Objective: To investigate the characteristics of Chinese characters morphological and phonetic working memory in early Parkinson disease (PD) patients and the underlying neuropsychological and patho-physiological mechanisms.
Methods: The Smith working memory software was modified and further developed to be used to investigate the Chinese characters morphological and phonetic working memory in early PD patients and healthy controls.
Results: Twenty early PD patients, 10 males and 10 females, aged (62.2 +/- 2.3), with (13.6 +/- 0.6) years of full-time study and the MMSE score of (28.2 +/- 0.5), and 25 sex, age, schooling time, and MMSE score-matched healthy controls underwent Chinese characters morphological working memory test. The correct rate of Chinese characters morphological working memory of the PD patients was 91.8% +/- 1.9%, not significantly different from that of the healthy controls (91.3% +/- 1.4%, P = 0.823). Twenty-five early PD patients, 13 males and 12 females, aged (64 +/- 11), with (14.4 +/- 2.2) years of full-time study and the MMSE score of (28.9 +/- 0.4), and 25 sex, age, schooling time, and MMSE score-matched healthy controls underwent Chinese characters phonetic working memory test. The correct rate of Chinese characters phonetic working memory of the PD patients was 89.3% +/- 6.3%, significantly lower than that of the healthy controls (94.1% +/- 5.1% , P = 0. 007). Further more the Chinese characters in the test were classified into four groups according to the syllable and intonation: with same syllable and same intonation, with same syllable and different intonation, with different syllable and same intonation, and with both different syllable and intonation. The correct rates to these groups were recorded separately. The correct rate to Chinese character group of the same syllable with different intonation of the PD patients was 80.2% +/- 2.5%, significantly lower than that of the healthy controls (86.3% +/- 1.8%, P = 0.01), and there were not significant differences in the correct rate to other Chinese character groups. The correct rate of phonetic working memory of the PD patients with left extremity onset was 88.0% +/- 6.5%, significantly lower than that of the healthy controls (94.1% +/- 5.1%, P = 0.003).
Conclusion: Phonetic verbal working memory impairment exists in early PD patients. Intonation may play a role in the phonetic verbal working memory impairment in the early PD patients. Different verbal working memory subsystems may use different neurocircuits.