Temperament at 5 years of age predicts amygdala and orbitofrontal volume in the right hemisphere in adolescence

Abstract

It was of interest to determine if hemispheric differences in orbitofrontal cortex (OFC) volume would be related to behavioral inhibition observed in a peer-play setting. Magnetic resonance imaging (MRI) was carried out in 23 individuals (19 males and 4 females) at an average age of 14.87+/-1.14 years who were either at high or low risk for alcohol dependence. All subjects had previously been evaluated in a preschool peer play paradigm (5.03+/-0.78 years) assessing behavioral inhibition. Region of interest measures were traced for the OFC and the amygdala, and confirmed with voxel based morphometry. Behavioral inhibition, a behavioral tendency that often occurs in a novel setting in reaction to strangers, includes the following: greater time spent next to the mother, greater time staring at another child, and longer latency to begin play with another child. A significant relationship was seen between greater right OFC volume and indicators of behavioral inhibition including greater time spent proximal to their mother and greater time staring at the other child. Also, larger amygdala volume was associated with more time spent proximal to the mother. Behavioral control, including both over- and under-control, is likely to be subserved by neural circuitry associated with emotion regulation including the right OFC and the amygdala.

Fig. 1

The boundaries and landmarks for the orbitofrontal cortex, right, left and total, followed the guidelines established by Lacerda et al (2003). Outlines for the left OFC are seen in blue, with the right OFC in red. The yellow line depicts the lateral and medial portions of the OFC in each hemisphere.

Fig. 2

Orbitofrontal cortex ratios were determined for each participant using the formula (Right−Left)/(Right+Left). Volumes were adjusted for intracranial volume before statistical analyses were performed. Depicted here are the adjusted means (adjustment for age and risk) and the standard errors for those below 15 s for time spent proximal to the mother and those greater than 15s.

Fig. 3

VBM results (SPM 5) with height threshold T=1.73, p=0.049 and extent threshold k=50 voxels for Inhibited versus Uninhibited groups based on time spent proximal to mother at <15 s versus >15s in the peer play setting at average age of 5.03 yrs±0.78 years.