Production and perception of the English sibilants /s/ and /∫/ in persons with Parkinson's disease

Abstract

Parkinson's disease (PD) presents with both sensory and motor deficits including speech, characterized by soft voice, monotonicity, and imprecise articulation. Both audition and somatosense are believed important for accurate speech production. Individual studies have identified auditory impairment and somatosensory impairment of the orofacial structures and the larynx. No studies have examined the relationship between imprecise articulation and sensory impairment. This research aims at examining sensory deficits and the relationship between sensory deficits and imprecise articulation in persons with PD. The production of /s/ and /∫/, auditory discrimination and identification in spectral shape, and somatosensory acuity on the tongue tip are examined. In the production task, participants read monosyllabic words beginning with /s/ and /∫/ embedded in a carrier sentence; measures of spectral shapes are made. Auditory tasks comprise an acuity task testing for participants' auditory acuity in perceiving spectral shapes and a /s/-/∫/ categorization task testing for their categorical boundaries. The somatosensory acuity task tests for participants' somatosensory acuity in spatial orientation on the tongue tip. Relationships between production of /s/ and /∫/ and sensory performance are tested in correlational tests.