GPI and Parkinson disease: In another study, the authors prospectively assessed the apathy score change preoperatively and postoperatively at the 6-month follow-up in PD patients with either unilateral GPi (11 left-sided, 4 right-sided) or unilateral STN (20 left-sided, 13 right-sided) DBS, and concluded that the incidence of postoperative apathy was not associated with the laterality of GPi or STN DBS44.