Imaging correlates of apathy and depression in Parkinson's disease.

Though the core symptoms of Parkinson's disease (PD) are motor-related, a majority of patients also have neuropsychiatric symptoms concerning mood, behavior and cognition. Apathy and depression are considered among the most frequent ones, and have a negative impact on global functioning and quality of life. Recent neuroimaging studies have provided specific findings related with these symptoms. Depression in PD has been specifically associated with morphological and functional changes in prefrontal cortex, cingulate and thalamus, as with 5-HT transmission reduction in posterior cingulated and amygdala-hippocampus complex. Apathy has received less attention, but has been related with gray matter volume reductions or functional deficits in many regions, as anterior and posterior cingulate and dorsolateral or inferior frontal gyrus. Some of these deficits may be also related with a more pronounced reduction in striatal dopamine transmission. As neuroimaging studies give more arguments to the mechanisms of these symptoms, they also stimulate research for a better individualization of specific affective dimensions in Parkinson's disease.