The Role of the Corpus Callosum in Psychosis

Abstract

Corticocortical dysconnectivity is thought to be a critical feature of the pathophysiology of psychotic disorders. However, although the corpus callosum is by far the largest structure within the white matter and contains some of the densest projections to and from cortical areas implicated in psychosis ( 1 McGuire P. Bates J. Goldman-Rakic P.S. Interhemispheric integration: I. Symmetry and convergence of the corticocortical connections of the left and right principal sulcus (PS) and the left and right supplementary motor area (SMA) in the rhesus monkey. Cereb Cortex. 1991; 1: 390-407 Crossref PubMed Scopus (109) Google Scholar ), most neuroimaging studies of connectivity in psychosis have examined pathways within rather than between the cerebral hemispheres ( 2 Pettersson-Yeo W. Allen P. Benetti S. McGuire P. Mechelli A. Dysconnectivity in schizophrenia: Where are we now?. Neurosci Biobehav Rev. 2011; 35: 1110-1124 Crossref PubMed Scopus (485) Google Scholar ). The precise location and the clinical significance of alterations in the corpus callosum in patients with psychotic disorders are still unclear. One potential contributory factor is that previous neuroimaging studies of the corpus callosum in psychotic disorders involved relatively modest numbers of participants. This is a general limitation of the neuroimaging literature in psychosis but can be addressed by using a multicenter design, with participants scanned at a number of different sites. In this issue of Biological Psychiatry, Francis et al. ( 3 Francis A.N. Mothi S.S. Mathew I.T. Tandon N. Clementz B. Pearlson G.D. et al. Callosal abnormalities across the psychosis dimension: Bipolar schizophrenia network on intermediate phenotypes. Biol Psychiatry. 2016; 80: 627-635 Abstract Full Text Full Text PDF PubMed Scopus (25) Google Scholar ) adopted this approach, which allowed the authors to examine magnetic resonance imaging data from 1381 participants—a sample an order of magnitude larger than in most previous studies in this field. The acquisition of data from several different sites may introduce potentially confounding effects because of differences in the type and age of the scanners used and in the image acquisition protocols ( 4 Gifford G. Crossley N. Fusar-Poli P. Schnack H. Kahn R. Koutsouleris N. et al. Using neuroimaging to help predict the onset of psychosis [published online ahead of print April 1]. Neuroimage. 2016; (http://dx.doi.org/10.1016/j.neuroimage.2016.03.075) Google Scholar ). However, the impact of these effects can be reduced by standardizing hardware and methodology across sites ( 4 Gifford G. Crossley N. Fusar-Poli P. Schnack H. Kahn R. Koutsouleris N. et al. Using neuroimaging to help predict the onset of psychosis [published online ahead of print April 1]. Neuroimage. 2016; (http://dx.doi.org/10.1016/j.neuroimage.2016.03.075) Google Scholar ), as in the study by Francis et al. ( 3 Francis A.N. Mothi S.S. Mathew I.T. Tandon N. Clementz B. Pearlson G.D. et al. Callosal abnormalities across the psychosis dimension: Bipolar schizophrenia network on intermediate phenotypes. Biol Psychiatry. 2016; 80: 627-635 Abstract Full Text Full Text PDF PubMed Scopus (25) Google Scholar ), in which each of five centers used the same Alzheimer’s Disease Neuroimaging Initiative acquisition protocol on 3T magnetic resonance scanners. However, as the authors observed, even when methods are standardized, there may still be significant site effects ( 4 Gifford G. Crossley N. Fusar-Poli P. Schnack H. Kahn R. Koutsouleris N. et al. Using neuroimaging to help predict the onset of psychosis [published online ahead of print April 1]. Neuroimage. 2016; (http://dx.doi.org/10.1016/j.neuroimage.2016.03.075) Google Scholar ). Nevertheless, overall, the benefits of scale probably outweigh the potentially confounding effects of including data from different sites, and multicenter designs are increasingly being used in neuroimaging studies in psychosis ( 5 Mechelli A. Riecher-Rössler A. Meisenzahl E. Tognin S. Wood S. Borgwardt S. et al. Neuroanatomical abnormalities that predate the onset of psychosis: A multicenter study. Arch Gen Psychiatry. 2011; 68: 489-495 Crossref PubMed Scopus (209) Google Scholar , 6 Cannon T.D. Chung Y. He G. Sun D. Jacobson A. van Erp T.G. et al. Progressive reduction in cortical thickness as psychosis develops: A multisite longitudinal neuroimaging study of youth at elevated clinical risk. Biol Psychiatry. 2015; 77: 147-157 Abstract Full Text Full Text PDF PubMed Scopus (400) Google Scholar ).