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Abstract: We examined resting state brain activity in the depressive phase of bipolar disorder (BD) by measuring the amplitude of low-frequency fluctuations (ALFF) in the functional magnetic resonance imaging (fMRI) signal. Unlike functional connectivity, the ALFF approach reflects local properties in specific regions and provides direct information about impaired foci. Groups of 26 patients with BD depression and 26 gender-, age-, and education-matched healthy subjects participated in fMRI scans. We examined group differences in ALFF findings as well as correlations between clinical measurements and ALFF in the regions showing significant group differences. Our results showed that patients with BD depression had significantly increased ALFF in the left insula, the right caudate nucleus, the temporal gyrus, the bilateral inferior frontal gyrus, and the posterior lobe of the cerebellum. They also had decreased ALFF in the left postcentral gyrus, the left parahippocampal gyrus, and the cerebellum. Moderate negative correlations were found between the Hamilton Depression Rating Scale score and ALFF in the left insular cortex in the patient group. These results support a model of BD that involves dysfunction in the prefrontal–limbic networks and associated striatal systems. We also demonstrated the feasibility of ALFF as a technique to investigate persistent cerebral dysfunction in BD. [Copyright &y& Elsevier]

Abstract: In the present study, we investigated differences in resting-state brain activity in patients with bipolar depression (BD) and unipolar depression (UD) by measuring the amplitude of low-frequency fluctuation (ALFF) of functional magnetic resonance imaging (fMRI) signals. Twenty-one BD and 21 gender-, age-, and education-matched UD patients participated in the fMRI analysis. We compared the differences in the ALFF between the two groups and investigated the correlation between clinical measurements and ALFF in the regions displaying significant group differences. BD subjects displayed significantly decreased ALFF in the left superior parietal lobule and the left posterior insula (l-PI). They also displayed increased ALFF in the right dorsal anterior insula (r-dAI) when compared to the UD group. Moderate negative correlations were found between the Hamilton Depression Rating Scale score (HAMD) and the ALFF in the l-PI for the BD (r =−0.44, P =0.02) and UD (r =−0.45, P =0.02) groups. Our results support the notion that insular subregions may contribute to the precise differentiation between BD and UD. [Copyright &y& Elsevier]