Early Variations in Amygdala Development May Signal Divergent Behavioral Outcomes

Behavioral Regulatory Problems Are Associated With a Lower Attentional Bias to Fearful Faces During Infancy

To investigate the role of early regulatory problems (RP), such as problems in feeding, sleeping, and calming down during later development, the association between parent-reported RP at 3 months (no-RP, n = 110; RP, n = 66) and attention to emotional faces at 8 months was studied. Eight-month-old infants had a strong tendency to look at faces and to specifically fearful faces, and the individual variance in this tendency was assessed with eye tracking using a face-distractor paradigm. The early RPs were related to a lower attention bias to fearful faces compared to happy and neutral faces after controlling for temperamental negative affectivity. This suggests that early RPs are related to the processing of emotional information later during infancy.

High Psychopathology Subgroup in Young Children With Autism: Associations With Biological Sex and Amygdala Volume

OBJECTIVE

The aims of this study were to identify a subset of children with autism spectrum disorder (ASD) and co-occurring symptoms of psychopathology, and to evaluate associations between this subgroup and biological sex and amygdala volume.

METHOD

Participants included 420 children (ASD: 91 girls, 209 boys; typically developing controls: 57 girls, 63 boys). Latent profile analysis was used to identify ASD subgroups based on symptoms of psychopathology, adaptive functioning, cognitive development, and autism severity. Differences in the proportions of girls and boys across subgroups were evaluated. Magnetic resonance imaging scans were acquired (346 children); amygdala volumes were evaluated in relation to subgroups and problem behavior scores.

RESULTS

Three ASD subgroups were identified. One group was characterized by high levels of psychopathology and moderate impairment on other measures (High Psychopathology Moderate Impairments [HPMI], comprising 27% of the sample). The other two subgroups had lower symptoms of psychopathology but were differentiated by high and low levels of impairment on other measures. A higher proportion of girls were classified into the HPMI subgroup (40% of girls versus 22% of boys). Relative to controls, amygdala volumes were enlarged only in the HPMI subgroup. There was a positive association between right amygdala volume and internalizing behaviors in girls but not in boys with ASD.

CONCLUSION

A higher proportion of girls with ASD faced greater challenges with psychopathology, suggesting a need for closer evaluation and potentially earlier intervention to help improve outcomes. Amygdala enlargement was associated with co-occurring symptoms of psychopathology, and sex-specific correlations with symptoms were observed.

Amygdala growth from youth to adulthood in the macaque monkey

Emerging evidence suggests that the human amygdala undergoes extensive growth through adolescence, coinciding with the acquisition of complex socioemotional learning. Our objective was to longitudinally map volumetric growth of the nonhuman primate amygdala in a controlled, naturalistic social environment from birth to adulthood. Magnetic resonance images were collected at five time-points in 24 male and female rhesus macaques from 6 months to adulthood at 5 years. We then compared amygdala growth to other brain regions, including newly collected isocortical gray and white matter volumes, and previously published data on the same cohort. We found that amygdala volume increases by nearly 50% from age 6 months to 5 years. This dramatic growth is in contrast to overall brain and hippocampal volume, which peak near 3 years, white matter, which slows from 3 to 5 years, and isocortical gray, which has a net decrease. Similar to isocortical gray and hippocampal volumes, amygdala volume is ~8% larger in males than females. Rate of growth does not differ by sex. Although the underlying neurobiological substrate for protracted amygdala growth into adulthood is unclear, we propose it may be due in part to the unique cellular development of immature neurons in paralaminar nucleus that mature in size and connectivity with age. Prolonged amygdala maturation raises the possibility that environmental and genetic perturbations that disrupt this trajectory may contribute to the emergence of psychiatric disorders, such as anxiety, depression, schizophrenia, and autism; all in which the amygdala is strongly implicated.