Amygdala and hippocampus enlargement during adolescence in autism

The amygdala and hippocampus are key components of the neural system mediating emotion perception and regulation and are thought to be involved in the pathophysiology of autism. Although some studies in children with autism suggest that there is an enlargement of amygdala and hippocampal volume, findings in adolescence are sparse.

We measured amygdala and hippocampus volume in a homogeneous group of adolescents with autism (12 through 18 years; n = 23) and compared them with an age-, sex-, and IQ-matched control group (n = 29) using a validated automated segmentation procedure in 1.5-T magnetic resonance images. All analyses were adjusted for total brain volume.

Repeated-measures analysis revealed a significant group x hemisphere x brain structure interaction (p = .038), even when corrected for total brain volume. Post-hoc analysis showed that the right amygdala and left hippocampus were significantly enlarged (p = .010; p = .015) in the autism compared with the control group. There were no significant correlations between age and amygdala or hippocampus volume.

The abnormal enlargement of the amygdala and hippocampus in adolescents with autism adds to previous findings of enlargement of these structures in children with autism. This may reflect increased activity of these structures and thereby altered emotion perception and regulation. Our results could therefore be interpreted in light of developmental adaptation of the autistic brain to a continuous overflow of emotional learning experiences.