Preservation of relational timing in speech of persons with Parkinson's disease with and without deep brain stimulation.

Background: Initial shortening of stem vowels in three-word derivational paradigms (e.g., zip, zipper, zippering) was studied in persons with Parkinson's disease (PWPD) with and without deep brain stimulation (DBS), and in normal speakers.

Method: Seven PWPD without DBS, 7 PWPD with DBS ON (DBSN) or OFF (DBSF), and 6 healthy control (CON) persons were studied. Stimuli were 7 three-word paradigms consisting of a stem word and two derived longer forms created by adding the suffixes er (+1), and er+ing (+2).

Results: Vowel durations decreased across word forms of increasing length (initial shortening) for DBSF, DBSN, PWPD, and CON. Vowel shortening did not interact with group. For each word form, CON vowel duration was shorter than those for PWPD, DBSN and DBSF but word duration did not differ between groups. DBS did not have a significant effect on either vowel or word duration.

Conclusion: These results agree with previous findings for a PWPD with accelerated speech and faster rates of speech in DBS-ON. Observations that vowel duration patterns are maintained in subcortical and cerebellar but not left hemisphere damage suggest that cortical control factors play a primary role in relational timing.