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Structural and functional brain asymmetries in human situs inversus totalis
D N Kennedy1, K M O'Craven, B S Ticho
1Center for Morphometric Analysis, Massachusetts General Hospital, Boston, USA.
Neurology
|October 16, 1999
Summary
Individuals with situs inversus totalis (SI) show reversed brain asymmetries, but maintain typical language dominance and handedness. This suggests distinct developmental pathways for organ and brain lateralization.
Area of Science:
- Neuroscience
- Developmental Biology
- Medical Imaging
Background:
- The human brain exhibits structural and functional asymmetries.
- Understanding the relationship between brain asymmetry and functional lateralization is complex.
- Situs inversus totalis (SI) offers a unique model to study these relationships.
Purpose of the Study:
- To investigate brain asymmetries in individuals with situs inversus totalis (SI).
- To explore potential correlations between visceral organ arrangement and brain structure/function lateralization.
Main Methods:
- Utilized anatomic and functional magnetic resonance imaging (MRI) techniques.
- Analyzed brain asymmetries in three individuals diagnosed with SI.
Main Results:
- Observed reversal of major anatomic asymmetries (frontal and occipital petalia) in SI brains.
- Functional MRI revealed left cerebral hemisphere language dominance in SI subjects.
- SI individuals exhibited strong right-handedness, consistent with the general population.
Conclusions:
- Developmental factors for visceral asymmetry and cerebral petalia asymmetry appear distinct.
- Functional lateralization of language is not directly dictated by the same factors influencing gross anatomic brain asymmetries.
- SI provides valuable insights into the independent development of organ and brain lateralization.