OBJECTIVE
The present study aimed at comparing the effects of deep brain stimulation (DBS) treatment of the subthalamic nucleus (STN) and the caudal zona incerta (cZi) on Parkinson's disease patients' proficiency in achieving oral closure and release during plosive production. METHODS Nineteen patients were evaluated preoperatively and 12 months after DBS surgery. Nine patients were implanted in the STN, seven bilaterally and two unilaterally (left). Ten were bilaterally implanted in the cZi. Postoperative examinations were made off and on stimulation. All patients received simultaneous L-dopa treatment in all conditions. For a series of plosives extracted from a reading passage, absolute and relative measures of duration of frication and amplitude of plosive release were compared between conditions within each treatment group. RESULTS Relative duration of frication increased in voiceless plosives in the on stimulation condition in cZi patients. Similar trends were observed across the data set. Duration of pre-release frication and the release peak prominence increased in voiceless plosives on stimulation for both groups. CONCLUSIONS The increased release prominence suggests that patients achieved a stronger closure gesture due to DBS, but that the increased energy available resulted in increased frication.