees are directed toward that part of a flower dummy which exhibits the highest spectral purity (Lunau 1990). In the present work it is shown that the bumblebees, while still in flight, make contact with this part using their antennal tips. The antennae reaction is followed by a landing reaction which is released by olfactory and optical signals. The specific optical signals of the guide area which release the landing reaction were investigated. Since in the flower dummies which were used, the guide had the highest spectral purity, most of the antennae reactions were executed at the guide. The antennae reaction allows for a precise orientation and may involve the stimulation of a specialized area of ommatidia. Minute changes in optical guide parameters could thus be detected. The following features of stamens which most effectively released the landing reaction were: a minimum of 2 theca dummies; an oval shape of theca dummies which face each other along the longitudinal axis (both these characteristics are found in genuine stamens); 4 mm distance between theca dummies (this coincides with the distance between the antennal tips of bumblebees); two equally sized theca dummies each with an area of 7 mm² (this size of theca dummies was preferred over larger or smaller ones; the latter parameter was not changed when the corolla size was varied). Colour parameters are not involved in releasing the landing reaction. Clearly, bumblebees possess an innate releasing mechanism (IRM) that responds to optical signals of anthers which release the landing reaction. The experimental results are in accordance with conclusions drawn from the comparative studies of Osche (1979, 1983a, 1983b) that many flower guides can be interpreted as stamen mimics. Therefore stamens as well as stamen mimics represent a highly standardized signal for the insect pollinators and they are well suited for innate orientation at flowers.     

Normalizing and scaling of data to derive human response corridors from impact tests

It is well known that variability is inherent in any biological experiment. Human cadavers (Post-Mortem Human Subjects, PMHS) are routinely used to determine responses to impact loading for crashworthiness applications including civilian (motor vehicle) and military environments. It is important to transform measured variables from PMHS tests (accelerations, forces and deflections) to a standard or reference population, termed normalization. The transformation process should account for inter-specimen variations with some underlying assumptions used during normalization. Scaling is a process by which normalized responses are converted from one standard to another (example, mid-size adult male to large-male and small-size female adults, and to pediatric populations). These responses are used to derive corridors to assess the biofidelity of anthropomorphic test devices (crash dummies) used to predict injury in impact environments and design injury mitigating devices. This survey examines the pros and cons of different approaches for obtaining normalized and scaled responses and corridors used in biomechanical studies for over four decades. Specifically, the equal-stress equal-velocity and impulse-momentum methods along with their variations are discussed in this review. Methods ranging from subjective to quasi-static loading to different approaches are discussed for deriving temporal mean and plus minus one standard deviation human corridors of time-varying fundamental responses and cross variables (e.g., force-deflection). The survey offers some insights into the potential efficacy of these approaches with examples from recent impact tests and concludes with recommendations for future studies. The importance of considering various parameters during the experimental design of human impact tests is stressed.     

The effects of stimulus type on consistency of responses to conflicting stimuli in Siamese fighting fish

Individuals must often decide among a range of behavioral responses in a given situation and individuals will likely vary from one another in the choices they make. A rarely explored example of this is when both a male and a female are present simultaneously and a male must decide to fight or court. Consistent individual differences have been found in decision-making in Siamese fighting fish; however, dummies were used to explore this question and it is possible that individuals respond differently in this situation when faced with live stimuli as a result of feedback. Therefore, this study investigated whether males behave similarly to dummy and live stimuli by exposing them to male and female conspecifics both simultaneously and separately. Subjects were tested first with dummies and then in the same situations using live conspecifics. It was hypothesized that males would respond in the same manner to both the dummy and live fish. The results indicated that individuals behaved similarly to the dummy fish and the live fish in corresponding conditions. In addition, repeatability levels suggest that individuals behaved similarly across trials of a given treatment type while differing from one another in their responses. This study demonstrates that males are consistent in their responses even when receiving feedback from conspecifics and supports the continued use of dummy stimuli as an effective tool.     

Anthropometric specification of child crash dummy pelves through statistical analysis of skeletal geometry

The pelves of the child dummies of the widely used Hybrid-III family are based on minimal data from children. Because an accurate pelvis design is critical for realistic assessments of belt restraint interactions, an analysis of medical imaging data was conducted to develop guidance for improved pelvis design. Three-dimensional polygonal meshes of the bony pelvis were generated from computed tomography (CT) data from 81 children from ages 5 to 11. After aligning to a uniform anatomical coordinate system, the meshes were resampled to create a quadrilateral mesh with 12,960 vertices for each pelvis. A principal components analysis was conducted with the mesh vertex coordinates and the locations of 31 landmarks. Over 99% of the variance in size and shape was accounted for by the first 40 components. A three-dimensional model representing the target for a new dummy pelvis was developed using bispinous breadth as the predictor variable. To obtain the appropriate geometry for the six-year-old (6YO) and 10YO Hybrid-III dummies, a regression analysis was conducted using a large sample of child anthropometry data from a previous study to obtain a target dimension for bispinous breadth, using the design stature for each dummy as input. A separate regression analysis was conducted to predict principal component scores from bispinous breadth. Reconstructing a pelvis model from the principal components scores predicted for the target bispinous breadth values yielded a three-dimensional design target for the each dummy. The new pelvis target is similar in overall size to the current pelvis components, but the location of the anterior-superior iliac spine is markedly lower, which has important implications for belt interaction.     

A two-step procedure for coupling development and usage of a pair of human neck models

Both finite element models and multi-body models of human head-neck complex had been widely used in neck injuries analysis, as the former could be used to generate detailed stress strain information and the later could generate dynamic responses with high efficiency. Sometimes, detailed stress and strain information were hoped to be obtained more efficiently, but current methods were not effective enough when they were used to analyze responses of human head neck complex to long duration undulate accelerations. In this paper, a two-step procedure for ‘parallel’ development and ‘sequential’ usage of a pair of human head neck models was discussed. The pair of models contained a finite element model and a multi-body model, which were developed based on the coupling ‘parallel’ procedure using the same bio-realistic geometry. After being validated using available data, the pair of human neck models were applied to analyze biomechanical responses of pilot’s neck during arrested landing operation according to the ‘sequential’ procedure, because typical sustained undulate accelerations usually appeared during such processes. The results, including both kinematic and detailed biomechanical responses of human head-neck complex, were obtained with preferable efficiency. This research provided an effective way for biomechanical analysis of human head neck responses to sustained undulate accelerations.     

Aggressive behaviour in subadult and adult black redstarts: status-signalling strategy?

In some birds, yearling males (subadults) are less brightly coloured than the adult ones. To explain this phenomenon known as delayed plumage maturation (DPM), several hypotheses have recently been proposed. The aim of this paper was to test predictions of status signal hypothesis (SSH). This hypothesis claims that the adults less frequently attack dull coloured subadult males, and consequently DPM facilitates survival of subadults during the first breeding season. The experiments were performed in two habitats in the Prague suburbs: a housing estate and garden city. Subadult and adult males of the black redstart (Phoenicurus ochruros) were exposed to stuffed dummies of both age categories. Contrary to predictions of SSH, brown (subadult like) coloration of the dummy had no suppressive effect on defensive behaviour of the resident males. On the other hand, subadult males were more active in vocal territorial defence such as singing and producing snarl and whistle sounds during the experiments. The defenders of smaller territories generally behaved more aggressively than defenders of large territories in habitat of garden city, and especially adult males responded more aggressively against dummies in this habitat. In a housing estate, a habitat of evenly distributed resources (i.e. vertical surfaces), the birds tended to observe the dummy prior to attack it directly.     

Interactions between common buzzard Buteo buteo and goshawk Accipiter gentilis: trade-offs revealed by a field experiment

I examined the behavioural interactions between common buzzard Buteo buteo and goshawk Accipiter gentilis and their effects on buzzard breeding success and brood defence with a two-year field experiment using dummies and playback calls. A priori I showed through an extensive nest site analysis that there is considerable nesting habitat overlap between the two species and hence potential for interspecific competition for prime nesting habitat. Buzzards had a significantly lower breeding success when presented with a goshawk dummy compared to control broods but there was no effect of buzzard dummies on reproductive success. Buzzards failing with their breeding attempt tended to select another nest site while successful buzzards more frequently used the same nest again. Buzzard pairs were less often attacked by common crows Corvus corone while exposed to goshawk dummies compared to buzzard dummies. The decision to desert a nest seems to be a trade-off between predation risk on the one hand and protection against crows on the other. Goshawks proved far more aggressive against an intraspecific dummy than buzzards. Buzzards adjusted their level of brood defence against both intra- and interspecific dummies according to the age of offspring but not offspring number, with an increasing brood defence level with increasing offspring age. Thus the behaviour of buzzards towards goshawks is a result of a complex system of trade-offs between predation risk, competition for prime nesting habitat and protection from crows on which brood value acts as a temporal modifier.     

Visual Assessment of Relative Body Size in a Cichlid Fish,the Oscar,Astronotus ocellatus

In cichlid fishes, fighting ability, success at nest defense, and fecundity are all positively correlated with body size. Selection should therefore favor the evolution of strategies for the assessment of relative body size during intraspecific interactions. The effect of relative body size on agonistic behavior in the oscar (Astronotus ocellatus) was tested using dummies. As predicted by game theory models, attack was strongly correlated with the size of the dummy relative to the subject. The most intense aggression occurred when dummy size was approximately 75% of subject size. These data support the prediciton that perceived body size asymmetries are important determinants of agonistic behavior in these fishes. Further, the results suggest that oscars can visually assess relative body size, and may estimate relative fighting ability without tests of strength. Subject size was positively correlated with intensity of aggressive behavior. Attack and display frequencies were positively correlated with a subject's body size, while latencies to approach and attack dummies were negatively correlated with subject size.     

A finite element model of an anthropomorphic test device lower limb to assess risk of injuries during vertical accelerative loading

Improvised explosive devices (IEDs) were used extensively to target occupants of military vehicles during the conflicts in Iraq and Afghanistan (2003–2011). War fighters exposed to an IED attack were highly susceptible to lower limb injuries. To appropriately assess vehicle safety and make informed improvements to vehicle design, a novel Anthropomorphic Test Device (ATD), called the Warrior Injury Assessment Manikin (WIAMan), was designed for vertical loading. The main objective of this study was to develop and validate a Finite Element (FE) model of the WIAMan lower limb (WIAMan-LL). Appropriate materials and contacts were applied to realistically model the physical dummy. Validation of the model was conducted based on experiments performed on two different test rigs designed to simulate the vertical loading experienced during an under-vehicle explosion. Additionally, a preliminary evaluation of the WIAMan and Hybrid-III test devices was performed by comparing force responses to post-mortem human surrogate (PMHS) corridors. The knee axial force recorded by the WIAMan-LL when struck on the plantar surface of the foot (2 m/s) fell mostly within the PMHS corridor, but the corresponding data predicted by the Hybrid-III was almost 60% higher. Overall, good agreements were observed between the WIAMan-LL FE predictions and experiments at various pre-impact speeds ranging from 2 m/s up to 5.8 m/s. Results of the FE model were backed by mean objective rating scores of 0.67–0.76 which support its accuracy relative to the physical lower limb dummy. The observations and objective rating scores show the model is validated within the experimental loading conditions. These results indicate the model can be used in numerical studies related to possible dummy design improvements once additional PMHS data is available. The numerical lower limb is currently incorporated into a whole body model that will be used to evaluate the vehicle design for underbody blast protection.     

On the possible role of egg mimics in speciation

Sexually active male haplochromine cichlid fishes possess pronounced yellow ovoid spots on the anal fm, which mimic eggs of the female and have therefore been called egg dummies (Wickler, 1962b).It is thought that divergence in egg dummy characteristics can considerably reduce gene flow and in this way may trigger off reproductive isolation. Two ways in which egg dummy divergence can develop are described. Both mechanisms may have been operating, at the same time and in the same area, in different species, or possibly even in a single species.Firstly, egg dummy divergence can develop in species with accurately mimetic egg dummies if selection pressures on egg characteristics (size, shape) differ in temporarily isolated demes. As soon as egg characteristics diverge, egg dummy characteristics follow. This type of egg dummy divergence leads to reproductive isolation by mimicry. Mimetic isolation is proposed as a term to describe the mechanism.Secondly, egg dummy divergence can develop if selection pressures on the egg dummy characteristics are different in two temporarily isolated demes. Upon secondary contact, this divergence may work as a sexual isolation mechanism, since female mate choice is important in haplochromines. Egg dummy divergence is likely to develop rapidly and, if this happens repeatedly, explosive speciation may result. Apparently, explosive speciation has occurred in haplochromines. Neither of the two models has been properly tested. Some preliminary evidence was found that the second model is valid, but so far there is no evidence in favour of the first model.     

Colour saturation triggers innate reactions to flower signals: Flower dummy experiments with bumblebees

Summary Innate behavioural reactions, i.e. reactions of untrained, flower-naive bumblebees (Bombus terrestris L., B. lucorum L.; Apidae) were observed in flower dummy experiments. It was proven that an innate releasing mechanism responds to optical flower signals: the spectral purity of corolla colour was found to be crucial for far attraction toward flower dummies. During the subsequent near orientation, that is when a bumblebee finally reaches a flower dummy, the bumblebee's antennae contact the part of highest spectral purity while the bee is still in flight. Guides such as stamen patches present in the center of flower dummies are used only for near orientation. Flower dummies receiving the greatest number of antennae reactions at the guide were always those with low spectral purity in the surrounding background colour, high spectral purity at the corolla colour and highest spectral purity at the guide colour. In contrast, dominant wavelength and intensity of flower dummy colours had no detectable influence on innate behavioural reactions, while colour contrast had some. These results are interpreted as follows: orientation toward guides is based upon a gradient of centripetally increasing, bee-subjective colour saturation which directs the bumblebee's approach toward the center of the flower dummy where additional factors may contribute to stimulating the landing reaction.     

Development and validation of a CO-C7 FE complex for biomechanical study

In this study, the digitized geometrical data of the embalmed skull and vertebrae (C0-C7) of a 68-year old male cadaver were processed to develop a comprehensive, geometrically accurate, nonlinear C0-C7 FE model. The biomechanical response of human neck under physiological static loadings, near vertex drop impact and rear-end impact (whiplash) conditions were investigated and compared with published experimental results. Under static loading conditions, the predicted moment-rotation relationships of each motion segment under moments in midsagittal plane and horizontal plane agreed well with experimental data. In addition, the respective predicted head impact force history and the S-shaped kinematics responses of head-neck complex under near-vertex drop impact and rear-end conditions were close to those observed in reported experiments. Although the predicted responses of the head-neck complex under any specific condition cannot perfectly match the experimental observations, the model reasonably reflected the rotation distributions among the motion segments under static moments and basic responses of head and neck under dynamic loadings. The current model may offer potentials to effectively reflect the behavior of human cervical spine suitable for further biomechanics and traumatic studies.     

Both olfactory and visual cues promote the hornet Vespa velutina to locate its honeybee prey Apis cerana

Predators use olfactory, visual and sometimes acoustic cues from the preys to assess food information. However, it is not known if the aggressive hornets (Vespa spp.) use olfactory, visual, or both types of information to find and recognize prey. In the present study, we trained hornet workers (Vespa velutina) to a feeding area. Once the hornets began consistently foraging at this feeding area, we determined whether they located prey (bees, Apis cerana) via olfactory or visual cues. We did this by testing whether hornets were attracted to a dummy bait (bee dummy bait or non-bee dummy bait) treated with extracts of honeybee cuticular hydrocarbons. We then tested whether hornets could distinguish between bee dummy bait and cotton ball dummy bait, both treated with bee odors. Hornets preferred the dummy treated with bee odors, and bee dummies (with bee images) were more attractive to the hornet than the cotton ball dummies with only bee odors. These results clearly indicate that a combination of olfactory and visual cues helps the hornet to locate its prey.     

Effect of a Dummy Audience on Male–Male Interactions in Siamese Fighting Fish, Betta splendens

Recent research on Siamese fighting fish, Betta splendens, and other taxa has demonstrated that an audience can cause males to alter their behavior in aggressive interactions. One factor not taken into account in these studies is how exactly the audience influences these interactions. It is possible that a live audience may interact with the subjects, creating an active communication network rather than a signaler–receiver dyad with a passive audience. Here, we used a dummy audience to control for information exchange between the audience and the interactants that might cause them to modify their behavior. Audience treatments included dummies of male and female B. splendens, a dummy cichlid, and a control condition with no audience present. The presence of a dummy audience did not influence male–male interactions. However, males spent the most time near the audience tank when the audience was a dummy of a B. splendens. This suggests that some factor other than the physical presence of the audience is responsible for the modification of behavior found in previous audience effect studies in Siamese fighting fish. However, we cannot rule out definitively that our dummy audience is viewed as unimportant by the opponents and, thus, ignored. Further research is necessary to determine which component of the audience is important for producing audience effects.     

Evolution of egg dummies in Tanganyikan cichlid fishes: the roles of parental care and sexual selection

Sexual selection has been suggested to be an important driver of speciation in cichlid fishes of the Great Lakes of Africa, and the presence of male egg dummies is proposed to have played a key role. Here, we investigate how mouthbrooding and egg dummies have evolved in Tanganyikan cichlids, the lineage which seeded the other African radiations, with a special emphasis on the egg dummies. Using modern phylogenetic comparative analyses and a phylogeny including 86% of the 200 described species, we provide formal evidence demonstrating correlated evolution between mouthbrooding and egg dummies in Tanganyikan cichlids. These results concur with existing evidence, suggesting that egg dummies have evolved through sensory exploitation. We also demonstrate that there is a strong evolutionary correlation between the presence of egg dummies and both pre‐ and post‐copulatory sexual selection. Moreover, egg dummy evolution was contingent on the intensity of pre‐ and post‐copulatory sexual selection in Tanganyikan cichlids. In sum, our results provide evidence supporting the hypothesis of egg dummies evolving through sensory exploitation and highlight the role of sexual selection in favouring the evolution and maintenance of this trait.     

Habituation and development of response specificity to a sign stimulus: male preference for female courtship posture in stickleback

I examined biased patterns of habituation that occur when reproductive male three-spined stickleback, Gasterosteus aculeatus, respond to a choice of two dummy females, one displaying the head-up posture of a sexually receptive female and an otherwise identical dummy lacking this sign stimulus (i.e. a dummy in a 'neutral' horizontal posture). Males initially courted both dummies about equally, but within 5 min, their courtship to the horizontal dummy began to habituate and was eventually replaced by attack behaviour, which increased about four-fold during the 1-h trial. Courtship to the head-up dummy continued unabated throughout the trial and by 5 min exceeded courtship to the horizontal dummy. Attack to the head-up dummy increased slightly in the first half of the trial then leveled off to about one-third that directed to the horizontal dummy. Both dummies were stationary and unreactive so could not directly provide differential feedback to the males. It is speculated that the self-arousal males obtain when responding to head-up posture reinforces their response to that cue. The salience of this sign stimulus may develop through an interactive process wherein the male's predisposition to recognize and court the head-up posture and the sexual self-arousal he obtains by doing so counter habituation and help maintain his sexual response to that cue. The stimulus-response specificity of male courtship is assumed to have an innate basis but requires experience to become fully differentiated. The results also illustrate that rate or extent of habituation to different stimuli, even on the same dimension, can differ within the same individual and in an adaptive manner. Copyright 2000 The Association for the Study of Animal Behaviour.     

Evaluation of cross-sectional geometry and mass density distributions of humans and laboratory animals using computerized tomography

The purpose of this study was to determine the cross-sectional geometry and mass density distribution of a young porcine subject using the X-ray computerized tomographic (CT) method and to perform a comparative study of anatomical features of this subject and a 3 yr old female child specimen. The cross-sectional CT scans of the porcine subject were obtained at 1 cm intervals. The outlines of each cross section and of selected anatomical components within each section were obtained by standard picture processing techniques. The mass and inertia tensor for each cross section and for each anatomical structure in a section were computed based on the CT numbers. The porcine subject was then sacrificed, frozen, sectioned and photographed. These sectional photographs were then compared with those obtained from the CT method. Tabulated cross-sectional mass and inertia tensor obtained from CT scans of the porcine subject were also used to compare with similar results derived from previously completed CT scans of the 3 yr old female child specimen. In particular, the comparisons were made on the location of the center of gravity and the inertia tensor in the head, neck, head and neck and cervical spine regions. Some immediate applications of this data are inputs to finite element models, lumped parameter biodynamic models, computer simulation of vehicle crash victims, and dummy design.