Diagnostic Discontinuity in Psychosis: A Combined Study of Cortical Gyrification and Functional Connectivity

Abstract

The point of rarity in brain structure and function that separates the 2 major psychotic disorders-schizophrenia and bipolar disorder-is presently unknown. The aim of this study is to combine surface anatomical and functional imaging modalities to quantify the integrity of cortical connectivity in pursuit of the neural basis of the Kraepelinian "line of divide." We tested the hypothesis that multimodal brain regions show overlapping abnormalities in both disorders, while schizophrenia-specific defects are likely to be localized to sensory processing regions. Cortical folding patterns (gyrification) and functional connectivity hub architecture (degree centrality) were studied in a sample of 39 subjects with established schizophrenia, 20 subjects with psychotic bipolar disorder, and 34 healthy controls. We observed a significant difference between the 2 groups in both gyrification and functional connectivity of the visual processing regions. Further, the aberrant functional connectivity of the visual processing regions predicted persistent symptom burden better than the diagnostic information. Using a spatial similarity analysis, we observed that the degree of overlap between the 2 disorders was small (25%) for changes in cortical gyrification and modest (51%) for changes in functional connectivity measured during a cognitive task (n-back). In conclusion, our results suggest that prominent unimodal sensory processing deficits are more likely to be present in schizophrenia than in bipolar disorder. Further, connectivity-based neuroimaging measures appear to be better indicators of diagnostic discontinuity than the symptom-based clinical information.

Increased short-range and long-range functional connectivity in first-episode, medication-naive schizophrenia at rest

“…When cognitive tasks are demanded, "non-specialized" brain regions must be recruited to meet the cognitive demands, resulting in excessive and inefficient recruitment. Several task-related fMRI studies in schizophrenia give support to this perspective (Potkin et al, 2009;Liddle et al, 2013;Palaniyappan and Liddle, 2014). The present results of increased FCS in the DMN suggest that "non-specialized" recruitment exists even when the patients are at rest.…”

Anatomical Distance Affects Functional Connectivity in Patients With Schizophrenia and Their Siblings

“…Several fMRI studies of task performance in patients support this notion. [47][48][49] We observed that in siblings, though the ADF is perturbed, there is some degree of recovery or compensation. Though long links are reduced in proportion, there is a degree of strengthening of relationship among the existing links, which is not seen in patients.…”

Local brain gyrification as a marker of neurological soft signs in schizophrenia

“…Details of the LGI computation process can be found in the validation paper [12], previous studies in psychiatric patients [13,16,42] and at https://surfer.nmr.mgh.harvard.edu/fswiki/LGI. Briefly, an outer envelope that tightly wraps the pial cortical surface is created before local measurement of circular GI is computed for …”