Purpose: This study compared bilateral deep brain stimulation (DBS) in subthalamic nucleus (STN) versus globus pallidus interna (GPI) on perceived Speech Severity in Parkinson’s disease. Methods: 12 individuals with STN-DBS and 8 individuals with GPI-DBS were audio-recorded with DBS ON and OFF while reading an excerpt from the Rainbow Passage and producing a conversational monologue. Using a within-speaker, paired comparison paradigm, 10 listeners judged Speech Severity for pairs of stimulation ON-OFF (and OFF-ON) reading passages and monologues masked to stimulation status and speaker group. The proportion of trials for which ON versus OFF stimuli in a given pair was judged to be less severe was calculated. Results: There was a task effect, with significant results for Rainbow Passage but not conversational monologue. Perceived Speech Severity differed with stimulation status for GPI-DBS but not STN-DBS, with a greater proportion of ON stimulation speech samples judged to be less severe versus OFF samples. At the participant level, response to ON/OFF stimulation was highly variable in STN-DBS group. Discussion: DBS stimulation differentially impacts perceived speech severity for STN-DBS and GPI-DBS. Results further suggest the perceptual benefit of DBS stimulation may be task specific
