A critical issue in the study of speech motor control is the identification of the mechanisms that generate the temporal flow of serially ordered articulatory events. Two staged models of serial ordered events (Lashley, 1951; Lindblom, 1963) claim that time controls events whereas dynamic models predict a relative relation between time and space. Each of these models predicts a different relation between the acoustic measures of formant frequency and segmental duration. The most recent method described herein provides a sensitive index of speech deterioration which is both acoustically robust and phonetically systematic. Both acoustic and magnetic resonance imaging measures were used to describe the speech disturbance in two neurologically distinct groups of cerebellar ataxia: Friedreich’s ataxia and olivo-ponto cerebellar ataxia. The speaking task was designed to elicit six different prosodic conditions and four prosodic contrasts. All subjects read the same syllable embedded in a sentence, under six different prosodic conditions. Pair-wise comparisons derived from the six conditions were used to describe (1) final lengthening, (2) phrasal accent, (3) nuclear accent and (4) syllable reduction. An estimate of speech deterioration as determined by individual and normal subects’ acoustic values of syllable duration, formant and fundamental frequencies was used in correlation analyses with magnetic resonance imaging ratings.