Declaration of interest
K.H. has stock ownership in NordicNeuroLab, which supplied audiovisual and other hardware equipment for the fMRI image acquisitions as well as software for fMRI data analysis. I.A. has served as an unpaid consultant for Eli Lilly. I.M. has received speaker’s honoraria from Janssen and AstraZeneca. O.A.A. has received speaker’s honoraria from AstraZeneca, Janssen, Bristol-Myers Squibb and GlaxoSmithKline.
Schizophrenia and bipolar disorder are severe mental disorders with overlapping genetic and clinical characteristics, including cognitive impairments. An important question is whether these disorders also have overlapping neuronal deficits.
To determine whether large-scale brain networks associated with working memory, as measured with functional magnetic resonance imaging (fMRI), are the same in both schizophrenia and bipolar disorder, and how they differ from those in healthy individuals.
Patients with schizophrenia (n = 100) and bipolar disorder (n = 100) and a healthy control group (n = 100) performed a 2-back working memory task while fMRI data were acquired. The imaging data were analysed using independent component analysis to extract large-scale networks of task-related activations.
Similar working memory networks were activated in all groups. However, in three out of nine networks related to the experimental task there was a graded response difference in fMRI signal amplitudes, where patients with schizophrenia showed greater activation than those with bipolar disorder, who in turn showed more activation than healthy controls. Secondary analysis of the patient groups showed that these activation patterns were associated with history of psychosis and current elevated mood in bipolar disorder.
The same brain networks were related to working memory in schizophrenia, bipolar disorder and controls. However, some key networks showed a graded hyperactivation in the two patient groups, in line with a continuum of neuronal abnormalities across psychotic disorders.
The study was financially supported by the Research Council of Norway (grant numbers 167153/V50, 163070/V50 and 183782/V50) and the South-Eastern (2004-123) and Western (91141) Norway Regional Health Authority.
- Royal College of Psychiatrists