Inhibitory control dysfunction of late-onset depression: an event-related fMRI study

Objective To investigate the neural circuit of inhibitory control in late-onset depressed patients(LOD) by functional magnetic resonance imaging(fMRI). Methods Fourteen late-onset depressed patients (LOD group) and thirteen elderly healthy subjects( control group) were recruited. The two groups were age, gender, and education matched. All the subjects performed a visual Go/Nogo task during the fMRI scan. Erect or inverted isosceles triangular figures were used for stimuli. The two groups were instructed to press a button as quickly and correctly as possible when the erect triangular figures(Go) were presented, but not to response when the inverted triangular figures(Nogo) were presented. The differences of brain activation between the two groups were compared. Results ( 1 ) During Go trials, there were no significant differences in reaction time and hit rate between the two groups (P ＞ 0.05 ). During Nogo trials, however, the late-onset depressed patients showed much higher false alarm rate(0.09 ±0.06) compared with control group(0.04 ±0.02) (P＜0.05＝. (2) During Go trials , LOD group showed significantly greater activity in left postcentral gyrus, left inferior parietal lobule, right precentral gyrus, left paracentral lobule, right inferior parietal lobule, right anterior cingulate cortex, left middle frontal gyrus, right middle frontal gyrus, right superior frontal gyrus compared with the control group. Whereas during Nogo trials, LOD group exhibited greater activity in left inferior parietal lobule and left middle frontal gyrus compared with the control group. Conclusion This study suggests that inhibitory control dysfunction in late-onset depressed patients may be closely related to frontostriatal circuit impairment. Over activation in left middle frontal gyrus, right middle frontal gyrus and right anterior cingulate cortex may contribute to the pathogenesis of late-onset depression. Key words: Late-onset depression; Functional magnetic resonance imaging; Inhibitory control