Abstract
Word retrieval difficulty has been reported as the most common and persistent problem that can be observed in individuals with aphasia. Word frequency effect on the behavioral naming performance has been well documented in normal subjects and individuals with aphasia. However, physiological correlates of word retrieval are relatively unstudied. The current study examined the effect of word frequency on physiological correlates (i.e., heart rate, heart rate variability, and respiratory rate) during a picture naming task. A group of individuals with aphasia (n=7) and a group of healthy elderly (n=38) participated in four different experimental conditions, including rest, counting, high frequency word, and low frequency word conditions, while their cardiovascular and respiratory activity were measured throughout the experimental session. Physiological parameters data indicated that there were significant differences in heart rate and high frequency power of heart rate variability while participants were engaged in speech and/or language tasks, for both groups. In addition, there were significant differences in low frequency power of heart rate variability in the group with aphasia. However, no significant difference in respiratory rate was revealed. Additionally, no significant difference was found in physiological parameters between the healthy group and the group with aphasia. For the healthy group, there were significant differences in naming accuracy and latency between two sets of words. A significant positive correlation between naming accuracy and word frequency and a significant negative correlation between naming latency and word frequency were revealed. For the group with aphasia, only a significant negative correlation between naming latency and word frequency was revealed. There were significant differences in naming accuracy and latency between two groups. Additionally, difficulty and stress ratings were obtained from each participant after counting and two naming conditions. Results revealed parallel patterns between subjective perceived stress level and cardiovascular responses. Taken together, word frequency influenced behavioral naming performance in both groups, and it seemed that word frequency effect was not enough to induce significant changes in cardiovascular and respiratory responses.
|
