Abstract
Background
While functional MRI and PET studies have shown altered task-related brain activity in bipolar depression and schizophrenia, recent studies suggest that such differences might also be found in the resting state (RS). Here we used ICA based analysis to investigate RS fMRI data to compare connectivity of 11 well known networks (Auditory, Cerebellum, DMN, Executive Control,
Frontoparietal 1, Frontoparietal 2, Salience, Sensorimotor, Visual1, Visual2, Visual3 network) between patients and healthy controls suggesting deficits in related neuropsychological functions.
Methods
We obtained RS fMRI series (3T, 3x3x3mm resolution, 45 slices, TR 2.55s, 210 volumes) in 22 bipolar patients (mean age 38.4a±11.3), on stable medication and 22 matched healthy controls (36.8a±11.7); 25 schizophrenia patients (mean age 30a±7.3), on stable antipsychotic medication were compared to 25 matched healthy controls (30.3a±8.6).
Subjects were asked to lie in the scanner keeping eyes closed with no further specific instructions.
Data were pre-processed; we applied FSL MELODIC (pICA) yielding IC, we used FIX to auto-classify ICA components which represent artifacts and an automated routine to select for each subject the component matching the anatomical definition of resting state networks. SPM12 was used for second level analysis, we used two sample t-test to compare networks functional connectivity between groups. We then analyzed PSD for the extracted networks, comparing power slope between groups.
Results
Patients with bipolar depression showed decreased FC (cluster p(FWE)<.05) in comparison to healthy controls in Cerebellum, DMN, Fronto-parietal1, Frontoparietal2, Visual1, Visual2 and Visual3 networks; in addition, patients showed increased FC in Cerebellum, Frontoparietal1 networks. The power spectrum of the bipolar patients and healthy control didn’t differ significantly in any of the brain networks. Patients with Schizophrenia showed decreased FC in Cerebellum, DMN,
Executive Control, Fronto-parietal1 and sensorimotor networks; in addition, patients showed increased FC in DMN network. Finally, PSD showed a significant lower power slope in patients with Schizophrenia when compared to healthy controls in Frontoparietal1, Sensorimotor, visual1 and visual2 networks.
Discussion
Well-known resting state networks were reliable identified from RS fMRI in Bipolar depression and schizophrenia patients. The differences in anatomical distribution point to possible alterations in functional connectivity in Bipolar depression and schizophrenia; these differences partially overlapped but also displayed different contribution of well-known resting state networks to the expression of the diseases.