Spontaneous Low-Frequency Fluctuations in the BOLD Signal in Schizophrenic Patients: Anomalies in the Default Network

Abstract

Spontaneous low-frequency fluctuations in the blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (MRI) signal have been shown to reflect neural synchrony between brain regions. A "default network" of spontaneous low-frequency fluctuations has been described in healthy volunteers during stimulus-independent thought. Negatively correlated with this network are regions activated during attention-demanding tasks. Both these networks involve brain regions and functions that have been linked with schizophrenia in previous research. The present study examined spontaneous slow fluctuations in the BOLD signal at rest, as measured by correlation with low-frequency oscillations in the posterior cingulate, in 17 schizophrenic patients, and 17 comparable healthy volunteers. Healthy volunteers demonstrated correlation between spontaneous low-frequency fluctuations of the BOLD signal in the posterior cingulate and fluctuations in the lateral parietal, medial prefrontal, and cerebellar regions, similar to previous reports. Schizophrenic patients had significantly less correlation between spontaneous slow activity in the posterior cingulate and that in the lateral parietal, medial prefrontal, and cerebellar regions. Connectivity of the posterior cingulate was found to vary with both positive and negative symptoms in schizophrenic patients. Because these data suggest significant abnormalities in resting-state neural networks in schizophrenia, further investigations of spontaneous slow fluctuations of the BOLD signal seem warranted in this population.

Copy number deletion burden is associated with cognitive, structural, and resting-state network differences in patients with schizophrenia

“…Aberrant functional connectivity in the default mode network has also been identified in patients with schizophrenia [64,65] as well as those at high genetic risk [66]. In the current study, using the mPFC and PCC as seed regions of the DMN, we identified negative correlations between total deletion burden and connectivity between the PCC and the orbitofrontal cortex and between the mPFC and the bilateral associative visual cortex.…”

A Review of the Functional and Anatomical Default Mode Network in Schizophrenia

“…In contrast to Bluhm et al [47], using the same restingstate fc-fMRI with ROI analyses, other researchers consistently found increased functional connectivity within the DMN in schizophrenia patients (including medicationnaïve and medicated chronic patients) [29,34] and in individuals at ultra-high risk for psychosis [48] relative to healthy volunteers. Liu et al extended these findings to unaffected siblings [29], suggesting that abnormally increased functional connectivity of the intrinsic networks may be an endophenotype of schizophrenia.…”

“…Abnormal functional connectivity of the DMN in schizophrenia patients has been investigated during both rest [29,34,[47][48][49] and task conditions [36,41]. Using resting-state fc-fMRI with ROI analysis, Bluhm et al [47] first reported anomalies in the temporal coherence of neuronal BOLD signals associated with the DMN in patients with schizophrenia.…”

“…Using resting-state fc-fMRI with ROI analysis, Bluhm et al [47] first reported anomalies in the temporal coherence of neuronal BOLD signals associated with the DMN in patients with schizophrenia. Specifically, patients in this study had decreased functional connectivity between the PCC seed region and other regions, including medial prefrontal, lateral parietal, and cerebellar regions, relative to controls.…”

Spontaneous brain activity observed with functional magnetic resonance imaging as a potential biomarker in neuropsychiatric disorders

“…Because the regions and functions of the DMN have been linked with schizophrenia, the PCC, as a core region in this network, was selected as the ROI to compare the SLFF pattern of chronic, medicated schizophrenic patients with that of control subjects (Bluhm et al 2007). The PCC was found to show decreased rsFCs in regions associated with the DMN including the PCC, lateral parietal, medial prefrontal cortex (MPFC) and cerebellar regions in chronic, medicated schizophrenic patients (Bluhm et al 2007).…”