Perceptual characteristics of Parkinsonian speech: a comparison of the pharmacological effects of levodopa across speech and non-speech motor systems. - Plowman-Prine EK; Okun MS; Sapienza CM; Shrivastav R; Fernandez HH; Foote KD; Ellis C; Rodriguez AD; Burkhead LM; Rosenbek JC (NeuroRehabilitation, 2009)