Working memory networks and activation patterns in schizophrenia and bipolar disorder: comparison with healthy
Christine Lycke Brandt1, Tom Eichele, Ingrid Melle
1Christine Lycke Brandt, MSc, K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, and Division of Mental Health and Addiction, Oslo University Hospital, Oslo; Tom Eichele, MD, PhD, Department of Biological and Medical Psychology, University of Bergen, Bergen; Ingrid Melle, MD, PhD, K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, and Division of Mental Health and Addiction, Oslo University Hospital, Oslo; Kjetil Sundet, PhD, Department of Psychology, University of Oslo, K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, and Division of Mental Health and Addiction, Oslo University Hospital, Oslo; Andrés Server, MD, Section of Neuroradiology, Department of Radiology and Nuclear Medicine, Oslo University Hospital, Oslo; Ingrid Agartz, MD, PhD, K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, and Department of Psychiatric Research, Diakonhjemmet Hospital, Oslo, Norway, and Department of Clinical Neuroscience, Psychiatry Section, Karolinska Institute, Stockholm, Sweden; Kenneth Hugdahl, PhD, Department of Biological and Medical Psychology, University of Bergen, and Division of Psychiatry, Department of Radiology, Haukeland University Hospital, Bergen, Norway; Jimmy Jensen, PhD, Centre for Psychology, Kristianstad University, Kristianstad, Sweden, K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo and Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway; Ole A. Andreassen, MD, PhD, K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, and Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway.
Background:
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.
Aims:
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.
Method:
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.
Results:
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.
Conclusions:
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.
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