SEQUENCE HETEROGENEITY IN PARKINSONIAN SPEECH

Parkinson's disease (PD) is a neurodegenerative movement disorder prim arily due to basal ganglia dysfunction. While much research has been c onducted on Parkinsonian deficits in the traditional arena of musculos keletal limb movement, research in other functional motor tasks is lac king. The present study examined articulation in PD with increasingly complex sequences of articulatory movement. Of interest was whether dy sfunction would affect articulation in the same manner as in limb-move ment impairment. In particular, since very Similar (homogeneous) artic ulatory sequences (the tongue twister effect) are more difficult for h ealthy individuals to achieve than dissimilar (heterogeneous) gestures , while the reverse may apply for skeletal movements in PD, we asked w hich factor would dominate when PD patients articulated various grades of artificial tongue twisters: the influence of disease or a possible difference between the two motor systems. Execution was especially im paired when articulation involved a sequence of motor program heteroge neous in terms of place of articulation. The results are suggestive of a hypokinesic tendency in complex sequential articulatory movement as in limb movement. It appears that PD patients do show abnormalities i n articulatory movement which are similar to those of the musculoskele tal system. The present study suggests that an underlying disease effe ct modulates movement impairment across different functional motor sys tems. (C) 1998 Academic Press.