Alterations of functional connectivity and intrinsic activity within the cingulate cortex of suicidal ideators

The ‘default mode network’ (DMN), a collection of brain regions including the posterior cingulate cortex (PCC),

shows reliable inter-regional functional connectivity at rest. It has been implicated in rumination and other

negative affective states, but its role in suicidal ideation is not well understood. We employed seed based

functional connectivity methods to analyze resting state fMRI data in 34 suicidal ideators and 40 healthy control

participants. Whole-brain connectivity with dorsal PCC or ventral PCC was broadly intact between the two

groups, but while the control participants showed greater coupling between the dorsal anterior cingulate cortex

(dACC) and dorsal PCC, compared to the dACC and ventral PCC, this difference was reversed in the ideators.

Furthermore, ongoing low frequency BOLD signal in these three regions (dorsal, ventral PCC, dACC) was

reduced in the ideators. The structural integrity of the cingulum bundle, as measured using diffusion tensor

imaging (DTI), also explained variation in the functional connectivity measures but did not abolish the group

differences. Together, these findings provide evidence of abnormalities in the DMN underlying the tendency

towards suicidal ideation.