MRI amygdala volume in Williams Syndrome.
In Williams Syndrome the amygdala looks large only because the whole brain is small.
01Research in Context
What this study did
The team scanned the brains of people with Williams Syndrome. They measured the size of the amygdala, the brain’s emotion hub. They also measured total head size to see if the amygdala only looks big because the whole brain is small.
What they found
Raw numbers showed no difference in amygdala volume. After correcting for smaller total brain size, the amygdala was relatively larger in Williams Syndrome. In short, the amygdala is not oversized; the rest of the brain is undersized.
How this fits with other research
Oliveira et al. (2014) used the same MRI trick on the same WS group. They found the cerebellum is also relatively big once you adjust for small head size.
Sampaio et al. (2010) looked at the hippocampus one year earlier. They saw normal raw volume but odd left-right shape, showing the whole limbic ring is quirky in WS.
Griffith et al. (2012) saw a true absolute amygdala enlargement in adults with Asperger syndrome. The WS and autism findings seem opposite, but the studies used different diagnoses and age groups, so they do not truly clash.
Why it matters
When you read a WS assessment, remember the brain is built small. A “big” amygdala on the report is probably a scaling effect, not a danger sign. Pair this with Oliveira et al. (2014) and you can reassure families that relative size is typical for WS. Use that calm to shift focus to skill-building programs instead of worry about brain volume.
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02At a glance
03Original abstract
One of the most intriguing characteristics of Williams Syndrome individuals is their hypersociability. The amygdala has been consistently implicated in the etiology of this social profile, particularly given its role in emotional and social behavior. This study examined amygdala volume and symmetry in WS individuals and in age and sex matched controls. Magnetic resonance imaging scans were obtained on a GE 1.5-T magnet with 1.5-mm contiguous slices and were used to measure whole gray matter, white matter and cerebrospinal fluid volumes, as well as amygdala volume (right and left). Results revealed significantly reduced intracranial volume in individuals with WS, compared with controls. There were no differences between groups in absolute amygdalae volume, although there was a relative increase in amygdalae volumes, when adjusted for total intracranial content. There were no inter-hemispheric differences in amygdalae volumes in both groups. These results suggest a relative increase in amygdala volume in WS compared with healthy controls that likely reflects abnormal neurodevelopmental processes of midline brain structures.
Research in developmental disabilities, 2011 · doi:10.1016/j.ridd.2011.05.033