Early Socioemotional Intervention Mediates Long-Term Effects of Atypical Rearing on Structural Covariation in Gray Matter in Adult Chimpanzees

Abstract

Atypical rearing has deleterious effects on chimpanzee behavior during development, some of which can be ameliorated with a responsive care intervention (RCI). Here, we obtained in vivo magnetic resonance images of adult brains of 27 chimpanzees given institutional care, with and without RCI, and compared them with those of 16 chimpanzees mother-reared from birth. We found significant long-term rearing effects on structural covariation and gray matter volume, specifically in the basal forebrain (i.e., caudate, putamen, nucleus accumbens, rectus gyrus, and orbital prefrontal cortex), indicating that RCI prevented brain changes due to atypical rearing. A significant correlation between covariation in these brain areas and caregiver nurturing, experienced in the first month of life, suggests a possible developmental mechanism for the effect of early experience on brain networks. We identified an early intervention that prevents changes in the basal forebrain that otherwise emerge as a consequence of institutionalized rearing without species-typical socioemotional experiences.

Keywords: brain; great apes; institutionalization; nurturing experiences; source-based morphometry.

Fig. 1.

Brain regions of Component 3. A 3-D rendering of the chimpanzee brain (a) is shown with lines indicating the approximate location of the five slices illustrated in (b). The five coronal sections (b; labeled 1 to 5, anterior to posterior, respectively) illustrate the brain regions of Component 3 from the source-based morphometry (SBM) analysis. The left column shows the color-coded weighted voxel scores of Component 3 projected onto each coronal slice. The right column indicates the anatomical regions corresponding to the SBM weighted scores.

Fig. 2.

Results for Component 3. Mean weighted source-based morphometry score (a) and mean gray matter volume from the region-of-interest analysis (b) are shown for chimpanzees exposed to standard care, the responsive care intervention, and mother rearing. Error bars show ±1 SE.