Differences In Head Shape Research Articles

A Review on Head-Related Transfer Function Generation for Spatial Audio

A head-related transfer function (HRTF) is a mathematical model that describes the acoustic path between a sound source and a listener’s ear. Using binaural synthesis techniques, HRTFs play a crucial role in creating immersive audio experiences through headphones or loudspeakers, using binaural synthesis techniques. HRTF measurements can be conducted either with standardised mannequins or with in-ear microphones on real subjects. However, various challenges arise in, for example, individual differences in head shape, pinnae geometry, and torso dimensions, as well as in the extensive number of measurements required for optimal audio immersion. To address these issues, numerous methods have been developed to generate new HRTFs from existing data or through computer simulations. This review paper provides an overview of the current approaches and technologies for generating, adapting, and optimising HRTFs, with a focus on physical modelling, anthropometric techniques, machine learning methods, interpolation strategies, and their practical applications.

Understanding Standard Procedure in Auditory Brainstem Response: Importance of Normative Data.

The auditory brainstem response (ABR) is a noninvasive test that measures neural activity in response to auditory stimuli. Racial differences in head shape have provided strong evidence for specific normative data and accurate device calibration. International standards emphasize the need for standardized procedures and references. This study aimed to outline the standard procedure and related normative ABR values. Standard procedures were performed according to International Electrotechnical Commission (IEC) standards. Five studies from two countries were included to compare the normative values of the ABR. The dataset from the National Standard Reference Data Center (NSRDC) was used as reference. Normative values were described in terms of stimuli, latency, and amplitude. For click stimuli, the latency of the ABR showed different patterns across populations, such as those from Korea and the USA. Although the latencies reported by the NSRDC and for Koreans were relatively short, those reported for USA populations were longer. Using clicks, it was shown that the USA population had the largest ABR amplitude compared to those reported for the other two datasets. For Wave V latency using tone bursts, a similar pattern was identified with click stimuli. Frequency-specific trends were also observed. Although there is a lack of ABR datasets, the information and insights of the present study could be utilized as standard guidelines in research on ABR.

Craniosynostosis-associated variants in the IL-11R complex: new insights and questions.

Skull growth involves the expansion of both the flat calvarial bones of the skull and the fibrous marginal zones, termed sutures, between them. This process depends on co-ordinated proliferation of mesenchymal-derived progenitor cells within the sutures, and their differentiation to osteoblasts which produce the bone matrix required to expand the size of the bony plates. Defects lead to premature closure of these sutures, termed craniosynostosis, resulting in heterogeneous head shape differences due to restricted growth of one or more sutures. The impact on the individual depends on how many and which sutures are affected and the severity of the effect. Several genetic loci are responsible, including a wide range of variants in the gene for the interleukin 11 receptor (IL11RA, OMIM#600939). Recent work from Kespohl and colleagues provides new insights into how some of these variants influence IL-11R function; we discuss their influences on IL-11R structure and IL-11 function as a stimulus of osteoblast differentiation.

Epidemiology, Genetics, and Pathophysiology of Craniosynostosis.

Craniosynostosis, the premature fusion of the infant cranial skulls, can be recognized by characteristic head shape differences that worsen with head growth. Craniosynostosis can be syndromic or nonsyndromic and can involve one suture or multiple sutures. Timely cranial vault surgery is recommended to expand and reshape the skull, with a goal of preventing increased intracranial pressure and providing sufficient space for brain growth. Several gene variants and environmental exposures are known to increase the risk of single suture craniosynostosis (SSC), including in utero constraint, exposure to specific toxins and medications, and medical conditions such as thyroid dysregulation and metabolic bone disorders.

A descriptive study of Cephalic and prosopic anthropometric indices in one-day-old infants in Imam Ali and Kamali Hospital, Karaj

Objective: There is no published literature about the types of head and face shapes in the Alborz newborns. Therefore, we designed this study to report these important regional data.
 Methods: Head length, head width, face length, face width, prosopic and cephalic indices were made on 150 newborns (75 males and 75 females) with a view to establish the criterion of cephalometry for this age group in Iran. A special emphasis was given to delivery mode in this study.
 Results: There was no significant difference in cephalic and prosopic indices between two groups (female: p=0.46; male: p=0.43). Brachycephalic type was dominant and dolicocephalic type was rare in male and female neonates. There was no significant difference in head shape between two groups. Hypereuriprosopic and hyperleptoprosopic were dominant and rare types, respectively, in newborns without significant difference between two groups.
 Conclusion: The head and face indices in the newborn infants born by cesarean section were not significantly different from vaginal delivery group. However, the role of nutrition and climate could not be ruled out.

Hair safe study: Effects of scalp cooling on hair preservation and hair regrowth in breast cancer patients receiving chemotherapy - A prospective interventional study

Hair safe study: Effects of scalp cooling on hair preservation and hair regrowth in breast cancer patients receiving chemotherapy - A prospective interventional study

Geographic Variation in the Green Rat Snake Senticolis triaspis (Squamata: Colubridae): Evidence from Mitochondrial DNA, Morphology, and Niche Modeling

Senticolis triaspis is a widespread polytypic colubrid snake that ranges from the southwestern United States southward along the Pacific Coast and part of the Atlantic Coast of Mexico to Costa Rica. Three subspecies have been described based on differences in color pattern and scutellation: S. t. intermedia, S. t. mutabilis, and S. t. triaspis. The last taxonomic revision was completed in 1960. Here, we present an integrative taxonomic analysis of geographic variation using multiple sources of evidence: mitochondrial DNA (817 bp ND4 from 62 samples), traditional morphology (meristic and mensural characters), geometric morphometrics of head shape, and bioclimatic estimates of environmental niche similarity. Molecular data revealed two deeply divergent mitochondrial lineages corresponding to northern and southern clades and eight well-supported clades within these two main groups. Head shape and niche models also showed north–south differences, while traditional morphological analyses did not discriminate among mtDNA lineages. Thus, our study suggests there are at least two candidate species within Senticolis triaspis based on the mtDNA divergence, differences in head shape, and non-overlapping ecological niches. However, we refrain from making taxonomic recommendations pending the addition of nuclear DNA sequence data, finer sampling at contact zones, and additional morphological data; these data are warranted to provide a more robust, stable species delimitation.

Quantifying Inter- and Intrasexual Head-Shape Polymorphism in Eurycea cf. wilderae (Blue-Ridge Two-Lined Salamanders)

Distinct morphological differences between and within sexes may reflect reproductive behaviors that have evolved under natural and sexual selection. In some members of the Eurycea bislineata (Two-Lined Salamander) species complex, inter- and intrasexual variation in head morphology result from secondary sexual characters used in locating, courting, and guarding mates. In populations of Eurycea cf. wilderae (Blue-Ridge Two-Lined Salamander), males possess one of two suites of morphological traits corresponding to alternative reproductive tactics. “Searching” males appear to be adapted for locating and courting females in terrestrial habitats and are characterized by the seasonal development of mental glands, protruding premaxillary teeth, and elongate cirri. “Guarding” males appear to be adapted for aggressively guarding females in aquatic habitats, lack all three aforementioned traits, and are instead characterized by seasonally enlarged jaw musculature. Traditionally, males have been categorized by treating these traits as binary (i.e., present or absent), but this fails to capture any continuous variation. Here, we evaluated the utility of geometric morphometric methods to quantify and describe differences in head morphology among female, searching male, and guarding male E. cf. wilderae. In the left-lateral view, we found significant pairwise differences among all three morph–sex groups. In the ventral view, we found significant pairwise differences between searching males and guarding males and between searching males and females, but not between guarding males and females. Deformation grids clearly demonstrated the enlarged jaw musculature of guarding males and wider, flatter rostrum of searching males. Our results demonstrate utility of geometric morphometric methods for describing head shape differences among these alternative reproductive tactics and provide baseline data for future studies of spatial and temporal variation.

Genetic, morphometric, and molecular analyses of interspecies differences in head shape and hybrid developmental defects in the wasp genus Nasonia.

Males in the parasitoid wasp genus Nasonia have distinct, species-specific, head shapes. The availability of fertile hybrids among the species, along with obligate haploidy of males, facilitates analysis of complex gene interactions in development and evolution. Previous analyses showed that both the divergence in head shape between Nasonia vitripennis and Nasonia giraulti, and the head-specific developmental defects of F2 haploid hybrid males, are governed by multiple changes in networks of interacting genes. Here, we extend our understanding of the gene interactions that affect morphogenesis in male heads. Use of artificial diploid male hybrids shows that alleles mediating developmental defects are recessive, while there are diverse dominance relationships among other head shape traits. At the molecular level, the sex determination locus doublesex plays a major role in male head shape differences, but it is not the only important factor. Introgression of a giraulti region on chromsome 2 reveals a recessive locus that causes completely penetrant head clefting in both males and females in a vitripennis background. Finally, a third species (N. longicornis) was used to investigate the timing of genetic changes related to head morphology, revealing that most changes causing defects arose after the divergence of N. vitripennis from the other species, but prior to the divergence of N. giraulti and N. longicornis from each other. Our results demonstrate that developmental gene networks can be dissected using interspecies crosses in Nasonia, and set the stage for future fine-scale genetic dissection of both head shape and hybrid developmental defects.

Reliable classification of intentional cranial vault modification and nonsynostotic deformational plagiocephaly using 3D geometric morphometrics.

The style and degree of cranial vault modification (CVM) can have a significant impact on the reliability of assigning crania into operational categories and correlates. These issues can, in turn, influence the interpretation of cultural practices in the archaeological record. If we intend to deploy head shape as a meaningful unit of analysis to address issues of anthropological significance, we need a reliable way to demarcate discrete categories. Here we employ 3D geometric morphometrics to study head shape variation and improve classification accuracy. The present study rendered 3D models of 52 crania (8 unmodified, 44 modified annular) affiliated with the prehispanic Chanka Culture (AD 1000-1400) of south-central Peru. A combination of landmarks and semi-landmarks captured the shape and curves of sampled crania. Principal components analysis (PCA) revealed clusters of shape categories, and agglomerative hierarchical cluster analysis quantified the spectrum of variation. Our methods found four categories of circumferential head shape: annular erect, annular oblique, unmodified, and a new operational category termed slight. This last category was most prone to misclassification through gross inspection. We argue that differences in head shape are due to diverse modes of babywearing and childcare in the late prehistoric Andes. This study provides 3D geometric morphometric techniques that can help alleviate some of the classification errors that have long confounded practicing bioarchaeologists.

How head shape and substrate particle size affect fossorial locomotion in lizards.

Granular substrates ranging from silt to gravel cover much of the Earth's land area, providing an important habitat for fossorial animals. Many of these animals use their heads to penetrate the substrate. Although there is considerable variation in head shape, how head shape affects fossorial locomotor performance in different granular substrates is poorly understood. Here, head shape variation for 152 species of fossorial lizards was quantified for head diameter, slope and pointiness of the snout. The force needed to penetrate different substrates was measured using 28 physical models spanning this evolved variation. Ten substrates were considered, ranging in particle size from 0.025 to 4 mm in diameter and consisting of spherical or angular particles. Head shape evolved in a weakly correlated manner, with snouts that were gently sloped being blunter. There were also significant clade differences in head shape among fossorial lizards. Experiments with physical models showed that as head diameter increased, absolute penetration force increased but force normalized by cross-sectional area decreased. Penetration force decreased for snouts that tapered more gradually and were pointier. Larger and angular particles required higher penetration forces, although intermediate size spherical particles, consistent with coarse sand, required the lowest force. Particle size and head diameter effect were largest, indicating that fossorial burrowers should evolve narrow heads and bodies, and select relatively fine particles. However, variation in evolved head shapes and recorded penetration forces suggests that kinematics of fossorial movement are likely an important factor in explaining evolved diversity.

Review on Phenotypic Characterization of Indigenous Chicken and Farmer Breeding Trait Preference Ecotypes in Sekela Woreda, Northern Ethiopia

This study was conducted in Sekela woreda in Surba Bifeta and Gisha Abay kebeles to characterize chickens phenotypically. A total of 226 chicken owner households were selected randomly. Ten qualitative traits from 446 local chickens and eleven quantitative traits from 48 local chickens were used. The overall predominant plumage color of chicken in the study area were red (34.4%) followed by gray mixture (17.7%) and brownish (17.3%). The commonest comb color observed was red color combs. The majority of chickens possessed comb shape was double shape (44.6%), followed by single (38.8%) comb shape. Double comb shape was predominant in male chicken in Surba Bifeta than Gish Abay Sekela. The result indicated that crest head shape were the common predominant observed head shape in Surba Bifeta both female (40.5%) and male (32.8%). while flat plain head shape were highest proportion observed in Gish Abay both female (86.5%) and male (91.2%), thus there was significancely (p<0.05) differences in head shape between the study area. The overall predominant earlobe color was red (36.1%) followed by red and white (34.3%). Almost all chickens (91.6%) of the study area were not having spurred. The spurs were more proportion observed in male chickens similarly in both study rather than female chickens. The predominant observed eye coloration was orange color in both study area. The most observed predominant feather distributions were normal feathered. The most predominant observed shank color was white (44.2%) followed by yellow (28.5%). Almost all chicken in the study area had no Shank feathers. The plumage color, comb type, sex of chicken, shank color, smoothness of shank, and body size were the major factors that cause vary in the price of chickens. The selection criteria of farmers’ used to breeding hen, egg size, plumage color, broodiness, disease resistance and hatchability was the highest selection criteria and ranking. The quantitative traits were indicated the significance differences (P<0.05) were observed between agro ecology with respect to wing spin (17.61), neck length (18.72), spur length (8.42), chest circumferences (28.3), body length (19.66), wing length (22.51), and shank length (11.47), But not significance differences were observed on the body weights (2.36), wattle length (2.33), thigh circumferences (11.40) and breast width (13.09) traits.

Sexual dimorphism, ontogeny and static allometry of a semi-fossorial snake (genus Atractus)

Sexual dimorphism in snakes has been mainly evaluated for size and number of some morphological traits, but few studies address on sexual shape dimorphism. Here we evaluated the existence of sexual size and shape dimorphism in the semi-fossorial snake Atractus reticulatus. We use linear and geometric morphometrics to evaluate differences between sexes and among different ontogenetic stages (neonates, juveniles and adults). We have shown that A. reticulatus is sexually dimorphic for some traits such as body length and head shape, with females being larger and having more robust heads than males, but the sexes do not differ in head size. Males and females are sexually dimorphic in head shape even in neonates, suggesting that this differentiation is prenatal. Differences in head shape may be associated with trophic segregation, allowing females to feed on larger prey than males. Body size dimorphism progressively increases throughout the ontogenetic stages, which is possibly related to the late sexual maturation of females and/or different growth rates between the sexes. We also found that males and females shows some sex-specific patterns towards static and ontogenetic allometry, with males showing stronger predictive response on static allometry than females, whereas females have ontogenetic allometry, but males do not. Additionally, the allometric slopes in A. reticulatus between sexes converge by presenting similar shapes as head size increases, an expected result for sexes with similar lifestyles. Further investigation on some physiological and natural history aspects in Atractus will be particularly useful for a better understanding of the significance of the morphological differences found in this study.

Within-stream phenotypic divergence in head shape of brown trout associated with invasive brook trout

Abstract Competition with a non-native species can lead to morphological changes in native organisms induced by phenotypic plasticity, and by selection against individuals that do not adjust their morphology to the novel selection pressure. The morphological changes in native organisms are often associated with rapid behavioural responses to competition with the invader. However, knowledge of the interaction between the behaviour and morphology of native organisms competing with a non-native species remains scarce. Here, we investigated the effect of competition with non-native brook trout Salvelinus fontinalis on head shape of native brown trout Salmo trutta in a stream system where changes in diet and territorial behaviour of sympatric brown trout have previously been demonstrated. We found that sympatric brown trout had smaller eyes, shorter lower jaws and more terminal mouth than allopatric conspecifics. These differences in head shape were highly repeatable over a period of 12 months. Apparent survival indicated that the selection on head shape of brown trout was weaker in the sympatric than in the allopatric stretch of the stream. The results suggest that these changes reinforce divergences of foraging strategies between the allopatric and sympatric brown trout, which can negatively affect their population dynamics and trophic function in the food-web.

The role of bite force in the evolution of head shape and head shape dimorphism in Anolis lizards

Abstract Patterns of convergent evolution in head shape, combined with performance measures, provide ideal opportunities to understand the processes driving its evolution. Anole lizards represent an excellent subject to test this, as recurrent habitat specialists or ecomorphs evolved independently across different islands. We show that phenotypic similarity corresponds to both phylogenetic similarity and similarity in habitat, indicating that there is convergent evolution in head shape among ecomorphs. Moreover, we show that the evolution of tall, wide heads correlate with the evolution of higher bite forces, driving head shape variation among and within ecomorphs. In addition, the processes affecting head shape variation can differ between sexes, leading to sexual head shape dimorphism. These processes might, however, still depend on the habitat. Consequently, there could also be convergent evolution in head shape dimorphism among ecomorphs. We found no evidence for convergent evolution in sexual head shape dimorphism. Moreover, the sexual head shape dimorphism correlates poorly with bite force, suggesting that intersexual head shape differences are related to other functions. Different processes are thus driving the evolution of head shape and head shape dimorphism. A free Plain Language Summary can be found within the Supporting Information of this article.

Differences in head size and shape during the growth of Deutero Malay children

Introduction: The growth periods of 0-18 years old can be studied with anthropometry by identifying the head size and shape of the human head. Study on vertical, transverse, and horizontal cephalic indexes can understand differences and growth between sexes and age groups. This study was aimed to analyse the averages and differences in the head size and shape of Deutero Malay children in different age groups. Methods: This research was a descriptive analytic study with cross-sectional design. The sample of 192 Deutero Malay children consisted of boys and girls with an age range of 7-18 years old. Measurement of head height, length, and width was performed to calculate the differences of vertical, transverse, and horizontal cephalic index values by sex and age group, and the classification of the head shape based on the cephalic index values. Results: There was a difference of vertical, transverse, and horizontal by age group, with p = 0.000 (p &lt; 0.05). The average of vertical, transverse, and horizontal cephalic index values was significantly higher in each age group. The average horizontal cephalic index was significantly higher in boys and girls. There was no significant difference in the head shape by the vertical and horizontal cephalic index in all age groups. The highest vertical cephalic index found was chamaecephalic (68%). The highest transverse cephalic index was tapeiocephalic (99%). The highest horizontal cephalic index was hyperbrachycephalic (80%). Conclusion: There is similar head shape of Deutero Malay children, although there may be increasing head size along with age. Keywords: Deutero Malay, head shape, cephalic index, transverse cephalic index, horizontal cephalic index, vertical cephalic index

Sexing Cape Vulture Gyps coprotheres based on head morphometrics

The Cape Vulture Gyps coprotheres is considered sexually monomorphic in the literature, but visual differences in head shape between the sexes have been observed. Furthermore, head morphometrics of other Gyps species show statistically significant variation between the sexes. We show that head morphometrics can be used to determine the sex of Cape Vultures. Males generally have wider and shorter heads, and larger bill depths than females. Discriminant function analysis with data from 63 individuals identified the three most predictive variables in sex determination to be head width, head length and bill depth. We also provide an equation that can be used in conjunction with head measurements as a method to determine the sex of Cape Vultures in the field with an overall accuracy of 84% (92% accuracy for females and 72% for males).

Robustness of newt heads in condition of co-existence: a case of the Carpathian newt and the alpine newt

Co-existence between potentially competing newt species can lead to niche differentiation (e.g., in terms of diet shifts). This may cause adaptive responses involving changes in head shape. Here, we tested the hypothesis: the head shape of Lissotriton montandoni is different in conditions of co-occurrence with Ichthyosaura alpestris than in conditions in which other newt species are absent. We analysed images depicting head shape of specimens of I. alpestris and L. montandoni from a museum collection. All specimens of I. alpestris originated in a habitat where L. montandoni also occurred, whereas specimens of L. montandoni derived from populations that cohabited with I. alpestris and populations in which the presence of another newt species was not recorded. In each image, landmarks and semilandmarks were digitised. Females of L. montandoni from the population where I. alpestris also occurred were characterised by more massive heads and longer mouths in lateral views than females from sites where no other newt species occurred. Significant differences in head shape were also found when analysing ventral views between these species when they occupied the same habitat. We confirmed that the head shape of female L. montandoni differs between conditions of co-occurrence and absence of I. alpestris; no differences were found for males. A differently shaped head may be an adaptation to diet; L. montandoni females with longer mouths and more robust basal parts of the head can feed on larger invertebrates and compete more effectively with I. alpestris. The co-existence of newt species should be taken into account in future ecomorphological studies.

A non-invasive geometric morphometrics method for exploring variation in dorsal head shape in urodeles: sexual dimorphism and geographic variation in Salamandra salamandra.

The study of morphological variation among and within taxa can shed light on the evolution of phenotypic diversification. In the case of urodeles, the dorso-ventral view of the head captures most of the ontogenetic and evolutionary variation of the entire head, which is a structure with a high potential for being a target of selection due to its relevance in ecological and social functions. Here, we describe a non-invasive procedure of geometric morphometrics for exploring morphological variation in the external dorso-ventral view of urodeles' head. To explore the accuracy of the method and its potential for describing morphological patterns we applied it to two populations of Salamandra salamandra gallaica from NW Iberia. Using landmark-based geometric morphometrics, we detected differences in head shape between populations and sexes, and an allometric relationship between shape and size. We also determined that not all differences in head shape are due to size variation, suggesting intrinsic shape differences across sexes and populations. These morphological patterns had not been previously explored in S. salamandra, despite the high levels of intraspecific diversity within this species. The methodological procedure presented here allows to detect shape variation at a very fine scale, and solves the drawbacks of using cranial samples, thus increasing the possibilities of using collection specimens and alive animals for exploring dorsal head shape variation and its evolutionary and ecological implications in urodeles. J. Morphol. 278:475-485, 2017. © 2017 Wiley Periodicals, Inc.

Examining Head-shape Differences and Ecology in Morphologically Similar Salamanders at Their Zone of Contact

Studying morphological features in addition to ecological characteristics of co-occurring species can provide insight into interactions between species. Determining factors that influence interactions between species provides a framework for understanding evolution in natural environments. Plethodontid salamanders are model taxa frequently used to study species interactions in regard to competition, coexistence, and exclusion. Past studies have suggested that P. ventralis and P. websteri exhibit character displacement in color and may competitively interact when in sympatry. We studied P. ventralis and P. websteri at a sympatric location in Jefferson County, Alabama and compared this population to allopatric populations of each species to identify whether these species differed in morphology and diet, which are indicators for interspecific competition. We found that P. ventralis and P. websteri differed in head shape, in general, and that head shape differed among populations within species. However, we d...