“…Mood problems are more common in patients treated with STN-DBS than those treated with GPi-DBS Follett et al, 2010;Moro et al, 2010;Bronstein et al, 2011). Although the underlying substrate of these side effects remains to be characterized, it has been suggested that they may be induced by stimulation in non-motor areas of STN or GPi, inadvertent involvement of limbic structures outside of the target regions (Bejjani et al, 1999;Krack and Vercueil, 2001;Kulisevsky et al, 2002;Romito et al, 2002;Herzog et al, 2003a;Okun et al, 2003;Stefurak et al, 2003), and preexisting psychiatric conditions (Lilleeng and Dietrichs, 2008). Although significant unpleasant mood side effects following STN or GPi DBS are relatively rare (Funkiewiez et al, 2004;Castelli et al, 2006;Tir et al, 2007), their occurrence significantly disrupts patients' quality of life.…”