Longitudinal Changes in Brain Activity in Progressive Ataxia: Broca's Activity
Increases while Other Areas Decline during Speech Production

J Sidtis, C Gomez

 

Functional brain activity during speech production was studied in subjects with hereditary ataxia that produces dysarthria using Positron Emission Tomography. Regional cerebral blood flow (rCBF) was measured twice over a two-year period in a group of 7 right-handed ataxic subjects (aged 3820 years) while repeating the syllables pa, ta, and ka, as quickly as possible. Clinical dysarthria ratings increased 8% from the first to second evaluation, remaining in the mild range. Acoustic measures showed a 6% increase in syllable production rate, a 14% decrease in the number of breath groups, a 20% decrease in the duration of pataka strings, and a 38% increase in their duration variability. Disease progression produced rCBF decreases of 7% in the inferior cerebellum, 4% in the middle cerebellum, and 3% in the superior cerebellum. In contrast, rCBF increased 4% in the left inferior frontal (Broca's) area. A decrease of 4% in the homologous right inferior frontal area was also observed. This pattern of brain activity reflects both loss of function and compensation suggesting a complex process in progressive motor speech disorders.