![]() ![]() The aim of this study was to test a three-step model in which structural dysconnectivity is correlated with an elevated consciousness threshold, which in turn is also associated with psychotic symptoms in patients. The observation of shared dysconnectivity patterns between schizophrenia and bipolar disorder with psychotic features ( McIntosh et al., 2008) also fits the hypothesis that psychotic symptoms may be related to an increased consciousness threshold. It has been proposed, but not yet tested, that a disruption in conscious access could increase the liability to psychosis because insufficient conscious access to information may cause cognitive impairments and make patients prone to developing false inferences that fuel delusional ideas ( Berkovitch et al., 2017). Only a few studies have explored their consciousness threshold, with mixed results ( Fleming and Green, 1995 McClure, 1999 Goghari and Sponheim, 2008 Chkonia et al., 2012). Importantly, alterations in structural connectivity were shown to be associated with clinical features of the disease ( Wolkin et al., 2003 Skelly et al., 2008 Canu et al., 2015 Kochunov et al., 2017 Griffa et al., 2019).ĭysconnectivity of white matter tracts has also been reported in patients with bipolar disorder ( Magioncalda et al., 2016 Favre et al., 2019), especially those with psychotic features ( Anticevic et al., 2013 Sarrazin et al., 2014), but to a lesser degree than that of patients with schizophrenia ( Skudlarski et al., 2013). Patients with schizophrenia exhibit impairments in conscious access ( Del Cul et al., 2006 Green et al., 2011 Mathis et al., 2012 Hanslmayr et al., 2013 Herzog et al., 2013 Berkovitch et al., 2018) and disorganized and/or insufficient myelinated fiber tracts ( Klauser et al., 2017 Kelly et al., 2018), even before treatments ( Li et al., 2018), particularly in the prefrontal cortex ( Wu et al., 2015) and cingulum ( Sun et al., 2003). This proposal is supported by a study showing that consciousness threshold was correlated with structural connectivity in patients with multiple sclerosis ( Reuter et al., 2009), although this hypothesis remains unexplored in other diseases showing structural dysconnectivity and impaired conscious access. The global neuronal workspace (GNW) theory ( Dehaene et al., 1998 Dehaene and Changeux, 2011) proposes that information becomes consciously accessible when it triggers sustained activity in a large network of interconnected neurons ( Sergent et al., 2005 Del Cul et al., 2007 van Vugt et al., 2018), leading to the prediction that structural integrity within the posteroanterior long-distance network may be one of the prerequisites for conscious access. Our findings support the hypothesis that long-distance structural connectivity within the GNW plays a crucial role in conscious access, and that conscious access may mediate the association between impaired structural connectivity and psychosis. Mediation analysis demonstrated that alterations in long-distance connectivity were associated with an increased masking threshold, which in turn was linked to psychotic symptoms. Masking threshold correlated negatively with the mean general fractional anisotropy of white matter tracts exclusively within the GNW network (inferior frontal-occipital fasciculus, cingulum, and corpus callosum). Patients with psychosis (schizophrenia and bipolar disorder with psychotic features) had an elevated masking threshold compared with control subjects and bipolar disorder patients without psychotic features. We used a visual masking paradigm to measure consciousness threshold, and diffusion MRI tractography to assess structural connectivity in 97 humans of either sex with varying degrees of psychosis: healthy control subjects ( n = 46), schizophrenia patients ( n = 25), and bipolar disorder patients with ( n = 17) and without ( n = 9) a history of psychosis. The aim of this study was to determine the extent to which structural connectivity is correlated with consciousness threshold, particularly in psychosis. ![]() The implications of abnormal structural connectivity for disrupted conscious access and the relationship between these two deficits and psychopathology remain unclear. In patients with schizophrenia and bipolar disorder, both alterations in cerebral connectivity and an increased threshold for conscious perception have been reported. According to global neuronal workspace (GNW) theory, conscious access relies on long-distance cerebral connectivity to allow a global neuronal ignition coding for conscious content. ![]()
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