Abstract
Recently, a growing body of data has revealed that beyond a dysfunction of connectivity among different brain areas in schizophrenia patients (SCZ), there is also an abnormal asymmetry of functional connectivity compared with healthy subjects. The loss of the cerebral torque and the abnormalities of gyrification, with an increased or more complex cortical folding in the right hemisphere may provide an anatomical basis for such aberrant connectivity in SCZ. Furthermore, diffusion tensor imaging studies have shown a significant reduction of leftward asymmetry in some key white-matter tracts in SCZ. In this paper, we review the studies that investigated both structural brain asymmetry and asymmetry of functional connectivity in healthy subjects and SCZ. From an analysis of the existing literature on this topic, we can hypothesize an overall generally attenuated asymmetry of functional connectivity in SCZ compared to healthy controls. Such attenuated asymmetry increases with the duration of the disease and correlates with psychotic symptoms. Finally, we hypothesize that structural deficits across the corpus callosum may contribute to the abnormal asymmetry of intra-hemispheric connectivity in schizophrenia.
Highlights
Left–right asymmetries of brain and behavior are known to be widespread among both vertebrates and invertebrates, and can arise through a number of genetic, epigenetic, or neural mechanisms (Corballis, 2014)
In human beings, such brain asymmetry is widely associated with complementary functions, with the lefthemisphere regarded as being dominant for language and handedness (Corballis, 2014), and the right hemisphere as being dominant for some non-verbal functions, such as spatial attention (Cai et al, 2013) and the processing of faces (Dundas et al, 2014)
Starting with a brief overview of the structural and functional asymmetry in healthy brains, in this manuscript, we will focus our attention on the recent works that investigated the asymmetry of functional connectivity in schizophrenia, suggesting that this aspect may represent a neurophysiological feature that is unique to this disorder
Summary
A growing body of data has revealed that beyond a dysfunction of connectivity among different brain areas in schizophrenia patients (SCZ), there is an abnormal asymmetry of functional connectivity compared with healthy subjects. We review the studies that investigated both structural brain asymmetry and asymmetry of functional connectivity in healthy subjects and SCZ. From an analysis of the existing literature on this topic, we can hypothesize an overall generally attenuated asymmetry of functional connectivity in SCZ compared to healthy controls. Such attenuated asymmetry increases with the duration of the disease and correlates with psychotic symptoms.
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