Cognitive and autonomic factors in speech motor control: Effects of the aging process.

摘要

The primary purposes of this study were to determine the effects of cognitive load and autonomic arousal on the speech motor control of healthy older adults and healthy younger adults as well as to advance our understanding of potential age-related changes in the relationship between cognitive, autonomic, and speech motor processes. Eight healthy older adults and eight healthy younger adults completed a novel experimental paradigm in which a Stroop task was embedded within a sentence production task. Participants produced multiple repetitions of sentences in each of two Stroop conditions, congruent and incongruent. The incongruent Stroop condition represented an increase in cognitive load, compared with that associated with the congruent Stroop condition. Articulatory kinematic, autonomic, and acoustic signals were simultaneously collected as participants completed the experimental task. In addition, several forms of perceptual and behavioral data were collected to supplement the physiological data.;Effects of age group (older adult or younger adult), Stroop condition (congruent or incongruent), and sentence segment (during the Stroop portion of the sentence or after the Stroop portion of the sentence, both five syllables in length) on kinematic measures of articulatory spatiotemporal coordination variability and duration were examined. Autonomic arousal was examined with measures of peripheral vascular, cardiac, and electrodermal function. Pulse measures for each sentence production were referenced to pulse measures collected during rest periods that preceded sentence production and were expressed as percents of these baseline levels. Effects of age group and Stroop condition on pulse volume, pulse period, and peak skin conductance response amplitude were examined. In addition, a measure of the relative change in peak skin conductance response amplitude between the congruent and incongruent Stroop conditions was computed for each participant and was compared between age groups.;Results indicated that increased cognitive load was associated with increased articulatory coordination variability and sentence segment duration. For both age groups, articulatory coordination variability and duration were significantly greater for the during Stroop sentence segment in the incongruent Stroop condition than for the same sentence segment in the congruent Stroop condition. Additionally, compared with younger adults, older adults' speech motor systems were disproportionately affected by increased cognitive load. Older adults demonstrated significantly greater articulatory coordination variability than younger adults across both sentence segments in the incongruent Stroop condition. Further, across both sentence segments, older adults' articulatory coordination variability was significantly greater in the incongruent Stroop condition than in the congruent Stroop condition.;Increased cognitive load elicited heightened autonomic arousal in both older adults and younger adults. For both age groups, peak skin conductance response amplitude was significantly greater in the incongruent Stroop condition than in the congruent Stroop condition. Further, older adults demonstrated greater effects of Stroop condition on autonomic arousal, as demonstrated by significantly increased peripheral vasoconstriction and reduced pulse cycle duration in the incongruent Stroop condition, compared with the congruent Stroop condition. In addition, compared with younger adults, older adults experienced approximately twice the relative increase in peak skin conductance response amplitude with increased cognitive load. Older adults' speech motor performance was significantly affected by increased autonomic arousal. This was evidenced by greater articulatory coordination variability in the after Stroop sentence segment in the incongruent Stroop condition than in the after Stroop sentence segment in the congruent Stroop condition.;This study provides empirical support for influences of cognitive and autonomic factors on speech motor control as well as for potential interactions between cognitive, autonomic, and speech motor systems. Furthermore, the observed age-related differences in the effects of increased cognitive load and autonomic arousal on speech motor performance indicate that aging may affect the relationship between cognitive, autonomic, and speech motor processes, contributing to speech motor systems that are more susceptible to destabilization in older adults.