Dysarthria is a significant feature of the dominantly inherited spinocerebellar ataxias (SCA), but little is known about the patterns of brain activity associated with this disorder of motor speech control. Positron emission tomography (PET) was used to study regional cerebral blood flow during speech and rest in a group of 24 subjects with hereditary ataxia with mild-to-moderate dysarthria. These data were compared to the results obtained from a group of 13 age-matched, normal speakers. In the ataxic subjects, speech rates during scanning were significantly slowed compared to normal speakers. Significant reductions in mean regional blood flow were found in the cerebellum but not in supratentorial regions in the ataxic subjects. Multiple linear regression was used to model speech rate from regional blood flow. Four regions were identified as having significant relationships with speech rate in the model: the left inferior frontal and transverse temporal regions, and the right inferior cerebellar region and caudate nucleus. The relationship between flow and rate was positive in the inferior frontal and cerebellar regions and negative in the caudate and the transverse temporal region. The ataxic model represents an elaboration of the relationship previously reported for normal speakers, likely reflecting both the effects of, and compensation for, cerebellar degeneration in motor speech control. Although the mean regional blood flow values presented a pattern of functional organization for motor speech control at odds with lesion data, the performance-based model was in agreement with clinical experience. Incorporating performance data in functional image analysis may be more revealing of system characteristics than simply examining mean blood flow values.
Bibliographical noteFunding Information:
Support was provided by the Parkinson's Disease Foundation, the Bob Allison Ataxia Research Center, the Program in Hereditary Ataxia (PO1NS33718), R01 NS37211, and the Human Brain Project Program in Visualization of Functional Connectivity in the Brain (P20 MH57180). The helpful comments of Dr. D. Sidtis on earlier versions of the manuscript are gratefully acknowledged. The assistance of J. Anderson, D. Daly, M. Kneer, C. Farmer, D. Hamm, C. Erickson, K. Connaghan, M. Alberg, and J. Mahowald in scanning, data collection, acoustic analysis, and data processing are also gratefully appreciated. This work would not have been possible without the efforts of Dr. Richard Price in establishing the Bob Allison Ataxia Research Center as a resource for interdisciplinary clinical research.
Copyright 2008 Elsevier B.V., All rights reserved.
- Human brain mapping
- PET imaging