Middle ear pneumatization in nonhuman primates: A comparative analysis.

OBJECTIVES: We test the effects of body mass and phylogeny on middle ear cavity pneumatization, and the role of pneumatization in hearing function, spanning the anatomical, ecological, and behavioral diversity of nonhuman primates. MATERIALS AND METHODS: All cavities were segmented in middle ear scans of 96 specimens, from 12 strepsirrhine and 15 haplorhine extant species. We measured the tympanic cavity (TC) separately, and all other middle ear spaces together (MES), calculating the degree of pneumatization with the surface area-to-volume ratio. We tested body mass effect with linear regression; we evaluated the phylogenetic signal and selection patterns, using a Kappa statistic test, and Ornstein-Uhlenbeck models (OU). We investigated the link between pneumatization and hearing sensitivity using phylogenetic regression. RESULTS: Testing body mass reveals an allometric pattern for both TC and MES dimensions. Degree of pneumatization in MES is dependent on body mass in haplorhines: larger animals have more pneumatized MES. Differences at various taxonomic ranks were observed for MES, while no phylogenetic influence was observed for TC. Infraorder selection patterns are different. Auditory performance is significantly related to degree of pneumatization, indicating that a pneumatized middle ear is associated with better perception of low frequencies. DISCUSSION: Pneumatization in MES is under differential selective pressure, indicating several optima for this trait. Pneumatization in MES probably modifies hearing sensitivity through pressure regulation mechanisms, auditory bulla size reduction, and frequency modulation. This could explain strepsirrhine adaptation to high-frequency perception, while haplorhine auditory perception is adapted to a broader sound range, including high and low frequencies.

Psychophysiological effects of oxytocin on parent-child interactions: A literature review on oxytocin and parent-child interactions.

Oxytocin (OT), often called the 'hormone of love' or 'hormone of attachment,' plays a fundamental role in the establishment and quality of parent-infant bonding. However, emerging evidence indicates that OT can also produce antisocial behavior. To clarify these effects, we review studies examining the role of endogenous and exogenous OT on several determinants of attachment: parental sensitivity, and bonding or synchrony in parent-child dyads. Contextual and individual factors moderating the effect of intranasal OT and its peripheral levels are also reviewed. Finally, potential therapeutic applications for OT and current limitations in human OT research are examined. This systematic literature review was based on the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines, with two electronic databases and other bibliographic sources. We identified a total of 47 relevant studies for inclusion in our review. Most of the findings are in accordance with recent ideas that OT administration may increase parent-child prosocial interaction, showing that OT exerts beneficial effects on processes thought to promote bonding, sensitivity, and synchrony. However, we found that OT can induce antisocial behavior (e.g., anxiety) or adverse effects (modulation of maternal care recollections) that are moderated by different contextual (e.g., maltreatment level, presence of unfamiliar people) and individual (attachment style) factors. This review reinforces the importance of context- and individual-dependent factors, which must be taken into account when analyzing the psychophysiological effects of OT.

Effects of Intranasal Oxytocin on Emotion Regulation in Insecure Adolescents: Study Protocol for a Double-Blind, Randomized Controlled Trial.

BACKGROUND: Emotional dysregulation and impaired attachment are potential contributors to the development of psychopathology in adolescence. This raises the question of whether oxytocin (OT), the paradigmatic "attachment hormone," may be beneficial in such contexts. Recent evidence suggests that intranasal administration of OT increases affiliative behavior, including trust and empathy. OT may also facilitate social reciprocity by attenuating the stress response to interpersonal conflict. To date, few studies have investigated the effects of intranasal oxytocin (IN-OT) on neurophysiological emotion regulation strategies in healthy adolescents, particularly during parent-adolescent interaction. To understand these mechanisms, our study will examine the effects of IN-OT on emotion regulation in adolescents during parent-adolescent stressful interactions, and on each adolescent's visual and neurophysiological strategies when visualizing attachment-related pictures. We hypothesize that IN-OT will influence psychophysiological outcomes under conditions of stress. We predict that IN-OT will momentarily increase feelings of safety and attenuate stress and hostile behavior during conflict situations. OT may also enhance attachment security by increasing comfort and proximity-seeking, and reducing neurophysiological hyperactivation. OBJECTIVE: The objective of this study is to evaluate the effects of IN-OT on insecure adolescents by studying their behavior and discourse during a disagreement with one of their parents. Their neurophysiological responses to pictures eliciting attachment-related emotions and their visual exploration strategies will also be investigated. METHODS: In this randomized, double-blind, placebo-controlled parallel-group design, 60 healthy male adolescents classified as insecurely attached will receive 24 international units (IU) of IN-OT versus placebo (PB), 45 minutes before the experimental tasks. Each adolescent will then be invited to engage in an experimental conflict discussion with one of his parents. The conflict session will be videotaped and coded for verbal and non-verbal interaction behavior, using the Goal-Corrected Partnership in Adolescence Coding System (GPACS). Each adolescent will then be asked to visualize attachment-related pictures on a screen. Eye-tracking (ET) and neurophysiological responses, including electrodermal activity (EDA) and heart rate (HR), will be recorded simultaneously and continuously during attachment-related picture viewing (Besançon Affective Picture Set-Adolescents, BAPS-Ado). RESULTS: Enrollment for the study was completed in May 2016. Data analysis commenced in July 2016. Study results will be submitted for publication in the winter of 2017. CONCLUSIONS: OT is a complex molecule with many facets that are not yet fully understood. This experimental protocol will increase scientific and clinical knowledge of emotion regulation skills in insecure adolescents by assessing the impact of IN-OT on parent-adolescent interaction and on the visual processing of attachment-related emotions. Positive results could lead to therapeutic uses of IN-OT to treat emotion dysregulation in adolescence.

Degree of terrestrial activity of the elusive sun-tailed monkey (Cercopithecus solatus) in Gabon: Comparative study of behavior and postcranial morphometric data.

We carried out a multidisciplinary study linking behavioral and morphological data from a little-known guenon species, Cercopithecus solatus, endemic to Gabon. Over a period of 9 months, we documented the pattern of stratum use associated with postural and locomotor behavior by direct observation (650 hrs) of a semi-free-ranging breeding colony. We also conducted a morphometric analysis of the humerus and limb proportions of 90 adult specimens from 16 guenon species, including C. solatus. Field observations indicated that C. solatus monkeys spent a third of their time on the ground, similar to semi-terrestrial guenon species. We detected two patterns of stratum use: at ground level, and in trees, at a height of 3-10 m. The monkeys spent more time on the ground during the dry season than the wet season, feeding mainly at ground level, while resting, and social behaviors occurred more frequently in the tree strata. Our study of humerus size and shape, together with the analysis of limb proportions, indicated morphofunctional adaptation of C. solatus to greater terrestriality than previously thought. We therefore characterize C. solatus as a semi-terrestrial guenon, and propose a new hypothesis for the ancestral condition. By combining behavioral and morphological results, we provide new information about the adaptive strategies of the species, and the evolutionary history of guenons, thus contributing to the conservation of the sun-tailed monkey in the wild.

Developmental integration in a functional unit: deciphering processes from adult dental morphology.

The evolution of mammalian dentition is constrained by functional necessity and by the non-independence of morphological structures. Efficient chewing implies coherent tooth coordination from development to motion, involving covariation patterns (integration) within dental parts. Using geometric morphometrics, we investigate the modular organization of the highly derived vole dentition. Integration patterns between and within the upper and lower molar rows are analyzed to identify potential modules and their origins (functional and developmental). Results support an integrated adult dentition pattern for both developmental and functional aspects. The integration patterns between opposing molar pairs suggest a transient role for the second upper and lower molars during the chewing motion. Upper and lower molar rows form coherent units but the relative integration of molar pairs is in contradiction with existing developmental models. Emphasis on the first three cusps to grow leads to a very different integration pattern, which would be congruent with developmental models. The early developmental architecture of traits is masked by later stages of growth, but may still be deciphered from the adult phenotype, if careful attention is paid to relevant features.