Speech perception deficits in Parkinson’s disease: underestimation of time intervals compromises identification of durational phonetic contrasts  

Oleh:

Graber, Susanne ; Hertrich, Ingo ; Daum, Irene ; Spieker, Sybille ; Ackermann, Hermann

Jenis: Article from Journal - ilmiah internasional
Dalam koleksi: Brain and Language (Full Text) vol. 82 no. 1 (2002), page 65-74.
Topik: Parkinson’s disease; Timing; Time estimation; Speech perception; Phoneme perception
Fulltext: 82_01_Gr-ber.pdf (120.74KB)

Isi artikel

Besides motor, vegetative, and cognitive signs, patients suffering from Parkinson’s disease (PD) mayshow distinct perceptual deficits such as underestimation of time intervals extending across several seconds. Assuming this impairment also to affect the domain of tens of milliseconds, disrupted encoding of the acoustic speech signal with respect to segment durations conveying linguistic information must be expected. To test this hypothesis, 10 PD patients and matched controls performed an identification task using a series of 10 stimuli derived from the utterance ‘‘Boten’’ (/bo:tn/, ‘messengers’; produced with nasal plosion) byexclusive manipulation of occlusion length (110–20 ms in steps of 10 ms). Under these conditions, word-medial silence cues the voicing categoryof the respective stop consonant. Seven PD subjects showed normal identification curves, i.e., categorized the shortest and longest stimuli with high probabilityeach as the minimal pair cognates ‘‘Boden’’ and ‘‘Boten,’’ respectively. In contrast, the remaining three patients labeled all items across the complete range of occlusion lengths as ‘‘Boden.’’ A subsequent experiment found a horizontal shift of the identification curves toward larger signal durations (> 120ms) in these three subjects. Bilateral cerebellar degeneration has been found to yield a different response pattern, i.e., near-chance level of performance. Considering recent information-processing models of scalar interval timing, striatal disorders seem to slow down an oscillatorypacemaker, whereas cerebellar dysfunctions mayimpair comparison of measured durations with stored reference memory traces.

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