Facial asymmetry tracks genetic diversity among Gorilla subspecies

Mountain gorillas are particularly inbred compared to other gorillas and even the most inbred human populations. As mountain gorilla skeletal material accumulated during the 1970s, researchers noted their pronounced facial asymmetry and hypothesized that it reflects a population-wide chewing side preference. However, asymmetry has also been linked to environmental and genetic stress in experimental models. Here, we examine facial asymmetry in 114 crania from three Gorilla subspecies using 3D geometric morphometrics. We measure fluctuating asymmetry (FA), defined as random deviations from perfect symmetry, and population-specific patterns of directional asymmetry (DA). Mountain gorillas, with a current population size of about 1000 individuals, have the highest degree of facial FA (explaining 17% of total facial shape variation), followed by Grauer gorillas (9%) and western lowland gorillas (6%), despite the latter experiencing the greatest ecological and dietary variability. DA, while significant in all three taxa, explains relatively less shape variation than FA does. Facial asymmetry correlates neither with tooth wear asymmetry nor increases with age in a mountain gorilla subsample, undermining the hypothesis that facial asymmetry is driven by chewing side preference. An examination of temporal trends shows that stress-induced developmental instability has increased over the last 100 years in these endangered apes

Heightened facial muscle reactivity in preadolescent girls with pathological anxiety

Abstract Objectives Anticipatory anxiety and heightened responses to uncertainty are central features of anxiety disorders (ADs) that contribute to clinical impairment. Anxiety symptoms typically emerge during childhood, and even subthreshold‐AD symptoms are associated with distress and risk for future psychopathology. This study compared facial emotional response to threat and uncertainty between preadolescent girls with ADs, girls with subthreshold‐AD symptoms, and controls. Methods Facial emotional responding was characterized in preadolescent girls (age 8–11) with a range of anxiety symptoms: no/low anxiety (controls, n = 41), subthreshold‐AD (n = 73), and DSM‐5 diagnoses of separation, social, and/or generalized ADs (n = 45). A threat anticipation paradigm examined how image valence (negative/neutral) and image anticipation (uncertain/certain timing) impacted activity of the corrugator supercilii, a forehead muscle implicated in the “frown” response that is modulated by emotional stimuli (negative > neutral). Corrugator magnitude and corrugator timecourse were compared between groups. Results Findings demonstrate greater corrugator activity during anticipation and viewing of negative stimuli, as well as increased corrugator reactivity in subthreshold‐AD and AD girls. Timecourse analyses of negative versus neutral stimuli revealed that AD and subthreshold‐AD girls had greater uncertainty‐related increases in corrugator activity compared to controls. Conclusion Results extend the physiological characterization of childhood pathological anxiety, highlighting the impact of subthreshold‐AD symptoms

Fear of the Unknown: Uncertain Anticipation Reveals Amygdala Alterations in Childhood Anxiety Disorders

Children with anxiety disorders (ADs) experience persistent fear and worries that are highly debilitating, conferring risk for lifelong psychopathology. Anticipatory anxiety is a core clinical feature of childhood ADs, often leading to avoidance of uncertain and novel situations. Extensive studies in non-human animals implicate amygdala dysfunction as a critical substrate for early life anxiety. To test specific amygdala-focused hypotheses in preadolescent children with ADs, we used fMRI to characterize amygdala activation during uncertain anticipation and in response to unexpected stimuli. Forty preadolescent (age 8-12 years) children, 20 unmedicated AD patients and 20 matched controls completed an anticipation task during an fMRI scan. In the task, symbolic cues preceded fear or neutral faces, such that 'certain' cues always predicted the presentation of fear or neutral faces, whereas 'uncertain' cues were equally likely to be followed by fear or neutral faces. Both AD children and controls showed robust amygdala response to faces. In response to the uncertain cues, AD children had increased amygdala activation relative to controls. Moreover, in the AD children, faces preceded by an 'uncertain' cue elicited increased amygdala activation, as compared with the same faces following a 'certain' cue. Children with ADs experience distress both in anticipation of and during novel and surprising events. Our findings suggest that increased amygdala activation may have an important role in the generation of uncertainty-related anxiety. These findings may guide the development of neuroscientifically informed treatments aimed at relieving the suffering and preventing the lifelong disability associated with pediatric ADs

Thirty-second student symposium on engineering mechanics

Engineering Mechanics seniors in TAM 293-294, Research and Design Project, work individually with UIUC faculty members and Illinois engineers during the academic year and prepare final written reports on their work. This year (1994-95), there were nineteen students in the course; eight of the students' final reports were judged to be exemplary and have been reproduced in these Proceedings

Connectivity between the central nucleus of the amygdala and the bed nucleus of the stria terminalis in the non-human primate: neuronal tract tracing and developmental neuroimaging studies

The lateral division of the bed nucleus of the stria terminalis (BSTL) and central nucleus of the amygdala (Ce) form the two poles of the 'central extended amygdala', a theorized subcortical macrostructure important in threat-related processing. Our previous work in nonhuman primates, and humans, demonstrating strong resting fMRI connectivity between the Ce and BSTL regions, provides evidence for the integrated activity of these structures. To further understand the anatomical substrates that underlie this coordinated function, and to investigate the integrity of the central extended amygdala early in life, we examined the intrinsic connectivity between the Ce and BSTL in non-human primates using ex vivo neuronal tract tracing, and in vivo diffusion-weighted imaging and resting fMRI techniques. The tracing studies revealed that BSTL receives strong input from Ce; however, the reciprocal pathway is less robust, implying that the primate Ce is a major modulator of BSTL function. The sublenticular extended amygdala (SLEAc) is strongly and reciprocally connected to both Ce and BSTL, potentially allowing the SLEAc to modulate information flow between the two structures. Longitudinal early-life structural imaging in a separate cohort of monkeys revealed that extended amygdala white matter pathways are in place as early as 3 weeks of age. Interestingly, resting functional connectivity between Ce and BSTL regions increases in coherence from 3 to 7 weeks of age. Taken together, these findings demonstrate a time period during which information flow between Ce and BSTL undergoes postnatal developmental changes likely via direct Ce → BSTL and/or Ce ↔ SLEAc ↔ BSTL projections

Overexpressing Corticotropin-Releasing Factor in the Primate Amygdala Increases Anxious Temperament and Alters Its Neural Circuit

BackgroundNonhuman primate models are critical for understanding mechanisms underlying human psychopathology. We established a nonhuman primate model of anxious temperament (AT) for studying the early-life risk to develop anxiety and depression. Studies have identified the central nucleus of the amygdala (Ce) as an essential component of AT's neural substrates. Corticotropin-releasing factor (CRF) is expressed in the Ce, has a role in stress, and is linked to psychopathology. Here, in young rhesus monkeys, we combined viral vector technology with assessments of anxiety and multimodal neuroimaging to understand the consequences of chronically increased CRF in the Ce region.MethodsUsing real-time intraoperative magnetic resonance imaging-guided convection-enhanced delivery, five monkeys received bilateral dorsal amygdala Ce-region infusions of adeno-associated virus serotype 2 containing the CRF construct. Their cagemates served as unoperated control subjects. AT, regional brain metabolism, resting functional magnetic resonance imaging, and diffusion tensor imaging were assessed before and 2 months after viral infusions.ResultsDorsal amygdala CRF overexpression significantly increased AT and metabolism within the dorsal amygdala. Additionally, we observed changes in metabolism in other AT-related regions, as well as in measures of functional and structural connectivity.ConclusionsThis study provides a translational roadmap that is important for understanding human psychopathology by combining molecular manipulations used in rodents with behavioral phenotyping and multimodal neuroimaging measures used in humans. The results indicate that chronic CRF overexpression in primates not only increases AT but also affects metabolism and connectivity within components of AT's neural circuitry

Facial asymmetry tracks genetic diversity among Gorilla subspecies

Mountain gorillas are particularly inbred compared to other gorillas and even the most inbred human populations. As mountain gorilla skeletal material accumulated during the 1970s, researchers noted their pronounced facial asymmetry and hypothesized that it reflects a population-wide chewing side preference. However, asymmetry has also been linked to environmental and genetic stress in experimental models. Here, we examine facial asymmetry in 114 crania from three Gorilla subspecies using 3D geometric morphometrics. We measure fluctuating asymmetry (FA), defined as random deviations from perfect symmetry, and population-specific patterns of directional asymmetry (DA). Mountain gorillas, with a current population size of about 1000 individuals, have the highest degree of facial FA (explaining 17% of total facial shape variation), followed by Grauer gorillas (9%) and western lowland gorillas (6%), despite the latter experiencing the greatest ecological and dietary variability. DA, while significant in all three taxa, explains relatively less shape variation than FA does. Facial asymmetry correlates neither with tooth wear asymmetry nor increases with age in a mountain gorilla subsample, undermining the hypothesis that facial asymmetry is driven by chewing side preference. An examination of temporal trends shows that stress-induced developmental instability has increased over the last 100 years in these endangered apes