Lateralized effects of subthalamic nucleus stimulation on different aspects of speech in Parkinson’s disease
Santens, P., De Letter, M., Van Borsel, J., De Reuck, J., Caemaert, J. (2003) Lateralized effects of subthalamic nucleus stimulation on different aspects of speech in Parkinson’s disease , 87(2), 253-258
This article analyzed the effects of left and right subthalamic nuclei (STN) stimulation separately on different aspects of speech. Seven patients were included, and two tasks were used to evaluate speech in different STN stimulation conditions. First, the seven patients were asked to read a 200-word standard passage, then they were asked to perform sustained vowel "ah" phonation (the sound made by the vibration of the vocal cords). The two tasks were performed in four different conditions of STN stimulation: (1) left on, right off; (2) right on, left off; (3) bilateral stimulation off; and (4) bilateral stimulation on. Significant differences were found between left and right stimulation. It appears that selective left-sided stimulation has a profoundly negative effect on prosody (e.g., intonation, rhythm, or inflection in one’s voice), articulation and hence intelligibility. Right-sided stimulation does not display this side-effect. There is no significant difference in speech characteristics between bilateral stimulation on and off. Thus, the authors suggest that a balanced tuning of bilateral basal ganglia networks (anatomical structures towards the middle of the brain that are effected by deep brain stimulation in PD patients) is necessary for good speech production.