Abstract
In the current study, we investigated the amplitude of low frequency fluctuations (ALFF) at rest and during a rumination induction. Specifically, we explored the differences of cortical blood oxygenation using fNIRS in subjects with Major Depressive Disorder (MDD) and healthy controls (HC). Rumination was assessed as state and trait measure, as well as with a qualitative semi-structured interview. Qualitative and quantitative measures of rumination indicated that the MDD group showed elevated rumination regarding state and trait measures. Furthermore, rumination differed qualitatively between the groups. The MDD group showed higher levels of general rumination and increased rumination during the rumination induction. However, the MDD group did not show a carry-over effect of elevated rumination after the induction paradigm to the following resting-state measurement. On a neuronal level, we observed a general hypoactivity in the MDD group compared to the HC group. Moreover, both groups showed increased ALFF during the rumination induction compared to the rest phase, especially in temporo-parietal areas. However, no interaction effect of MDD status and rumination induction was found. The current findings are discussed with respect to the literature of paradigms used in the investigation of rumination and suggestions on general improvements in rumination research are given.
Highlights
In the current study, we investigated the amplitude of low frequency fluctuations (ALFF) at rest and during a rumination induction
Counterfactual thinking during rumination was more present in Major Depressive Disorder (MDD) patients (90% vs. 27%) and ruminations were less often followed by actions compared to healthy controls (10% vs. 54%)
The current study aimed to investigate the effects of depressive rumination on ALFF assessed with functional near infrared spectroscopy (fNIRS) during resting state and a rumination induction paradigm
Summary
We investigated the amplitude of low frequency fluctuations (ALFF) at rest and during a rumination induction. We investigated the qualitative nature of rumination in depressed patients and healthy controls (HC) and measured the neuronal correlates during spontaneous rumination and induced rumination by implementing an induction method that has been used by Berman et al (2014) in an fMRI approach. In comparison to classical block designs, the index can be applied without computing event-related averages and is able to reflect a measure of cortical activity at resting state and during investigations of longer time periods that are suboptimal for classical averaging Applying this method to the context of depression and rumination, Jing et al (2013) showed an increased mean ALFF in the right medial frontal gyrus and a decreased mean ALFF in the right precuneus and left lingual gyrus for currently depressed patients relative to a healthy control group[44]. We expected that the increase in state rumination and related brain activity would be higher in the MDD group than in the HC group
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