Inhibitory Control Dysfunction Of Late-life Depression: An Event-related FMRI Study

Objective: To investigate regional activity abnormalities of late-onset depression using a event related functional magnetic resonance imaging (fMRI), and to study the neuromechanism of inhibitory control dysfunction in late-onset depression.Methods: 14 elderly depressed subjects(older than 60 years) and 13 elderly nondepressed healthy control subjects matched for age, gender, and education were included. All subjects were measured by neuropsychological tests including 17 items Hamilton Rating Scales of Depression and Mini-Mental State Examination .All subjects underwent an event-related functional magnetic resonance imaging (fMRI) design with a Go/Nogo task including Go and Nogo conditions. The stimulus were erect or inverted triangular figures, and appeared pseudorandomly with equal probability. The subjects were instructed to press a button as quickly and correctly as possible when the erect triangular figure was presented(i.e.,Go), but make no response to the inverted triangular figure(i.e.,Nogo). To compare the different regional activitities between the two groups under the two diff- erent stimulus.Results:1,Behavioral data revealed that during Go conditions, there were no significant differences in reaction time and hit rate between the two groups.However, during Nogo conditions ,the late-onset depressed patients showed a higher false alarm rate compared with controls(P<0.05).2,In the direct comparisons between group,during Go conditions,there was greater activation in the LOD group compared with the control group in left postcentral gyrus,left inferior parietal lobule,right inferior parietal lobule,left middle frontal gyrus,right middle frontal gyrus,right superior frontal gyrus,right precentral gyrus.3,During Nogo conditions,there was greater activation in the LOD group compared with the control group in left inferior parietal lobule,right anterior cingulate cortex,left middle frontal gyrus.Conclusion:1,Behavioral data revealed that late-onset depressed patients showed inhibitory control dysfunction to some extent.2,There was regional activity abnormalities in ACC when late-onset depressed patients executed Nogo task,which showed late-onset depressed patients had ACC dysfunction.3,Our observations of significant differences in DLPFC,ACC,inferior parietal lobule regions in the depressed elderly subjects relative to elderly control subjects supported the frontostriatal dysfunction hypothesis of late-onset depression and provided functional imaging evidence in the pathogenesis of late-onset depression.