Respiratory sinus arrhythmia responses to cognitive tasks: effects of task factors and RSA indices.

Many studies show that respiratory sinus arrhythmia (RSA) decreases while performing cognitive tasks. However, there is uncertainty about the role of contaminating factors such as physical activity and stress-inducing task variables. Different methods to quantify RSA may also contribute to variable results. In 83 healthy subjects, we studied RSA responses to a working memory task requiring varying levels of cognitive control and a perceptual attention task not requiring strong cognitive control. RSA responses were quantified in the time and frequency domain and were additionally corrected for differences in mean interbeat interval and respiration rate, resulting in eight different RSA indices. The two tasks were clearly differentiated by heart rate and facial EMG reference measures. Cognitive control induced inhibition of RSA whereas perceptual attention generally did not. However, the results show several differences between different RSA indices, emphasizing the importance of methodological variables. Age and sex did not influence the results.