fMRI activation in late-life anxious depression: a potential biomarker.

Objective And Methods: The neurobiology of late-life anxious depression (LLAD) is poorly characterized despite evidence that this is a common and severe subtype of late-life depression. To identify the neuroanatomical substrate of LLAD, we examined event-related fMRI data collected in eight subjects with late-life depression, half of whom had high levels of comorbid anxiety. Subjects were trained on the Preparing to Overcome Prepotency (POP) task, which is an executive control task that reliably activates the lateral prefrontal cortex-anterior cingulate cortex (ACC) cognitive control circuit.

Results: Time series analysis showed that, when compared with elderly depressed subjects, elderly subjects with anxious depression performing the POP task produced a significantly greater and more sustained signal in three regions: BA24 (dorsal anterior cingulate), BA31 (posterior cingulate), and BA6 (prefrontal cortex). While elderly subjects with pure depression presented a bimodal activation curve in the dorsal anterior cingulate and the posterior cingulate, elderly subjects with anxious depression presented a sustained unimodal activation pattern.

Conclusions: Our preliminary results suggest specific activation patterns unique to anxious depression that may suggest greater and more sustained efforts of the ACC to carry out cognitive control tasks. Further research is needed to clarify the neuroanatomical basis of LLAD.