Emotional blunting following left basal ganglia stroke: the role of depression and fronto-limbic functional alterations

Abstract

Disorders of the basal ganglia (BG) alter perception and experience of emotions. Left hemisphere BG (LBG) stroke is also associated with depression. The interplay between depression and alterations in emotional processing following LBG stroke was examined. Evoked affective responses to emotion-laden pictorial stimuli were compared among LBG stroke and healthy participants and participants with stroke damage in brain regions not including the LBG selected to equate depression severity (measured using the Hamilton Depression Scale) with LBG damage participants. Brain activity {[O(15)]water positron emission tomography, PET} was measured in LBG stroke relative to healthy participants to identify changes in regions associated with emotion processing and depression. LBG stroke subjects reported less intense emotions compared with healthy, but not stroke comparison participants. Depression negatively correlated with emotional experience for positive and negative emotions. In response to positive stimuli, LBG subjects exhibited higher activity in amygdala, anterior cingulate, dorsal prefrontal cortex, and insula compared to healthy volunteers. In response to negative stimuli, LBG subjects demonstrated lower activity in right frontal-polar region and fusiform gyrus. Higher baseline activity in amygdala and ventral and mesial prefrontal cortex and lower activity in left dorsal lateral prefrontal cortex were associated with higher depression scores. LBG stroke led to blunted emotions, and brain activity alterations accounting for reduced affective experience, awareness and depression. Depression and fronto-limbic activity changes may contribute to emotional blunting following LBG stroke.

Figure 1

MRI scans (T1 or T2 where indicated) showing the lesion location of LBG subjects (arrows). Slice orientation was chosen based on ability to display the damage. Orientation follows radiological convention. For full description of damaged structures see Table 3.

Figure 2

MR images showing the lesion location (arrows) in SDC participants. Slice orientation (axial vs. coronal) was chosen based on ability to display the damage. Orientation follows radiological convention.

Figure 3

Axial view of thresholded depression baseline brain activity correlation map among LBG damage and NSNDH participants (overlaid onto an average of their MRI scans) showing positive correlation including the right amygdala (red arrow, rho=.73, p=.005) and negative correlation including the left frontal polar and dorsal lateral prefrontal cortex (white arrow, rho=-.60, p=.008). Image follows radiological convention (right side of brain is on the left). Color pallet (right aspect of the Figure) indicates the strength of the correlations (rho values).